Papers on Australia wildfires and climate change

This is a list of papers on Australia wildfires and climate change. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

UPDATE (January 10, 2020): Cai et al. (2009) added.

Climate change effects on the frequency, seasonality and interannual variability of suitable prescribed burning weather conditions in south-eastern Australia – Clarke et al. (2019)
“Despite the importance of prescribed burning in contemporary fire management, there is little understanding of how climate change will influence the weather conditions under which it is deployed. We provide quantitative estimates of potential changes in the number of prescribed burning days in coastal NSW in south-eastern Australia, a fire-prone area dominated by dry sclerophyll forests. Burning days are calculated from an objectively designed regional climate model ensemble using three definitions of suitable weather conditions based on: a literature search (Literature), actual weather observed during recorded prescribed burns (Observed) and operational guidelines (Operational). Contrary to some claims, evidence for a decrease in prescribed burning days under projected future climates is weak. We found a complex pattern of changes, with the potential for substantial and widespread increases in the current burning seasons of autumn (March-May) and spring (August-October). Projected changes were particularly uncertain in northern NSW, spanning substantial increases and decreases during autumn. The magnitude of projected changes in the frequency of burning days was highly sensitive to which definition of suitable weather conditions was used, with a relatively small change for the Operational definition (+0.3 to +1.9 days per year across the study area) and larger ranges for the Observed (+0.2 to +7.9 days) and Literature (+1.7 to +6.2 days) definitions. Interannual variability in the number of burning days is projected to increase slightly under projected climate change. Our study highlights the need for a better understanding of the weather conditions required for safe and effective prescribed burning. Our analysis provides practitioners with quantitative information to assess their exposure to a range of potential changes in the frequency, seasonality and variability of prescribed burning weather conditions.”
Hamish Clarke, Bruce Tran, Matthias M. Boer, Owen Price, Belinda Kenny, Ross Bradstock (2019). Agricultural and Forest Meteorology 271(15):148-157. doi:https://doi.org/10.1016/j.agrformet.2019.03.005.

Future changes in extreme weather and pyroconvection risk factors for Australian wildfires – Dowdy et al. (2019)
“Extreme wildfires have recently caused disastrous impacts in Australia and other regions of the world, including events with strong convective processes in their plumes (i.e., strong pyroconvection). Dangerous wildfire events such as these could potentially be influenced by anthropogenic climate change, however, there are large knowledge gaps on how these events might change in the future. The McArthur Forest Fire Danger Index (FFDI) is used to represent near-surface weather conditions and the Continuous Haines index (CH) is used here to represent lower to mid-tropospheric vertical atmospheric stability and humidity measures relevant to dangerous wildfires and pyroconvective processes. Projected changes in extreme measures of CH and FFDI are examined using a multi-method approach, including an ensemble of global climate models together with two ensembles of regional climate models. The projections show a clear trend towards more dangerous near-surface fire weather conditions for Australia based on the FFDI, as well as increased pyroconvection risk factors for some regions of southern Australia based on the CH. These results have implications for fields such as disaster risk reduction, climate adaptation, ecology, policy and planning, noting that improved knowledge on how climate change can influence extreme wildfires can help reduce future impacts of these events.”
Andrew J. Dowdy, Hua Ye, Acacia Pepler, Marcus Thatcher, Stacey L. Osbrough, Jason P. Evans, Giovanni Di Virgilio & Nicholas McCarthy (2019). Scientific Reports 9:10073. doi:10.1038/s41598-019-46362-x. [FULL TEXT]

Exploring the future change space for fire weather in southeast Australia – Clarke & Evans (2019)
“High-resolution projections of climate change impacts on fire weather conditions in southeast Australia out to 2080 are presented. Fire weather is represented by the McArthur Forest Fire Danger Index (FFDI), calculated from an objectively designed regional climate model ensemble. Changes in annual cumulative FFDI vary widely, from − 337 (− 21%) to + 657 (+ 24%) in coastal areas and − 237 (− 12%) to + 1143 (+ 26%) in inland areas. A similar spread is projected in extreme FFDI values. In coastal regions, the number of prescribed burning days is projected to change from − 11 to + 10 in autumn and − 10 to + 3 in spring. Across the ensemble, the most significant increases in fire weather and decreases in prescribed burn windows are projected to take place in spring. Partial bias correction of FFDI leads to similar projections but with a greater spread, particularly in extreme values. The partially bias-corrected FFDI performs similarly to uncorrected FFDI compared to the observed annual cumulative FFDI (ensemble root mean square error spans 540 to 1583 for uncorrected output and 695 to 1398 for corrected) but is generally worse for FFDI values above 50. This emphasizes the need to consider inter-variable relationships when bias-correcting for complex phenomena such as fire weather. There is considerable uncertainty in the future trajectory of fire weather in southeast Australia, including the potential for less prescribed burning days and substantially greater fire danger in spring. Selecting climate models on the basis of multiple criteria can lead to more informative projections and allow an explicit exploration of uncertainty.”
Clarke, H. & Evans, J.P. Theor Appl Climatol (2019) 136: 513. https://doi.org/10.1007/s00704-018-2507-4. [FULL TEXT]

On Determining the Impact of Increasing Atmospheric CO2 on the Record Fire Weather in Eastern Australia in February 2017 – Hope et al. (2019)
“February 2017 saw a broad region with record fire weather across central-eastern Australia. A hybrid attribution technique using modified observations and a seasonal forecast framework did not give a clear signal as to the influence of increasing atmospheric CO2 on the fire weather.”
Pandora Hope, Mitchell T. Black, Eun-Pa Lim, Andrew Dowdy, Guomin Wang, Acacia S. Pepler, and Robert J. B. Fawcett (2019). Bulletin of the American Meteorological Society, vol. 100, issue 1, pp. S111-S117. doi:10.1175/BAMS-D-18-0135.1. [FULL TEXT]

Climatological Variability of Fire Weather in Australia – Dowdy (2018)
“Long-term variations in fire weather conditions are examined throughout Australia from gridded daily data from 1950 to 2016. The McArthur forest fire danger index is used to represent fire weather conditions throughout this 67-yr period, calculated on the basis of a gridded analysis of observations over this time period. This is a complementary approach to previous studies (e.g., those based primarily on model output, reanalysis, or individual station locations), providing a spatially continuous and long-term observations-based dataset to expand on previous research and produce climatological guidance information for planning agencies. Long-term changes in fire weather conditions are apparent in many regions. In particular, there is a clear trend toward more dangerous conditions during spring and summer in southern Australia, including increased frequency and magnitude of extremes, as well as indicating an earlier start to the fire season. Changes in fire weather conditions are attributable at least in part to anthropogenic climate change, including in relation to increasing temperatures. The influence of El Niño–Southern Oscillation (ENSO) on fire weather conditions is found to be broadly consistent with previous studies (indicating more severe fire weather in general for El Niño conditions than for La Niña conditions), but it is demonstrated that this relationship is highly variable (depending on season and region) and that there is considerable potential in almost all regions of Australia for long-range prediction of fire weather (e.g., multiweek and seasonal forecasting). It is intended that improved understanding of the climatological variability of fire weather conditions will help lead to better preparedness for risks associated with dangerous wildfires in Australia.”
Dowdy, A.J., 2018: Climatological Variability of Fire Weather in Australia. J. Appl. Meteor. Climatol., 57, 221–234, https://doi.org/10.1175/JAMC-D-17-0167.1. [FULL TEXT]

Pyroconvection Risk in Australia: Climatological Changes in Atmospheric Stability and Surface Fire Weather Conditions – Dowdy & Pepler (2018)
“Extreme wildfires with strong convective processes in their plumes have recently led to disastrous impacts on various regions of the world. The Continuous Haines index (CH) is used in Australia to represent vertical atmospheric stability and humidity measures relating to pyroconvective processes. CH climatology is examined here using reanalysis data from 1979 to 2016, revealing large spatial and seasonal variations throughout Australia. Various measures of severity are investigated, including regionally specific thresholds. CH is combined with near‐surface fire weather conditions, as a type of compound event, and is examined in relation to environmental conditions associated with pyroconvection. Significant long‐term changes in CH are found for some regions and seasons, with these changes corresponding to changes in near‐surface conditions in some cases. In particular, an increased risk of pyroconvection is identified for southeast Australia during spring and summer, due to decreased vertical atmospheric stability and humidity combined with more severe near‐surface conditions.”
Dowdy, A. J., & Pepler, A. ( 2018). Pyroconvection risk in Australia: Climatological changes in atmospheric stability and surface fire weather conditions. Geophysical Research Letters, 45, 2005– 2013. https://doi.org/10.1002/2017GL076654. [FULL TEXT]

Fire frequency analysis for different climatic stations in Victoria, Australia – Khastagir (2018)
“Frequent occurrence of fire events will have severe impact on Victoria’s water supply catchments. Hence, it is important to perform fire frequency analysis to obtain fire frequency curves (FFC) on fire intensity using Forest Fire Danger Index (FFDI) at different parts of Victoria. FFDI is a measure of fire initiation, spreading speed and containment difficulty. FFC will guide water harvesting by providing information with regard to future fire events and the subsequent impact on catchment yield. Five probability distributions, namely normal, Log Pearson Type III (LPIII), gamma, log-normal and Weibull distributions were used for the development of FFCs at ten selected meteorological stations spread all over Victoria. LPIII distribution was identified as the best fit distribution for Victoria and subsequently applied for an additional 30 more stations to show spatial variability for the entire Victoria.”
Anirban Khastagir (2018). Natural Hazards volume 93, pages 787–802. doi:https://doi.org/10.1007/s11069-018-3324-x.

Fanning the Blame: Media Accountability, Climate and Crisis on the Australian “Fire Continent” – Anderson et al. (2018)
“This paper raises questions of media coverage of “compounded crises” related to extreme weather disaster, in the context of urgent calls to address the implications of a changing climate. Through media analysis, it examines the ways debate over bushfire protection policy was framed and made culturally meaningful, thereby politically consequential, in the wake of the worst bushfires in modern Australian history, Black Saturday (2009). The fires, in which 173 people died, led to a Royal Commission and fierce debate over the use of prescribed burning to reduce bushfire hazard. Longitudinal analysis of local, state and national mainstream media coverage (2009–2016) reveals blame games that targeted environmentalists and the government, which near-silenced meaningful discussion of the complexity of fire science, impacts of climate change on weather conditions, and calls for adaptation. By exploring the media’s constitutive role in crisis response, the paper highlights the legacy and potency of ideological conflict that shapes the media-policy nexus in Australia.”
Deb Anderson, Philip Chubb & Monika Djerf-Pierre (2018) Fanning the Blame: Media Accountability, Climate and Crisis on the Australian “Fire Continent”, Environmental Communication, 12:7, 928-941, DOI: 10.1080/17524032.2018.1424008. [FULL TEXT]

Big data integration shows Australian bush-fire frequency is increasing significantly – Dutta et al. (2016)
“Increasing Australian bush-fire frequencies over the last decade has indicated a major climatic change in coming future. Understanding such climatic change for Australian bush-fire is limited and there is an urgent need of scientific research, which is capable enough to contribute to Australian society. Frequency of bush-fire carries information on spatial, temporal and climatic aspects of bush-fire events and provides contextual information to model various climate data for accurately predicting future bush-fire hot spots. In this study, we develop an ensemble method based on a two-layered machine learning model to establish relationship between fire incidence and climatic data. In a 336 week data trial, we demonstrate that the model provides highly accurate bush-fire incidence hot-spot estimation (91% global accuracy) from the weekly climatic surfaces. Our analysis also indicates that Australian weekly bush-fire frequencies increased by 40% over the last 5 years, particularly during summer months, implicating a serious climatic shift.”
Ritaban Dutta, Aruneema Das and Jagannath Aryal (2016). Royal Society Open Science 3(2). doi:https://doi.org/10.1098/rsos.150241. [FULL TEXT]

Natural hazards in Australia: extreme bushfire – Sharples et al. (2016)
“Bushfires are one of the most frequent natural hazards experienced in Australia. Fires play an important role in shaping the landscape and its ecological dynamics, but may also have devastating effects that cause human injuries and fatalities, as well as broad-scale environmental damage. While there has been considerable effort to quantify changes in the occurrence of bushfire in Australia, a comprehensive assessment of the most extreme bushfire cases, which exact the greatest economic and environmental impacts, is lacking. In this paper we reflect upon recently developed understanding of bushfire dynamics to consider (i) historical changes in the occurrence of extreme bushfires, and (ii) the potential for increasing frequency in the future under climate change projections. The science of extreme bushfires is still a developing area, thus our conclusions about emerging patterns in their occurrence should be considered tentative. Nonetheless, historical information on noteworthy bushfire events suggests an increased occurrence in recent decades. Based on our best current understanding of how extreme bushfires develop, there is strong potential for them to increase in frequency in the future. As such there is a pressing need for a greater understanding of these powerful and often destructive phenomena.”
Sharples, J.J., Cary, G.J., Fox-Hughes, P. et al. Climatic Change (2016) 139: 85. https://doi.org/10.1007/s10584-016-1811-1. [FULL TEXT]

ENSO controls interannual fire activity in southeast Australia – Mariani et al. (2016)
“El Niño–Southern Oscillation (ENSO) is the main mode controlling the variability in the ocean‐atmosphere system in the South Pacific. While the ENSO influence on rainfall regimes in the South Pacific is well documented, its role in driving spatiotemporal trends in fire activity in this region has not been rigorously investigated. This is particularly the case for the highly flammable and densely populated southeast Australian sector, where ENSO is a major control over climatic variability. Here we conduct the first region‐wide analysis of how ENSO controls fire activity in southeast Australia. We identify a significant relationship between ENSO and both fire frequency and area burnt. Critically, wavelet analyses reveal that despite substantial temporal variability in the ENSO system, ENSO exerts a persistent and significant influence on southeast Australian fire activity. Our analysis has direct application for developing robust predictive capacity for the increasingly important efforts at fire management.”
Mariani, M., Fletcher, M.‐S., Holz, A., and Nyman, P. ( 2016), ENSO controls interannual fire activity in southeast Australia, Geophys. Res. Lett., 43, 10,891– 10,900, doi:10.1002/2016GL070572. [FULL TEXT]

People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands – Bird et al. (2016)
“While evidence mounts that indigenous burning has a significant role in shaping pyrodiversity, the processes explaining its variation across local and external biophysical systems remain limited. This is especially the case with studies of climate–fire interactions, which only recognize an effect of humans on the fire regime when they act independently of climate. In this paper, we test the hypothesis that an anthropogenic fire regime (fire incidence, size and extent) does not covary with climate. In the lightning regime, positive El Niño southern oscillation (ENSO) values increase lightning fire incidence, whereas La Niña (and associated increases in prior rainfall) increase fire size. ENSO has the opposite effect in the Martu regime, decreasing ignitions in El Niño conditions without affecting fire size. Anthropogenic ignition rates covary positively with high antecedent rainfall, whereas fire size varies only with high temperatures and unpredictable winds, which may reduce control over fire spread. However, total area burned is similarly predicted by antecedent rainfall in both regimes, but is driven by increases in fire size in the lightning regime, and fire number in the anthropogenic regime. We conclude that anthropogenic regimes covary with climatic variation, but detecting the human–climate–fire interaction requires multiple measures of both fire regime and climate.”
Bliege Bird Rebecca, Bird Douglas W. and Codding Brian F. People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands. Phil. Trans. R. Soc. B. 371(1696). doi:https://doi.org/10.1098/rstb.2015.0343. [FULL TEXT]

Responses of resilience traits to gradients of temperature, rainfall and fire frequency in fire-prone, Australian forests: potential consequences of climate change – Hammill et al. (2016)
“The composition of plant communities may be driven by responses of key plant resilience traits (resprouting R+, non-resprouting R−, persistent P+ and transient P− seedbanks) to either resource competition or disturbance regimes. We explored responses of overall species richness and the richness of herbs and shrubs within the three most common functional types (i.e. facultative resprouters R+P+, obligate resprouters R+P−, obligate seeders R−P+) to orthogonal combinations of temperature (MAT), rainfall (MAP) and fire frequency (FF) in Dry Sclerophyll Forest in the Sydney basin (south-eastern Australia). R+ and P+ species were predominant (>72 % of total species). Overall richness was a significant positive function of MAT, MAP and FF. Positive relationships between species richness and MAP, MAT and FF occurred across all trait and functional type groups, with MAP being the most influential and FF the least. Responses of proportions of species within trait- and functional-type groups were complex. Proportion of R+ species was negatively related to MAT and MAP, but species-rich herb and shrub R+P+ proportions were positively and negatively related to MAT, respectively. The herb R+P+ proportion was negatively related to FF. The results were inconsistent with the disturbance frequency and resource competition models of resilience variation. Rises in MAT under climate change have the potential not only to increase overall species plus richness across all trait groups but also to diminish shrubs relative to herbs in the key R+P+ functional types. Such a scenario is highly uncertain given the variability in future MAP projections for the region.”
Hammill, K., Penman, T. & Bradstock, R. Plant Ecol (2016) 217: 725. https://doi.org/10.1007/s11258-016-0578-9.

Divergent responses of fire to recent warming and drying across south‐eastern Australia – Bradstock et al. (2014)
“The response of fire to climate change may vary across fuel types characteristic of differing vegetation types (i.e. litter vs. grass). Models of fire under climatic change capture these differing potential responses to varying degrees. Across south‐eastern Australia, an elevation in the severity of weather conditions conducive to fire has been measured in recent decades. We examined trends in area burned (1975–2009) to determine if a corresponding increase in fire had occurred across the diverse range of ecosystems found in this part of the continent. We predicted that an increase in fire, due to climatic warming and drying, was more likely to have occurred in moist, temperate forests near the coast than in arid and semiarid woodlands of the interior, due to inherent contrasts in the respective dominant fuel types (woody litter vs. herbaceous fuels). Significant warming (i.e. increased temperature and number of hot days) and drying (i.e. negative precipitation anomaly, number of days with low humidity) occurred across most of the 32 Bioregions examined. The results were mostly consistent with predictions, with an increase in area burned in seven of eight forest Bioregions, whereas area burned either declined (two) or did not change significantly (nine) in drier woodland Bioregions. In 12 woodland Bioregions, data were insufficient for analysis of temporal trends in fire. Increases in fire attributable mostly to warming or drying were confined to three Bioregions. In the remainder, such increases were mostly unrelated to warming or drying trends and therefore may be due to other climate effects not explored (e.g. lightning ignitions) or possible anthropogenic influences. Projections of future fire must therefore not only account for responses of different fuel systems to climatic change but also the wider range of ecological and human effects on interactions between fire and vegetation.”
Bradstock, R., Penman, T., Boer, M., Price, O. and Clarke, H. (2014), Divergent responses of fire to recent warming and drying across south‐eastern Australia. Glob Change Biol, 20: 1412-1428. doi:10.1111/gcb.12449.

Changes in Australian fire weather between 1973 and 2010 – Clarke et al. (2013)
“A data set of observed fire weather in Australia from 1973–2010 is analysed for trends using the McArthur Forest Fire Danger Index (FFDI). Annual cumulative FFDI, which integrates daily fire weather across the year, increased significantly at 16 of 38 stations. Annual 90th percentile FFDI increased significantly at 24 stations over the same period. None of the stations examined recorded a significant decrease in FFDI. There is an overall bias in the number of significant increases towards the southeast of the continent, while the largest trends occur in the interior of the continent and the smallest occur near the coast. The largest increases in seasonal FFDI occurred during spring and autumn, although with different spatial patterns, while summer recorded the fewest significant trends. These trends suggest increased fire weather conditions at many locations across Australia, due to both increased magnitude of FFDI and a lengthened fire season. Although these trends are consistent with projected impacts of climate change on FFDI, this study cannot separate the influence of climate change, if any, with that of natural variability.”
Clarke, H., Lucas, C. and Smith, P. (2013), Changes in Australian fire weather between 1973 and 2010. Int. J. Climatol., 33: 931-944. doi:10.1002/joc.3480. [FULL TEXT]

Fire and carbon dynamics under climate change in south-eastern Australia: insights from FullCAM and FIRESCAPE modelling – King et al. (2011)
“This study used simulation modelling to investigate fire and carbon dynamics for projected warmer and drier climates in the south-eastern Australian high country. A carbon accounting model FullCAM and the landscape fire regime simulator FIRESCAPE were combined and used to simulate several fire management options under three climate scenarios – the recent climate (1975–2005); a moderate climate projected for 2070 (B1); and a more extreme climate projected for 2070 (A1FI). For warmer and drier climates, model simulations predicted (i) an increase in fire incidence; (ii) larger areas burned; (iii) higher mean fire intensities; (iv) shorter fire cycle lengths; (v) a greater proportion of fires burning earlier in the fire season; (vi) a reduction in carbon stores; (vii) a reduction in carbon sequestration rates; and (viii) an increase in the proportion of stored carbon emitted to the atmosphere. Prescribed burning at historical or twice historical levels had no effect on fire or carbon dynamics. In contrast, increasing the initial attack success (a surrogate for suppression) partially offset the adverse effects of warmer and drier climates on fire activity, but not on carbon dynamics. For the south-eastern Australian high country, simulations indicated that fire and carbon dynamics are sensitive to climate change, with simulated fire management only being able to partially offset the adverse effects of warmer and drier climate.”
King Karen J., de Ligt Robert M., Cary Geoffrey J. (2011) Fire and carbon dynamics under climate change in south-eastern Australia: insights from FullCAM and FIRESCAPE modelling. International Journal of Wildland Fire 20, 563-577. doi:https://doi.org/10.1071/WF09073.

Assessing the impact of climate change on extreme fire weather events over southeastern Australia – Hasson et al. (2009)
“Extreme fire weather events in southeastern Australia are frequently associated with strong cold fronts moving through the area. A recent study has shown that the 850 hPa temperature and the magnitude of its gradient over a small region of southeastern Australia provide a simple means of discriminating the most extreme cold frontal events during the last 40 yr from reanalysis data sets. Applying this technique to 10 general circulation models (GCMs) from the Coupled Model Intercomparison Project and calibrating the temperature gradient and temperature climatology of each model’s simulation of the climate of the 20th century against the reanalysis climates allows estimates of likely changes in frequency of this type of extreme cold front in the middle and end of the 21st century. Applying this analysis to the output of 10 GCM simulations of the 21st century, using low and high greenhouse gas emissions scenarios, suggests that the frequency of such events will increase from around 1 event every 2 yr during the late 20th century to around 1 event per year in the middle of the 21st century and 1 to 2 events per year by the end of the 21st century; however, there is a great degree of variation between models. In addition to a greater overall increase under the high emissions scenario, the rate at which the increase occurs amplifies during the second half of the century, whereas under the low emissions scenario the number of extreme cases stabilizes, although still at a higher rate than that experienced in the late 20th century.”
Hasson AEA, Mills GA, Timbal B, Walsh K (2009) Assessing the impact of climate change on extreme fire weather events over southeastern Australia. Clim Res 39:159-172. https://doi.org/10.3354/cr00817. [FULL TEXT]

Positive Indian Ocean Dipole events precondition southeast Australia bushfires – Cai et al. (2009)
“The devastating “Black Saturday” bushfire inferno in the southeast Australian state of Victoria in early February 2009 and the “Ash Wednesday” bushfires in February 1983 were both preceded by a positive Indian Ocean Dipole (pIOD) event. Is there a systematic pIOD linkage beyond these two natural disasters? We show that out of 21 significant bushfires seasons since 1950, 11 were preceded by a pIOD. During Victoria’s wet season, particularly spring, a pIOD contributes to lower rainfall and higher temperatures exacerbating the dry conditions and increasing the fuel load leading into summer. Consequently, pIODs are effective in preconditioning Victoria for bushfires, more so than El Niño events, as seen in the impact on soil moisture on interannual time scales and in multi‐decadal changes since the 1950s. Given that the recent increase in pIOD occurrences is consistent with what is expected from global warming, an increased bushfire risk in the future is likely across southeast Australia.”
Cai, W., Cowan, T., and Raupach, M. ( 2009), Positive Indian Ocean Dipole events precondition southeast Australia bushfires, Geophys. Res. Lett., 36, L19710, doi:10.1029/2009GL039902. [FULL TEXT]

The impact of climate change on the risk of forest and grassland fires in Australia – Pitman et al. (2007)
“We explore the impact of future climate change on the risk of forest and grassland fires over Australia in January using a high resolution regional climate model, driven at the boundaries by data from a transitory coupled climate model. Two future emission scenarios (relatively high and relatively low) are used for 2050 and 2100 and four realizations for each time period and each emission scenario are run. Results show a consistent increase in regional-scale fire risk over Australia driven principally by warming and reductions in relative humidity in all simulations, under all emission scenarios and at all time periods. We calculate the probability density function for the fire risk for a single point in New South Wales and show that the probability of extreme fire risk increases by around 25% compared to the present day in 2050 under both relatively low and relatively high emissions, and that this increases by a further 20% under the relatively low emission scenario by 2100. The increase in the probability of extreme fire risk increases dramatically under the high emission scenario by 2100. Our results are broadly in-line with earlier analyses despite our use of a significantly different methodology and we therefore conclude that the likelihood of a significant increase in fire risk over Australia resulting from climate change is very high. While there is already substantial investment in fire-related management in Australia, our results indicate that this investment is likely to have to increase to maintain the present fire-related losses in Australia.”
Pitman, A.J., Narisma, G.T. & McAneney, J. The impact of climate change on the risk of forest and grassland fires in Australia. Climatic Change 84, 383–401 (2007) doi:10.1007/s10584-007-9243-6. [FULL TEXT]

The Sensitivity of Australian Fire Danger to Climate Change – Williams et al. (2001)
“Global climate change, such as that due to the proposed enhanced greenhouse effect, is likely to have a significant effect on biosphere-atmosphere interactions, including bushfire regimes. This study quantifies the possible impact of climate change on fire regimes by estimating changes in fire weather and the McArthur Forest Fire Danger Index (FDI), an index that is used throughout Australia to estimate fire danger. The CSIRO 9-level general circulation model(CSIRO9 GCM)is used to simulate daily and seasonal fire danger for the present Australian climate and for a doubled-CO2 climate. The impact assessment includes validation of the GCMs daily control simulation and the derivation of ‘correction factors’ which improve the accuracy of the fire danger simulation. In summary, the general impact of doubled-CO2 is to increase fire danger at all sites by increasing the number of days of very high and extreme fire danger.Seasonal fire danger responds most to the large CO2-induced changes in maximum temperature.”
Williams, A.A.J., Karoly, D.J. & Tapper, N. Climatic Change (2001) 49: 171. https://doi.org/10.1023/A:1010706116176. [FULL TEXT]

Fire Regime Sensitivity to Global Climate Change: An Australian Perspective – Cary & Banks (2000)
“The Australian eucalypt forests are highly adapted to fire, and their component species possess well-developed response mechanisms that ensure post-fire recovery of these ecosystems. Fire regimes, which may alter forest floristics and structure, have changed since pre-European times because of management practices and may again change because of a changing climate. Two complimentary approaches are used to determine spatial and temporal patterns of fire regimes, a) dendrochronology to determine pre- and post-European fire histories for specific sites and b) fire-climate-landscape modelling to predict spatial patterns in fire regimes for topographically complex landscapes. This paper brings together these two approaches which have been applied independently to the same forest in the Southern Tablelands of New South Wales. The model predictions of spatial patterns in fire regimes under the present climate provide reasonable results when compared with observed site fire histories. Also, model results indicate that around half of the landscape is likely to experience a significant increase in fire frequency as a result of climate change. These findings, which have implications for fire-prone forest environments world-wide, are discussed in relation to the effects that anthropogenic ignition have had on the fire frequency in the study area over the last century.”
Cary G.J., Banks J.C.G. (2000) Fire Regime Sensitivity to Global Climate Change: An Australian Perspective. In: Innes J.L., Beniston M., Verstraete M.M. (eds) Biomass Burning and Its Inter-Relationships with the Climate System. Advances in Global Change Research, vol 3. Springer, Dordrecht.

Papers on California wildfires

This is a list of papers on California wildfires with an emphasis on climate related papers. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Distribution and frequency of wildfire in California riparian ecosystems (Bendix and Commons, 2017) [FULL TEXT]
Abstract: “Although wildfire has been recognized as having important ecological impacts on California’s riparian environments, understanding of its occurrence is largely anecdotal, based on studies of fire impacts in scattered locations. In this paper we use data for 21 years of wildfires to examine the distribution, seasonality and climatic context of riparian wildfire across the state. We used the Monitoring Trends in Burn Severity and LANDFIRE databases to identify fires that had burned in areas classified as having riparian vegetation, and matched those fires with the Fire and Resource Assessment Program database to determine the date of occurrence of each. From 1990 through 2010, an average of 1197 ha of riparian vegetation burned per year, which extrapolates to a fire return interval of 843 years. The statewide totals are misleading, however, because there is substantial geographic variance in the occurrence of riparian fire. In southern California ecoregions, extrapolated return intervals are as low as 74 years, contrasting with the Basin and Range ecoregions, where return intervals exceed 1000 years. Moreover, there is substantial geographic variation in the season of riparian fire, and in the relationship between fire occurrence and climatic variables. Both the widespread occurrence of riparian fire and its spatial variability are potentially important for management of critical riparian habitat.”
Citation: Jacob Bendix and Michael G Commons 2017 Environ. Res. Lett. 12 075008, https://doi.org/10.1088/1748-9326/aa7087.

Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California (Mann et al. 2016) [FULL TEXT]
Abstract: “The costly interactions between humans and wildfires throughout California demonstrate the need to understand the relationships between them, especially in the face of a changing climate and expanding human communities. Although a number of statistical and process-based wildfire models exist for California, there is enormous uncertainty about the location and number of future fires, with previously published estimates of increases ranging from nine to fifty-three percent by the end of the century. Our goal is to assess the role of climate and anthropogenic influences on the state’s fire regimes from 1975 to 2050. We develop an empirical model that integrates estimates of biophysical indicators relevant to plant communities and anthropogenic influences at each forecast time step. Historically, we find that anthropogenic influences account for up to fifty percent of explanatory power in the model. We also find that the total area burned is likely to increase, with burned area expected to increase by 2.2 and 5.0 percent by 2050 under climatic bookends (PCM and GFDL climate models, respectively). Our two climate models show considerable agreement, but due to potential shifts in rainfall patterns, substantial uncertainty remains for the semiarid inland deserts and coastal areas of the south. Given the strength of human-related variables in some regions, however, it is clear that comprehensive projections of future fire activity should include both anthropogenic and biophysical influences. Previous findings of substantially increased numbers of fires and burned area for California may be tied to omitted variable bias from the exclusion of human influences. The omission of anthropogenic variables in our model would overstate the importance of climatic ones by at least 24%. As such, the failure to include anthropogenic effects in many models likely overstates the response of wildfire to climatic change.”
Citation: Mann ML, Batllori E, Moritz MA, Waller EK, Berck P, Flint AL, et al. (2016) Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California. PLoS ONE 11(4): e0153589. https://doi.org/10.1371/journal.pone.0153589.

Large wildfire trends in the western United States, 1984–2011 (Dennison et al. 2014) [FULL TEXT]
Abstract: “We used a database capturing large wildfires (> 405 ha) in the western U.S. to document regional trends in fire occurrence, total fire area, fire size, and day of year of ignition for 1984–2011. Over the western U.S. and in a majority of ecoregions, we found significant, increasing trends in the number of large fires and/or total large fire area per year. Trends were most significant for southern and mountain ecoregions, coinciding with trends toward increased drought severity. For all ecoregions combined, the number of large fires increased at a rate of seven fires per year, while total fire area increased at a rate of 355 km2 per year. Continuing changes in climate, invasive species, and consequences of past fire management, added to the impacts of larger, more frequent fires, will drive further disruptions to fire regimes of the western U.S. and other fire‐prone regions of the world.”
Citation: Dennison, P. E., S. C. Brewer, J. D. Arnold, and M. A. Moritz (2014), Large wildfire trends in the western United States, 1984–2011, Geophys. Res. Lett., 41, 2928–2933, doi: 10.1002/2014GL059576.

Trends in wildfire severity: 1984 to 2010 in the Sierra Nevada, Modoc Plateau, and southern Cascades, California, USA (Miller and Safford, 2012) [FULL TEXT]
Abstract: “Data from recent assessments indicate that the annual area of wildfires burning at high severity (where most trees are killed) has increased since 1984 across much of the southwestern United States. Increasing areas of high-severity fire can occur when greater area is burned at constant proportion of high-severity fire, or when the proportion of high-severity fire within fire perimeters increases, or some combination of both. For the Sierra Nevada Forest Plan Amendment (SNFPA) area, which includes forestlands in eastern California and western Nevada, Miller et al. (2009a) concluded that the proportion of area burning at high severity in mixed-conifer forests had risen over the 1984 to 2004 period. However, no statistical assessment was made of the temporal trend in high-severity fire area because the analyzed dataset was incomplete in the early years of the study period. In this update, we use satellite-derived estimates of fire severity from the three most widely distributed SNFPA forest types to examine the trend in percent high severity and highseverity fire area for all wildfires ≥80 ha that occurred during the 1984 to 2010 period. Time-series regression modeling indicates that the percentage of total high severity per year for a combination of yellow pine (ponderosa pine [Pinus ponderosa Lawson & C. Lawson] or Jeffrey pine [P. jeffreyi Balf.]) and mixed-conifer forests increased significantly over the 27-year period. The annual area of high-severity fire also increased significantly in yellow pine-mixed-conifer forests. The percentage of high severity in fires ≥400 ha burning in yellow pine-mixed-conifer forests was significantly higher than in fires <400 ha. Additionally, the number of fires ≥400 ha significantly increased over the 1950 to 2010 period. There were no significant trends in red fir (Abies magnifica A. Murray bis) forests. These results confirm and expand our earlier published results for a shorter 21-year period."
Citation: Jay D. Miller, Hugh Safford, Fire Ecology, 8(3), doi: 10.4996/fireecology.0803041.

Climate change and growth scenarios for California wildfire (Westerling et al. 2011) [FULL TEXT]
Abstract: “Large wildfire occurrence and burned area are modeled using hydroclimate and landsurface characteristics under a range of future climate and development scenarios. The range of uncertainty for future wildfire regimes is analyzed over two emissions pathways (the Special Report on Emissions Scenarios [SRES] A2 and B1 scenarios); three global climate models (Centre National de Recherches Météorologiques CM3, Geophysical Fluid Dynamics Laboratory CM2.1 and National Center for Atmospheric Research PCM1); three scenarios for future population growth and development footprint; and two thresholds for defining the wildland-urban interface relative to housing density. Results were assessed for three 30-year time periods centered on 2020, 2050, and 2085, relative to a 30-year reference period centered on 1975. Increases in wildfire burned area are anticipated for most scenarios, although the range of outcomes is large and increases with time. The increase in wildfire burned area associated with the higher emissions pathway (SRES A2) is substantial, with increases statewide ranging from 36% to 74% by 2085, and increases exceeding 100% in much of the forested areas of Northern California in every SRES A2 scenario by 2085.”
Citation: Westerling, A.L., Bryant, B.P., Preisler, H.K. et al. Climatic Change (2011) 109(Suppl 1): 445. https://doi.org/10.1007/s10584-011-0329-9.

Paleofire reconstruction for high-elevation forests in the Sierra Nevada, California, with implications for wildfire synchrony and climate variability in the late Holocene (Hallett and Anderson, 2010) [FULL TEXT]
Abstract: “Here, we present two high-resolution records of macroscopic charcoal from high-elevation lake sites in the Sierra Nevada, California, and evaluate the synchroneity of fire response for east- and west-side subalpine forests during the past 9200 yr. Charcoal influx was low between 11,200 and 8000 cal yr BP when vegetation consisted of sparse Pinus-dominated forest and montane chaparral shrubs. High charcoal influx after 8000 cal yr BP marks the arrival of Tsuga mertensiana and Abies magnifica, and a higher-than-present treeline that persisted into the mid-Holocene. Coeval decreases in fire episode frequency coincide with neoglacial advances and lower treeline in the Sierra Nevada after 3800 cal yr BP. Independent fire response occurs between 9200 and 5000 cal yr BP, and significant synchrony at 100- to 1000-yr timescales emerges between 5000 cal yr BP and the present, especially during the last 2500 yr. Indistinguishable fire-return interval distributions and synchronous fires show that climatic control of fire became increasingly important during the late Holocene. Fires after 1200 cal yr BP are often synchronous and corroborate with inferred droughts. Holocene fire activity in the high Sierra Nevada is driven by changes in climate linked to insolation and appears to be sensitive to the dynamics of the El Niño–Southern Oscillation.”
Citation: Hallett, D., & Anderson, R. (2010). Paleofire reconstruction for high-elevation forests in the Sierra Nevada, California, with implications for wildfire synchrony and climate variability in the late Holocene. Quaternary Research, 73(2), 180-190. doi:10.1016/j.yqres.2009.11.008.

Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States (Spracklen et al. 2009) [FULL TEXT]
Abstract: “We investigate the impact of climate change on wildfire activity and carbonaceous aerosol concentrations in the western United States. We regress observed area burned onto observed meteorological fields and fire indices from the Canadian Fire Weather Index system and find that May–October mean temperature and fuel moisture explain 24–57% of the variance in annual area burned in this region. Applying meteorological fields calculated by a general circulation model (GCM) to our regression model, we show that increases in temperature cause annual mean area burned in the western United States to increase by 54% by the 2050s relative to the present day. Changes in area burned are ecosystem dependent, with the forests of the Pacific Northwest and Rocky Mountains experiencing the greatest increases of 78 and 175%, respectively. Increased area burned results in near doubling of wildfire carbonaceous aerosol emissions by midcentury. Using a chemical transport model driven by meteorology from the same GCM, we calculate that climate change will increase summertime organic carbon (OC) aerosol concentrations over the western United States by 40% and elemental carbon (EC) concentrations by 20% from 2000 to 2050. Most of this increase (75% for OC and 95% for EC) is caused by larger wildfire emissions with the rest caused by changes in meteorology and for OC by increased monoterpene emissions in a warmer climate. Such an increase in carbonaceous aerosol would have important consequences for western U.S. air quality and visibility.”
Citation: Spracklen, D. V., L. J. Mickley, J. A. Logan, R. C. Hudman, R. Yevich, M. D. Flannigan, and A. L. Westerling (2009), Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States, J. Geophys. Res., 114, D20301, doi: 10.1029/2008JD010966.

Environmental controls on the distribution of wildfire at multiple spatial scales (Parisien and Moritz, 2009) [FULL TEXT]
Abstract: “Despite its widespread occurrence globally, wildfire preferentially occupies an environmental middle ground and is significantly less prevalent in biomes characterized by environmental extremes (e.g., tundra, rain forests, and deserts). We evaluated the biophysical “environmental space” of wildfire from regional to subcontinental extents, with methods widely used for modeling habitat distributions. This approach is particularly suitable for the biogeographic study of wildfire, because it simultaneously considers patterns in multiple factors controlling wildfire suitability over large areas. We used the Maxent and boosted regression tree algorithms to assess wildfire–environment relationships for three levels of complexity (in terms of inclusion of variables) at three spatial scales: the conterminous United States, the state of California, and five wildfire‐prone ecoregions of California. The resulting models were projected geographically to obtain spatial predictions of wildfire suitability and were also applied to other regions to assess their generality and spatial transferability. Predictions of the potential range of wildfire had high classification accuracy; they also highlighted areas where wildfires had not recently been observed, indicating the potential (or past) suitability of these areas. The models identified several key variables that were not suspected to be important in the large‐scale control of wildfires, but which might indirectly affect control by influencing the presence of flammable vegetation. Models transferred to different areas were useful only when they overlapped appreciably with the target area’s environmental space. This approach should allow exploration of the potential shifts in wildfire range in a changing climate, the potential for restoration of wildfire where it has been “extirpated,” and, conversely, the “invasiveness” of wildfire after changes in plant species composition. Our study demonstrates that habitat distribution models and related concepts can be used to characterize environmental controls on a natural disturbance process, but also that future work is needed to refine our understanding of the direct causal factors controlling wildfire at multiple spatial scales.”
Citation: Parisien, M. and Moritz, M. A. (2009), Environmental controls on the distribution of wildfire at multiple spatial scales. Ecological Monographs, 79: 127-154. doi:10.1890/07-1289.1.

Climate and wildfire area burned in western U.S. ecoprovinces, 1916–2003 (Littell et al. 2009) [FULL TEXT]
Abstract: “The purpose of this paper is to quantify climatic controls on the area burned by fire in different vegetation types in the western United States. We demonstrate that wildfire area burned (WFAB) in the American West was controlled by climate during the 20th century (1916–2003). Persistent ecosystem‐specific correlations between climate and WFAB are grouped by vegetation type (ecoprovinces). Most mountainous ecoprovinces exhibit strong year‐of‐fire relationships with low precipitation, low Palmer drought severity index (PDSI), and high temperature. Grass‐ and shrub‐dominated ecoprovinces had positive relationships with antecedent precipitation or PDSI. For 1977–2003, a few climate variables explain 33–87% (mean = 64%) of WFAB, indicating strong linkages between climate and area burned. For 1916–2003, the relationships are weaker, but climate explained 25–57% (mean = 39%) of the variability. The variance in WFAB is proportional to the mean squared for different data sets at different spatial scales. The importance of antecedent climate (summer drought in forested ecosystems and antecedent winter precipitation in shrub and grassland ecosystems) indicates that the mechanism behind the observed fire–climate relationships is climatic preconditioning of large areas of low fuel moisture via drying of existing fuels or fuel production and drying. The impacts of climate change on fire regimes will therefore vary with the relative energy or water limitations of ecosystems. Ecoprovinces proved a useful compromise between ecologically imprecise state‐level and localized gridded fire data. The differences in climate–fire relationships among the ecoprovinces underscore the need to consider ecological context (vegetation, fuels, and seasonal climate) to identify specific climate drivers of WFAB. Despite the possible influence of fire suppression, exclusion, and fuel treatment, WFAB is still substantially controlled by climate. The implications for planning and management are that future WFAB and adaptation to climate change will likely depend on ecosystem‐specific, seasonal variation in climate. In fuel‐limited ecosystems, fuel treatments can probably mitigate fire vulnerability and increase resilience more readily than in climate‐limited ecosystems, in which large severe fires under extreme weather conditions will continue to account for most area burned.”
Citation: Littell, J. S., McKenzie, D. , Peterson, D. L. and Westerling, A. L. (2009), Climate and wildfire area burned in western U.S. ecoprovinces, 1916–2003. Ecological Applications, 19: 1003-1021. doi:10.1890/07-1183.1.

Climate change and wildfire in California (Westerling and Bryant, 2008) [FULL TEXT]
Abstract: “Wildfire risks for California under four climatic change scenarios were statistically modeled as functions of climate, hydrology, and topography. Wildfire risks for the GFDL and PCM global climate models and the A2 and B1 emissions scenarios were compared for 2005–2034, 2035–2064, and 2070–2099 against a modeled 1961–1990 reference period in California and neighboring states. Outcomes for the GFDL model runs, which exhibit higher temperatures than the PCM model runs, diverged sharply for different kinds of fire regimes, with increased temperatures promoting greater large fire frequency in wetter, forested areas, via the effects of warmer temperatures on fuel flammability. At the same time, reduced moisture availability due to lower precipitation and higher temperatures led to reduced fire risks in some locations where fuel flammability may be less important than the availability of fine fuels. Property damages due to wildfires were also modeled using the 2000 U.S. Census to describe the location and density of residential structures. In this analysis the largest changes in property damages under the climate change scenarios occurred in wildland/urban interfaces proximate to major metropolitan areas in coastal southern California, the Bay Area, and in the Sierra foothills northeast of Sacramento.”
Citation: Westerling, A.L. & Bryant, B.P. Climatic Change (2008) 87(Suppl 1): 231. https://doi.org/10.1007/s10584-007-9363-z.

Human influence on California fire regimes (Syphard et al. 2007) [FULL TEXT]
Abstract: “Periodic wildfire maintains the integrity and species composition of many ecosystems, including the mediterranean‐climate shrublands of California. However, human activities alter natural fire regimes, which can lead to cascading ecological effects. Increased human ignitions at the wildland–urban interface (WUI) have recently gained attention, but fire activity and risk are typically estimated using only biophysical variables. Our goal was to determine how humans influence fire in California and to examine whether this influence was linear, by relating contemporary (2000) and historic (1960–2000) fire data to both human and biophysical variables. Data for the human variables included fine‐resolution maps of the WUI produced using housing density and land cover data. Interface WUI, where development abuts wildland vegetation, was differentiated from intermix WUI, where development intermingles with wildland vegetation. Additional explanatory variables included distance to WUI, population density, road density, vegetation type, and ecoregion. All data were summarized at the county level and analyzed using bivariate and multiple regression methods. We found highly significant relationships between humans and fire on the contemporary landscape, and our models explained fire frequency (R2 = 0.72) better than area burned (R2 = 0.50). Population density, intermix WUI, and distance to WUI explained the most variability in fire frequency, suggesting that the spatial pattern of development may be an important variable to consider when estimating fire risk. We found nonlinear effects such that fire frequency and area burned were highest at intermediate levels of human activity, but declined beyond certain thresholds. Human activities also explained change in fire frequency and area burned (1960–2000), but our models had greater explanatory power during the years 1960–1980, when there was more dramatic change in fire frequency. Understanding wildfire as a function of the spatial arrangement of ignitions and fuels on the landscape, in addition to nonlinear relationships, will be important to fire managers and conservation planners because fire risk may be related to specific levels of housing density that can be accounted for in land use planning. With more fires occurring in close proximity to human infrastructure, there may also be devastating ecological impacts if development continues to grow farther into wildland vegetation.”
Citation: Syphard, A. D., Radeloff, V. C., Keeley, J. E., Hawbaker, T. J., Clayton, M. K., Stewart, S. I. and Hammer, R. B. (2007), HUMAN INFLUENCE ON CALIFORNIA FIRE REGIMES. Ecological Applications, 17: 1388-1402. doi:10.1890/06-1128.1.

Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity (Westerling et al. 2006) [FULL TEXT]
Abstract: “Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.”
Citation: A. L. Westerling, H. G. Hidalgo, D. R. Cayan, T. W. Swetnam, Science 18 Aug 2006: Vol. 313, Issue 5789, pp. 940-943, DOI: 10.1126/science.1128834.

Climate change projected fire weather sensitivity: California Santa Ana wind occurrence (Miller and Schlegel, 2006) [FULL TEXT]
Abstract: “A new method based on global climate model pressure gradients was developed for identifying coastal high‐wind fire weather conditions, such as the Santa Ana Occurrence (SAO). Application of this method for determining southern California Santa Ana wind occurrence resulted in a good correlation between derived large‐scale SAOs and observed offshore winds during periods of low humidity. The projected change in the number of SAOs was analyzed using two global climate models, one a low temperature sensitivity and the other a middle‐temperature sensitivity, both forced with low and high emission scenarios, for three future time periods. This initial analysis shows consistent shifts in SAO events from earlier (September–October) to later (November–December) in the season, suggesting that SAOs may significantly increase the extent of California coastal areas burned by wildfires, loss of life, and property.”
Citation: Spracklen, D. V., L. J. Mickley, J. A. Logan, R. C. Hudman, R. Yevich, M. D. Flannigan, and A. L. Westerling (2009), Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States, J. Geophys. Res., 114, D20301, doi: 10.1029/2008JD010966.

The Impact of Climate Change on Wildfire Severity: A Regional Forecast for Northern California (Fried et al. 2004) [FULL TEXT]
Abstract: “We estimated the impact of climatic change on wildland fire and suppression effectiveness in northern California by linking general circulation model output to local weather and fire records and projecting fire outcomes with an initial-attack suppression model. The warmer and windier conditions corresponding to a 2 × CO2 climate scenario produced fires that burned more intensely and spread faster in most locations. Despite enhancement of fire suppression efforts, the number of escaped fires (those exceeding initial containment limits) increased 51% in the south San Francisco Bay area, 125% in the Sierra Nevada, and did not change on the north coast. Changes in area burned by contained fires were 41%, 41% and –8%, respectively. When interpolated to most of northern California’s wildlands, these results translate to an average annual increase of 114 escapes (a doubling of the current frequency) and an additional 5,000 hectares (a 50% increase) burned by contained fires. On average, the fire return intervals in grass and brush vegetation types were cut in half. The estimates reported represent a minimum expected change, or best-case forecast. In addition to the increased suppression costs and economic damages, changes in fire severity of this magnitude would have widespread impacts on vegetation distribution, forest condition, and carbon storage, and greatly increase the risk to property, natural resources and human life.”
Citation: Fried, J.S., Torn, M.S. & Mills, E. Climatic Change (2004) 64: 169. https://doi.org/10.1023/B:CLIM.0000024667.89579.ed.

Climate and Wildfire in the Western United States (Westerling et al. 2003) [FULL TEXT]
Abstract: “A 21-yr gridded monthly fire-starts and acres-burned dataset from U.S. Forest Service, Bureau of Land Management, National Park Service, and Bureau of Indian Affairs fire reports recreates the seasonality and interannual variability of wild fire in the western United States. Despite pervasive human influence in western fire regimes, it is striking how strongly these data reveal a fire season responding to variations in climate. Correlating anomalous wildfire frequency and extent with the Palmer Drought Severity Index illustrates the importance of prior and accumulated precipitation anomalies for future wildfire season severity. This link to antecedent seasons’ moisture conditions varies widely with differences in predominant fuel type. Furthermore, these data demonstrate that the relationship between wildfire season severity and observed moisture anomalies from antecedent seasons is strong enough to forecast fire season severity at lead times of one season to a year in advance.”
Citation: Westerling, A.L., A. Gershunov, T.J. Brown, D.R. Cayan, and M.D. Dettinger, 2003: Climate and Wildfire in the Western United States. Bull. Amer. Meteor. Soc., 84, 595–604, https://doi.org/10.1175/BAMS-84-5-595.

Climate change effects on vegetation distribution, carbon, and fire in California (Lenihan et al. 2003) [FULL TEXT]
Abstract: “The objective of this study was to dynamically simulate the response of vegetation distribution, carbon, and fire to the historical climate and to two contrasting scenarios of climate change in California. The results of the simulations for the historical climate compared favorably to independent estimates and observations, but validation of the results was complicated by the lack of land use effects in the model. The response to increasing temperatures under both scenarios was characterized by a shift in dominance from needle‐leaved to broad‐leaved life‐forms and by increases in vegetation productivity, especially in the relatively cool and mesic regions of the state. The simulated response to changes in precipitation were complex, involving not only the effect of changes in soil moisture on vegetation productivity, but also changes in tree–grass competition mediated by fire. Summer months were warmer and persistently dry under both scenarios, so the trends in simulated fire area under both scenarios were primarily a response to changes in vegetation biomass. Total ecosystem carbon increased under both climate scenarios, but the proportions allocated to the wood and grass carbon pools differed. The results of the simulations underscore the potentially large impact of climate change on California ecosystems, and the need for further use and development of dynamic vegetation models using various ensembles of climate change scenarios.”
Citation: Lenihan, J. M., Drapek, R. , Bachelet, D. and Neilson, R. P. (2003), CLIMATE CHANGE EFFECTS ON VEGETATION DISTRIBUTION, CARBON, AND FIRE IN CALIFORNIA. Ecological Applications, 13: 1667-1681. doi:10.1890/025295.

Papers on changes in Atlantic Meridional Overturning Circulation

This is a list of papers on changes in Atlantic Meridional Overturning Circulation. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Current Atlantic Meridional Overturning Circulation weakest in last millennium – Caesar et al. (2021). [FULL TEXT]
Abstract: The Atlantic Meridional Overturning Circulation (AMOC)—one of Earth’s major ocean circulation systems—redistributes heat on our planet and has a major impact on climate. Here, we compare a variety of published proxy records to reconstruct the evolution of the AMOC since about AD 400. A fairly consistent picture of the AMOC emerges: after a long and relatively stable period, there was an initial weakening starting in the nineteenth century, followed by a second, more rapid, decline in the mid-twentieth century, leading to the weakest state of the AMOC occurring in recent decades.
Citation: Caesar, L., McCarthy, G.D., Thornalley, D.J.R. et al. Current Atlantic Meridional Overturning Circulation weakest in last millennium. Nat. Geosci. 14, 118–120 (2021). https://doi.org/10.1038/s41561-021-00699-z.

A stable Atlantic Meridional Overturning Circulation in a changing North Atlantic Ocean since the 1990s – Fu et al. (2020). [FULL TEXT]
Abstract: The Atlantic Meridional Overturning Circulation (AMOC) is crucially important to global climate. Model simulations suggest that the AMOC may have been weakening over decades. However, existing array-based AMOC observations are not long enough to capture multidecadal changes. Here, we use repeated hydrographic sections in the subtropical and subpolar North Atlantic, combined with an inverse model constrained using satellite altimetry, to jointly analyze AMOC and hydrographic changes over the past three decades. We show that the AMOC state in the past decade is not distinctly different from that in the 1990s in the North Atlantic, with a remarkably stable partition of the subpolar overturning occurring prominently in the eastern basins rather than in the Labrador Sea. In contrast, profound hydrographic and oxygen changes, particularly in the subpolar North Atlantic, are observed over the same period, suggesting a much higher decoupling between the AMOC and ocean interior property fields than previously thought.
Citation: Yao Fu, Feili Li, Johannes Karstensen, Chunzai Wang (2020). Science Advances 6(48):eabc7836. DOI: 10.1126/sciadv.abc7836.

Atlantic Meridional Overturning Circulation: Observed Transport and Variability – Frajka-Williams et al. (2019). [FULL TEXT]
Abstract: The Atlantic Meridional Overturning Circulation (AMOC) extends from the Southern Ocean to the northern North Atlantic, transporting heat northwards throughout the South and North Atlantic, and sinking carbon and nutrients into the deep ocean. Climate models indicate that changes to the AMOC both herald and drive climate shifts. Intensive trans-basin AMOC observational systems have been put in place to continuously monitor meridional volume transport variability, and in some cases, heat, freshwater and carbon transport. These observational programs have been used to diagnose the magnitude and origins of transport variability, and to investigate impacts of variability on essential climate variables such as sea surface temperature, ocean heat content and coastal sea level. AMOC observing approaches vary between the different systems, ranging from trans-basin arrays (OSNAP, RAPID 26°N, 11°S, SAMBA 34.5°S) to arrays concentrating on western boundaries (e.g., RAPID WAVE, MOVE 16°N). In this paper, we outline the different approaches (aims, strengths and limitations) and summarize the key results to date. We also discuss alternate approaches for capturing AMOC variability including direct estimates (e.g., using sea level, bottom pressure, and hydrography from autonomous profiling floats), indirect estimates applying budgetary approaches, state estimates or ocean reanalyses, and proxies. Based on the existing observations and their results, and the potential of new observational and formal synthesis approaches, we make suggestions as to how to evaluate a comprehensive, future-proof observational network of the AMOC to deepen our understanding of the AMOC and its role in global climate.
Citation: Frajka-Williams Eleanor, Ansorge Isabelle J., Baehr Johanna, Bryden Harry L., Chidichimo Maria Paz, et al. (2019). Frontiers in Marine Science 6:260. DOI=10.3389/fmars.2019.00260.

Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis – Weijer et al. (2019). [FULL TEXT]
Abstract: The notion that the Atlantic Meridional Overturning Circulation (AMOC) can have more than one stable equilibrium emerged in the 1980s as a powerful hypothesis to explain rapid climate variability during the Pleistocene. Ever since, the idea that a temporary perturbation of the AMOC—or a permanent change in its forcing—could trigger an irreversible collapse has remained a reason for concern. Here we review literature on the equilibrium stability of the AMOC and present a synthesis that puts our understanding of past and future AMOC behavior in a unifying framework. This framework is based on concepts from Dynamical Systems Theory, which has proven to be an important tool in interpreting a wide range of model behavior. We conclude that it cannot be ruled out that the AMOC in our current climate is in, or close to, a regime of multiple equilibria. But there is considerable uncertainty in the location of stability thresholds with respect to our current climate state, so we have no credible indications of where our present-day AMOC is located with respect to thresholds. We conclude by identifying gaps in our knowledge and proposing possible ways forward to address these gaps.
Citation: Weijer, W., Cheng, W., Drijfhout, S. S., Federov, A.V., Hu, A., Jackson, L. C., et al. (2019). Stability of the Atlantic Meridional Overturning Circulation: A review and synthesis. Journal of Geophysical Research: Oceans, 124, 5336– 5375. https://doi.org/10.1029/2019JC015083.

Observed fingerprint of a weakening Atlantic Ocean overturning circulation – Caesar et al. (2018) [FULL TEXT]
Abstract: The Atlantic meridional overturning circulation (AMOC)—a system of ocean currents in the North Atlantic—has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature ‘fingerprint’—consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region—and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years.
Citation: L. Caesar, S. Rahmstorf, A. Robinson, G. Feulner & V. Saba (2018) Naturevolume 556, pages191–196. doi:10.1038/s41586-018-0006-5.

Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years – Thornalley et al. (2018) [FULL TEXT]
Abstract: The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that has an essential role in Earth’s climate, redistributing heat and influencing the carbon cycle1, 2. The AMOC has been shown to be weakening in recent years1; this decline may reflect decadal-scale variability in convection in the Labrador Sea, but short observational datasets preclude a longer-term perspective on the modern state and variability of Labrador Sea convection and the AMOC1, 3,4,5. Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately AD 1850) compared with the preceding 1,500 years. Our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the LIA, or as a more gradual, continued decline over the past 150 years; this ambiguity probably arises from non-AMOC influences on the various proxies or from the different sensitivities of these proxies to individual components of the AMOC. We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA—sourced from melting glaciers and thickened sea ice that developed earlier in the LIA—weakened Labrador Sea convection and the AMOC. The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet6. Our results suggest that recent decadal variability in Labrador Sea convection and the AMOC has occurred during an atypical, weak background state. Future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the AMOC weakening described here.
Citation: David J. R. Thornalley, Delia W. Oppo, Pablo Ortega, Jon I. Robson, Chris M. Brierley, Renee Davis, Ian R. Hall, Paola Moffa-Sanchez, Neil L. Rose, Peter T. Spooner, Igor Yashayaev & Lloyd D. Keigwin (2018) Nature, volume 556, pages 227–230. doi:10.1038/s41586-018-0007-4.

Multi-centennial variability of the AMOC over the Holocene: A new reconstruction based on multiple proxy-derived SST records – Ayache et al. (2018)
Abstract: The Meridional Overturning Circulation (AMOC) is believed to have played a key role in climate variability over the Holocene, but the reconstruction of its variations remains limited by inconsistencies among different proxy records used. To circumvent this issue, we propose a new statistical method to reconstruct the AMOC variations based on multiple sources of information, i.e. 22 proxy records of annual Sea Surface Temperature (SST) compiled in the North Atlantic and covering the Holocene (HAMOC database). Our approach consists of isolating the main variability modes hidden in the Atlantic Ocean through principal component analysis (PCA) and then evaluating their link with the AMOC. To estimate the skill of our method, we use a pseudo-proxy approach applied to observational SST data covering the period 1870–2010, as well as simulations from a comprehensive climate model (IPSL-CM5A-LR) where the AMOC variations are known. In instrumental observations and most of the model simulations, the first mode of SST variations from the PCA analysis over the North Atlantic can be related with the external radiative forcing, while the second mode is reminiscent of the AMOC variability and of its signature on SST. When computed over the Holocene period using the HAMOC database, the first mode is indeed well correlated with the insolation changes, marked by a general cooling of the Northern Atlantic from 9 thousand years ago (ka). The second mode, that we consider here as a reconstruction of standardized AMOC variations following the pseudo-proxy analysis in the model simulations and in the observations, is in general agreement with a few independent reconstructions of the deep branch of the AMOC recorded in the North Atlantic. Based on this new AMOC index reconstruction, we highlight that the Early Holocene may have been associated with an AMOC enhancement, followed by a general weakening trend from around 6–7 ka up to 2 ka, in line with the major hydro-dynamical re-organization which occurred in the North Atlantic from the mid-Holocene period. We find that the late Holocene period is marked by two fluctuations, with maxima at about 4.2 and 5 ka, in line with short-term variations identified in proxy records of the velocity of the Greenland-Iceland-Scotland overflow waters..
Citation: Mohamed Ayache, Didier Swingedouw, Yannick Mary, Frédérique Eynaud, Christophe Colin (2018). Global and Planetary Change 170(November 2018):172-189. https://doi.org/10.1016/j.gloplacha.2018.08.016.

Timescales of AMOC decline in response to fresh water forcing – Jackson & Wood (2017)
Abstract: The Atlantic meridional overturning circulation (AMOC) is predicted to weaken over the coming century due to warming from greenhouse gases and increased input of fresh water into the North Atlantic, however there is considerable uncertainty as to the amount and rate of AMOC weakening. Understanding what controls the rate and timescale of AMOC weakening may help to reduce this uncertainty and hence reduce the uncertainty surrounding associated impacts. As a first step towards this we consider the timescales associated with weakening in response to idealized freshening scenarios. Here we explore timescales of AMOC weakening in response to a freshening of the North Atlantic in a suite of experiments with an eddy-permitting global climate model (GCM). When the rate of fresh water added to the North Atlantic is small (0.1 Sv; 1 Sv =1×106 m 3 /s), the timescale of AMOC weakening depends mainly on the rate of fresh water input itself and can be longer than a century. When the rate of fresh water added is large ( ≥ 0.3 Sv) however, the timescale is a few decades and is insensitive to the actual rate of fresh water input. This insensitivity is because with a greater rate of fresh water input the advective feedbacks become more important at exporting fresh anomalies, so the rate of freshening is similar. We find advective feedbacks from: an export of fresh anomalies by the mean flow; less volume import through the Bering Strait; a weakening AMOC transporting less subtropical water northwards; and anomalous subtropical circulations which amplify export of the fresh anomalies. This latter circulation change is driven itself by the presence of fresh anomalies exported from the subpolar gyre through geostrophy. This feedback has not been identified in previous model studies and when the rate of freshening is strong it is found to dominate the total export of fresh anomalies, and hence the timescale of AMOC decline. Although results may be model dependent, qualitatively similar mechanisms are also found in a single experiment with a different GCM.
Citation: Laura C. Jackson, Richard A. Wood (2017). Climate Dynamics, https://doi.org/10.1007/s00382-017-3957-6.

Arctic sea-ice decline weakens the Atlantic Meridional Overturning Circulation – Sévellec et al. (2017)
Abstract: The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes, resulting in positive buoyancy anomalies that can affect ocean circulation. In this study, we use an optimal flux perturbation framework and comprehensive climate model simulations to estimate the sensitivity of the Atlantic Meridional Overturning Circulation (AMOC) to such buoyancy forcing over the Arctic and globally, and more generally to sea-ice decline. It is found that on decadal timescales, flux anomalies over the subpolar North Atlantic have the largest impact on the AMOC, while on multi-decadal timescales (longer than 20 years), flux anomalies in the Arctic become more important. These positive buoyancy anomalies spread to the North Atlantic, weakening the AMOC and its poleward heat transport. Therefore, the Arctic sea-ice decline may explain the suggested slow-down of the AMOC and the ‘Warming Hole’ persisting in the subpolar North Atlantic.
Citation: Florian Sévellec, Alexey V. Fedorov & Wei Liu (2017) Nature Climate Change, volume 7, pages 604–610 (2017). doi:10.1038/nclimate3353.

Fate of the Atlantic Meridional Overturning Circulation: Strong decline under continued warming and Greenland melting – Bakker et al. (2016) [FULL TEXT]
Abstract: The most recent Intergovernmental Panel on Climate Change assessment report concludes that the Atlantic Meridional Overturning Circulation (AMOC) could weaken substantially but is very unlikely to collapse in the 21st century. However, the assessment largely neglected Greenland Ice Sheet (GrIS) mass loss, lacked a comprehensive uncertainty analysis, and was limited to the 21st century. Here in a community effort, improved estimates of GrIS mass loss are included in multicentennial projections using eight state‐of‐the‐science climate models, and an AMOC emulator is used to provide a probabilistic uncertainty assessment. We find that GrIS melting affects AMOC projections, even though it is of secondary importance. By years 2090–2100, the AMOC weakens by 18% [−3%, −34%; 90% probability] in an intermediate greenhouse‐gas mitigation scenario and by 37% [−15%, −65%] under continued high emissions. Afterward, it stabilizes in the former but continues to decline in the latter to −74% [+4%, −100%] by 2290–2300, with a 44% likelihood of an AMOC collapse. This result suggests that an AMOC collapse can be avoided by CO2 mitigation.
Citation: Bakker, P., et al. (2016), Fate of the Atlantic Meridional Overturning Circulation: Strong decline under continued warming and Greenland melting, Geophys. Res. Lett., 43, 12,252–12,260, doi:10.1002/2016GL070457.

Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation – Rahmstorf et al. (2015) [FULL TEXT]
Abstract: Possible changes in Atlantic meridional overturning circulation (AMOC) provide a key source of uncertainty regarding future climate change. Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. This time evolution is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference, by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland Ice Sheet to the slowdown. Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99). Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC.
Citation: Stefan Rahmstorf, Jason E. Box, Georg Feulner, Michael E. Mann, Alexander Robinson, Scott Rutherford & Erik J. Schaffernicht (2015). Nature Climate Change volume 5, pages 475–480 (2015) doi:10.1038/nclimate2554.

Detecting changes in the transport of the Gulf Stream and the Atlantic overturning circulation from coastal sea level data: The extreme decline in 2009–2010 and estimated variations for 1935–2012 – Ezer (2015) [FULL TEXT]
Abstract: “Recent studies reported weakening in the Atlantic Meridional Overturning Circulation (AMOC) and in the Gulf Stream (GS), using records of about a decade (RAPID project) or two (altimeter data). Coastal sea level records are much longer, so the possibility of detecting climatic changes in ocean circulation from sea level data is intriguing and thus been examined here. First, it is shown that variations in the AMOC transport from the RAPID project since 2004 are consistent with the flow between Bermuda and the U. S. coast derived from the Oleander measurements and from sea level difference (SLDIF). Despite apparent disagreement between recent studies on the ability of data to detect weakening in the GS flow, estimated transport changes from 3 different independent data sources agree quite well with each other on the extreme decline in transport in 2009–2010. Due to eddies and meandering, the flow representing the GS part of the Oleander line is not correlated with AMOC or with the Florida Current, only the flow across the entire Oleander line from the U.S. coast to Bermuda is correlated with climatic transport changes. Second, Empirical Mode Decomposition (EMD) analysis shows that SLDIF can detect (with lag) the portion of the variations in the AMOC transport that are associated with the Florida Current and the wind-driven Ekman transport (SLDIF-transport correlations of ~ 0.7–0.9). The SLDIF has thus been used to estimate variations in transport since 1935 and compared with AMOC obtained from reanalysis data. The significant weakening in AMOC after ~ 2000 (~ 4.5 Sv per decade) is comparable to weakening seen in the 1960s to early 1970s. Both periods of weakening AMOC, in the 1960s and 2000s, are characterized by faster than normal sea level rise along the northeastern U.S. coast, so monitoring changes in AMOC has practical implications for coastal protection.”
Citation: Tal Ezer, Detecting changes in the transport of the Gulf Stream and the Atlantic overturning circulation from coastal sea level data: The extreme decline in 2009–2010 and estimated variations for 1935–2012, Global and Planetary Change, 129, June 2015, 23–36.

Impact of Greenland orography on the Atlantic Meridional Overturning Circulation – Davini et al. (2015)
Abstract: “We show that the absence of the Greenland ice sheet would have important consequences on the North Atlantic Ocean circulation, even without taking into account the effect of the freshwater input to the ocean from ice melting. These effects are investigated in a 600year long coupled ocean-atmosphere simulation with the high-resolution global climate model EC-Earth 3.0.1. Once a new equilibrium is established, a cooling of Eurasia and of the North Atlantic and a poleward shift of the subtropical jet are observed. These hemispheric changes are ascribed to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) by about 12%. We attribute this slowdown to a reduction in salinity of the Arctic basin and to the related change of the mass and salt transport through the Fram Strait—a consequence of the new surface wind pattern over the lower orography. This idealized experiment illustrates the sensitivity of the AMOC to local surface winds.”
Citation: Davini, P., vonHardenberg, J., Filippi, L. and Provenzale, A. (2015), Impact of Greenland orography on the Atlantic Meridional Overturning Circulation. Geophys. Res. Lett., 42: 871–879. doi: 10.1002/2014GL062668.

Impact of a 30% reduction in Atlantic meridional overturning during 2009–2010 – Bryden et al. (2014) [FULL TEXT]
Abstract: “The Atlantic meridional overturning circulation comprises warm upper waters flowing northward, becoming colder and denser until they form deep water in the Labrador and Nordic Seas that then returns southward through the North and South Atlantic. The ocean heat transport associated with this circulation is 1.3 PW, accounting for 25% of the maximum combined atmosphere–ocean heat transport necessary to balance the Earth’s radiation budget. We have been monitoring the circulation at 25° N since 2004. A 30% slowdown in the circulation for 14 months during 2009–2010 reduced northward ocean heat transport across 25° N by 0.4 PW and resulted in colder upper ocean waters north of 25° N and warmer waters south of 25° N. The spatial pattern of upper ocean temperature anomalies helped push the wintertime circulation 2010–2011 into record-low negative NAO (North Atlantic Oscillation) conditions with accompanying severe winter conditions over northwestern Europe. The warmer temperatures south of 25° N contributed to the high intensity hurricane season in summer 2010.”
Citation: Bryden, H. L., King, B. A., McCarthy, G. D., and McDonagh, E. L.: Impact of a 30% reduction in Atlantic meridional overturning during 2009–2010, Ocean Sci., 10, 683-691, doi:10.5194/os-10-683-2014, 2014.

On the long-term stability of Gulf Stream transport based on 20 years of direct measurements – Rossby et al. (2014)
Abstract: “In contrast to recent claims of a Gulf Stream slowdown, two decades of directly measured velocity across the current show no evidence of a decrease. Using a well-constrained definition of Gulf Stream width, the linear least square fit yields a mean surface layer transport of 1.35 × 105 m² s⁻¹ with a 0.13% negative trend per year. Assuming geostrophy, this corresponds to a mean cross-stream sea level difference of 1.17 m, with sea level decreasing 0.03 m over the 20 year period. This is not significant at the 95% confidence level, and it is a factor of 2–4 less than that alleged from accelerated sea level rise along the U.S. Coast north of Cape Hatteras. Part of the disparity can be traced to the spatial complexity of altimetric sea level trends over the same period.”
Citation: Rossby, T., C. N. Flagg, K. Donohue, A. Sanchez-Franks, and J. Lillibridge (2014), On the long-term stability of Gulf Stream transport based on 20 years of direct measurements, Geophys. Res. Lett., 41, 114–120, doi:10.1002/2013GL058636.

Two Modes of Gulf Stream Variability Revealed in the Last Two Decades of Satellite Altimeter Data – Pérez-Hernández & Joyce (2014) [FULL TEXT]
Abstract: “Monthly mapped sea level anomalies (MSLAs) of the NW Atlantic in the region immediately downstream of the Gulf Stream (GS) separation point reveal a leading mode in which the path shifts approximately 100 km meridionally about a nominal latitude of 39°N, producing coherent sea level anomaly (SLA) variability from 72° to 50°W. This mode can be captured by use of a simple 16-point index based on SLA data taken along the maximum of the observed variability in the region 33°–46°N and 45°–75°W. The GS shifts between 2010 and 2012 are the largest of the last decade and equal to the largest of the entire record. The second group of EOF modes of variability describes GS meanders, which propagate mainly westward interrupted by brief periods of eastward or stationary meanders. These meanders have wavelengths of approximately 400 km and can be seen in standard EOFs by spatial phase shifting of a standing meander pattern in the SLA data. The spectral properties of these modes indicate strong variability at interannual and longer periods for the first mode and periods of a few to several months for the meanders. While the former is quite similar to a previous use of the altimeter for GS path, the simple index is a useful measure of the large-scale shifts in the GS path that is quickly estimated and updated without changes in previous estimates. The time-scale separation allows a low-pass filtered 16-point index to be reflective of large-scale, coherent shifts in the GS path.”
Citation: M. Dolores Pérez-Hernández and Terrence M. Joyce, 2014: Two Modes of Gulf Stream Variability Revealed in the Last Two Decades of Satellite Altimeter Data. J. Phys. Oceanogr., 44, 149–163. doi: http://dx.doi.org/10.1175/JPO-D-13-0136.1.

Probabilistic projections of the Atlantic overturning – Schleussner et al. (2014) [FULL TEXT]
Abstract: Changes in the Atlantic overturning circulation have a strong influence on European temperatures, North American sea level and other climate phenomena worldwide. A meaningful assessment of associated societal impacts needs to be based on the full range of its possible future evolution. This requires capturing both the uncertainty in future warming pathways and the inherently long-term response of the ocean circulation. While probabilistic projections of the global mean and regional temperatures exist, process-based probabilistic assessments of large-scale dynamical systems such as the Atlantic overturning are still missing. Here we present such an assessment and find that a reduction of more than 50 % in Atlantic overturning strength by the end of the 21 s t century is within the likely range under an unmitigated climate change scenario (RCP8.5). By combining linear response functions derived from comprehensive climate simulations with the full range of possible future warming pathways, we provide probability estimates of overturning changes by the year 2100. A weakening of more than 25 % is found to be very unlikely under a climate protection scenario (RCP2.6), but likely for unmitigated climate change. The method is able to reproduce the modelled recovery caused by climatic equilibration under climate protection scenarios which provides confidence in the approach. Within this century, a reduction of the Atlantic overturning is a robust climatic phenomena that intensifies with global warming and needs to be accounted for in global adaptation strategies.
Citation: Schleussner, CF., Levermann, A. & Meinshausen, M. Climatic Change (2014) 127: 579. https://doi.org/10.1007/s10584-014-1265-2.

Linear weakening of the AMOC in response to receding glacial ice sheets in CCSM3 – Zhu et al. (2014) [FULL TEXT]
Abstract: The transient response of the Atlantic Meridional Overturning Circulation (AMOC) to a deglacial ice sheet retreat is studied using the Community Climate System Model version 3 (CCSM3), with a focus on orographic effects rather than meltwater discharge. It is found that the AMOC weakens significantly (41%) in response to the deglacial ice sheet retreat. The AMOC weakening follows the decrease of the Northern Hemisphere ice sheet volume linearly, with no evidence of abrupt thresholds. A wind‐driven mechanism is proposed to explain the weakening of the AMOC: lowering the Northern Hemisphere ice sheets induces a northward shift of the westerlies, which causes a rapid eastward sea ice transport and expanded sea ice cover over the subpolar North Atlantic; this expanded sea ice insulates the ocean from heat loss and leads to suppressed deep convection and a weakened AMOC. A sea ice‐ocean positive feedback could be further established between the AMOC decrease and sea ice expansion.
Citation: Zhu, J., Z. Liu, X. Zhang, I. Eisenman, and W. Liu (2014), Linear weakening of the AMOC in response to receding glacial ice sheets in CCSM3, Geophys. Res. Lett., 41, 6252–6258, doi:10.1002/2014GL060891.

Atlantic Meridional Overturning Circulation (AMOC) in CMIP5 Models: RCP and Historical Simulations – Cheng et al. (2013) [FULL TEXT]
Abstract: The Atlantic meridional overturning circulation (AMOC) simulated by 10 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) for the historical (1850–2005) and future climate is examined. The historical simulations of the AMOC mean state are more closely matched to observations than those of phase 3 of the Coupled Model Intercomparison Project (CMIP3). Similarly to CMIP3, all models predict a weakening of the AMOC in the twenty-first century, though the degree of weakening varies considerably among the models. Under the representative concentration pathway 4.5 (RCP4.5) scenario, the weakening by year 2100 is 5%–40% of the individual model’s historical mean state; under RCP8.5, the weakening increases to 15%–60% over the same period. RCP4.5 leads to the stabilization of the AMOC in the second half of the twenty-first century and a slower (then weakening rate) but steady recovery thereafter, while RCP8.5 gives rise to a continuous weakening of the AMOC throughout the twenty-first century. In the CMIP5 historical simulations, all but one model exhibit a weak downward trend [ranging from −0.1 to −1.8 Sverdrup (Sv) century−1; 1 Sv ≡ 106 m3 s−1] over the twentieth century. Additionally, the multimodel ensemble–mean AMOC exhibits multidecadal variability with a ~60-yr periodicity and a peak-to-peak amplitude of ~1 Sv; all individual models project consistently onto this multidecadal mode. This multidecadal variability is significantly correlated with similar variations in the net surface shortwave radiative flux in the North Atlantic and with surface freshwater flux variations in the subpolar latitudes. Potential drivers for the twentieth-century multimodel AMOC variability, including external climate forcing and the North Atlantic Oscillation (NAO), and the implication of these results on the North Atlantic SST variability are discussed.
Citation: Cheng, W., J.C. Chiang, and D. Zhang, 2013: Atlantic Meridional Overturning Circulation (AMOC) in CMIP5 Models: RCP and Historical Simulations. J. Climate, 26, 7187–7197, https://doi.org/10.1175/JCLI-D-12-00496.1.

Past, Present, and Future Changes in the Atlantic Meridional Overturning Circulation – Srokosz et al. (2012) [FULL TEXT]
Abstract: “Observations and numerical modeling experiments provide evidence for links between variability in the Atlantic meridional overturning circulation (AMOC) and global climate patterns. Reduction in the strength of the overturning circulation is thought to have played a key role in rapid climate change in the past and may have the potential to significantly influence climate change in the future, as noted in the last two Intergovernmental Panel on Climate Change (IPCC) assessment reports (Houghton et al.; Solomon et al.). Both IPCC reports also highlighted the significant uncertainties that exist regarding the future behavior of the AMOC under global warming. Model results suggest that changes in the AMOC can impact surface air temperature, precipitation patterns, and sea level, particularly in areas bordering the North Atlantic, thus affecting human populations. Here, the current understanding of past, present, and future changes in the AMOC and the effects of such changes on climate are reviewed. The focus is on observations of the AMOC, how the AMOC influences climate, and in what way the AMOC is likely to change over the next few decades and the twenty-first century. The potential for decadal prediction of the AMOC is also discussed. Finally, the outstanding challenges and possible future directions for AMOC research are outlined.”
Citation: M. Srokosz, M. Baringer, H. Bryden, S. Cunningham, T. Delworth, S. Lozier, J. Marotzke, and R. Sutton, 2012: Past, Present, and Future Changes in the Atlantic Meridional Overturning Circulation. Bull. Amer. Meteor. Soc., 93, 1663–1676. doi: http://dx.doi.org/10.1175/BAMS-D-11-00151.1.

Surface changes in the North Atlantic meridional overturning circulation during the last millennium – Wanamaker et al. (2012) [FULL TEXT]
Abstract: “Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.”
Citation: Wanamaker, A., Butler, P., Scourse, J. et al. Surface changes in the North Atlantic meridional overturning circulation during the last millennium. Nat Commun 3, 899 (2012). https://doi.org/10.1038/ncomms1901.

Northward intensification of anthropogenically forced changes in the Atlantic meridional overturning circulation (AMOC) – Zhang (2010) [FULL TEXT]
Abstract: Extensive modeling studies show that changes in the anthropogenic forcing due to increasing greenhouse gases might lead to a slowdown of the Atlantic meridional overturning circulation (AMOC) in the 21st century, but the AMOC weakening estimated in most previous modeling studies is in depth space. Using a coupled ocean atmosphere model (GFDL CM2.1), this paper shows that in density space, the anthropogenically forced AMOC changes over the 21st century are intensified at northern high latitudes (nearly twice of those at lower latitudes) due to changes in the North Atlantic Deep Water (NADW) formation. In contrast, anthropogenically forced AMOC changes are much smaller in depth space at the same northern high latitudes. Hence projecting AMOC changes in depth space would lead to a significant underestimation of AMOC changes associated with changes in the NADW formation. The result suggests that monitoring AMOC changes at northern high latitudes in density space might reveal much larger signals than those at lower latitudes. The simulated AMOC changes in density space under anthropogenic forcing can not be distinguished from that induced by natural AMOC variability for at least the first 20 years of the 21st century, although the signal can be detected over a much longer period.
Citation: Zhang, R. (2010), Northward intensification of anthropogenically forced changes in the Atlantic meridional overturning circulation (AMOC), Geophys. Res. Lett., 37, L24603, doi:10.1029/2010GL045054.

Response of the Atlantic meridional overturning circulation to increasing atmospheric CO2: Sensitivity to mean climate state – Weaver et al. (2007) [FULL TEXT]
Abstract: The dependence on the mean climate state of the response of the Atlantic meridional overturning circulation (AMOC) is investigated in 17 increasing greenhouse gas experiments with different initial conditions. The AMOC declines in all experiments by 15% to 31%, with typically the largest declines in those experiments with the strongest initial AMOC. In all cases, changes in surface heat fluxes, rather than changes in surface freshwater fluxes, are the dominant cause for the transient AMOC decrease. Surface freshwater fluxes actually switch from reducing the transient AMOC decrease, for low values of atmospheric CO2, to reinforcing the transient AMOC decrease, for higher values of atmospheric CO2. In addition, we find that due to changes in the strengths of feedbacks associated with water vapour and snow/sea ice, the climate sensitivity and transient climate response of the UVic model strongly depends on the mean climate state.
Citation: Bryden, H. L., King, B. A., McCarthy, G. D., and McDonagh, E. L.: Impact of a 30% reduction in Atlantic meridional overturning during 2009–2010, Ocean Sci., 10, 683-691, doi:10.5194/os-10-683-2014, 2014.

Quantifying the AMOC feedbacks during a 2×CO2 stabilization experiment with land-ice melting – Swingedouw et al. (2007) [FULL TEXT]
Abstract: The response of the Atlantic Meridional Overturning Circulation (AMOC) to an increase in atmospheric CO2 concentration is analyzed using the IPSL-CM4 coupled ocean–atmosphere model. Two simulations are integrated for 70 years with 1%/year increase in CO2 concentration until 2×CO2, and are then stabilized for further 430 years. The first simulation takes land-ice melting into account, via a simple parameterization, which results in a strong freshwater input of about 0.13 Sv at high latitudes in a warmer climate. During this scenario, the AMOC shuts down. A second simulation does not include this land-ice melting and herein, the AMOC recovers after 200 years. This behavior shows that this model is close to an AMOC shutdown threshold under global warming conditions, due to continuous input of land-ice melting. The analysis of the origin of density changes in the Northern Hemisphere convection sites allows an identification as to the origin of the changes in the AMOC. The processes that decrease the AMOC are the reduction of surface cooling due to the reduction in the air–sea temperature gradient as the atmosphere warms and the local freshening of convection sites that results from the increase in local freshwater forcing. Two processes also control the recovery of the AMOC: the northward advection of positive salinity anomalies from the tropics and the decrease in sea-ice transport through the Fram Strait toward the convection sites. The quantification of the AMOC related feedbacks shows that the salinity related processes contribute to a strong positive feedback, while feedback related to temperature processes is negative but remains small as there is a compensation between heat transport and surface heat flux in ocean–atmosphere coupled model. We conclude that in our model, AMOC feedbacks amplify land-ice melting perturbation by 2.5.
Citation: D. Swingedouw, P. Braconnot, P. Delecluse, E. Guilyardi, O. Marti (2007). Climate Dynamics, Volume 29, Issue 5, pp 521–534. DOI: https://doi.org/10.1007/s00382-007-0250-0.

Will Greenland melting halt the thermohaline circulation? – Jungclaus et al. (2006) [FULL TEXT]
Abstract: Climate projections for the 21st century indicate a gradual decrease of the Atlantic Meridional Overturning Circulation (AMOC). The weakening could be accelerated substantially by meltwater input from the Greenland Ice Sheet (GIS). Here we repeat recent experiments conducted for the Intergovernmental Panel of Climate Change, providing an idealized additional source of freshwater along Greenland’s coast. For conservative and high melting estimates, the AMOC reduction is 35% and 42%, respectively, compared to a weakening of 30% for the original A1B scenario. Even for the high meltwater estimate the AMOC recovers in the 22nd century. The impact of the additional fresh water is limited to further enhancing the static stability in the Irminger and Labrador Seas, whereas the backbone of the overturning is maintained by the overflows across the Greenland‐Scotland Ridge. Our results suggest that abrupt climate change initiated by GIS melting is not a realistic scenario for the 21st century.
Citation: Jungclaus, J. H., H. Haak, M. Esch, E. Roeckner, and J. Marotzke (2006), Will Greenland melting halt the thermohaline circulation? Geophys. Res. Lett., 33, L17708, doi:10.1029/2006GL026815.

Carbon dioxide – a medical view from 1866

I noticed a paper, “Transactions Of Branches” by Charles Trustram (1866), in The British Medical Journal. It contains an interesting passage, which I give below in its entirety. I have highlighted especially interesting parts:

“Medicine. I propose, on the present occasion, to depart from the course pursued by my predecessors, and instead of confining myself to that stale subject, medical reform, and that everyday recurring matter of medical ethics, to take a cursory glance of the progress that medicine has made since our last meeting.

With the exception of those improvements that the treatment of diseases of the nervous centres has derived from the researches of Brown-Séquard and Lockhart Clarke, and the introduction of that new instrument for testing the character of the circulation (which, by the kindness of one of our members, Dr. Clapton, is now on the table, and which I have no doubt he will kindly explain to us), medicine proper seems to have made no very important advance. Pathology, physiology, and vital chemistry, have been pursuing the usual course of verifying, correcting, or rejecting the discoveries of past days. Chemistry, in its more extended sense, has been investigating the condition of the atmosphere, and trying to determine how far its constitution, as to that condition of its oxygen called ozone, determines the spread of epidemics and the character of disease; but as yet with no great practical result. But the question must some day arise, if it have not already done so, whether there is not another constituent which is exerting an influence on the animal economy; I mean an increase, at present inappreciable, of its carbonic acid gas. You are all aware that the subject of the possible exhaustion of our coal-fields, and its relation to the future of our country, which has often been hinted at by the philosopher, has just now seriously engaged the attention of our senate, not as a matter of public health, but as one of political economy. A new senator, but an old philosopher, feeling that the consideration of the subject of the taxation of his country was one, and not the least important one, of his duties, and yet too honest to regard taxes as one of the many means of spending without regard to repaying, suggested that we should try to repay some portion at least of our national debt before we had exhausted that mine of wealth which our coal-beds give us. A new feature most certainly in politics, but one that speaks well for the coming times of legislation, and one from which I hope medicine may soon derive some advantage. “Sufficient for the day is the evil thereof,” and “After us the Deluge,” has been too long the ruling creed of Governments, at all events in matters of finance.

But, I think, had he consulted the two sciences of physiology and chemistry, he need hardly have troubled himself about the matter. They would, I think, have told him that, when our coal-beds (at all events, if there be the quantity presumed) were gone, there would be nobody left to claim or to pay; for, before even the half of the coal of the world is consumed (and I do not suppose our national energy will before that time have exhausted the stock of our own country), the atmosphere will have again assumed a condition fatal to animal life – nearly that condition which a Book, in which I trust we all believe, describes it to have had, when its density, nearly three times that of the present atmosphere, held up and divided the firmament of water that was above it from that which was below it; when the very matter of these coal-beds floated in a gaseous form round earth’s surface, waiting to be fixed and solidified by the action of a gigantic flora, and stored for the use of coming man.

From the sublime to the ridiculous is said to be but one step; and from our gigantic national debt to our own fireside, and domestic expenditure in this matter, is but a short one, and to us an equally interesting and important one. What would be our feelings, if told one snowy morning in December that we had come to our last bushel of coal? We who live near the woods of Sussex might hope to get through the winter with their aid; but we should certainly feel a strong disposition to move off to a warmer climate ere the next winter began, and leave our houses and lands to settle our debt; for, in this free country, whilst coal does last, the manufacturer will take care to have his wants supplied in spite of all forebodings.

To return to that medical point at which I hinted. Let me ask this question, Is the atmosphere suffering from the extraordinary evolution of carbonic acid gas which is now going on? Is the pigmy and stunted flora of the present age equal to its decomposition, to the absorption of the carbon which combustion is now daily producing? and if so, will it continue to be so, seeing that the spread of the human family is daily diminishing the forest growths? Must there not some day be a perceptible increase of the present proportion of carbon in the atmosphere? and may not some already inappreciable increase be the cause of the present type of disease, as distinguished from that which prevailed at the beginning of this century, and which I myself have lived long enough to witness?

May not the altered type of disease have been produced rather from the presence of a depressing agent in the shape of carbonic acid gas, than from a less vivifying condition of the oxygen or its compounds of ozone?

We all, I am sure, regret to find that that dire and fatal malady, the cholera, has again reached our shores. Though it is now nearly fifty yers since this malady first skewed itself in our dependencies, where it has pretty constantly been under the eyes of our professional brethren, and more than thirty years since it came among us, it must be confessed that, beyond treating the symptoms and succouring the powers of life, we have learned but little about it. Various plans of cure have been tried, and each has had its advocates; but as yet there has not been one that has been admitted to be the best by the general voice of the profession. I have ventured to bring this subject to your notice, because I hold that it will, should this malady again spread in this country as it did in 1832, be the duty of every one of us to try to add his mite to the elucidation of the disease or verification of any plan of treatment that may come before him. The last plan of treatment propounded, which its author calls the eliminative one, is founded on the assumption, undoubtedly a true one, that the disease is a blood-poison, and that, therefore, it is desirable to assist Nature in the efforts she makes to rid herself of the poison by mild purgatives, and not by the opiates and stimulants that have been hitherto used. It is asserted that the one rids the system of the poison, which the other locks up. Before we place implicit confidence in this view, it must, I think, be shown that the diarrhoea that generally prevails at the same time as the cholera is not choleraic, or connected with that disease, but only an accompaniment, under the influence of which the poison of cholera has a better chance of exerting its power; for most assuredly hitherto it has been set down as a fact, that the cholera has generally attacked those in whom this condition has been neglected. Now, if elimination is to be the plan, it surely ought to be applied before that storm of symptoms begins, which, however curative they may be, so frequently prove fatal by their own severity. There is unquestionably a stage of incubation, even in those cases which die ere Nature sets up this eliminative action. The poison cannot well begin its action the moment it is taken into the system. Is there, then, no symptom by which this period can be distinguished? and is there no mode by which the poison can be neutralised, ere it makes itself an integral part of the blood? Can inhalation and hypodermic injection offer us no ready means of making a quick impression on the system? Certainly, if we are to look upon spasm of the smaller pulmonary arteries as the chief of the pathological conditions, inhalation would seem to offer us the readiest mode of reaching it. There is another plan of treatment which has been suggested in our JOURNAL; namely, that of transfusion of defibrinated blood. But I think the proposers of this would have done well to have taken a leaf out of the book of that sagacious cook who advised her readers to catch the hare before deciding how it was to be dressed; for, however good this plan, it would be only the rich who could hope to get it in any extensive epidemic.

Whilst doing all we can to treat this disease, we surely should not neglect to ask why and whence it comes, and what are the conditions that favour its spread? However convinced we might have been that the first epidemic was an imported one, we have lately had unmistakable evidence that it can arise in our own country. Then whence comes the poison, and what is it? Is it gaseous or molecular? Abounding, as the sunbeam shews us our atmosphere does, with matter, we can hardly regard it, however much it may assist the propagation of the disease by the deportation of its poisonous molecules, as the source of the poison. The mode of the progress of the disease forbids that. Dirt and bad water seem its almost invariable associates; but we had these for years without cholera. May we come to a conclusion that Nature occasionally loses her power of re-combining the poisonous results of decomposition? or do some intensified electro-magnetic currents occasionally revivify some dormant changes and so evolve this poison? or does this agent occasionally act electrically on some older source which was locked up in the earth’s crust ages past. The fitfulness of the disease favours the idea, either that the poison is not always present, or not liable to be evoked by every day recurring agency. On the other hand, if we are to believe what we bear of its origin among the Arabian Pilgrims, and look at what has lately occurred on board some emigrant ships, it would almost seem, that this poison, like that of typhus, may be produced by overcrowding and bad diet. What if in the end we should find it to be a modified typhus, which, instead of attacking the brain, tries conclusions with the sympathetic? If so, spasm of artery and engorgement of veins may be more dependent on the sympathetic than the direct action of a morbid agent.”

New research – atmospheric and oceanic circulation (October 27, 2016)

Some of the latest papers on atmospheric and oceanic circulation are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

On the atmospheric response experiment to a Blue Arctic Ocean (Nakamura et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070526/abstract

Abstract: We demonstrated atmospheric responses to a reduction in Arctic sea ice via simulations in which Arctic sea ice decreased stepwise from the present-day range to an ice-free range. In all cases, the tropospheric response exhibited a negative Arctic Oscillation (AO)-like pattern. An intensification of the climatological planetary-scale wave due to the present-day sea ice reduction on the Atlantic side of the Arctic Ocean induced stratospheric polar vortex weakening and the subsequent negative AO. Conversely, strong Arctic warming due to ice-free conditions across the entire Arctic Ocean induced a weakening of the tropospheric westerlies corresponding to a negative AO without troposphere-stratosphere coupling, for which the planetary-scale wave response to a surface heat source extending to the Pacific side of the Arctic Ocean was responsible. Because the resultant negative AO-like response was accompanied by secondary circulation in the meridional plane, atmospheric heat transport into the Arctic increased, accelerating the Arctic amplification.

Atlantic multi-decadal oscillation influence on weather regimes over Europe and the Mediterranean in spring and summer (Zampieri et al. 2016) http://www.sciencedirect.com/science/article/pii/S092181811630371X

Abstract: We analyze the influence of the Atlantic sea surface temperature multi-decadal variability on the day-by-day sequence of large-scale atmospheric circulation patterns (i.e. the “weather regimes”) over the Euro-Atlantic region. In particular, we examine of occurrence of weather regimes from 1871 to present. This analysis is conducted by applying a clustering technique on the daily mean sea level pressure field provided by the 20th Century Reanalysis project, which was successfully applied in other studies focused on the Atlantic Multi-decadal Oscillation (AMO). In spring and summer, results show significant changes in the frequencies of certain weather regimes associated with the phase shifts of the AMO. These changes are consistent with the seasonal surface pressure, precipitation, and temperature anomalies associated with the AMO shifts in Europe.

Ocean and atmosphere feedbacks affecting AMOC hysteresis in a GCM (Jackson et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3336-8

Abstract: Theories suggest that the Atlantic Meridional Overturning Circulation (AMOC) can exhibit a hysteresis where, for a given input of fresh water into the north Atlantic, there are two possible states: one with a strong overturning in the north Atlantic (on) and the other with a reverse Atlantic cell (off). A previous study showed hysteresis of the AMOC for the first time in a coupled general circulation model (Hawkins et al. in Geophys Res Lett. doi:10.1029/2011GL047208, 2011). In this study we show that the hysteresis found by Hawkins et al. (2011) is sensitive to the method with which the fresh water input is compensated. If this compensation is applied throughout the volume of the global ocean, rather than at the surface, the region of hysteresis is narrower and the off states are very different: when the compensation is applied at the surface, a strong Pacific overturning cell and a strong Atlantic reverse cell develops; when the compensation is applied throughout the volume there is little change in the Pacific and only a weak Atlantic reverse cell develops. We investigate the mechanisms behind the transitions between the on and off states in the two experiments, and find that the difference in hysteresis is due to the different off states. We find that the development of the Pacific overturning cell results in greater atmospheric moisture transport into the North Atlantic, and also is likely responsible for a stronger Atlantic reverse cell. These both act to stabilize the off state of the Atlantic overturning.

Arctic amplification: does it impact the polar jet stream? (Meleshko et al. 2016) http://www.tellusa.net/index.php/tellusa/article/view/32330

Abstract: It has been hypothesised that the Arctic amplification of temperature changes causes a decrease in the northward temperature gradient in the troposphere, thereby enhancing the oscillation of planetary waves leading to extreme weather in mid-latitudes. To test this hypothesis, we study the response of the atmosphere to Arctic amplification for a projected summer sea-ice-free period using an atmospheric model with prescribed surface boundary conditions from a state-of-the-art Earth system model. Besides a standard global warming simulation, we also conducted a sensitivity experiment with sea ice and sea surface temperature anomalies in the Arctic. We show that when global climate warms, enhancement of the northward heat transport provides the major contribution to decrease the northward temperature gradient in the polar troposphere in cold seasons, causing more oscillation of the planetary waves. However, while Arctic amplification significantly enhances near-surface air temperature in the polar region, it is not large enough to invoke an increased oscillation of the planetary waves.

Skilful predictions of the winter North Atlantic Oscillation one year ahead (Dunstone et al. 2016) http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2824.html

Abstract: The winter North Atlantic Oscillation is the primary mode of atmospheric variability in the North Atlantic region and has a profound influence on European and North American winter climate. Until recently, seasonal variability of the North Atlantic Oscillation was thought to be largely driven by chaotic and inherently unpredictable processes. However, latest generation seasonal forecasting systems have demonstrated significant skill in predicting the North Atlantic Oscillation when initialized a month before the onset of winter. Here we extend skilful dynamical model predictions to more than a year ahead. The skill increases greatly with ensemble size due to a spuriously small signal-to-noise ratio in the model, and consequently larger ensembles are projected to further increase the skill in predicting the North Atlantic Oscillation. We identify two sources of skill for second-winter forecasts of the North Atlantic Oscillation: climate variability in the tropical Pacific region and predictable effects of solar forcing on the stratospheric polar vortex strength. We also identify model biases in Arctic sea ice that, if reduced, may further increase skill. Our results open possibilities for a range of new climate services, including for the transport, energy, water management and insurance sectors.

Other papers

Narrowing of the ITCZ in a warming climate: physical mechanisms (Byrne & Schneider, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070396/abstract

Observed and simulated fingerprints of multidecadal climate variability, and their contributions to periods of global SST stagnation (Barcikowska et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0443.1

Observed Changes in the Southern Hemispheric Circulation in May (Ivy et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0394.1

Annual Variations of the Tropopause Height over the Tibetan Plateau Compared with those over other regions (Yang et al. 2016) http://www.sciencedirect.com/science/article/pii/S0377026516300951

The influences of the Atlantic Multidecadal Oscillation on the Mean Strength of the North Pacific Subtropical High during Boreal Winter (Lyu et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0525.1

The Role of Tropical Inter-Basin SST Gradients in Forcing Walker Circulation Trends (Zhang & Karnauskas, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0349.1

The role of low-frequency variation in the manifestation of warming trend and ENSO amplitude (Yeo et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3376-0

Changes in meandering of the Northern Hemisphere circulation (Di Capua & Coumou, 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094028/meta

Direct observations of the Antarctic Slope Current transport at 113°E (Peña-Molino et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2015JC011594/abstract

Accounting for Centennial Scale Variability when Detecting Changes in ENSO: a study of the Pliocene (Tindall et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016PA002951/abstract

The Quasi-Biennial Oscillation of 2015-16: Hiccup or Death Spiral? (Dunkerton, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070921/abstract

The weakening of the ENSO–Indian Ocean Dipole (IOD) coupling strength in recent decades (Ham et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3339-5

On the Recent Destabilization of the Gulf Stream Path downstream of Cape Hatteras (Andres, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069966/abstract

The relationship between the Madden Julian Oscillation and the North Atlantic Oscillation (Jiang et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/qj.2917/abstract

Lessened response of boreal winter stratospheric polar vortex to El Niño in recent decades (Hu et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3340-z

Warming and weakening trends of the Kuroshio during 1993-2013 (Wang et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069432/abstract

Prolonged El Niño conditions in 2014–15 and the rapid intensification of Hurricane Patricia in the eastern Pacific (Foltz et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070274/abstract

Connection between Anomalous Zonal Activities of the South Asian High and Eurasian Summer Climate Anomalies (Shi & Qian, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0823.1

Ranking the strongest ENSO events while incorporating SST uncertainty (Huang et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070888/abstract

The influence of the Gulf Stream on wintertime European blocking (O’Reilly et al. 2016) http://link.springer.com/article/10.1007%2Fs00382-015-2919-0

Projected changes in atmospheric rivers affecting Europe in CMIP5 models (Ramos et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070634/abstract

Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing (Brown & Galbraith, 2016) http://www.clim-past.net/12/1663/2016/

An Oceanic Heat Content Based Definition for the Pacific Decadal Oscillation (Kumar & Wen, 2016) http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-16-0080.1

An investigation of the presence of atmospheric rivers over the North Pacific during planetary-scale wave life cycles and their role in Arctic warming (Baggett et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-16-0033.1

Alternative modelling approaches for the ENSO time series: persistence and seasonality (Gil-Alana, 2016) http://onlinelibrary.wiley.com/doi/10.1002/joc.4850/abstract

Changes in the width of the tropical belt due to simple radiative forcing changes in the GeoMIP simulations (Davis et al. 2016) http://www.atmos-chem-phys.net/16/10083/2016/

Atmospheric River Landfall-Latitude Changes in Future Climate Simulations (Shields & Kiehl, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070470/abstract

New research – past climate (October 14, 2016)

Some of the latest papers on past climate changes are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

Proxy-based Northern Hemisphere temperature reconstruction for the mid-to-late Holocene (Pei et al. 2016) http://rd.springer.com/article/10.1007%2Fs00704-016-1932-5

Abstract: The observed late twentieth century warming must be assessed in relation to natural long-term variations of the climatic system. Here, we present a Northern Hemisphere (NH) temperature reconstruction for the mid-to-late Holocene of the past 6000 years, based on a synthesis of existing paleo-temperature proxies that are capable of revealing centennial-scale variability. This includes 56 published temperature records across the NH land areas, with a sampling resolution ranging from 1 to 100 years and a time span of at least 1000 years. The composite plus scale (CPS) method is adopted with spatial weighting to develop the NH temperature reconstruction. Our reconstruction reveals abrupt cold epochs that match well the Bond events during the past 6000 years. The study further reveals two prominent cycles in NH temperature: 1700–2000-year cycle during the mid-to-late Holocene and 1200–1500-year cycle during the past 3500 years. Our reconstruction indicates that the late twentieth century NH temperature and its rate of warming are both unprecedentedly high over the past 5000 years. By comparing our reconstruction with the projected temperature increase scenarios, we find that temperature by the end of the twenty-first century would likely exceed any peaks during the mid-to-late Holocene.

How warm was Greenland during the last interglacial period? (Landais et al. 2016) http://www.clim-past.net/12/1933/2016/

Abstract: The last interglacial period (LIG,~129–116 thousand years ago) provides the most recent case study of multimillennial polar warming above the preindustrial level and a response of the Greenland and Antarctic ice sheets to this warming, as well as a test bed for climate and ice sheet models. Past changes in Greenland ice sheet thickness and surface temperature during this period were recently derived from the North Greenland Eemian Ice Drilling (NEEM) ice core records, northwest Greenland. The NEEM paradox has emerged from an estimated large local warming above the preindustrial level (7.5 ± 1.8 °C at the deposition site 126 kyr ago without correction for any overall ice sheet altitude changes between the LIG and the preindustrial period) based on water isotopes, together with limited local ice thinning, suggesting more resilience of the real Greenland ice sheet than shown in some ice sheet models. Here, we provide an independent assessment of the average LIG Greenland surface warming using ice core air isotopic composition (δ¹⁵N) and relationships between accumulation rate and temperature. The LIG surface temperature at the upstream NEEM deposition site without ice sheet altitude correction is estimated to be warmer by +8.5 ± 2.5 °C compared to the preindustrial period. This temperature estimate is consistent with the 7.5 ± 1.8 °C warming initially determined from NEEM water isotopes but at the upper end of the preindustrial period to LIG temperature difference of +5.2 ± 2.3 °C obtained at the NGRIP (North Greenland Ice Core Project) site by the same method. Climate simulations performed with present-day ice sheet topography lead in general to a warming smaller than reconstructed, but sensitivity tests show that larger amplitudes (up to 5 °C) are produced in response to prescribed changes in sea ice extent and ice sheet topography.

Response of Central European SST to atmospheric pCO₂ forcing during the Oligocene – A combined proxy data and numerical climate model approach (Walliser et al. 2016) http://www.sciencedirect.com/science/article/pii/S0031018216302887

Abstract: CO₂-induced global warming will affect seasonal to decadal temperature patterns. Expected changes will be particularly strong in extratropical regions where temperatures will increase at faster rates than at lower latitudes. Despite that, it is still poorly constrained how precisely short-term climate dynamics will change in a generally warmer world, particularly in nearshore surface waters in the extratropics, i.e., the ecologically most productive regions of the ocean on which many human societies depend. Specifically, a detailed knowledge of the relationship between pCO₂ and seasonal SST is crucial to understand interactions between the ocean and the atmosphere. In the present investigation, we have studied for the first time how rising atmospheric pCO₂ levels forced surface temperature changes in Central Europe (paleolatitude ~ 45 °N) during the mid-Oligocene (from ca. 31 to 25 Ma), a time interval of Earth history during which global conditions were comparable to those predicted for the next few centuries. For this purpose, we computed numerical climate models for the Oligocene (winter, summer, annual average) assuming an atmospheric carbon dioxide rise from 400 to 560 ppm (current level to two times pre-industrial levels, PAL) and from 400 to 840 ppm (= three times PAL), respectively. These models were compared to seasonally resolved sea surface temperatures (SST) reconstructed from δ¹⁸O values of fossil bivalve shells (Glycymeris planicostalis, G. obovata, Palliolum pictum, Arctica islandica and Isognomon maxillata sandbergeri) and shark teeth (Carcharias cuspidata, C. acutissima and Physogaleus latus) collected from the shallow water deposits of the Mainz and Kassel Basins (Germany). Multi-taxon oxygen isotope-based reconstructions suggest a gradual rise of temperatures in surface waters (upper 30 to 40 m), on average, by as much as 4 °C during the Rupelian stage followed by a 4 °C cooling during the Chattian stage. Seasonal temperature amplitudes increased by ca. 2 °C during the warmest time interval of the Rupelian stage, with warming being more pronounced during summer (5 °C) than during winter (3 °C). According to numerical climate simulations, the warming of surface waters during the early Oligocene required a CO₂ increase by at least 160 ppm, i.e., 400 ppm to 560 ppm. Given that atmospheric carbon dioxide levels predicted for the near future will likely exceed this value significantly, the Early Oligocene warming gives a hint of the possible future climate in Central Europe under elevated CO₂ levels.

Low Florida coral calcification rates in the Plio-Pleistocene (Brachert et al. 2016) http://www.biogeosciences.net/13/4513/2016/

Abstract: In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO₃) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands often allow for reconstructions of annual extension ( =  growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. This report presents the bulk density, extension rates and calcification rates of fossil reef corals which underwent minor diagenetic alteration only. The corals derive from unlithified shallow water carbonates of the Florida platform (south-eastern USA), which formed during four interglacial sea level highstands dated approximately 3.2, 2.9, 1.8, and 1.2 Ma in the mid-Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, voids are commonly present along centres of calcification which lack secondary cements. Mean extension rates were 0.44 ± 0.19 cm yr⁻¹ (range 0.16 to 0.86 cm yr⁻¹), mean bulk density was 0.96 ± 0.36 g cm−3 (range 0.55 to 1.83 g cm⁻³) and calcification rates ranged from 0.18 to 0.82 g cm⁻² yr⁻¹ (mean 0.38 ± 0.16 g cm⁻² yr⁻¹), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification rates with those of modern zooxanthellate corals (z corals) from the Western Atlantic (WA) and Indo-Pacific calibrated against sea surface temperature (SST). In the fossil data, we found a widely analogous relationship with SST in z corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localised to account also for low extension rates of Pliocene z corals throughout the tropical WA region. Low aragonite saturation on a more global scale in response to rapid glacial–interglacial CO₂ cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO₂ is generally believed to have been broadly similar to the present day. Heat stress related to globally high interglacial SST only episodically moderated by intermittent upwelling affecting the Florida platform seems to be another likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming.

The ‘Little Ice Age’ in the Himalaya: A review of glacier advance driven by Northern Hemisphere temperature change (Rowan, 2016) http://hol.sagepub.com/content/early/2016/08/08/0959683616658530.abstract

Abstract: Northern Hemisphere cooling between 1400 and 1900 in the Common Era (CE) resulted in the expansion of glaciers during a period known as the ‘Little Ice Age’ (LIA). Early investigation of recent advances of Himalayan glaciers assumed that these events were synchronous with LIA advances identified in Europe, based on the appearance and position of moraines and without numerical age control. However, applications of Quaternary dating techniques such as terrestrial cosmogenic nuclide dating have allowed researchers to determine numerical ages for these young moraines and clarify when glacial maxima occurred. This paper reviews geochronological evidence for the last advance of glaciers in the Himalaya. The 66 ages younger than 2000 years (0–2000 CE) calculated from 138 samples collected from glacial landforms demonstrate that peak moraine building occurred between 1300 and 1600 CE, slightly earlier than the coldest period of Northern Hemisphere air temperatures. The timing of LIA advances varied spatially, likely influenced by variations in topography and meteorology across and along the mountain range. Palaeoclimate proxies indicate cooling air temperatures from 1300 CE leading to a southward shift in the Asian monsoon, increased Westerly winter precipitation and generally wetter conditions across the range around 1400 and 1800 CE. The last advance of glaciers in the Himalaya during a period of variable climate resulted from cold Northern Hemisphere air temperatures and was sustained by increased snowfall as atmospheric circulation reorganised in response to cooling during the LIA.

Other papers

Dendroclimatology and historical climatology of Voronezh region, European Russia, since 1790s (Matskovsky et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/joc.4896/abstract

Can stable oxygen and hydrogen isotopes from Australian subfossil Chironomus head capsules be used as proxies for past temperature change? (Chang et al. 2016) http://rd.springer.com/article/10.1007%2Fs10933-016-9920-4

Global deep water circulation between 2.4 and 1.7 Ma and its connection to the onset of Northern Hemisphere Glaciation (Du et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2015PA002906/abstract

Evidence of temperature and precipitation change over the past 100 years in a high-resolution pollen record from the boreal forest of Central European Russia (Olchev et al. 2016) http://hol.sagepub.com/content/early/2016/10/04/0959683616670472.abstract

The Bølling-age Blomvåg Beds, western Norway: implications for the Older Dryas glacial re-advance and the age of the deglaciation (Mangerud et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/bor.12208/abstract

Impact of meltwater on high-latitude early Last Interglacial climate (Stone et al. 2016) http://www.clim-past.net/12/1919/2016/

Late Miocene global cooling and the rise of modern ecosystems (Herbert et al. 2016) http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2813.html

On the palaeoclimatic potential of a millennium-long oak ring width chronology from Slovakia (Prokop et al. 2016) http://www.sciencedirect.com/science/article/pii/S1125786516300893

A 414-year tree-ring-based April–July minimum temperature reconstruction and its implications for the extreme climate events, northeast China (Lyu et al. 2016) http://www.clim-past.net/12/1879/2016/

Interactions between climate change and human activities during the early to mid-Holocene in the eastern Mediterranean basins (Berger et al. 2016) http://www.clim-past.net/12/1847/2016/

The effect of greenhouse gas concentrations and ice sheets on the glacial AMOC in a coupled climate model (Klockmann et al. 2016) http://www.clim-past.net/12/1829/2016/

The MMCO-EOT conundrum: same benthic δ18O, different CO2 (Stap et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016PA002958/abstract

Bayesian hierarchical regression analysis of variations in sea surface temperature change over the past million years (Snyder, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016PA002944/abstract

Leaf margin analysis of Chinese woody plants and the constraints on its application to palaeoclimatic reconstruction (Li et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/geb.12498/abstract

The demise of the early Eocene greenhouse – Decoupled deep and surface water cooling in the eastern North Atlantic (Bornemann et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818116300054

Impact of ice sheet meltwater fluxes on the climate evolution at the onset of the Last Interglacial (Goelzer et al. 2016) http://www.clim-past.net/12/1721/2016/

The Response of Phanerozoic Surface Temperature to Variations in Atmospheric Oxygen Concentration (Payne et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JD025459/abstract

Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise (Gregoire et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070356/abstract

Early- to mid-Holocene forest-line and climate dynamics in southern Scandes mountains inferred from contrasting megafossil and pollen data (Paus & Haugland, 2016) http://hol.sagepub.com/content/early/2016/08/22/0959683616660172.abstract

Low frequency Pliocene climate variability in the eastern Nordic Seas (Risebrobakken et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2015PA002918/abstract

Water and carbon stable isotope records from natural archives: a new database and interactive online platform for data browsing, visualizing and downloading (Bolliet et al. 2016) http://www.clim-past.net/12/1693/2016/

Diagenetic disturbances of marine sedimentary records from methane-influenced environments in the Fram Strait as indications of variation in seep intensity during the last 35 000 years (Sztybor & Rasmussen, 2016) http://onlinelibrary.wiley.com/doi/10.1111/bor.12202/abstract

Evidence of solar activity and El Niño signals in tree rings of Araucaria araucana and A. angustifolia in South America (Perone et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818115301077

Simulated response of the mid-Holocene Atlantic Meridional Overturning Circulation in ECHAM6-FESOM/MPIOM (Shi & Lohmann, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2015JC011584/abstract

Holocene fire regimes and treeline migration rates in sub-arctic Canada (Sulphur et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818115300710

Hydroclimatic variability on the Indian-subcontinent in the past millennium: Review and assessment (Dixit & Tandon, 2016) http://www.sciencedirect.com/science/article/pii/S0012825216302136

Interglacial/glacial changes in coccolith-rich deposition in the SW Pacific Ocean: An analogue for a warmer world? (Duncan et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818115300783

Tibetan Plateau Geladaindong black carbon ice core record (1843‒1982): Recent increases due to higher emissions and lower snow accumulation (Jenkins et al. 2016) http://www.sciencedirect.com/science/article/pii/S1674927816300028

New research – cryosphere (October 11, 2016)

Some of the latest papers on climate change impacts on cryosphere are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

Grounding line retreat of Pope, Smith, and Kohler Glaciers, West Antarctica, measured with Sentinel-1a radar interferometry data (Scheuchl et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069287/abstract

Abstract: We employ Sentinel-1a C band satellite radar interferometry data in Terrain Observation with Progressive Scans mode to map the grounding line and ice velocity of Pope, Smith, and Kohler glaciers, in West Antarctica, for the years 2014–2016 and compare the results with those obtained using Earth Remote Sensing Satellites (ERS-1/2) in 1992, 1996, and 2011. We observe an ongoing, rapid grounding line retreat of Smith at 2 km/yr (40 km since 1996), an 11 km retreat of Pope (0.5 km/yr), and a 2 km readvance of Kohler since 2011. The variability in glacier retreat is consistent with the distribution of basal slopes, i.e., fast along retrograde beds and slow along prograde beds. We find that several pinning points holding Dotson and Crosson ice shelves disappeared since 1996 due to ice shelf thinning, which signal the ongoing weakening of these ice shelves. Overall, the results indicate that ice shelf and glacier retreat in this sector remain unabated.

On the recent contribution of the Greenland ice sheet to sea level change (van den Broeke et al. 2016) http://www.the-cryosphere.net/10/1933/2016/

Abstract: We assess the recent contribution of the Greenland ice sheet (GrIS) to sea level change. We use the mass budget method, which quantifies ice sheet mass balance (MB) as the difference between surface mass balance (SMB) and solid ice discharge across the grounding line (D). A comparison with independent gravity change observations from GRACE shows good agreement for the overlapping period 2002–2015, giving confidence in the partitioning of recent GrIS mass changes. The estimated 1995 value of D and the 1958–1995 average value of SMB are similar at 411 and 418 Gt yr⁻¹, respectively, suggesting that ice flow in the mid-1990s was well adjusted to the average annual mass input, reminiscent of an ice sheet in approximate balance. Starting in the early to mid-1990s, SMB decreased while D increased, leading to quasi-persistent negative MB. About 60 % of the associated mass loss since 1991 is caused by changes in SMB and the remainder by D. The decrease in SMB is fully driven by an increase in surface melt and subsequent meltwater runoff, which is slightly compensated by a small (< 3 %) increase in snowfall. The excess runoff originates from low-lying (< 2000 m a.s.l.) parts of the ice sheet; higher up, increased refreezing prevents runoff of meltwater from occurring, at the expense of increased firn temperatures and depleted pore space. With a 1991–2015 average annual mass loss of ~ 0.47 ± 0.23 mm sea level equivalent (SLE) and a peak contribution of 1.2 mm SLE in 2012, the GrIS has recently become a major source of global mean sea level rise.

Tropical Pacific SST drivers of recent Antarctic sea ice trends (Purich et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0440.1

Abstract: A strengthening of the Amundsen Sea Low from 1979-2013 has been shown to largely explain the observed increase in Antarctic sea ice concentration in the eastern Ross Sea and decrease in the Bellingshausen Sea. Here we show that while these changes are not generally seen in freely-running coupled climate model simulations, they are reproduced in simulations of two independent coupled climate models; one constrained by observed sea surface temperature anomalies in the tropical Pacific, and the other by observed surface wind-stress in the tropics. Our analysis confirms previous results and strengthens the conclusion that the phase change in the Interdecadal Pacific Oscillation from positive to negative over 1979-2013 contributed to the observed strengthening of the Amundsen Sea Low and associated pattern of Antarctic sea ice change during this period. New support for this conclusion is provided by simulated trends in spatial patterns of sea ice concentrations that are similar to those observed. Our results highlight the importance of accounting for teleconnections from low to high latitudes in both model simulations and observations of Antarctic sea ice variability and change.

Quantifying ice loss in the eastern Himalayas since 1974 using declassified spy satellite imagery (Maurer et al. 2016) http://www.the-cryosphere.net/10/2203/2016/

Abstract: Himalayan glaciers are important natural resources and climate indicators for densely populated regions in Asia. Remote sensing methods are vital for evaluating glacier response to changing climate over the vast and rugged Himalayan region, yet many platforms capable of glacier mass balance quantification are somewhat temporally limited due to typical glacier response times. We here rely on declassified spy satellite imagery and ASTER data to quantify surface lowering, ice volume change, and geodetic mass balance during 1974–2006 for glaciers in the eastern Himalayas, centered on the Bhutan–China border. The wide range of glacier types allows for the first mass balance comparison between clean, debris, and lake-terminating (calving) glaciers in the region. Measured glaciers show significant ice loss, with an estimated mean annual geodetic mass balance of −0.13 ± 0.06 m w.e. yr⁻¹ (meters of water equivalent per year) for 10 clean-ice glaciers, −0.19 ± 0.11 m w.e. yr⁻¹ for 5 debris-covered glaciers, −0.28 ± 0.10 m w.e. yr⁻¹ for 6 calving glaciers, and −0.17±0.05 m w.e. yr⁻¹ for all glaciers combined. Contrasting hypsometries along with melt pond, ice cliff, and englacial conduit mechanisms result in statistically similar mass balance values for both clean-ice and debris-covered glacier groups. Calving glaciers comprise 18 % (66 km²) of the glacierized area yet have contributed 30 % (−0.7 km³) to the total ice volume loss, highlighting the growing relevance of proglacial lake formation and associated calving for the future ice mass budget of the Himalayas as the number and size of glacial lakes increase.

Quantifying the uncertainty in historical and future simulations of Northern Hemisphere spring snow cover (Thackeray et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0341.1

Abstract: Projections of 21st century Northern Hemisphere (NH) spring snow cover extent (SCE) from two climate model ensembles are analyzed to characterize their uncertainty. The Fifth Coupled Model Intercomparison Project (CMIP5) multi-model ensemble exhibits variability due to both model differences and internal climate variability, whereas spread generated from a Canadian Earth System Model large ensemble (CanESM-LE) experiment is solely due to internal variability. The analysis shows that simulated 1981-2010 spring SCE trends are slightly weaker than observed (using an ensemble of snow products). Spring SCE is projected to decrease by -3.7±1.1% decade^-1 within the CMIP5 ensemble over the 21st century. SCE loss is projected to accelerate for all spring months over the 21st century, with the exception of June (because most snow in this month has melted by the latter half of the 21st century). For 30-year spring SCE trends over the 21st century, internal variability estimated from CanESM-LE is substantial, but smaller than inter-model spread from CMIP5. Additionally, internal variability in NH extratropical land warming trends can affect SCE trends in the near-future (R² = 0.45), while variability in winter precipitation can also have a significant (but lesser) impact on SCE trends. On the other hand, a majority of the inter-model spread is driven by differences in simulated warming (dominant in March, April, May), and snow cover available for melt (dominant in June). The strong temperature/SCE linkage suggests that model uncertainty in projections of SCE could be potentially reduced through improved simulation of spring season warming over land.

Other papers

Persistent artifacts in the NSIDC ice motion dataset and their implications for analysis (Szanyi et al. 2016)
http://onlinelibrary.wiley.com/doi/10.1002/2016GL069799/abstract

Distributed ice thickness and glacier volume in southern South America (Carrivick et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818116301515

Century-scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions (Hobbs et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JC012111/abstract

Identifying dynamically induced variability in glacier mass-balance records (Christian et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0128.1

Impacts of marine instability across the East Antarctic Ice Sheet on Southern Ocean dynamics (Phipps et al. 2016) http://www.the-cryosphere.net/10/2317/2016/

Effects of bryophyte and lichen cover on permafrost soil temperature at large scale (Porada et al. 2016) http://www.the-cryosphere.net/10/2291/2016/

Meltwater Pathways from Marine Terminating Glaciers of the Greenland Ice Sheet (Gillard et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070969/abstract

Assimilation of surface velocities between 1996 and 2010 to constrain the form of the basal friction law under Pine Island Glacier (Gillet-Chaulet et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069937/abstract

Linked trends in the south Pacific sea ice edge and Southern Oscillation Index (Kwok et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070655/abstract

Greenland during the last interglacial: the relative importance of insolation and oceanic changes (Pedersen et al. 2016) http://www.clim-past.net/12/1907/2016/

The impact of melt ponds on summertime microwave brightness temperatures and sea-ice concentrations (Kern et al. 2016) http://www.the-cryosphere.net/10/2217/2016/

The EUMETSAT sea ice concentration climate data record (Tonboe et al. 2016) http://www.the-cryosphere.net/10/2275/2016/

Temperature reconstruction from the length fluctuations of small glaciers in the eastern Alps (northeastern Italy) (Zecchetto et al. 2016) http://link.springer.com/article/10.1007%2Fs00382-016-3347-5

Variability, trends, and predictability of seasonal sea ice retreat and advance in the Chukchi Sea (Serreze et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JC011977/abstract

Producing cloud-free MODIS snow cover products with conditional probability interpolation and meteorological data (Dong & Menzel, 2016) http://www.sciencedirect.com/science/article/pii/S0034425716303625

ICESat laser altimetry over small mountain glaciers (Treichler & Kääb, 2016) http://www.the-cryosphere.net/10/2129/2016/

Heterogeneous glacier thinning patterns over the last 40 years in Langtang Himal, Nepal (Ragettli et al. 2016) http://www.the-cryosphere.net/10/2075/2016/

Arctic sea ice patterns driven by the Asian Summer Monsoon (Grunseich & Wang, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0207.1

Impact of climate warming on snow processes in ny-Ålesund, a polar maritime site at Svalbard (López-Moreno et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818116303903

Variations in ice velocities of Pine Island Glacier Ice Shelf evaluated using multispectral image matching of Landsat time series data (Han et al. 2016) http://www.sciencedirect.com/science/article/pii/S0034425716303443

Application of GRACE to the assessment of model-based estimates of monthly Greenland Ice Sheet mass balance (2003–2012) (Schlegel et al. 2016) http://www.the-cryosphere.net/10/1965/2016/

Near-real-time Arctic sea ice thickness and volume from CryoSat-2 (Tilling et al. 2016) http://www.the-cryosphere.net/10/2003/2016/

Potential for estimation of snow depth on Arctic sea ice from CryoSat-2 and SARAL/AltiKa missions (Guerreiro et al. 2016) http://www.sciencedirect.com/science/article/pii/S0034425716302711

Sliding of temperate basal ice on a rough, hard bed: creep mechanisms, pressure melting, and implications for ice streaming (Krabbendam, 2016) http://www.the-cryosphere.net/10/1915/2016/

Monte Carlo modelling projects the loss of most land-terminating glaciers on Svalbard in the 21st century under RCP 8.5 forcing (Möller et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094006/meta

North-east sector of the Greenland Ice Sheet to undergo the greatest inland expansion of supraglacial lakes during the 21st century (Ignéczi et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070338/abstract

New research – biosphere (October 10, 2016)

Some of the latest papers on climate change impacts on biosphere are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

Population trends influence species ability to track climate change (Ralston et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13478/abstract

Abstract: Shifts of distributions have been attributed to species tracking their fundamental climate niches through space. However, several studies have now demonstrated that niche tracking is imperfect, that species’ climate niches may vary with population trends, and that geographic distributions may lag behind rapid climate change. These reports of imperfect niche tracking imply shifts in species’ realized climate niches. We argue that quantifying climate niche shifts and analyzing them for a suite of species reveal general patterns of niche shifts and the factors affecting species’ ability to track climate change. We analyzed changes in realized climate niche between 1984 and 2012 for 46 species of North American birds in relation to population trends in an effort to determine whether species differ in the ability to track climate change and whether differences in niche tracking are related to population trends. We found that increasingly abundant species tended to show greater levels of niche expansion (climate space occupied in 2012 but not in 1980) compared to declining species. Declining species had significantly greater niche unfilling (climate space occupied in 1980 but not in 2012) compared to increasing species due to an inability to colonize new sites beyond their range peripheries after climate had changed at sites of occurrence. Increasing species, conversely, were better able to colonize new sites and therefore showed very little niche unfilling. Our results indicate that species with increasing trends are better able to geographically track climate change compared to declining species, which exhibited lags relative to changes in climate. These findings have important implications for understanding past changes in distribution, as well as modeling dynamic species distributions in the face of climate change.

Phylogenetic conservatism and climate factors shape flowering phenology in alpine meadows (Li et al. 2016) http://rd.springer.com/article/10.1007%2Fs00442-016-3666-6

Abstract: The study of phylogenetic conservatism in alpine plant phenology is critical for predicting climate change impacts; currently we have a poor understanding of how phylogeny and climate factors interactively influence plant phenology. Therefore, we explored the influence of phylogeny and climate factors on flowering phenology in alpine meadows. For two different types of alpine plant communities, we recorded phenological data, including flowering peak, first flower budding, first flowering, first fruiting and the flowering end for 62 species over the course of 5 years (2008–2012). From sequences in two plastid regions, we constructed phylogenetic trees. We used Blomberg’s K and Pagel’s lambda to assess the phylogenetic signal in phenological traits and species’ phenological responses to climate factors. We found a significant phylogenetic signal in the date of all reproductive phenological events and in species’ phenological responses to weekly day length and temperature. The number of species in flower was strongly associated with the weekly day lengths and followed by the weekly temperature prior to phenological activity. Based on phylogenetic eigenvector regression (PVR) analysis, we found a highly shared influence of phylogeny and climate factors on alpine species flowering phenology. Our results suggest the phylogenetic conservatism in both flowering and fruiting phenology may depend on the similarity of responses to external environmental cues among close relatives.

Sea-ice indicators of polar bear habitat (Stern & Laidre, 2016) http://www.the-cryosphere.net/10/2027/2016/

Abstract: Nineteen subpopulations of polar bears (Ursus maritimus) are found throughout the circumpolar Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology – the cycle of biological events – is linked to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979–2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from −3 to −9 days decade⁻¹ in spring and from +3 to +9 days decade⁻¹ in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days) and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of −7 to −19 days decade⁻¹, with larger trends in the Barents Sea and central Arctic Basin. The June–October sea-ice concentration is declining in all regions at rates ranging from −1 to −9 percent decade⁻¹. These sea-ice metrics (or indicators of habitat change) were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.

Lagging behind: have we overlooked previous-year rainfall effects in annual grasslands? (Dudney et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/1365-2745.12671/abstract

Abstract: 1.Rainfall is a key determinant of production and composition in arid and semiarid systems. Long-term studies relating composition and water availability primarily focus on current-year precipitation patterns, though mounting evidence highlights the importance of previous-year rainfall particularly in grasslands dominated by perennial species. The extent to which lagged precipitation effects occur in annual grasslands, however, remains largely unexplored.

2.We pair a long-term study with two manipulative experiments to identify patterns and mechanisms of lagged precipitation effects in annual grasslands. The long-term study captured variation in functional group (exotic annual forbs and grasses) abundance and precipitation across eight years at three northern California grassland sites. We then tested whether lagged rainfall effects were created through seed production and litter (residual dry matter) by manipulating rainfall and litter, respectively.

3.Rainfall from the previous-year growing season (both seasonal and total rainfall) shifted functional group abundance. High lagged rainfall was associated with increased grass and decreased forb abundance the following year. Current-year seasonal rainfall also influenced species composition, with winter rain increasing forb and decreasing grass abundance. Lagged precipitation effects were generally stronger for forbs than for grasses. Our experimental studies provided evidence for two mechanisms that contributed to lagged effects in annual grasslands. Higher rainfall increased seed production for grasses, which translated to more germinable seed the following year. Higher rainfall also increased biomass production and residual dry matter, which benefited grasses and reduced forb abundance.

4.Synthesis. Our results highlight the importance of previous-year precipitation in structuring annual community composition and suggest two important biotic pathways, seed rain and RDM, that regulate lagged community responses to rainfall. Incorporating lagged effects into models of grassland diversity and productivity could improve predictions of climate change impacts in annual grasslands.

Effects of high latitude protected areas on bird communities under rapid climate change (Santangeli et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13518/abstract

Abstract: Anthropogenic climate change is rapidly becoming one of the main threats to biodiversity, along with other threats triggered by human-driven land-use change. Species are already responding to climate change by shifting their distributions polewards. This shift may create a spatial mismatch between dynamic species distributions and static protected areas (PAs). As protected areas represent one of the main pillars for preserving biodiversity today and in the future, it is important to assess their contribution in sheltering the biodiversity communities they were designated to protect. A recent development to investigate climate-driven impacts on biological communities is represented by the community temperature index (CTI). CTI provides a measure of the relative temperature average of a community in a specific assemblage. CTI value will be higher for assemblages dominated by warm species compared to those dominated by cold-dwelling species. We here model changes in the CTI of Finnish bird assemblages, as well as changes in species densities, within and outside of PAs during the past four decades in a large boreal landscape under rapid change. We show that CTI has markedly increased over time across Finland, with this change being similar within and outside PAs and five to seven times slower than the temperature increase. Moreover, CTI has been constantly lower within than outside of PAs, and PAs still support communities which show colder thermal index than those outside of PAs in the 70s and 80s. This result can be explained by the higher relative density of northern species within PAs than outside. Overall, our results provide some, albeit inconclusive, evidence that PAs may play a role in supporting the community of northern species. Results also suggest that communities are however shifting rapidly, both inside and outside of PAs, highlighting the need for adjusting conservation measures before it’s too late.

Other papers

Impact of temperature and precipitation extremes on the flowering dates of four German wildlife shrub species (Siegmund et al. 2016) http://www.biogeosciences.net/13/5541/2016/

Cyanobacteria in aquaculture systems: linking the occurrence, abundance and toxicity with rising temperatures (Sinden & Sinang, 2016) http://rd.springer.com/article/10.1007%2Fs13762-016-1112-2

Under-ice habitats for Antarctic krill larvae: could less mean more under climate warming? (Melbourne-Thomas et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070846/abstract

Responses of land evapotranspiration to Earth’s greening in CMIP5 Earth System Models (Zeng et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/10/104006/meta

Impacts of droughts on the growth resilience of Northern Hemisphere forests (Gazol et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/geb.12526/abstract

Environmental status of the Gulf of California: A review of responses to climate change and climate variability (Páez-Osuna et al. 2016) http://www.sciencedirect.com/science/article/pii/S0012825216301416

High-resolution tide projections reveal extinction threshold in response to sea-level rise (Field et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13519/abstract

Quantifying full phenological event distributions reveals simultaneous advances, temporal stability and delays in spring and autumn migration timing in long-distance migratory birds (Miles et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13486/abstract

Can we predict ectotherm responses to climate change using thermal performance curves and body temperatures? (Sinclair et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/ele.12686/abstract

Ectomycorrhizal fungal response to warming is linked to poor host performance at the boreal-temperate ecotone (Fernandez et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13510/abstract

Spatiotemporal variability of stone pine (Pinus pinea L.) growth response to climate across the Iberian Peninsula (Natalini et al. 2016) http://www.sciencedirect.com/science/article/pii/S1125786516300777

Nonlinear, interacting responses to climate limit grassland production under global change (Zhu et al. 2016) http://www.pnas.org/content/113/38/10589.short

An unprecedented coastwide toxic algal bloom linked to anomalous ocean conditions (McCabe et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070023/abstract

Increased activity of lysozyme and complement system in Atlantic halibut exposed to elevated CO2 at six different temperatures (de Souza et al. 2016) http://www.sciencedirect.com/science/article/pii/S0141113616301696

Multisite analysis of land surface phenology in North American temperate and boreal deciduous forests from Landsat (Melaas et al. 2016) http://www.sciencedirect.com/science/article/pii/S0034425716303571

Responses of spring phenology in a fruit tree species (Pyrus sp. cv. Pingguoli) to the changes in surface air temperature in Northeast China (Shen & Kobayashi, 2016) http://onlinelibrary.wiley.com/doi/10.1002/joc.4877/abstract

Climate change impacts on net primary production (NPP) and export production (EP) regulated by increasing stratification and phytoplankton community structure in the CMIP5 models (Fu et al. 2016) http://www.biogeosciences.net/13/5151/2016/

Decreased photosynthesis and growth with reduced respiration in the model diatom Phaeodactylum tricornutum grown under elevated CO2 over 1800 generations (Li et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13501/abstract

Where do they go? The effects of topography and habitat diversity on reducing climatic debt in birds (Gaüzère et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13500/abstract

Precipitation, not air temperature, drives functional responses of trees in semi-arid ecosystems (Grossiord et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/1365-2745.12662/abstract

Relationships between individual-tree mortality and water-balance variables indicate positive trends in water stress-induced tree mortality across North America (Hember et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13428/abstract

Disturbances catalyze the adaptation of forest ecosystems to changing climate conditions (Thom et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13506/abstract

Extreme climatic events constrain space use and survival of a ground-nesting bird (Tanner et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13505/abstract

Spatial and evolutionary parallelism between shade and drought tolerance explains the distributions of conifers in the conterminous United States (Rueda et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/geb.12511/abstract

Effects of climate change on the distribution of indigenous species in oceanic islands (Azores) (Ferreira et al. 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1754-6

Northern ragweed ecotypes flower earlier and longer in response to elevated CO2: what are you sneezing at? (Stinson et al. 2016) http://rd.springer.com/article/10.1007%2Fs00442-016-3670-x

Australian vegetation phenology: new insights from satellite remote sensing and digital repeat photography (Moore et al. 2016) http://www.biogeosciences.net/13/5085/2016/

Temporal variability in the thermal requirements for vegetation phenology on the Tibetan plateau and its implications for carbon dynamics (Jin et al. 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1736-8

New research – climate and mankind (October 6, 2016)

Some of the latest papers on climate change impacts on mankind are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

The limits of poverty reduction in support of climate change adaptation (Nelson et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094011/meta

Abstract: The relationship between poverty and climate change vulnerability is complex and though not commensurate, the distinctions between the two are often blurred. There is widespread recognition of the need to better understand poverty-vulnerability dynamics in order to improve risk management and poverty reduction investments. This is challenging due to the latent nature of adaptive capacities, frequent lack of baseline data, and the need for high-resolution studies. Here we respond to these challenges by analyzing household-level data in Northeast Brazil to compare drought events 14 years apart. In the period between droughts, the government implemented an aggressive anti-poverty program that includes financial and human capital investments. Poverty declined significantly, but the expected reduction in vulnerability did not occur, in part because the households were not investing in risk management strategies. Our findings complement other research that shows that households make rational decisions that may not correspond with policymaker expectations. We emphasize the need for complementary investments to help channel increased household wealth into risk reduction, and to ensure that the public sector itself continues to prioritize the public functions of risk management, especially in areas where the social cost of climatic risk is high.

Perceptions of thermal comfort in heatwave and non-heatwave conditions in Melbourne, Australia (Lam et al. 2016) http://www.sciencedirect.com/science/article/pii/S2212095516300396

Abstract: Heatwaves can cause discomfort and illnesses due to heat stress. However, how people perceive thermal comfort and adapt to extreme heat conditions on heatwave days is uncertain. Most outdoor thermal comfort studies have been conducted under non-extreme conditions and very few during heatwaves. For those studies that encountered a heatwave, sample size tends to be small or modelling approaches were used to assess thermal comfort. It is important to understand people’s perceptions in relation to the physiological experience during extreme heat, as it would help practitioners apply the extreme heat range of thermal indices in outdoor settings. To understand people’s thermal perception and clothing behaviour during a heatwave, we combined meteorological measurements and thermal comfort surveys at two botanic gardens in Melbourne, Australia. The variations in respondents’ thermal comfort and clothing are assessed during heatwave and non-heatwave conditions, where temperatures during heatwave conditions exceeded 36°C. We observed that local visitors felt significantly hotter and wore less clothing for the same ranges of the Universal Thermal Climate Index (UTCI) during heatwave than non-heatwave conditions. Thus, we suggest that thermal expectation influences changes in thermal perceptions and clothing, even over the course of several days to a week.

How do we assess vulnerability to climate change in India? A systematic review of literature (Singh et al. 2016) http://rd.springer.com/article/10.1007%2Fs10113-016-1043-y

Abstract: In countries like India where multiple risks interact with socio-economic differences to create and sustain vulnerability, assessing the vulnerability of people, places, and systems to climate change is a critical tool to prioritise adaptation. In India, several vulnerability assessment tools have been designed spanning multiple disciplines, by multiple actors, and at multiple scales. However, their conceptual, methodological, and disciplinary underpinnings, and resulting implications on who is identified as vulnerable, have not been interrogated. Addressing this gap, we systematically review peer-reviewed publications (n = 78) and grey literature (n = 42) to characterise how vulnerability to climate change is assessed in India. We frame our enquiry against four questions: (1) How is vulnerability conceptualised (vulnerability of whom/what, vulnerability to what), (2) who assesses vulnerability, (3) how is vulnerability assessed (methodology, scale), and (4) what are the implications of methodology on outcomes of the assessment. Our findings emphasise that methods to assess vulnerability to climate change are embedded in the disciplinary traditions, methodological approaches, and often-unstated motivations of those designing the assessment. Further, while most assessments acknowledge the importance of scalar and temporal aspects of vulnerability, we find few examples of it being integrated in methodology. Such methodological myopia potentially overlooks how social differentiation, ecological shifts, and institutional dynamics construct and perpetuate vulnerability. Finally, we synthesise the strengths and weaknesses of current vulnerability assessment methods in India and identify a predominance of research in rural landscapes with a relatively lower coverage in urban and peri-urban settlements, which are key interfaces of transitions.

Drought effects on US maize and soybean production: spatiotemporal patterns and historical changes (Zipper et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094021/meta

Abstract: Maximizing agricultural production on existing cropland is one pillar of meeting future global food security needs. To close crop yield gaps, it is critical to understand how climate extremes such as drought impact yield. Here, we use gridded, daily meteorological data and county-level annual yield data to quantify meteorological drought sensitivity of US maize and soybean production from 1958 to 2007. Meteorological drought negatively affects crop yield over most US crop-producing areas, and yield is most sensitive to short-term (1–3 month) droughts during critical development periods from July to August. While meteorological drought is associated with 13% of overall yield variability, substantial spatial variability in drought effects and sensitivity exists, with central and southeastern US becoming increasingly sensitive to drought over time. Our study illustrates fine-scale spatiotemporal patterns of drought effects, highlighting where variability in crop production is most strongly associated with drought, and suggests that management strategies that buffer against short-term water stress may be most effective at sustaining long-term crop productivity.

Climate change discourse among Iranian farmers (Zobeidi et al. 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1741-y

Abstract: Climate change poses a severe threat to agriculture and rural populations around the world, with the potential to devastate lives and livelihoods. Farmers need to adapt their farming methods and land management decisions to reduce the negative consequences associated with climate change. Understanding farmers’ beliefs and perceptions regarding climate change is a good starting point for addressing current and future policy. As there is no one-size-fits-all strategy to promote adaptation, local adaptation-support strategies must be tailored to the particular needs and constraints of specific groups of farmers. To determine the policy implications of such strategies, a prudent and cost-effective approach is to categorize farmers into homogenous groupings using Q methodology to establish their perceptual frameworks with respect to climate change. Forty six farmers completed the Q sort procedure in this study. Data analysis identified that there are three different types of farmers’ attitudes to climate change: fatalism, support seekers, and technocrats. These findings are critical for decision makers to help them develop more appropriate adaptation strategies for the agricultural sector.

Other papers

Long-term trend analysis in climate variables and agricultural adaptation strategies to climate change in the Senegal River Basin (Djaman et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/joc.4885/abstract

The Evolution of Agricultural Drought Transition Periods in the United States Corn Belt (Schiraldi & Roundy, 2016) http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-16-0225.1

Do Western and Eastern Europe have the same agricultural climate response? Taking adaptive capacity into account (Vanschoenwinkel et al. 2016) http://www.sciencedirect.com/science/article/pii/S0959378016302060

Patterns of crop cover under future climates (Porfirio et al. 2016) http://rd.springer.com/article/10.1007%2Fs13280-016-0818-1

Longitudinal assessment of climate vulnerability: a case study from the Canadian Arctic (Archer et al. 2016) http://rd.springer.com/article/10.1007%2Fs11625-016-0401-5

Effects of Rainfall on Vehicle Crashes in Six U.S. States (Black et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/WCAS-D-16-0035.1

The prevalence of heat-related cardiorespiratory symptoms: the vulnerable groups identified from the National FINRISK 2007 Study (Näyhä et al. 2016) http://rd.springer.com/article/10.1007%2Fs00484-016-1243-7

Trade agreements, labour mobility and climate change in the Pacific Islands (Weber, 2016) http://link.springer.com/article/10.1007%2Fs10113-016-1047-7

Atmospheric CO2 enrichment and drought stress modify root exudation of barley (Calvo et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13503/abstract

Physical activity profile of 2014 FIFA World Cup players, with regard to different ranges of air temperature and relative humidity (Chmura et al. 2016) http://rd.springer.com/article/10.1007%2Fs00484-016-1245-5

Assessing climate change vulnerability in urban America: stakeholder-driven approaches (McCormick, 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1757-3

Spatio-temporal analyses of impacts of multiple climatic hazards in a savannah ecosystem of Ghana (Yiran et al. 2016) http://www.sciencedirect.com/science/article/pii/S2212096316300493

Health sector preparedness for adaptation planning in India (Dasgupta et al. 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1745-7

The effect of climate change on rural land cover patterns in the Central United States (Lant et al. 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1738-6

Intensity and economic loss assessment of the snow, low-temperature and frost disasters: a case study of Beijing City (Wang et al. 2016) http://rd.springer.com/article/10.1007%2Fs11069-016-2429-3

A good farmer pays attention to the weather (Morton et al. 2016) http://www.sciencedirect.com/science/article/pii/S2212096316300481

Responding to the Millennium drought: comparing domestic water cultures in three Australian cities (Lindsay et al. 2016) http://link.springer.com/article/10.1007%2Fs10113-016-1048-6

Assessing climate adaptation options and uncertainties for cereal systems in West Africa (Guan et al. 2016) http://www.sciencedirect.com/science/article/pii/S0168192316303471

Contract farming and the adoption of climate change coping and adaptation strategies in the northern region of Ghana (Azumah et al. 2016) http://link.springer.com/article/10.1007%2Fs10668-016-9854-z

Present and future assessment of growing degree days over selected Greek areas with different climate conditions (Paparrizos & Matzarakis, 2016) http://rd.springer.com/article/10.1007%2Fs00703-016-0475-8

New research – hydrosphere (September 26, 2016)

Some of the latest papers on climate change impacts on hydrosphere are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

Ocean acidification over the next three centuries using a simple global climate carbon-cycle model: projections and sensitivities (Hartin et al. 2016) http://www.biogeosciences.net/13/4329/2016/

Abstract: Continued oceanic uptake of anthropogenic CO₂ is projected to significantly alter the chemistry of the upper oceans over the next three centuries, with potentially serious consequences for marine ecosystems. Relatively few models have the capability to make projections of ocean acidification, limiting our ability to assess the impacts and probabilities of ocean changes. In this study we examine the ability of Hector v1.1, a reduced-form global model, to project changes in the upper ocean carbonate system over the next three centuries, and quantify the model’s sensitivity to parametric inputs. Hector is run under prescribed emission pathways from the Representative Concentration Pathways (RCPs) and compared to both observations and a suite of Coupled Model Intercomparison (CMIP5) model outputs. Current observations confirm that ocean acidification is already taking place, and CMIP5 models project significant changes occurring to 2300. Hector is consistent with the observational record within both the high- (> 55°) and low-latitude oceans (< 55°). The model projects low-latitude surface ocean pH to decrease from preindustrial levels of 8.17 to 7.77 in 2100, and to 7.50 in 2300; aragonite saturation levels (Ω_Ar) decrease from 4.1 units to 2.2 in 2100 and 1.4 in 2300 under RCP 8.5. These magnitudes and trends of ocean acidification within Hector are largely consistent with the CMIP5 model outputs, although we identify some small biases within Hector’s carbonate system. Of the parameters tested, changes in [H⁺] are most sensitive to parameters that directly affect atmospheric CO₂ concentrations – Q₁₀ (terrestrial respiration temperature response) as well as changes in ocean circulation, while changes in Ω_Ar saturation levels are sensitive to changes in ocean salinity and Q₁₀. We conclude that Hector is a robust tool well suited for rapid ocean acidification projections and sensitivity analyses, and it is capable of emulating both current observations and large-scale climate models under multiple emission pathways.

Anthropogenic and climate-driven water depletion in Asia (Yi et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069985/abstract

Abstract: Anthropogenic depletion of terrestrial water storage (TWS) can be alleviated in wet years and intensified in dry years, and this wet/dry pattern spanning seasons to years is termed climate variability. However, the anthropogenic and climate-driven changes have not been isolated in previous studies; thus, the estimated trend of changes in TWS is strongly dependent on the study period. Here we try to remove the influence of climate variability from the estimation of the anthropogenic contribution, which is an indicator of the environmental burden and important for TWS projections. Toward this end, we propose a linear relationship between the variation in water storage and precipitation. Factors related to the sensitivity of water storage to precipitation are given to correct for the climate variability, and the anthropogenic depletion of terrestrial water and groundwater in Asia is estimated to be −187 ± 38 Gt/yr and −100 ± 47 Gt/yr, respectively.

Are long tide gauge records in the wrong place to measure global mean sea level rise? (Thompson et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070552/abstract

Abstract: Ocean dynamics, land motion, and changes in Earth’s gravitational and rotational fields cause local sea level change to deviate from the rate of global mean sea level rise. Here, we use observations and simulations of spatial structure in sea level change to estimate the likelihood that these processes cause sea level trends in the longest and highest-quality tide gauge records to be systematically biased relative to the true global mean rate. The analyzed records have an average 20th century rate of approximately 1.6 mm/yr, but based on the locations of these gauges, we show the simple average underestimates the 20th century global mean rate by 0.1  ±  0.2 mm/yr. Given the distribution of potential sampling biases, we find < 1% probability that observed trends from the longest and highest-quality TG records are consistent with global mean rates less than 1.4 mm/yr.

Development of a 0.5 deg global monthly raining day product from 1901-2010 (Stillman & Zeng, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070244/abstract

Abstract: While several long-term global datasets of monthly precipitation amount (P) are widely available, only the Climate Research Unit (CRU) provides long-term global monthly raining day number (N) data (i.e., daily precipitation frequency in a month), with P/N representing the daily precipitation intensity. However, because CRU N is based on a limited number of gauges, it is found to perform poorly over data sparse regions. By combining the CRU method with a short-term gauge-satellite merged global daily precipitation dataset (CMORPH) and a global long-term monthly precipitation dataset (GPCC) with far more gauges than used in CRU, a new 0.5 deg global N dataset from 1901-2010 is developed, which differs significantly from CRU N. Compared with three independent regional daily precipitation products over U.S., China, and South America based on much denser gauge networks than used in CRU, the new product shows significant improvement over CRU N.

Detection and delineation of glacial lakes and identification of potentially dangerous lakes of Dhauliganga basin in the Himalaya by remote sensing techniques (Jha & Khare, 2016) http://link.springer.com/article/10.1007%2Fs11069-016-2565-9

Abstract: Glaciers are retreating and thinning in the high altitude of the Himalayas due to global warming, causing into formation of numerous glacial lakes. It is necessary to monitor these glacial lakes consistently to save properties and lives downstream from probable disastrous glacial lake outburst flood. In this study, image processing software ArcGIS and ERDAS Imagine have been used to analyse multispectral image obtained by Earth resource satellite Landsat for delineating the glacial lakes with the help of image enhancement technique like NDWI. Landsat data since 1972 through 2013 have been used and maximum seven glacial lakes (L1–L7) have been detected and delineated in Dhauliganga catchment, they are situated above 4000 masl. The Glacial Lake L2 (Lat 30°26′45″E and Long 80°23′16″N) is the largest whose surface area was 132,300 m2 in Sept 2009, and L6 (Lat 30°23′27″E and Long 80°31′52″N) is highly unstable with variation rate −55 to +145 % with increasing trend. Additionally, glacial lakes L2 (Lat 30°26′45″E and Long 80°23′16″N) and L6 (Lat 30°23′27″E and Long 80°31′52″N) have been identified as potentially hazardous. These lakes may probably burst; as a result, huge reserve of water and debris may be released all on a sudden. This may transform into hazardous flash flood in downstream causing loss of lives, as well as the destruction of houses, bridges, fields, forests, hydropower stations, roads, etc. It is to note that Dhauliganga river considered in this study is a tributary of Kaliganga river, and should not be confused with its namesake the Dhauliganga river, which is a tributary of Alaknanda river.

Other papers

Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century (Pagán et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094026/meta

Regionalizing Africa: Patterns of Precipitation Variability in Observations and Global Climate Models (Badr et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0182.1

Evidencing decadal and interdecadal hydroclimatic variability over the Central Andes (Segura et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094016/meta

The uncertainties and causes of the recent changes in global evapotranspiration from 1982 to 2010 (Dong & Dai, 2016) http://link.springer.com/article/10.1007%2Fs00382-016-3342-x

Spatial pattern of reference evapotranspiration change and its temporal evolution over Southwest China (Sun et al. 2016) http://rd.springer.com/article/10.1007%2Fs00704-016-1930-7

Climate change in the Blue Nile Basin Ethiopia: implications for water resources and sediment transport (Wagena et al. 2016) http://rd.springer.com/article/10.1007%2Fs10584-016-1785-z

Rainfall in Qatar: Is it changing? (Mamoon & Rahman, 2016) http://link.springer.com/article/10.1007%2Fs11069-016-2576-6

Global Precipitation Measurement (GPM) Mission Products and Services at the NASA Goddard Earth Sciences (GES) Data and Information Services Center (DISC) (Liu et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0023.1

A multi-satellite climatology of clouds, radiation and precipitation in southern West Africa and comparison to climate models (Hill et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JD025246/abstract

Detection, Attribution and Projection of Regional Rainfall Changes on (Multi-) Decadal Time Scales: A Focus on Southeastern South America (Zhang et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0287.1

Which weather systems are projected to cause future changes in mean and extreme precipitation in CMIP5 simulations? (Utsumi et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JD024939/abstract

Out-phased decadal precipitation regime shift in China and the United States (Yang & Fu, 2016) http://rd.springer.com/article/10.1007%2Fs00704-016-1907-6

Forcing of recent decadal variability in the Equatorial and North Indian Ocean (Thompson et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JC012132/abstract

Proxy-based reconstruction of surface water acidification and carbonate saturation of the Levant Sea during the Anthropocene (Bialik & Sisma-Ventura, 2016) http://www.sciencedirect.com/science/article/pii/S2213305416300881

Understanding decreases in land relative humidity with global warming: conceptual model and GCM simulations (Byrne & O’Gorman, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0351.1

Spatial trend analysis of Hawaiian rainfall from 1920 to 2012 (Frazier & Giambelluca, 2016) http://onlinelibrary.wiley.com/doi/10.1002/joc.4862/abstract

Mapping of West Siberian taiga wetland complexes using Landsat imagery: implications for methane emissions (Terentieva et al. 2016) http://www.biogeosciences.net/13/4615/2016/

Wind driven mixing at intermediate depths in an ice-free Arctic Ocean (Lincoln et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070454/abstract

Seasonal Evolution of Supraglacial Lakes on an East Antarctic Outlet Glacier (Langley et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069511/abstract

Temperature-salinity structure of the North Atlantic circulation and associated heat and freshwater transports (Xu et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0798.1

Eustatic and Relative Sea Level Changes (Rovere et al. 2016) http://rd.springer.com/article/10.1007%2Fs40641-016-0045-7

A mechanism for the response of the zonally asymmetric subtropical hydrologic cycle to global warming (Levine & Boos, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0826.1

Quantifying the contribution of glacier-melt water in the expansion of the largest lake in Tibet (Tong et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JD025424/abstract