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Observations of anthropogenic global warming

Archive for November, 2012

New research from last week 47/2012

Posted by Ari Jokimäki on November 26, 2012

This week we have papers on snowfall, rainfall, Arctic vegetation, Arctic sea ice, ozone, Svalbard glaciers, ice cores, ocean waters and others.


Characteristics of ocean waters reaching Greenland’s glaciers

Characteristics of ocean waters reaching Greenland’s glaciers – Straneo et al. (2012) [FULL TEXT]

Abstract: “Interaction of Greenland’s marine-terminating glaciers with the ocean has emerged as a key term in the ice-sheet mass balance and a plausible trigger for their recent acceleration. Our knowledge of the dynamics, however, is limited by scarcity of ocean measurements at the glacier/ocean boundary. Here data collected near six marine-terminating glaciers (79 North, Kangerdlugssuaq, Helheim and Petermann glaciers, Jakobshavn Isbræ, and the combined Sermeq Kujatdleq and Akangnardleq) are compared to investigate the water masses and the circulation at the ice/ocean boundary. Polar Water, of Arctic origin, and Atlantic Water, from the subtropical North Atlantic, are found near all the glaciers. Property analysis indicates melting by Atlantic Water (AW; found at the grounding line depth near all the glaciers) and the influence of subglacial discharge at depth in summer. AW temperatures near the glaciers range from 4.5°C in the southeast, to 0.16°C in northwest Greenland, consistent with the distance from the subtropical North Atlantic and cooling across the continental shelf. A review of its offshore variability suggests that AW temperature changes in the fjords will be largest in southern and smallest in northwest Greenland, consistent with the regional distribution of the recent glacier acceleration.”

Citation: Straneo, Fiammetta; Sutherland, David A.; Holland, David; Gladish, Carl; Hamilton, Gordon S.; Johnson, Helen L.; Rignot, Eric; Xu, Yun; Koppes, Michele, Annals of Glaciology, Volume 53, Number 60, November 2012 , pp. 202-210(9), DOI: http://dx.doi.org/10.3189/2012AoG60A059.


Ice core researchers got tired of counting ice layers manually

Automated ice-core layer-counting with strong univariate signals – Wheatley et al. (2012) [FULL TEXT]

Abstract: “We present an automated process for determining the annual layer chronology of an ice-core with a strong annual signal, utilising the hydrogen peroxide record from an Antarctic Peninsula ice-core as a test signal on which to count annual cycles and explain the methods. The signal is de-trended and normalised before being split into sections with a deterministic cycle count and those that need more attention. Possible reconstructions for the uncertain sections are determined which could be used as a visual aid for manual counting, and a simple method for assigning probability measures to each reconstruction is discussed. The robustness of this process is explored by applying it to versions of two different chemistry signals from the same stretch of the NGRIP (North Greenland Ice Core Project) ice-core, which shows more variation in annual layer thickness, with and without thinning to mimic poorer quality data. An adapted version of these methods is applied to the more challenging non-sea-salt sulphur signal from the same Antarctic Peninsula core from which the hydrogen peroxide signal was taken. These methods could readily be adapted for use on much longer datasets, thereby reducing manual effort and providing a robust automated layer-counting methodology.”

Citation: Wheatley, J. J., Blackwell, P. G., Abram, N. J., McConnell, J. R., Thomas, E. R., and Wolff, E. W.: Automated ice-core layer-counting with strong univariate signals, Clim. Past, 8, 1869-1879, doi:10.5194/cp-8-1869-2012, 2012.


Arctic sea ice limits methane emission from ocean and also absorbs methane from atmosphere

Sea ice in the Arctic Ocean: Role of shielding and consumption of methane – He et al. (2012)

Highlights: ► We compared methane fluxes under two conditions, with and without ice cover. ► There is considerable methane potentially storing in central Arctic Ocean. ► Sea ice limits methane emission in Arctic. ► Sea ice absorbs methane in atmosphere potentially related to both photochemical and biochemical oxidation.

Abstract: “Sources and sinks of methane, one of the most important greenhouse gases, have attracted intensive attention due to its role in global warming. We show that sea ice in the Arctic Ocean regulates methane level through two mechanisms, shielding of methane emission from the ocean, and consumption of methane. Using a static chamber technique, we estimated that the methane flux from under-ice water was 0.56 mg(CH4) m−2 d−1 on average in central Arctic Ocean, relatively higher than that in other oceans, indicating considerable methane storage in this region under sea ice. Average methane flux on under-ice water was higher than that above sea ice, which suggests that sea ice could limit methane emission. In addition, negative fluxes on sea ice suggest that there are methane consuming processes, which are possibly associated with both photochemical and biochemical oxidation. Our results provide a general understanding about how sea ice in Arctic affects regional and global methane balance.”

Citation: Xin He, Liguang Sun, Zhouqing Xie, Wen Huang, Nanye Long, Zheng Li, Guangxi Xing, Atmospheric Environment, Volume 67, March 2013, Pages 8–13, http://dx.doi.org/10.1016/j.atmosenv.2012.10.029.


Strong evidence for warming, wetting and intensified rainfall in South America

Warming and wetting signals emerging from analysis of changes in climate extreme indices over South America – de los Milagros Skansi et al. (2012)

Highlights: ► Strong evidence for warming, wetting and intensified rainfall in South America ► Cold (warm) extremes are decreasing (increasing) over the 1950–2010 period ► Local trends are spatially more coherent for temperature than for precipitation ► Precipitation is increasing, with SE South America and Amazonia contributing more ► Intensification of heavy rainy events over eastern part of the continent is found.

Abstract: “Here we show and discuss the results of an assessment of changes in both area-averaged and station-based climate extreme indices over South America (SA) for the 1950–2010 and 1969–2009 periods using high-quality daily maximum and minimum temperature and precipitation series. A weeklong regional workshop in Guayaquil (Ecuador) provided the opportunity to extend the current picture of changes in climate extreme indices over SA. Our results provide evidence of warming and wetting across the whole SA since the mid-20th century onwards. Nighttime (minimum) temperature indices show the largest rates of warming (e.g. for tropical nights, cold and warm nights), while daytime (maximum) temperature indices also point to warming (e.g. for cold days, summer days, the annual lowest daytime temperature), but at lower rates than for minimums. Both tails of night-time temperatures have warmed by a similar magnitude, with cold days (the annual lowest nighttime and daytime temperatures) seeing reductions (increases). Trends are strong and moderate (moderate to weak) for regional-averaged (local) indices, most of them pointing to a less cold SA during the day and warmer night-time temperatures. Regionally-averaged precipitation indices show clear wetting and a signature of intensified heavy rain events over the eastern part of the continent. The annual amounts of rainfall are rising strongly over south-east SA (26.41 mm/decade) and Amazonia (16.09 mm/decade), but north-east Brazil and the western part of SA have experienced non-significant decreases. Very wet and extremely days, the annual maximum 5-day and 1-day precipitation show the largest upward trends, indicating an intensified rainfall signal for SA, particularly over Amazonia and south-east SA. Local trends for precipitation extreme indices are in general less coherent spatially, but with more general spatially coherent upward trends in extremely wet days over all SA.”

Citation: María de los Milagros Skansia, Manola Brunet, Javier Sigró, Enric Aguilar, Juan Andrés Arevalo Groening, Oscar J. Bentancur, Yaruska Rosa Castellón Geier, Ruth Leonor Correa Amaya, Homero Jácome, Andrea Malheiros Ramos, Clara Oria Rojas, Alejandro Max Pasten, Sukarni Sallons Mitro, Claudia Villaroel Jiménez, Rodney Martínez, Lisa V. Alexander, P.D. Jones, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.11.004.


Observations of enhanced thinning in the upper reaches of Svalbard glaciers

Observations of enhanced thinning in the upper reaches of Svalbard glaciers – James et al. (2012) [FULL TEXT]

Abstract: “Changes in the volume and extent of land ice of the Svalbard archipelago have been the subject of considerable research since their sensitivity to changes in climate was first noted. However, the measurement of these changes is often necessarily based on point or profile measurements which may not be representative if extrapolated to a whole catchment or region. Combining high-resolution elevation data from contemporary laser-altimetry surveys and archived aerial photography makes it possible to measure historical changes across a glacier’s surface without the need for extrapolation. Here we present a high spatial resolution time-series for six Arctic glaciers in the Svalbard archipelago spanning 1961 to 2005. We find high variability in thinning rates between sites with prevalent elevation changes at all sites averaging −0.59 ± 0.04 m a−1 between 1961–2005. Prior to 1990, ice surface elevation was changing at an average rate of −0.52 ± 0.09 m a−1 which decreased to −0.76 ± 0.10 m a−1 after 1990. Setting the elevation changes against the glaciers’ altitude distribution reveals that significant increases in thinning rates are occurring most notably in the glaciers’ upper reaches. We find that these changes are coincident with a decrease in winter precipitation at the Longyearbyen meteorological station and could reflect a decrease in albedo or dynamic response to lower accumulation. Further work is required to understand fully the causes of this increase in thinning rates in the glaciers’ upper reaches. If on-going and occurring elsewhere in the archipelago, these changes will have a significant effect on the region’s future mass balance. Our results highlight the importance of understanding the climatological context of geodetic mass balance measurements and demonstrate the difficulty of using index glaciers to represent regional changes in areas of strong climatological gradients.”

Citation: James, T. D., Murray, T., Barrand, N. E., Sykes, H. J., Fox, A. J., and King, M. A.: Observations of enhanced thinning in the upper reaches of Svalbard glaciers, The Cryosphere, 6, 1369-1381, doi:10.5194/tc-6-1369-2012, 2012.


Stratospheric ozone and temperature simulated from the preindustrial era to the present day

Stratospheric ozone and temperature simulated from the preindustrial era to the present day – Austin et al. (2012)

Abstract: “Results from the simulation of a coupled chemistry climate model are presented for the period 1860 to 2005 using the observed greenhouse gas (GHG) and halocarbon concentrations. The model is coupled to a simulated ocean and uniquely includes both detailed tropospheric chemistry and detailed middle atmosphere chemistry, seamlessly from the surface to the model top layer centered at 0.02 hPa. It is found that there is no statistically significant change in simulated stratospheric temperature and ozone prior to the year 1960. As the halocarbon amounts increase after 1970, model stratospheric ozone decreases approximately continuously until about 2000. The steadily increasing GHG concentrations cool the stratosphere from the beginning of the 20th century at a rate which increases with height. During the early period the cooling leads to increased stratospheric ozone. The model results show a strong, albeit temporary, response to volcanic eruptions. While CFC concentrations remain low, the effect of eruptions is shown to increase the amount of HNO3, reducing ozone destruction by the NOx catalytic cycle. In the presence of anthropogenic chlorine, after the eruption of El Chichón and Mt. Pinatubo, chlorine radicals increased and the chlorine reservoirs decreased. The net volcanic effect on nitrogen and chlorine chemistry depends on altitude and, for these two volcanoes, leads to an ozone increase in the middle stratosphere and a decrease in the lower stratosphere. Model lower stratospheric temperatures are also shown to increase during the last three major volcanic eruptions, by about 0.6 K in the global and annual average, consistent with observations.”

Citation: John Austin, Larry W. Horowitz, M. Daniel Schwarzkopf, R. John Wilson, and Hiram Levy II, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00162.1.


Satellite measurements show overall greening in Arctic but also some browning areas

Relationships between declining summer sea ice, increasing temperatures and changing vegetation in the Siberian Arctic tundra from MODIS time series (2000–11) – Dutrieux et al. (2012) [FULL TEXT]

Abstract: “The concern about Arctic greening has grown recently as the phenomenon is thought to have significant influence on global climate via atmospheric carbon emissions. Earlier work on Arctic vegetation highlighted the role of summer sea ice decline in the enhanced warming and greening phenomena observed in the region, but did not contain enough details for spatially characterizing the interactions between sea ice, temperature and vegetation photosynthetic absorption. By using 1 km resolution data from the Moderate Resolution Imaging Spectrometer (MODIS) as a primary data source, this study presents detailed maps of vegetation and temperature trends for the Siberian Arctic region, using the time integrated normalized difference vegetation index (TI-NDVI) and summer warmth index (SWI) calculated for the period 2000–11 to represent vegetation greenness and temperature respectively. Spatio-temporal relationships between the two indices and summer sea ice conditions were investigated with transects at eight locations using sea ice concentration data from the Special Sensor Microwave/Imager (SSM/I). In addition, the derived vegetation and temperature trends were compared among major Arctic vegetation types and bioclimate subzones. The fine resolution trend map produced confirms the overall greening (+1% yr−1) and warming (+0.27% yr−1) of the region, reported in previous studies, but also reveals browning areas. The causes of such local decreases in vegetation, while surrounding areas are experiencing the opposite reaction to changing conditions, are still unclear. Overall correlations between sea ice concentration and SWI as well as TI-NDVI decreased in strength with increasing distance from the coast, with a particularly pronounced pattern in the case of SWI. SWI appears to be driving TI-NDVI in many cases, but not systematically, highlighting the presence of limiting factors other than temperature for plant growth in the region. Further unravelling those limiting factors constitutes a priority in future research. This study demonstrates the use of medium resolution remotely sensed data for studying the complexity of spatio-temporal vegetation dynamics in the Arctic.”

Citation: L P Dutrieux, H Bartholomeus, M Herold and J Verbesselt, 2012 Environ. Res. Lett. 7 044028 doi:10.1088/1748-9326/7/4/044028.


Snowfall is projected to decrease in western and central Europe

On the future reduction of snowfall in western and central Europe – de Vries et al. (2012) [FULL TEXT]

Abstract: “Large parts of western and central Europe face a 20–50 % future reduction in snowfall on Hellmann days (days with daily-mean temperatures below freezing). This strong reduction occurs in addition to the expected 75 % decrease of the number of Hellmann days near the end of the twenty first century. The result is insensitive to the exact freezing-level threshold, but is in sharp contrast with the winter daily precipitation, which increases under most global warming scenarios. Not only climate model simulations show this. Observational records also reveal that probabilities for precipitation on Hellmann days have been larger in the past. The future reduction is a consequence of the freezing-level threshold becoming a more extreme quantile of the temperature distribution in the future. Only certain circulation types permit these quantiles to be reached, and it is shown that these have intrinsically low precipitation probability.”

Citation: Hylke de Vries, Reindert J. Haarsma, Wilco Hazeleger, Climate Dynamics, November 2012, DOI: 10.1007/s00382-012-1583-x.


Other studies from last week

Non-linear effects of climate on boreal rodent dynamics: mild winters do not negate high-amplitude cycles – Korpela et al. (2012)

Unexpected increase in precipitation intensity with temperature — A result of mixing of precipitation types? – Berg & Haerter (2012)

Dynamic thinning of Antarctic glaciers from along-track repeat radar altimetry – Flament & Rémy (2012)

Tidewater glacier fluctuations in central East Greenland coastal and fjord regions (1980s-2005) – Jiskoot et al. (2012)

Role of vegetation change in future climate under the A1B scenario and a climate stabilisation scenario, using the HadCM3C Earth system model – Falloon et al. (2012) [FULL TEXT]

Comparative analysis of the influence of climate change and nitrogen deposition on carbon sequestration in forest ecosystems in European Russia: simulation modelling approach – Komarov & Shanin (2012) [FULL TEXT]

Late Pleistocene vegetation change in Korea and its possible link to East Asian monsoon and Dansgaard–Oeschger (D–O) cycles – Lim et al. (2012)

Lake levels in Asia at the Last Glacial Maximum as indicators of hydrologic sensitivity to greenhouse gas concentrations – Li & Morrill (2012)

Scaled biotic disruption during early Eocene global warming events – Gibbs et al. (2012) [FULL TEXT]

Constraining projections of summer Arctic sea ice – Massonnet et al. (2012) [FULL TEXT]

A Multi-sensor Perspective on the Radiative Impacts of Clouds and Aerosols – Henderson et al. (2012)

Contrasting impacts of climate change across seasons: effects on flatfish cohorts – Vinagre et al. (2012)

The impact of climate change on rainfall Intensity–Duration–Frequency (IDF) curves in Alabama – Mirhosseini et al. (2012)

Modeling the climatic effects of urbanization in the Beijing–Tianjin–Hebei metropolitan area – Wang et al. (2012) [FULL TEXT]

Summer temperature extremes in northeastern Spain: spatial regionalization and links to atmospheric circulation (1960–2006) – El Kenawy et al. (2012) [FULL TEXT]

Reexamining the warming in the tropical upper troposphere: Models versus radiosonde observations – Seidel et al. (2012)

Adapting dryland agriculture to climate change: Farming implications and research and development needs in Western Australia – Asseng & Pannell (2012) [FULL TEXT]

The effect of diurnal sea surface temperature warming on climatological air-sea fluxes – Clayson & Bogdanoff (2012)

Reducing biases in XBT measurements by including discrete information from pressure switches – Goes et al. (2012)

Cultivating C4 crops in a changing climate: sugarcane in Ghana – Black et al. (2012) [FULL TEXT]

Which metric of ambient ozone to predict daily mortality? – Moshammer et al. (2012)

Seasonal climate change across the Roman Warm Period/Vandal Minimum transition using isotope sclerochronology in archaeological shells and otoliths, southwest Florida, USA – Wang et al. (2012)

Carbon dioxide exchange rates from short- and long-hydroperiod Everglades freshwater marsh – Jimenez et al. (2012)


CLASSIC OF THE WEEK: Reid (1895)

The Variations of Glaciers – Reid (1895) [FULL TEXT]

Abstract: No abstract.

Citation: Harry Fielding Reid, The Journal of Geology, Vol. 3, No. 3 (Apr. – May, 1895) (pp. 278-288).


About this series. When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

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New research from last week 46/2012

Posted by Ari Jokimäki on November 19, 2012

This was somewhat quiet week for climate science. You can also see it from papers below – there are quite a few papers that are from related fields of science. However, I think this is just natural variability and not indicative of some long-term changes in publication activity in climate science. I received 364 papers to my RSS feed reader this week. Below I have included 12 (in the main section) + 26 (in other studies section) = 38, which is 10.4 % of new papers I saw last week. Not bad percentage, I think.

Let’s take some open access news. Royal Society Publishing: “All our content is free to access until 29 November 2012″ (if you are interested in science history, you could have some fun visiting their journals, some of which started publishing hundreds of years ago). Also, Springer: “View for free on the new SpringerLink through November 30,2012″ for Climatic Change, Climate Dynamics, and Theoretical and Applied Climatology (and for some other journals as well).


North Atlantic tropical cyclone intensity is projected to increase

Projected Increases in North Atlantic Tropical Cyclone Intensity from CMIP5 Models – Villarini & Vecchi (2012) [FULL TEXT]

Abstract: “Tropical cyclones – particularly intense ones – are a hazard to life and property, so an assessment of the changes in North Atlantic tropical cyclone intensity has important socio-economic implications. In this study we focus on the seasonally integrated Power Dissipation Index (PDI) as a metric to project changes in tropical cyclone intensity. Based on a recently developed statistical model, we examine projections in North Atlantic PDI using output from 17 state-of-the-art global climate models and three radiative forcing scenarios. Overall, we find that North Atlantic PDI is projected to increase with respect to the 1986-2005 period across all scenarios. The difference between the PDI projections and those of the number of North Atlantic tropical cyclones, which are not projected to increase significantly, indicates an intensification of North Atlantic tropical cyclones in response to both greenhouse gas (GHG) increases and aerosol changes over the current century. At the end of the 21st century, the magnitude of these increases shows a positive dependence on projected GHG forcing. The projected intensification is significantly enhanced by non-GHG (primarily aerosol) forcing in the first half of the 21st century.”

Citation: Gabriele Villarini and Gabriel A. Vecchi, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00441.1.


Extreme precipitation events have become more common in Europe

Trends in European precipitation extremes over 1951–2010 – van den Besselaar et al. (2012)

Abstract: “Significant trends in precipitation extremes over Europe since the middle of the 20th century have been found in earlier studies. Most of these studies are based on descriptive indices of moderate extremes that occur on average a few times per year. Here we have analyzed rarer precipitation events which occur on average once in 5, 10 and 20 years in the 1950s and 1960s using extreme value theory. We have focused on the 1-d and 5-d precipitation amounts in Northern and Southern Europe in all four seasons. Changes over the time period 1951–2010 are studied by considering five consecutive 20-year time intervals with 10-year overlap. Despite considerable decadal variability, our results indicate that 5-, 10- and 20-year events of 1-d and 5-d precipitation for the first 20-year period generally became more common during this 60-year period. For all regions, seasons and return periods, the median reduction in return period between the first and last 20-year periods is ∼21% with variations between a decrease of ∼2% and ∼58%.”

Citation: E. J. M. van den Besselaar, A. M. G. Klein Tank, T. A. Buishand, International Journal of Climatology, DOI: 10.1002/joc.3619.


The global energy balance from a surface perspective

The global energy balance from a surface perspective – Wild et al. (2012) [FULL TEXT]

Abstract: “In the framework of the global energy balance, the radiative energy exchanges between Sun, Earth and space are now accurately quantified from new satellite missions. Much less is known about the magnitude of the energy flows within the climate system and at the Earth surface, which cannot be directly measured by satellites. In addition to satellite observations, here we make extensive use of the growing number of surface observations to constrain the global energy balance not only from space, but also from the surface. We combine these observations with the latest modeling efforts performed for the 5th IPCC assessment report to infer best estimates for the global mean surface radiative components. Our analyses favor global mean downward surface solar and thermal radiation values near 185 and 342 Wm−2, respectively, which are most compatible with surface observations. Combined with an estimated surface absorbed solar radiation and thermal emission of 161 and 397 Wm−2, respectively, this leaves 106 Wm−2 of surface net radiation available globally for distribution amongst the non-radiative surface energy balance components. The climate models overestimate the downward solar and underestimate the downward thermal radiation, thereby simulating nevertheless an adequate global mean surface net radiation by error compensation. This also suggests that, globally, the simulated surface sensible and latent heat fluxes, around 20 and 85 Wm−2 on average, state realistic values. The findings of this study are compiled into a new global energy balance diagram, which may be able to reconcile currently disputed inconsistencies between energy and water cycle estimates.”

Citation: Martin Wild, Doris Folini, Christoph Schär, Norman Loeb, Ellsworth G. Dutton, Gert König-Langlo, Climate Dynamics, November 2012, DOI: 10.1007/s00382-012-1569-8.


New Arctic sea ice extent time series from the 1950s to present

A simple approach to providing a more consistent Arctic sea ice extent time series from the 1950s to present – Meier et al. (2012) [FULL TEXT]

Abstract: “Observations from passive microwave satellite sensors have provided a continuous and consistent record of sea ice extent since late 1978. Earlier records, compiled from ice charts and other sources exist, but are not consistent with the satellite record. Here, a method is presented to adjust a compilation of pre-satellite sources to remove discontinuities between the two periods and create a more consistent combined 59-yr time series spanning 1953–2011. This adjusted combined time series shows more realistic behavior across the transition between the two individual time series and thus provides higher confidence in trend estimates from 1953 through 2011. The long-term time series is used to calculate linear trend estimates and compare them with trend estimates from the satellite period. The results indicate that trends through the 1960s were largely positive (though not statistically significant) and then turned negative by the mid-1970s and have been consistently negative since, reaching statistical significance (at the 95% confidence level) by the late 1980s. The trend for September (when Arctic extent reaches its seasonal minimum) for the satellite period, 1979–2011 is −12.9% decade−1, nearly double the 1953–2011 trend of−6.8% decade−1 (percent relative to the 1981–2010 mean). The recent decade (2002–2011) stands out as a period of persistent decline in ice extent. The combined 59-yr time series puts the strong observed decline in the Arctic sea ice cover during 1979–2011 in a longer-term context and provides a useful resource for comparisons with historical model estimates.”

Citation: Meier, W. N., Stroeve, J., Barrett, A., and Fetterer, F.: A simple approach to providing a more consistent Arctic sea ice extent time series from the 1950s to present, The Cryosphere, 6, 1359-1368, doi:10.5194/tc-6-1359-2012, 2012.


Air pollution around Paris seems to increase lightning activity

Lightning ground flash patterns over Paris area between 1992 and 2003: Influence of pollution? – Coquillat et al. (2012)

Highlights: ► First time lightning data used in France to investigate anthropogenic influence ► General lightning production more intense on Tuesday, Wednesday, and Thursday ► Lightning activity indicative of convection enhanced over Paris (UHI influence) ► Lightning favoured downwind of Paris on Tuesday and Thursday (most worked days) ► High percentage of + CG downwind of Paris during weekend.

Abstract: “12 summers of cloud-to-ground (CG) lightning flashes data over a 200 km × 200 km domain centred on Paris (France) have been analyzed to infer the possible influence of pollution on lightning activity. Lightning flashes densities are calculated on a 5 km × 5 km grid, filtered for discarding extremely high events, and differentiated from week days to week-end days, with a specific insight upwind, over, and downwind Paris. Lightning flashes are more numerous in the North-East part of the domain and increasingly large events progressively concentrate over Paris and over some hills around. The former result indicates a possible influence of pollution on lightning activity downwind of Paris; the latter probably illustrates the influence of the urban heat island and of the relief on the convection strengthening. Furthermore, the number of positive CG flashes is rather uniformly distributed on the whole domain, except in the North-East where it appears somewhat relatively lower meanwhile negative CG are relatively more numerous in that region. This corresponds to a reduction in the percentage of positive CG downwind of Paris. Additionally, lightning activity appears weaker downwind of Paris during weekend days. A specific daily analysis of the lightning density in circles distributed along the direction of prevailing wind through Paris shows that the lightning activity appears higher downwind during the days most worked as Tuesday, Wednesday and Thursday. This higher electric activity persists up to about 40 km on Wednesday, and up to about 80 km on Tuesday and Thursday (most days worked). The electrification seems therefore more important downwind of Paris during the more polluted days.”

Citation: Sylvain Coquillat, Marie-Pierre Boussaton, Magalie Buguet, Dominique Lambert, Jean-François Ribaud, Andy Berthelot, Atmospheric Research, http://dx.doi.org/10.1016/j.atmosres.2012.10.032.


Greenland ice sheet runoff has increased since mid 1980s

Reconstructing Greenland ice sheet runoff using coralline algae – Kamenos et al. (2012)

Abstract: “The Greenland ice sheet (GrIS) contains the largest store of fresh water in the Northern Hemisphere, equivalent to ∼7.4 m of eustatic sea-level rise, but its impacts on current, past, and future sea level, ocean circulation, and European climate are poorly understood. Previous estimates of GrIS melt, from 26 yr of satellite observations and temperature-driven melt models over 48 yr, show increasing melt trends. There are, however, no runoff data of comparable duration with which to validate the relationship between the spatial extent of melting and runoff or temperature-based runoff models. Further, longer runoff records are needed to extend the melt pattern of Greenland to centennial timescales, enabling recent observations and trends to be put into a better historical context. We have developed a new GrIS runoff proxy by extracting information on relative salinity changes from annual growth bands of red coralline algae. We observed significant negative relationships between historic runoff, relative salinity, and marine summer temperature in Søndre Strømfjord, Greenland. We produce the first reconstruction of runoff from a section of the GrIS that discharges into Søndre Strømfjord over several decades (1939–2002) and record a trend of increasing reconstructed runoff since the mid 1980s. In situ summer marine temperatures followed an equivalent trend. We suggest that since A.D. 1939, atmospheric temperatures have been important in forcing runoff. These results show that our technique has significant potential to enhance understanding of runoff from large ice sheets as it will enable melt reconstruction over centennial to millennial timescales.”

Citation: Nicholas A. Kamenos, Trevor B. Hoey, Peter Nienow, Anthony E. Fallick and Thomas Claverie, Geology, v. 40 no. 12 p. 1095-1098, doi: 10.1130/G33405.1.


Multi-annual temperature forecasts in the ECMWF model are reliable

Reliability of decadal predictions – Corti et al. (2012)

Highlights: •A reliability analysis has been applied to probabilistic decadal predictions. •Multi-annual temperature forecasts in the ECMWF model are, in general, reliable. •Long-term climate trends are a major but not the only source of skill.

Abstract: “The reliability of multi-year predictions of climate is assessed using probabilistic Attributes Diagrams for near-surface air temperature and sea surface temperature, based on 54 member ensembles of initialised decadal hindcasts using the ECMWF coupled model. It is shown that the reliability from the ensemble system is good over global land areas, Europe and Africa and for the North Atlantic, Indian Ocean and, to a lesser extent, North Pacific basins for lead times up to 6–9 years. North Atlantic SSTs are reliably predicted even when the climate trend is removed, consistent with the known predictability for this region. By contrast, reliability in the Indian Ocean, where external forcing accounts for most of the variability, deteriorates severely after detrending. More conventional measures of forecast quality, such as the anomaly correlation coefficient (ACC) of the ensemble mean, are also considered, showing that the ensemble has significant skill in predicting multi-annual temperature averages.”

Citation: Corti, S., A. Weisheimer, T. N. Palmer, F. J. Doblas-Reyes, and L. Magnusson (2012), Reliability of decadal predictions, Geophys. Res. Lett., 39, L21712, doi:10.1029/2012GL053354.


How are ecosystems doing in Chernobyl these days?

Ecosystems effects 25 years after Chernobyl: pollinators, fruit set and recruitment – Møller et al. (2012) [FULL TEXT]

Abstract: “Animals are assumed to play a key role in ecosystem functioning through their effects on seed set, seed consumption, seed dispersal, and maintenance of plant communities. However, there are no studies investigating the consequences of animal scarcity on seed set, seed consumption and seed dispersal at large geographical scales. We exploited the unprecedented scarcity of pollinating bumblebees and butterflies in the vicinity of Chernobyl, Ukraine, linked to the effects of radiation on pollinator abundance, to test for effects of pollinator abundance on the ecosystem. There were considerably fewer pollinating insects in areas with high levels of radiation. Fruit trees and bushes (apple Malus domestica, pear Pyrus communis, rowan Sorbus aucuparia, wild rose Rosa rugosa, twistingwood Viburnum lantana, and European cranberry bush Viburnum opulus) that are all pollinated by insects produced fewer fruit in highly radioactively contaminated areas, partly linked to the local reduction in abundance of pollinators. This was the case even when controlling for the fact that fruit trees were generally smaller in more contaminated areas. Fruit-eating birds like thrushes and warblers that are known seed dispersers were less numerous in areas with lower fruit abundance, even after controlling for the effects of radiation, providing a direct link between radiation, pollinator abundance, fruit abundance and abundance of frugivores. Given that the Chernobyl disaster happened 25 years ago, one would predict reduced local recruitment of fruit trees if fruit set has been persistently depressed during that period; indeed, local recruitment was negatively related to the level of radiation and positively to the local level of fruit set. The patterns at the level of trees were replicated at the level of villages across the study site. This study provides the first large-scale study of the effects of a suppressed pollinator community on ecosystem functioning.”

Citation: Anders Pape Møller, Florian Barnier, Timothy A. Mousseau, Oecologia, December 2012, Volume 170, Issue 4, pp 1155-1165, DOI: 10.1007/s00442-012-2374-0.


Trying to see global warming locally

Emerging local warming signals in observational data – Mahlstein et al. (2012)

Highlights: •Significant shift in observed temperatures. •Large parts of the Earth have seen a significant change.

Abstract: “The global average temperature of the Earth has increased, but year-to-year variability in local climates impedes the identification of clear changes in observations and human experience. For a signal to become obvious in data records or in a human lifetime it needs to be greater than the noise of variability and thereby lead to a significant shift in the distribution of temperature. We show that locations with the largest amount of warming may not display a clear shift in temperature distributions if the local variability is also large. Based on observational data only we demonstrate that large parts of the Earth have experienced a significant local shift towards warmer temperatures in the summer season, particularly at lower latitudes. We also show that these regions are similar to those that are found to be significant in standard detection methods, thus providing an approach to link locally significant changes more closely to impacts.”

Citation: Mahlstein, I., G. Hegerl, and S. Solomon (2012), Emerging local warming signals in observational data, Geophys. Res. Lett., 39, L21711, doi:10.1029/2012GL053952.


Temperature of ultimate happiness is 13.9 degrees Celsius

Weather and Individual Happiness – Tsutsui (2012)

Abstract: “This paper investigates the influence of weather on happiness. While previous studies have examined climatic influence by comparing the well-being of people living in different regions, this paper focuses on how daily changes in weather affect individuals living in a single location. Our data set consists of 516 days of data on 75 students from Osaka University. Daily information on outside events, as well as the daily physical condition and individual characteristics of the respondents, are used as controls. Subjective happiness is related to temperature: in a quadratic model, happiness is maximized at 13.9 degrees Celsius. The effects of other meteorological variables—humidity, wind speed, precipitation, and sunshine—are not significant. The sensitivity of happiness to temperature also depends on attributes such as sex, age, and academic department. Happiness is more strongly affected by current temperature than by average temperature over the day. While enjoyment (a positive affect measure) is affected by weather in a similar way to happiness, sadness and depression (negative affect measures) behave somewhat differently.”

Citation: Yoshiro Tsutsui, Weather, Climate, and Society 2012, doi: http://dx.doi.org/10.1175/WCAS-D-11-00052.1.


Recently delayed spring phenology in temperate biomes of China

Consistent shifts in spring vegetation green-up date across temperate biomes in China, 1982–2006 – Wu & Liu (2012) [FULL TEXT]

Abstract: “Understanding spring phenology changes in response to the rapid climate change at biome-level is crucial for projecting regional ecosystem carbon exchange and climate–biosphere interactions. In this study, we assessed the long–term changes and responses to changing climate of the spring phenology in six temperate biomes of China by analyzing the GIMMS NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) and concurrent mean temperature and precipitation data for 1982–2006. Results show that the spring phenology trends in the six temperate biomes are not continuous throughout the 25-year period. The spring phenology in most areas of the six biomes showed obvious advancing trends (ranging from -0.09 to -0.65 day year-1) during the 1980s and early 1990s, but has subsequently suffered consistently delaying trends (ranging from 0.22 to 1.22 day year–1). Changes in spring (February–April) temperature are the dominating factor governing the pattern of spring vegetation phenology in the temperate biomes of China. The recently delayed spring phenology in these temperate biomes has been mainly triggered by the stalling or reversal of the warming trend in spring temperatures. Results in this study also reveal that precipitation during November–January can explain 16.1% (p < 0.05), 20.9% (p < 0.05) and 14.2% (p < 0.05) of the variations in temperate deciduous forest, temperate steppe and temperate desert, respectively, highlighting the important role of winter precipitation in regulating changes in the spring vegetation phenology of water–limited biomes.”

Citation: Xiuchen Wu, Hongyan Liu, Global Change Biology, DOI: 10.1111/gcb.12086.


Past and future sea-level change from the surface mass balance of glaciers

Past and future sea-level change from the surface mass balance of glaciers – Marzeion et al. (2012) [FULL TEXT]

Abstract: “We present estimates of sea-level change caused by the global surface mass balance of glaciers, based on the reconstruction and projection of the surface mass balance of all the individual glaciers of the world, excluding the ice sheets in Greenland and Antarctica. The model is validated using a leave-one-glacier-out cross-validation scheme against 3997 observed surface mass balances of 255 glaciers, and against 756 geodetically observed, temporally integrated volume and surface area changes of 341 glaciers. When forced with observed monthly precipitation and temperature data, the glaciers of the world are reconstructed to have lost mass corresponding to 114 ± 5 mm sea-level equivalent (SLE) between 1902 and 2009. Using projected temperature and precipitation anomalies from 15 coupled general circulation models from the Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble, they are projected to lose an additional 148 ± 35 mm SLE (scenario RCP26), 166 ± 42 mm SLE (scenario RCP45), 175 ± 40 mm SLE (scenario RCP60), or 217 ± 47 mm SLE (scenario RCP85) during the 21st century. Based on the extended RCP scenarios, glaciers are projected to approach a new equilibrium towards the end of the 23rd century, after having lost either 248 ± 66 mm SLE (scenario RCP26), 313 ± 50 mm SLE (scenario RCP45), or 424 ± 46 mm SLE (scenario RCP85). Up until approximately 2100, ensemble uncertainty within each scenario is the biggest source of uncertainty for the future glacier mass loss; after that, the difference between the scenarios takes over as the biggest source of uncertainty. Ice mass loss rates are projected to peak 2040 ∼ 2050 (RCP26), 2050 ∼ 2060 (RCP45), 2070 ∼ 2090 (RCP60), or 2070 ∼ 2100 (RCP85).”

Citation: Marzeion, B., Jarosch, A. H., and Hofer, M.: Past and future sea-level change from the surface mass balance of glaciers, The Cryosphere, 6, 1295-1322, doi:10.5194/tc-6-1295-2012, 2012.


Other studies from last week

Analysis of temporal-spatial variation characteristics of extreme air temperature in Xinjiang, China – Ling et al. (2012)

Spring onset variations and trends in the continental United States: past and regional assessment using temperature-based indices – Schwartz et al. (2012)

Carbon sequestration via wood harvest and storage: An assessment of its harvest potential – Zeng et al. (2012) [FULL TEXT]

Identification of contrasting seasonal sea ice conditions during the Younger Dryas – Cabedo-Sanz et al. (2012)

The changing radiative forcing of fires: global model estimates for past, present and future – Ward et al. (2012) [FULL TEXT]

Ocean temperature response to idealized Gleissberg and de Vries solar cycles in a comprehensive climate model – Seidenglanz et al. (2012)

Oxygen decreases and variability in the eastern equatorial Pacific – Czeschel et al. (2012)

Positive climate feedbacks of soil microbial communities in a semi-arid grassland – Nie et al. (2012)

Brief communication “Historical glacier length changes in West Greenland” – Leclercq et al. (2012) [FULL TEXT]

Estimating the permafrost-carbon-climate response in the CMIP5 climate models using a simplified approach – Burke et al. (2012)

Local genetic adaptation generates latitude-specific effects of warming on predator-prey interactions – de Block et al. (2012)

Holocene tephras highlight complexity of volcanic signals in Greenland ice cores – Coulter et al. (2012)

A cost-efficient method to assess carbon stocks in tropical peat soil – Warren et al. (2012) [FULL TEXT]

Oceanic carbon and water masses during the Mystery Interval: A model-data comparison study – Huiskamp & Meissner (2012)

Carbon dioxide and methane emissions from the Yukon River system – Striegl et al. (2012)

Cold Season Thunderstorms in Finland and Their Effect on Aviation Safety – Mäkelä et al. (2012)

Multidecadal to centennial variability of the AMOC: HadCM3 and a perturbed physics ensemble – Jackson & Vellinga (2012)

The role of oceans and sea ice in abrupt transitions between multiple climate states – Rose et al. (2012)

Modelling coral polyp calcification in relation to ocean acidification – Hohn & Merico (2012) [FULL TEXT]

The carbon count of 2000 years of rice cultivation – Kalbitz et al. (2012)

Contrasting effects of climate change in continental versus oceanic environments on population persistence and micro-evolution of Atlantic salmon – Piou & Prévost (2012)

1,500-year cycle in the Arctic Oscillation identified in Holocene Arctic sea-ice drift – Darby et al. (2012)

Wind-driven trends in Antarctic sea-ice drift – Holland & Kwok (2012)

Observations of increasing carbon dioxide concentration in Earth’s thermosphere – Emmert et al. (2012)

Repetitiveness and underlying characteristics of climatologic parameters in winter – Paskota et al. (2012) [FULL TEXT]

Influence of the Arctic Oscillation on the vertical distribution of clouds as observed by the A-Train constellation of satellites – Devasthale et al. (2012) [FULL TEXT]


CLASSIC OF THE WEEK: Glaisher (1848)

On the Corrections to be Applied to the Monthly Means of Meteorological Observations Taken at Any Hour, to Convert Them into Mean Monthly Values – Glaisher (1848) [FULL TEXT]

Abstract: No abstract. Note that full text might not be freely accessible after November 29, 2012.

Citation: James Glaisher, Phil. Trans. R. Soc. Lond. January 1, 1848 138 125-139; doi:10.1098/rstl.1848.0008.


About this series. When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

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About New research from last week series

Posted by Ari Jokimäki on November 13, 2012

The goal of the New research from last week series is to offer an additional climate research news resource to other news medias. Also, I would like to show that a lot of climate related research is published continuously and that this research is diverse in their study subjects. The New research from last week series does not cover all climate science published in certain week. Below it is briefly discussed what gets included and what doesn’t.

Paper coverage

Papers in the weekly batch are only a minor fraction of all climate related papers that got published in certain week. I have some journals in my RSS feed reader and from their feeds I select those that catch my eye for some reason. The reasons why some paper catches my eye vary from week to week. Sometimes there’s a geographic angle, for example a study from a country that has not been covered in the series before. Sometimes the study subject is so uncommon that I might add it to increase diversity of study subjects.

At the time of writing, there are 76 journals in my feed reader. In a good week, these journals might easily feed me 500 papers. From these I select the 10-20 papers you see each week in the post (or in Facebook or Twitter). Rough calculation shows that I don’t cover more than 5 % of weekly climate research (and the coverage is usually less than that).

There are lot of journals I don’t cover. Some of these are conscious decisions, such as Science, Nature, and PNAS (as an exception, sometimes I do include papers from Nature Geoscience) because their output is mostly from other branches of science and the papers they publish already get publicity from other media. But there are also some other journals missing from my feed reader. I constantly add some journals but there are always some that fly under my radar. Then there are the ones that don’t even have RSS feeds for their new papers, such as Climate Research. I won’t browse journal websites to see if they have published new papers (because that is how I originally did this series and it was very time-consuming). There are also lot of climate related papers published in journals that usually cover some other branches of science and those I won’t notice.

Only peer-reviewed papers are included (with few very rare exceptions).

Paper publication date

I go by my feed reader. Some journals publish in their RSS feeds papers that are in press and some journals publish them only after they have been officially published. So the official publication date is not necessarily from last week. On the other hand, you might see in my batch a paper that you already saw couple of months ago as a pre-print.

Other studies from last week

Originally there were lot of papers that I weren’t sure if I should include them to the weekly batch or not. Many times those papers were left out. Situation was improved with the addition of other studies section. There I can include such papers with little effort and the reader at least gets to know the paper exists.

Classic of the week

In order to be included to the series, the weekly classic needs to have full text freely available online.

Feedback

Is welcome.

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New research from last week 45/2012

Posted by Ari Jokimäki on November 12, 2012

Warming is from human actions even if AMO shows up in Romania. Methane sinking boreal plants and forest bioenergy. Simulating arctic climate, effects of ice retreat, monsoon failure, and future extreme weather. Weather and global warming beliefs, ENSO characteristics, North Greenland ice mass loss. And lots of other stuff.


Forest bioenergy can be used to reduce carbon emissions only in long term

Forest bioenergy at the cost of carbon sequestration? – Vanhala et al. (2012)

Highlights: ► Forest bioenergy can be used to reduce carbon emissions only in long term. ► Forest bioenergy is not carbon neutral if forest carbon stocks or sinks are reduced. ► Climate impacts can be improved by using biomass that decomposes fast in forest.

Abstract: “Bioenergy from forest residues can be used to substitute fossil energy sources and reduce carbon emissions. However, increasing biomass removals from forests reduce carbon stocks and carbon input to litter and soil. The magnitude and timeframe of these changes in the forest carbon balance largely determine how effectively forest biomass reduces greenhouse gas emissions from the energy sector and helps to mitigate climate change. This paper reviews the impacts of harvest-residue-based bioenergy on the carbon balance of forests and discusses aspects linked to the concept of carbon neutrality. This type of forest bioenergy will reduce the emissions in a long run but near-term reductions depend essentially on the longevity of the residues used.”

Citation: Pekka Vanhala, Anna Repo, Jari Liski, Current Opinion in Environmental Sustainability, http://dx.doi.org/10.1016/j.cosust.2012.10.015.


Expected warming due to all human influences since 1950 is very similar to the observed warming

A probabilistic quantification of the anthropogenic component of twentieth century global warming – Wigley & Santer (2012) [FULL TEXT]

Abstract: “This paper examines in detail the statement in the 2007 IPCC Fourth Assessment Report that “Most of the observed increase in global average temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”. We use a quantitative probabilistic analysis to evaluate this IPCC statement, and discuss the value of the statement in the policy context. For forcing by greenhouse gases (GHGs) only, we show that there is a greater than 90 % probability that the expected warming over 1950–2005 is larger than the total amount (not just “most”) of the observed warming. This is because, following current best estimates, negative aerosol forcing has substantially offset the GHG-induced warming. We also consider the expected warming from all anthropogenic forcings using the same probabilistic framework. This requires a re-assessment of the range of possible values for aerosol forcing. We provide evidence that the IPCC estimate for the upper bound of indirect aerosol forcing is almost certainly too high. Our results show that the expected warming due to all human influences since 1950 (including aerosol effects) is very similar to the observed warming. Including the effects of natural external forcing factors has a relatively small impact on our 1950–2005 results, but improves the correspondence between model and observations over 1900–2005. Over the longer period, however, externally forced changes are insufficient to explain the early twentieth century warming. We suggest that changes in the formation rate of North Atlantic Deep Water may have been a significant contributing factor.”

Citation: T. M. L. Wigley, B. D. Santer, Climate Dynamics, November 2012, DOI: 10.1007/s00382-012-1585-8.


Atlantic Multidecadal Oscillation might show in Romania summer temperatures

Multidecadal variability of summer temperature over Romania and its relation with Atlantic Multidecadal Oscillation – Ionita et al. (2012)

Abstract: “We investigate the multidecadal variability of summer temperature over Romania as measured at 14 meteorological stations with long-term observational records. The dominant pattern of summer temperature variability has a monopolar structure and shows pronounced multidecadal variations. A correlation analysis reveals that these multidecadal variations are related with multidecadal variations in the frequency of four daily atmospheric circulation patterns from the North Atlantic region. It is found that on multidecadal time scales, negative summer mean temperature (TT) anomalies are associated with positive sea level pressure (SLP) anomalies centered over the northern part of the Atlantic Ocean and Scandinavia and negative SLP anomalies centered over the northern part of Africa. It is speculated that a possible cause of multidecadal fluctuations in the frequency of these four patterns are the sea surface temperature (SST) anomalies associated to the Atlantic Multidecadal Oscillation (AMO). These results have implications for predicting the evolution of summer temperature over Romania on multidecadal time scales.”

Citation: Monica Ionita, Norel Rimbu, Silvia Chelcea, Simona Patrut, Theoretical and Applied Climatology, November 2012, DOI: 10.1007/s00704-012-0786-8.


Not much changes in ENSO characteristics since mid-19th century

Historical changes in El Niño and La Niña characteristics in an ocean reanalysis – Ray & Giese (2012)

Abstract: “The variation of El Niño Southern Oscillation (ENSO) events from the mid-nineteenth century until the beginning of the twenty-first century is explored using an ocean reanalysis. A comparison of the reanalysis with three sea surface temperature reconstructions shows that the timing of events is similar in all four products, however there are important differences in the strength and location of events. The difference between the reconstructions is sometimes larger than the difference between the reanalysis and a given reconstruction. These differences are larger in the first half of the record, a period for which there are relatively sparse observations. The reanalysis is used to explore decadal variability and trends in the frequency, duration, and propagation direction of ENSO events. There is considerable decadal variability of these ENSO characteristics with the time between events ranging from several months to ten years and the duration of ENSO varying from 5 to 27 months. As has been previously shown for the strength and location of ENSO there is little overall trend in the characteristics. Having a three dimensional representation of the ocean from the reanalysis allows exploration of subsurface changes during ENSO. An analysis of subsurface anomalies shows that during ENSO events the subsurface anomalies are highly correlated with the strength of surface anomalies over the 140 year period. Overall, there is no evidence that there are changes in the strength, frequency, duration, location or direction of propagation of El Niño and La Niña anomalies caused by global warming during the period from 1871 to 2008.”

Citation: Ray, S. and B. S. Giese (2012), Historical changes in El Niño and La Niña characteristics in an ocean reanalysis, J. Geophys. Res., 117, C11007, doi:10.1029/2012JC008031.


Arctic climate simulations of past 1150 years

Arctic climate over the past millennium: Annual and seasonal responses to external forcings – Crespin et al. (2012)

Abstract: “The annual and seasonal temperatures in the Arctic over the past 1150 years are analyzed in simulations performed with the three-dimensional Earth system model of intermediate complexity LOVECLIM forced by changes in solar irradiance, volcanic activity, land use, greenhouse gas concentrations and orbital parameters. The response of the system to individual forcings for each season is examined in order to evaluate the contribution of each forcing to the seasonal contrast. For summer, our results agree relatively well with the reconstruction of Kaufman et al. (2009). Our modelling results suggest that the temperature changes during this period were characterized by large seasonal differences. In particular, while annual mean temperatures display a decreasing trend during the pre-industrial period, spring temperatures appear to rise. The variations in the Earth’s orbital parameters are the main cause for those seasonal differences. Larger climate variations are simulated in autumn compared with the other seasons in response to each forcing, particularly in response to changes in greenhouse gas concentration during the industrial period and in response to land use forcing, which surprisingly has a significant impact on Arctic temperature. These contrasting changes for the different seasons also underline the need for an adequate estimate of the season represented by a proxy.”

Citation: E Crespin, H Goosse, T Fichefet, A Mairesse, Y Sallaz-Damaz, The Holocene November 6, 2012 0959683612463095, doi: 10.1177/0959683612463095.


Monsoon full-season failure becomes much more frequent under future warming in India

A statistically predictive model for future monsoon failure in India – Schewe & Levermann (2012) [FULL TEXT]

Abstract: “Indian monsoon rainfall is vital for a large share of the world’s population. Both reliably projecting India’s future precipitation and unraveling abrupt cessations of monsoon rainfall found in paleorecords require improved understanding of its stability properties. While details of monsoon circulations and the associated rainfall are complex, full-season failure is dominated by large-scale positive feedbacks within the region. Here we find that in a comprehensive climate model, monsoon failure is possible but very rare under pre-industrial conditions, while under future warming it becomes much more frequent. We identify the fundamental intraseasonal feedbacks that are responsible for monsoon failure in the climate model, relate these to observational data, and build a statistically predictive model for such failure. This model provides a simple dynamical explanation for future changes in the frequency distribution of seasonal mean all-Indian rainfall. Forced only by global mean temperature and the strength of the Pacific Walker circulation in spring, it reproduces the trend as well as the multidecadal variability in the mean and skewness of the distribution, as found in the climate model. The approach offers an alternative perspective on large-scale monsoon variability as the result of internal instabilities modulated by pre-seasonal ambient climate conditions.”

Citation: Jacob Schewe and Anders Levermann, 2012 Environ. Res. Lett. 7 044023 doi:10.1088/1748-9326/7/4/044023.


How continental ice retreat affects future global climate

Influence of continental ice retreat on future global climate – Hu et al. (2012)

Abstract: “Evidence from observations indicates a net loss of global land-based ice and a rise of global sea level. Other than sea level rise, it is not clear how this loss of land-based ice could affect other aspects of global climate in the future. Here, we use the Community Climate System Model version 3 to evaluate the potential influence of shrinking land-based ice on the Atlantic meridional overturning circulation (AMOC) and surface climate in the next two centuries under the IPCC A1B scenario with prescribed rates of melting for the Greenland Ice Sheet, Western Antarctic Ice Sheet, and mountain glaciers and ice caps. Results show that the AMOC, in general, is only sensitive to the freshwater discharge directly into the North Atlantic (NA) in the next two centuries. If the loss of the Western Antarctic Ice Sheet would not significant increase from its current rate, it wouldn’t have much effect on the AMOC. The AMOC slows down further only when the surface freshwater input due to runoff from land-based ice melt becomes large enough to generate a net freshwater gain in the upper NA. This further weakened AMOC does not cool the global mean climate, but it does cause less warming, especially in the Northern high latitudes in general and in Europe in particular. The projected precipitation increase in North America in the standard run becomes a net reduction in the simulation that includes land ice runoff. But there are precipitation increases in west Australia in the simulations where the AMOC slows down due to the inclusion of land-based ice runoff.”

Citation: Aixue Hu, Gerald A. Meehl, Weiqing Han, Jianjun Yin, Bingyi Wu, and Masahide Kimoto, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00102.1.


Heat waves and the extreme precipitation are more severe in 2050’s than present climate in Eastern US

Projected changes of extreme weather events in the eastern United States based on a high resolution climate modeling system – Gao et al. (2012) [FULL TEXT]

Abstract: “This study is the first evaluation of dynamical downscaling using the Weather Research and Forecasting (WRF) Model on a 4 km × 4 km high resolution scale in the eastern US driven by the new Community Earth System Model version 1.0 (CESM v1.0). First we examined the global and regional climate model results, and corrected an inconsistency in skin temperature during the downscaling process by modifying the land/sea mask. In comparison with observations, WRF shows statistically significant improvement over CESM in reproducing extreme weather events, with improvement for heat wave frequency estimation as high as 98%. The fossil fuel intensive scenario Representative Concentration Pathway (RCP) 8.5 was used to study a possible future mid-century climate extreme in 2057–9. Both the heat waves and the extreme precipitation in 2057–9 are more severe than the present climate in the Eastern US. The Northeastern US shows large increases in both heat wave intensity (3.05 °C higher) and annual extreme precipitation (107.3 mm more per year).”

Citation: Y Gao et al 2012 Environ. Res. Lett. 7 044025 doi:10.1088/1748-9326/7/4/044025.


Evidence from last interglacial suggests that increased rate of mass loss of North Greenland ice sheet might be expected

Melting of Northern Greenland during the last interglaciation – Born & Nisancioglu (2012) [FULL TEXT]

Abstract: “Using simulated climate data from the comprehensive coupled climate model IPSL CM4, we simulate the Greenland ice sheet (GrIS) during the Eemian interglaciation with the three-dimensional ice sheet model SICOPOLIS. The Eemian is a period 126 000 yr before present (126 ka) with Arctic temperatures comparable to projections for the end of this century. In our simulation, the northeastern part of the GrIS is unstable and retreats significantly, despite moderate melt rates. This result is found to be robust to perturbations within a wide parameter space of key parameters of the ice sheet model, the choice of initial ice temperature, and has been reproduced with climate forcing from a second coupled climate model, the CCSM3. It is shown that the northeast GrIS is the most vulnerable. Even a small increase in melt removes many years of ice accumulation, giving a large mass imbalance and triggering the strong ice-elevation feedback. Unlike the south and west, melting in the northeast is not compensated by high accumulation. The analogy with modern warming suggests that in coming decades, positive feedbacks could increase the rate of mass loss of the northeastern GrIS, exceeding the recent observed thinning rates in the south.”

Citation: Born, A. and Nisancioglu, K. H.: Melting of Northern Greenland during the last interglaciation, The Cryosphere, 6, 1239-1250, doi:10.5194/tc-6-1239-2012, 2012.


Weather affects beliefs about global warming especially for people with conservative political ideology

How do people update? The effects of local weather fluctuations on beliefs about global warming – Deryugina (2012) [FULL TEXT]

Abstract: “Global warming has become a controversial public policy issue in spite of broad scientific consensus that it is real and that human activity is a contributing factor. It is likely that public consensus is also needed to support policies that might counteract it. It is therefore important to understand how people form and update their beliefs about climate change. Using unique survey data on beliefs about the occurrence of the effects of global warming, I estimate how local temperature fluctuations influence what individuals believe about these effects. I find that some features of the updating process are consistent with rational updating. I also test explicitly for the presence of several heuristics known to affect belief formation and find strong evidence for representativeness, some evidence for availability, and no evidence for spreading activation. I find that very short-run temperature fluctuations (1 day–2 weeks) have no effect on beliefs about the occurrence of global warming, but that longer-run fluctuations (1 month–1 year) are significant predictors of beliefs. Only respondents with a conservative political ideology are affected by temperature abnormalities.”

Citation: Tatyana Deryugina, Climatic Change, DOI: 10.1007/s10584-012-0615-1.


Boreal plants seem to be methane sinks

Atmospheric methane removal by boreal plants – Sundqvist et al. (2012)

Highlights: •In situ measurements show that boreal plants are a significant sink of methane.

Abstract: “Several studies have proposed aerobic methane (CH4) emissions by plants. If confirmed, these findings would further increase the imbalance in the global CH4 budget which today underestimates CH4 sinks. Oxidation by OH-radicals in the troposphere is the major identified sink followed by smaller contribution from stratospheric loss and oxidation by methano- and methylotrophic bacteria in soils. This study directly investigated CH4 exchange by plants in their natural environment. At a forest site in central Sweden, in situ branch chamber measurements were used to study plant ambient CH4 exchange by spruce (Picea abies), birch (Betula pubescens), rowan (Sorbus aucuparia) and pine (Pinus sylvestris). The results show a net uptake of CH4 by all the studied plants, which might be of importance for the methane budget.”

Citation: Sundqvist, E., P. Crill, M. Mölder, P. Vestin, and A. Lindroth (2012), Atmospheric methane removal by boreal plants, Geophys. Res. Lett., 39, L21806, doi:10.1029/2012GL053592.


Other studies from last week

On the effect of decreasing CO2 concentration in the atmosphere – Bordi et al. (2012) [FULL TEXT]

Meridional overturning circulation: stability and ocean feedbacks in a box model – Cimatoribus et al. (2012) [FULL TEXT]

Summer temperatures in Europe and land heat fluxes in observation-based data and regional climate model simulations – Stegehuis et al. (2012) [FULL TEXT]

Ecosystem size structure response to 21st century climate projection: large fish abundance decreases in the central North Pacific and increases in the California Current – Woodworth-Jefcoats et al. (2012)

Remote sensing of atmospheric aerosol using spaceborne optical observations – Kokhanovsky (2012)

Greenland ice sheet surface mass balance: evaluating simulations and making projections with regional climate models – Rae et al. (2012) [FULL TEXT]

Relationship between the Pacific and Atlantic stepwise climate change during the 1990s – Chikamoto et al. (2012)

Local people’s accounts of climate change: to what extent are they influenced by the media? – Marin & Berkes (2012)

Ethics and geoengineering: reviewing the moral issues raised by solar radiation management and carbon dioxide removal – Preston (2012)

Aerosol optical depth retrieval in the Arctic region using MODIS data over snow – Mei et al. (2012)

2C or not 2C? – Guivarch & Hallegatte (2012)

Arctic surface temperatures from Metop AVHRR compared to in situ ocean and land data – Dybkjær et al. (2012) [FULL TEXT]

A multi-model study of impacts of climate change on surface ozone in Europe – Langner et al. (2012) [FULL TEXT]

Seasonal forecasts of Arctic sea ice initialized with observations of ice thickness – Lindsay et al. (2012)

Lake highstands in the Pensacola Mountains and Shackleton Range 4300–2250 cal. yr BP: Evidence of a warm climate anomaly in the interior of Antarctica – Hodgson & Bentley (2012)

Complementary explanation of temperature response in the lower atmosphere – Esau et al. (2012) [FULL TEXT]

21st century projections of surface mass balance changes for major drainage systems of the Greenland ice sheet – Tedesco & Fettweis (2012) [FULL TEXT]

Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico – Chanton et al. (2012) [FULL TEXT]

Response of switchgrass yield to future climate change – Tulbure et al. (2012) [FULL TEXT]

Anatomy of an Extreme Event – Hoerling et al. (2012)

Changes in temperature and precipitation extremes observed in Modena, Italy – Boccolari & Malmusi (2012)

European summer surface ozone 1990–2100 – Langner et al. (2012) [FULL TEXT]

Modelling snow accumulation on Greenland in Eemian, glacial inception, and modern climates in a GCM – Punge et al. (2012) [FULL TEXT]

Future change of global monsoon in the CMIP5 – Lee & Wang (2012) [FULL TEXT]

Modeling and understanding persistence of climate variability – Vyushin et al. (2012)


CLASSIC OF THE WEEK: Tyndall (1863)

On the Relation of Radiant Heat to Aqueous Vapour – Tyndall (1863) [FULL TEXT]

Abstract: No abstract. Note that the full text might not be available after November 29, 2012.

Citation: John Tyndall, Phil. Trans. R. Soc. Lond. January 1, 1863 153 1-12; doi:10.1098/rstl.1863.0001.


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 1 Comment »

Papers on wind turbine noise

Posted by Ari Jokimäki on November 6, 2012

This is a list of papers on wind turbine noise. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Update (November 13, 2012): Hubbard & Shepherd (1991), Jakobsen (2005), Pedersen & Larsman (2008), Pedersen et al. (2009), Hessler et al. (2008), Knopper & Ollson (2011), and Bolin et al. (2011) added. Thanks to Martin for pointing these out (in private communication).
Update (November 7, 2012): Taylor et al. (2012) added.

The influence of negative oriented personality traits on the effects of wind turbine noise – Taylor et al. (2012) “Concern about invisible environmental agents from new technologies, such as radiation, radio-waves, and odours, have been shown to act as a trigger for reports of ill health. However, recently, it has been suggested that wind turbines – an archetypal green technology, are a new culprit in explanations of medically unexplained non-specific symptoms (NSS): the so-called Wind Turbine Syndrome (Pierpont, 2009). The current study assesses the effect of negative orientated personality (NOP) traits (Neuroticism, Negative Affectivity and Frustration Intolerance) on the relationship between both actual and perceived noise on NSS. All households near ten small and micro wind turbines in two UK cities completed measures of perceived turbine noise, Neuroticism, Negative Affectivity, Frustration Intolerance, attitude to wind turbines, and NSS (response N = 138). Actual turbine noise level for each household was also calculated. There was no evidence for the effect of calculated actual noise on NSS. The relationship between perceived noise and NSS was only found for individuals high in NOP traits the key role of individual differences in the link between perceived (but not actual) environmental characteristics and symptom reporting. This is the first study to show this effect in relation to a so called ‘green technology’.” Jennifer Taylor, Carol Eastwick, Robin Wilson, Claire Lawrence, Personality and Individual Differences, http://dx.doi.org/10.1016/j.paid.2012.09.018.

Effects of industrial wind turbine noise on sleep and health – Nissenbaum et al. (2012) “Industrial wind turbines (IWTs) are a new source of noise in previously quiet rural environments. Environmental noise is a public health concern, of which sleep disruption is a major factor. To compare sleep and general health outcomes between participants living close to IWTs and those living further away from them, participants living between 375 and 1400 m (n = 38) and 3.3 and 6.6 km (n = 41) from IWTs were enrolled in a stratified cross-sectional study involving two rural sites. Validated questionnaires were used to collect information on sleep quality (Pittsburgh Sleep Quality Index – PSQI), daytime sleepiness (Epworth Sleepiness Score – ESS), and general health (SF36v2), together with psychiatric disorders, attitude, and demographics. Descriptive and multivariate analyses were performed to investigate the effect of the main exposure variable of interest (distance to the nearest IWT) on various health outcome measures. Participants living within 1.4 km of an IWT had worse sleep, were sleepier during the day, and had worse SF36 Mental Component Scores compared to those living further than 1.4 km away. Significant dose-response relationships between PSQI, ESS, SF36 Mental Component Score, and log-distance to the nearest IWT were identified after controlling for gender, age, and household clustering. The adverse event reports of sleep disturbance and ill health by those living close to IWTs are supported.” Michael A Nissenbaum, Jeffery J Aramini, Christopher D Hanning, Noise & Health, 2012, 14, 60, 237-243, DOI: 10.4103/1463-1741.102961.

Infrasound and low frequency noise from wind turbines: exposure and health effects – Bolin et al. (2011) “Wind turbines emit low frequency noise (LFN) and large turbines generally generate more LFN than small turbines. The dominant source of LFN is the interaction between incoming turbulence and the blades. Measurements suggest that indoor levels of LFN in dwellings typically are within recommended guideline values, provided that the outdoor level does not exceed corresponding guidelines for facade exposure. Three cross-sectional questionnaire studies show that annoyance from wind turbine noise is related to the immission level, but several explanations other than low frequency noise are probable. A statistically significant association between noise levels and self-reported sleep disturbance was found in two of the three studies. It has been suggested that LFN from wind turbines causes other, and more serious, health problems, but empirical support for these claims is lacking.” Karl Bolin et al 2011 Environ. Res. Lett. 6 035103 doi:10.1088/1748-9326/6/3/035103. [FULL TEXT]

Health effects and wind turbines: A review of the literature – Knopper & Ollson (2011) “Background: Wind power has been harnessed as a source of power around the world. Debate is ongoing with respect to the relationship between reported health effects and wind turbines, specifically in terms of audible and inaudible noise. As a result, minimum setback distances have been established world-wide to reduce or avoid potential complaints from, or potential effects to, people living in proximity to wind turbines. People interested in this debate turn to two sources of information to make informed decisions: scientific peer-reviewed studies published in scientific journals and the popular literature and internet. Methods: The purpose of this paper is to review the peer-reviewed scientific literature, government agency reports, and the most prominent information found in the popular literature. Combinations of key words were entered into the Thomson Reuters Web of KnowledgeSM and the internet search engine Google. The review was conducted in the spirit of the evaluation process outlined in the Cochrane Handbook for Systematic Reviews of Interventions. Results: Conclusions of the peer reviewed literature differ in some ways from those in the popular literature. In peer reviewed studies, wind turbine annoyance has been statistically associated with wind turbine noise, but found to be more strongly related to visual impact, attitude to wind turbines and sensitivity to noise. To date, no peer reviewed articles demonstrate a direct causal link between people living in proximity to modern wind turbines, the noise they emit and resulting physiological health effects. If anything, reported health effects are likely attributed to a number of environmental stressors that result in an annoyed/stressed state in a segment of the population. In the popular literature, self-reported health outcomes are related to distance from turbines and the claim is made that infrasound is the causative factor for the reported effects, even though sound pressure levels are not measured. Conclusions: What both types of studies have in common is the conclusion that wind turbines can be a source of annoyance for some people. The difference between both types is the reason for annoyance. While it is acknowledged that noise from wind turbines can be annoying to some and associated with some reported health effects (e.g., sleep disturbance), especially when found at sound pressure levels greater than 40 db(A), given that annoyance appears to be more strongly related to visual cues and attitude than to noise itself, self reported health effects of people living near wind turbines are more likely attributed to physical manifestation from an annoyed state than from wind turbines themselves. In other words, it appears that it is the change in the environment that is associated with reported health effects and not a turbine-specific variable like audible noise or infrasound. Regardless of its cause, a certain level of annoyance in a population can be expected (as with any number of projects that change the local environment) and the acceptable level is a policy decision to be made by elected officials and their government representatives where the benefits of wind power are weighted against their cons. Assessing the effects of wind turbines on human health is an emerging field and conducting further research into the effects of wind turbines (and environmental changes) on human health, emotional and physical, is warranted.” Loren D Knopper and Christopher A Ollson, Environmental Health 2011, 10:78 doi:10.1186/1476-069X-10-78. [FULL TEXT]

Evaluating the impact of wind turbine noise on health-related quality of life – Shepherd et al. (2011) “We report a cross-sectional study comparing the health-related quality of life (HRQOL) of individuals residing in the proximity of a wind farm to those residing in a demographically matched area sufficiently displaced from wind turbines. The study employed a nonequivalent comparison group posttest-only design. Self-administered questionnaires, which included the brief version of the World Health Organization quality of life scale, were delivered to residents in two adjacent areas in semirural New Zealand. Participants were also asked to identify annoying noises, indicate their degree of noise sensitivity, and rate amenity. Statistically significant differences were noted in some HRQOL domain scores, with residents living within 2 km of a turbine installation reporting lower overall quality of life, physical quality of life, and environmental quality of life. Those exposed to turbine noise also reported significantly lower sleep quality, and rated their environment as less restful. Our data suggest that wind farm noise can negatively impact facets of HRQOL.” Daniel Shepherd, David McBride, David Welch, Kim N Dirks, Erin M Hill, Noise & Health, 2011, 13, 54, 333-339, DOI: 10.4103/1463-1741.85502. [FULL TEXT]

Low-frequency noise from large wind turbines – Møller & Pedersen (2011) “As wind turbines get larger, worries have emerged that the turbine noise would move down in frequency and that the low-frequency noise would cause annoyance for the neighbors. The noise emission from 48 wind turbines with nominal electric power up to 3.6 MW is analyzed and discussed. The relative amount of low-frequency noise is higher for large turbines (2.3–3.6 MW) than for small turbines (≤ 2 MW), and the difference is statistically significant. The difference can also be expressed as a downward shift of the spectrum of approximately one-third of an octave. A further shift of similar size is suggested for future turbines in the 10-MW range. Due to the air absorption, the higher low-frequency content becomes even more pronounced, when sound pressure levels in relevant neighbor distances are considered. Even when A-weighted levels are considered, a substantial part of the noise is at low frequencies, and for several of the investigated large turbines, the one-third-octave band with the highest level is at or below 250 Hz. It is thus beyond any doubt that the low-frequency part of the spectrum plays an important role in the noise at the neighbors.” Henrik Møller and Christian Sejer Pedersen, J. Acoust. Soc. Am. Volume 129, Issue 6, pp. 3727-3744, http://dx.doi.org/10.1121/1.3543957. [FULL TEXT]

Wind Turbine Noise – Harrison (2011) “Following an introduction to noise and noise regulation of wind turbines, the problem of adverse health effects of turbine noise is discussed. This is attributed to the characteristics of turbine noise and deficiencies in the regulation of this noise. Both onshore and offshore wind farms are discussed.” John P. Harrison, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 256-261, doi: 10.1177/0270467611412549. [FULL TEXT]

The Problems With “Noise Numbers” for Wind Farm Noise Assessment – Thorne (2011) “Human perception responds primarily to sound character rather than sound level. Wind farms are unique sound sources and exhibit special audible and inaudible characteristics that can be described as modulating sound or as a tonal complex. Wind farm compliance measures based on a specified noise number alone will fail to address problems with noise nuisance. The character of wind farm sound, noise emissions from wind farms, noise prediction at residences, and systemic failures in assessment processes are examined. Human perception of wind farm sound is compared with noise assessment measures and complaint histories. The adverse effects on health of persons susceptible to noise from wind farms are examined and a hypothesis, the concept of heightened noise zones (pressure variations), as a marker for cause and effect is advanced. A sound level of LAeq 32 dB outside a residence and above an individual’s threshold of hearing inside the home are identified as markers for serious adverse health effects affecting susceptible individuals. The article is referenced to the author’s research, measurements, and observations at different wind farms in New Zealand and Victoria, Australia.” Bob Thorne, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 262-290, doi: 10.1177/0270467611412557.

The Noise From Wind Turbines: Potential Adverse Impacts on Children’s Well-Being – Bronzaft (2011) “Research linking loud sounds to hearing loss in youngsters is now widespread, resulting in the issuance of warnings to protect children’s hearing. However, studies attesting to the adverse effects of intrusive sounds and noise on children’s overall mental and physical health and well-being have not received similar attention.This, despite the fact that many studies have demonstrated that intrusive noises such as those from passing road traffic, nearby rail systems, and overhead aircraft can adversely affect children’s cardiovascular system, memory, language development, and learning acquisition. While some schools in the United States have received funds to abate intrusive aircraft noise, for example, many schools still expose children to noises from passing traffic and overhead aircraft. Discussion focuses on the harmful effects of noise on children, what has to be done to remedy the situation, and the need for action to lessen the impacts of noise from all sources. Furthermore, based on our knowledge of the harmful effects of noise on children’s health and the growing body of evidence to suggest the potential harmful effects of industrial wind turbine noise, it is strongly urged that further studies be conducted on the impacts of industrial wind turbines on their health, as well as the health of their parents, before forging ahead in siting industrial wind turbines.” Arline L. Bronzaft, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 291-295, doi: 10.1177/0270467611412548. [FULL TEXT]

Infrasound From Wind Turbines Could Affect Humans – Salt & Kaltenbach (2011) “Wind turbines generate low-frequency sounds that affect the ear. The ear is superficially similar to a microphone, converting mechanical sound waves into electrical signals, but does this by complex physiologic processes. Serious misconceptions about low-frequency sound and the ear have resulted from a failure to consider in detail how the ear works. Although the cells that provide hearing are insensitive to infrasound, other sensory cells in the ear are much more sensitive, which can be demonstrated by electrical recordings. Responses to infrasound reach the brain through pathways that do not involve conscious hearing but instead may produce sensations of fullness, pressure or tinnitus, or have no sensation. Activation of subconscious pathways by infrasound could disturb sleep. Based on our current knowledge of how the ear works, it is quite possible that low-frequency sounds at the levels generated by wind turbines could affect those living nearby.” Alec N. Salt, James A. Kaltenbach, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 296-302, doi: 10.1177/0270467611412555.

Properly Interpreting the Epidemiologic Evidence About the Health Effects of Industrial Wind Turbines on Nearby Residents – Phillips (2011) “There is overwhelming evidence that wind turbines cause serious health problems in nearby residents, usually stress-disorder-type diseases, at a nontrivial rate. The bulk of the evidence takes the form of thousands of adverse event reports. There is also a small amount of systematically gathered data. The adverse event reports provide compelling evidence of the seriousness of the problems and of causation in this case because of their volume, the ease of observing exposure and outcome incidence, and case-crossover data. Proponents of turbines have sought to deny these problems by making a collection of contradictory claims including that the evidence does not “count,” the outcomes are not “real” diseases, the outcomes are the victims’ own fault, and that acoustical models cannot explain why there are health problems so the problems must not exist. These claims appeared to have swayed many nonexpert observers, though they are easily debunked. Moreover, though the failure of models to explain the observed problems does not deny the problems, it does mean that we do not know what, other than kilometers of distance, could sufficiently mitigate the effects. There has been no policy analysis that justifies imposing these effects on local residents. The attempts to deny the evidence cannot be seen as honest scientific disagreement and represent either gross incompetence or intentional bias.” Carl V. Phillips, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 303-315, doi: 10.1177/0270467611412554. [FULL TEXT]

Toward a Case Definition of Adverse Health Effects in the Environs of Industrial Wind Turbines: Facilitating a Clinical Diagnosis – McMurtry (2011) “Internationally, there are reports of adverse health effects (AHE) in the environs of industrial wind turbines (IWT). There was multidisciplinary confirmation of the key characteristics of the AHE at the first international symposium on AHE/IWT. The symptoms being reported are consistent internationally and are characterized by crossover findings or a predictable appearance of signs and symptoms present with exposure to IWT sound energy and amelioration when the exposure ceases. There is also a revealed preference of victims to seek restoration away from their homes. This article identifies the need to create a case definition to establish a clinical diagnosis. A case definition is proposed that identifies the sine qua non diagnostic criteria for a diagnosis of adverse health effects in the environs of industrial wind turbines. Possible, probable, and confirmed diagnoses are detailed. The goal is to foster the adoption of a common case definition that will facilitate future research efforts.” Robert Y. McMurtry, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 316-320, doi: 10.1177/0270467611415075. [FULL TEXT]

Industrial Wind Turbine Development and Loss of Social Justice? – Krogh (2011) “This article explores the loss of social justice reported by individuals living in the environs of industrial wind turbines (IWTs). References indicate that some individuals residing in proximity to IWT facilities experience adverse health effects. These adverse health effects are severe enough that some families have abandoned their homes. Individuals report they welcomed IWTs into their community and the negative consequences were unexpected. Expressions of grief are exacerbated by the emotional and physical toll of individuals’ symptoms, loss of enjoyment of homes and property, disturbed living conditions, financial loss, and the lack of society’s recognition of their situation. The author has investigated the reported loss of social justice through a review of literature, personal interviews with, and communications from, those reporting adverse health effects. The author’s intention is to create awareness that loss of social justice is being associated with IWT development. This loss of justice arises from a number of factors, including the lack of fair process, the loss of rights, and associated disempowerment. These societal themes require further investigation. Research by health professionals and social scientists is urgently needed to address the health and social impacts of IWTs operating near family homes.” Carmen M. E. Krogh, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 321-333, doi: 10.1177/0270467611412550.

WindVOiCe, a Self-Reporting Survey: Adverse Health Effects, Industrial Wind Turbines, and the Need for Vigilance Monitoring – Krogh et al. (2011) “Industrial wind turbines have been operating in many parts of the globe. Anecdotal reports of perceived adverse health effects relating to industrial wind turbines have been published in the media and on the Internet. Based on these reports, indications were that some residents perceived they were experiencing adverse health effects. The purpose of the WindVOiCe health survey was to provide vigilance monitoring for those wishing to report their perceived adverse health effects. This article discusses the results of a self reporting health survey regarding perceived adverse health effects associated with industrial wind turbines.” Carmen M.E. Krogh, Lorrie Gillis, Nicholas Kouwen, Jeff Aramini, Bulletin of Science Technology Society August 2011 vol. 31 no. 4 334-345, doi: 10.1177/0270467611412551.

Can road traffic mask sound from wind turbines? Response to wind turbine sound at different levels of road traffic sound – Pedersen et al. (2010) “Wind turbines are favoured in the switch-over to renewable energy. Suitable sites for further developments could be difficult to find as the sound emitted from the rotor blades calls for a sufficient distance to residents to avoid negative effects. The aim of this study was to explore if road traffic sound could mask wind turbine sound or, in contrast, increases annoyance due to wind turbine noise. Annoyance of road traffic and wind turbine noise was measured in the WINDFARMperception survey in the Netherlands in 2007 (n=725) and related to calculated levels of sound. The presence of road traffic sound did not in general decrease annoyance with wind turbine noise, except when levels of wind turbine sound were moderate (35–40 dB(A) Lden) and road traffic sound level exceeded that level with at least 20 dB(A). Annoyance with both noises was intercorrelated but this correlation was probably due to the influence of individual factors. Furthermore, visibility and attitude towards wind turbines were significantly related to noise annoyance of modern wind turbines. The results can be used for the selection of suitable sites, possibly favouring already noise exposed areas if wind turbine sound levels are sufficiently low.” Eja Pedersen, Frits van den Berg, Roel Bakker, Jelte Bouma, Energy Policy, Volume 38, Issue 5, May 2010, Pages 2520–2527, http://dx.doi.org/10.1016/j.enpol.2010.01.001. [FULL TEXT]

Response to noise from modern wind farms in The Netherlands – Pedersen et al. (2009) “The increasing number and size of wind farms call for more data on human response to wind turbine noise, so that a generalized dose-response relationship can be modeled and possible adverse health effects avoided. This paper reports the results of a 2007 field study in The Netherlands with 725 respondents. A dose-response relationship between calculated A-weighted sound pressure levels and reported perception and annoyance was found. Wind turbine noise was more annoying than transportation noise or industrial noise at comparable levels, possibly due to specific sound properties such as a “swishing” quality, temporal variability, and lack of nighttime abatement. High turbine visibility enhances negative response, and having wind turbines visible from the dwelling significantly increased the risk of annoyance. Annoyance was strongly correlated with a negative attitude toward the visual impact of wind turbines on the landscape. The study further demonstrates that people who benefit economically from wind turbines have a significantly decreased risk of annoyance, despite exposure to similar sound levels. Response to wind turbine noise was similar to that found in Sweden so the dose-response relationship should be generalizable.” Eja Pedersen, Frits van den Berg, Roel Bakker, and Jelte Bouma, J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 634-643 (2009), DOI: http://dx.doi.org/10.1121/1.3160293. [FULL TEXT]

The impact of visual factors on noise annoyance among people living in the vicinity of wind turbines – Pedersen & Larsman (2008) “Wind turbines are highly visible objects and the response to wind turbine noise is possibly influenced by visual factors. In this study, visibility of the noise source, visual attitude and vertical visual angle (VVA) in different landscapes were explored. Data from two cross-sectional field studies carried out among people living near wind turbines (n=1095) were used for structural equation modelling. A proposed model of the influence of visual attitude on noise annoyance, also comprising the influence of noise level and general attitude, was tested among respondents who could see vs. respondents who could not see wind turbines from their homes, living in flat vs. hilly/rocky terrain, and living in built-up vs. rural areas. Visual attitude towards the noise source was associated with noise annoyance to different degrees in different situations. A negative visual attitude, more than multi-modal effects between auditory and visual stimulation, enhanced the risk for noise annoyance and possibly also prevented psychophysiological restoration possibilities. Aesthetic evaluations of the noise source should be taken into account when exploring response to environmental noise.” Eja Pedersen, Pernilla Larsman, Journal of Environmental Psychology, Volume 28, Issue 4, December 2008, Pages 379–389, http://dx.doi.org/10.1016/j.jenvp.2008.02.009.

Experimental study to determine wind-induced noise and windscreen attenuation effects on microphone response for environmental wind turbine and other applications – Hessler et al. (2008) “Despite the use of windscreens, the measurement of ambient sound levels or noise emissions in quiet environments can be adversely affected by wind blowing over the microphone. This is especially true when environmental impact assessments are being carried out for proposed wind turbine power projects – where the objective is to determine the level of background masking noise available as a function of wind speed, since any potential noise impact from the project will only occur under moderately windy conditions. Under calm conditions the project will produce no noise at all. A number of windscreen products are commercially available for short and long-term sound level monitoring in adverse weather conditions. Generally, these windscreens vary by physical size and the method of preventing water from reaching the microphone. High frequency attenuation effects are usually available from the product suppliers but, in general, low frequency turbulence effects are not available. Consequently, a controlled laboratory test program was carried out in a state-of-the-art wind tunnel at the Fraunhofer Institut fu¨r Bauphysik in Stuttgart, Germany to quantify the level of low frequency interference (down to 6.3 Hz) associated with a number of different foam windscreens and an aerodynamic microphone nose cone. A total of nine configurations were tested with “quiet“ airflow only, artificial noise only and noise plus airflow to evaluate both low frequency wind induced noise and high frequency attenuation effects. The test program demonstrated that the largest size foam-based windscreens provided the most protection from flow induced noise due to wind. Flow induced noise by air flow alone was estimated from the study results and compared to community noise measurements at a typical wind turbine site. It was determined that flow induced wind noise does not have a significant or detrimental effect on the measurement of A-weighted sound levels under wind conditions of concern as long as the suggested measurement techniques described herein are followed.” Hessler, George F.; Hessler, David M.; Brandsta¨tt, Peter; Bay, Karlheinz, Noise Control Engineering Journal, Volume 56, Number 4, 1 July 2008 , pp. 300-309(10), DOI: http://dx.doi.org/10.3397/1.2949926.

Wind turbine noise, annoyance and self-reported health and well-being in different living environments – Pedersen & Waye (2007) “Objectives: To evaluate the prevalence of perception and annoyance due to wind turbine noise among people living near the turbines, and to study relations between noise and perception/annoyance, with focus on differences between living environments. Methods: A cross-sectional study was carried out in seven areas in Sweden across dissimilar terrain and different degrees of urbanisation. A postal questionnaire regarding living conditions including response to wind turbine noise was completed by 754 subjects. Outdoor A-weighted sound pressure levels (SPLs) were calculated for each respondent. Perception and annoyance due to wind turbine noise in relation to SPLs was analysed with regard to dissimilarities between the areas. Results: The odds of perceiving wind turbine noise increased with increasing SPL (OR 1.3; 95% CI 1.25 to 1.40). The odds of being annoyed by wind turbine noise also increased with increasing SPLs (OR 1.1; 95% CI 1.01 to 1.25). Perception and annoyance were associated with terrain and urbanisation: (1) a rural area increased the risk of perception and annoyance in comparison with a suburban area; and (2) in a rural setting, complex ground (hilly or rocky terrain) increased the risk compared with flat ground. Annoyance was associated with both objective and subjective factors of wind turbine visibility, and was further associated with lowered sleep quality and negative emotions. Conclusion: There is a need to take the unique environment into account when planning a new wind farm so that adverse health effects are avoided. The influence of area-related factors should also be considered in future community noise research.” Eja Pedersen, Kerstin Persson Waye, Occup Environ Med 2007;64:480-486, doi:10.1136/oem.2006.031039. [FULL TEXT]

Living in the Vicinity of Wind Turbines — A Grounded Theory Study – Pedersen et al. (2007) “Little is known of wind turbines’ impact on people living in their vicinity. The aim of this study was to gain a deeper understanding of how people perceive and are affected by wind turbines in their living environment. In-depth interviews with 15 informants, strategically chosen to form a heterogeneous group, were analyzed using the constant comparative method of grounded theory. The informants were to different extents affected by the swishing noise, flickering light, and constant movement of the turbines’ rotor blades. Some informants perceived the exposures as outside their territory while others perceived them as intrusion into privacy; a divergence partly determined by the informants’ personal values about the living environment. The feeling of intrusion was associated with feeling a lack of control, subjected to injustice, a lack of influence, and not being believed. Informants used various coping strategies, such as rebuilding their houses or complaining, but mainly tried to ignore exposures from the wind turbines. The findings can help us to better understand the severe reactions wind turbines sometimes evoke and contribute to the knowledge base used when planning for new wind farms.” E. Pedersen, LR-M. Hallberg & K.P. Waye, Qualitative Research in Psychology, Volume 4, Issue 1-2, 2007, DOI:10.1080/14780880701473409.

Perception of low-frequency acoustic signals by a harbour porpoise (Phocoena phocoena) in the presence of simulated offshore wind turbine noise – Lucke et al. (2007) “Using auditory evoked potential (AEP) methods, a study was conducted on a harbour porpoise (Phocoena phocoena) at the Dolfinarium Harderwijk in The Netherlands. The study measured the audible range of wind turbine sounds and their potential masking effects on the acoustic perception of the animal. AEPs were evoked with two types of acoustic stimuli: (1) click-type signals and (2) amplitude-modulated signals. The masking noise resembling the underwater sound emissions of an operational wind turbine was simulated. At first, the animal’s hearing threshold was measured at frequencies between 0.7 and 16 kHz. Subsequently, these measurements were repeated at frequencies between 0.7 and 2.8 kHz in the presence of two different levels of masking noise. The resulting data show a masking effect of the simulated wind turbine sound at 128 dB re 1 μPa at 0.7, 1.0, and 2.0 kHz. This masking effect varied between 4.8 and 7.3 dB at those frequencies. No significant masking was measured at a masking level of 115 dB re 1 μPa. The available data indicate that the potential masking effect would be limited to short ranges in the open sea, but limitations exist to this conclusion and all estimates are based on existing turbine types, not taking into account future developments of larger and potentially noisier turbine types.” Lucke, Klaus, Lepper, Paul A., Hoeve, Bert, Everaarts, Eligius, van Elk, Niels, Siebert, Ursula, Aquatic Mammals, 33 (1), pp. 55-68, DOI 10.1578/AM.33.1.2007.55. [FULL TEXT]

Location and quantification of noise sources on a wind turbine – Oerlemans et al. (2007) “Acoustic field measurements were carried out on a three-bladed wind turbine with a rotor diameter of 58 m, in order to characterize the noise sources and to verify whether trailing edge noise from the blades was dominant. To assess the effect of blade roughness, one blade was cleaned, one blade was tripped, and one blade remained untreated. A large horizontal microphone array, positioned about one rotor diameter upwind from the turbine, was used to measure the distribution of the noise sources in the rotor plane and on the individual blades. The operation parameters of the turbine were recorded in parallel to the acoustic tests. In total more than 100 measurements were performed at wind speeds between 6 and 10 m/s. The array results reveal that besides a minor source at the rotor hub, practically all noise (emitted to the ground) is produced during the downward movement of the blades. This strongly asymmetric source pattern can be explained by convective amplification and trailing edge noise directivity. The blade noise is produced at the outer part of the blades (but not at the very tip), and the level scales with the fifth power of the local flow speed. Comparison of the noise from the individual blades shows that the tripped blade is significantly noisier than the other two. Narrowband analysis of the de-dopplerized blade noise spectra indicates that trailing edge bluntness noise is not important. All in all, the test results convincingly show that broadband trailing edge noise is the dominant noise source for this wind turbine.” S. Oerlemans, P. Sijtsma, B. Méndez López, Journal of Sound and Vibration, Volume 299, Issues 4–5, 6 February 2007, Pages 869–883, http://dx.doi.org/10.1016/j.jsv.2006.07.032.

Wind turbine underwater noise and marine mammals: implications of current knowledge and data needs – Madsen et al. (2006) “The demand for renewable energy has led to construction of offshore wind farms with high-power turbines, and many more wind farms are being planned for the shallow waters of the world’s marine habitats. The growth of offshore wind farms has raised concerns about their impact on the marine environment. Marine mammals use sound for foraging, orientation and communication and are therefore possibly susceptible to negative effects of man-made noise generated from constructing and operating large offshore wind turbines. This paper reviews the existing literature and assesses zones of impact from different noise-generating activities in conjunction with wind farms on 4 representative shallow-water species of marine mammals. Construction involves many types of activities that can generate high sound pressure levels, and pile-driving seems to be the noisiest of all. Both the literature and modeling show that pile-driving and other activities that generate intense impulses during construction are likely to disrupt the behavior of marine mammals at ranges of many kilometers, and that these activities have the potential to induce hearing impairment at close range. The reported noise levels from operating wind turbines are low, and are unlikely to impair hearing in marine mammals. The impact zones for marine mammals from operating wind turbines depend on the low-frequency hearing-abilities of the species in question, on sound-propagation conditions, and on the presence of other noise sources such as shipping. The noise impact on marine mammals is more severe during the construction of wind farms than during their operation.” P. T. Madsen, M. Wahlberg, J. Tougaard, K. Lucke, P. Tyack, Marine Ecology Progress Series, 309:279-295 (2006), doi:10.3354/meps309279. [FULL TEXT]

Infrasound Emission from Wind Turbines – Jakobsen (2005) “A critical survey of all known published measurement results of infrasound from wind turbines has been made. The survey indicates that wind turbines of contemporary design with an upwind rotor generate very faint infrasound with a level far below the threshold of perception even at a rather short distance. From considerations on propagation and transmission of infrasound it is concluded that infrasound from such upwind turbines can be neglected when evaluating the environment effects of wind turbines. Turbines with downwind rotors produce 10 – 30 dB higher infrasound levels, and these may exceed relevant assessment criteria for dwellings in the immediate neighbourhood. When longer distances are considered, neither downwind nor upwind turbines are capable of violating assessment criteria for infrasound. This paper considers whether other aspects of the noise than the infrasound can explain the indicated adverse public reactions to large downwind turbines.” Jørgen Jakobsen, Low Frequency Noise, Vibration and Active Control, Volume 24, Number 3 / September 2005, DOI: 10.1260/026309205775374451. [FULL TEXT]

Perception and annoyance due to wind turbine noise—a dose–response relationship – Pedersen & Waye (2004) “Installed global wind power increased by 26% during 2003, with U.S and Europe accounting for 90% of the cumulative capacity. Little is known about wind turbines’ impact on people living in their vicinity. The aims of this study were to evaluate the prevalence of annoyance due to wind turbine noise and to study dose–response relationships. Interrelationships between noise annoyance and sound characteristics, as well as the influence of subjective variables such as attitude and noise sensitivity, were also assessed. A cross-sectional study was performed in Sweden in 2000. Responses were obtained through questionnaires (n = 351; response rate 68.4%), and doses were calculated as A-weighted sound pressure levels for each respondent. A statistically significant dose–response relationship was found, showing higher proportion of people reporting perception and annoyance than expected from the present dose–response relationships for transportation noise. The unexpected high proportion of annoyance could be due to visual interference, influencing noise annoyance, as well as the presence of intrusive sound characteristics. The respondents’ attitude to the visual impact of wind turbines on the landscape scenery was found to influence noise annoyance.” Eja Pedersen and Kerstin Persson Waye, J. Acoust. Soc. Am. Volume 116, Issue 6, pp. 3460-3470, http://dx.doi.org/10.1121/1.1815091. [FULL TEXT]

Effects of the wind profile at night on wind turbine sound – van den Berg (2004) “Since the start of the operation of a 30 MW, 17 turbine wind park, residents living 500 m and more from the park have reacted strongly to the noise; residents up to 1900 m distance expressed annoyance. To assess actual sound immission, long term measurements (a total of over 400 night hours in 4 months) have been performed at 400 and 1500 m from the park. In the original sound assessment a fixed relation between wind speed at reference height (10 m) and hub height (98 m) had been used. However, measurements show that the wind speed at hub height at night is up to 2.6 times higher than expected, causing a higher rotational speed of the wind turbines and consequentially up to 15 dB higher sound levels, relative to the same reference wind speed in daytime. Moreover, especially at high rotational speeds the turbines produce a ‘thumping’, impulsive sound, increasing annoyance further. It is concluded that prediction of noise immission at night from (tall) wind turbines is underestimated when measurement data are used (implicitly) assuming a wind profile valid in daytime.” G.P. van den Berg, Journal of Sound and Vibration, Volume 277, Issues 4–5, 5 November 2004, Pages 955–970, http://dx.doi.org/10.1016/j.jsv.2003.09.050.

Psycho-acoustic characters of relevance for annoyance of wind turbine noise – Waye & Öhrström (2002) “The knowledge of annoyance and perception of wind turbine noise is limited, although some previous studies have found that the relationship between the equivalent noise level and annoyance was weak. The hypothesis for this study was that different sound characters in the noise not fully described by the equivalent noise level, are of importance for annoyance and noise perception. In total, 25 subjects were exposed to five different wind turbine noises at the level of 40 dBLAeq. Subjective ratings of annoyance, relative annoyance and for how long they were aware of the noises were carried out after 10 min exposures. This was followed by 3 min exposures where perception and annoyance of 14 psycho-acoustic descriptors were evaluated. The results showed that the rating of annoyance, relative annoyance and awareness was different between the wind turbine noises, although they had the same equivalent noise level. A psycho-acoustic profile was obtained for each noise, which subjectively described the most and the least annoying sound parameters. None of the psycho-acoustic parameters, sharpness, loudness, roughness, fluctuation strength or modulation could explain the differences in annoyance response.” K.Persson Waye, E. Öhrström, Journal of Sound and Vibration, Volume 250, Issue 1, 7 February 2002, Pages 65–73, http://dx.doi.org/10.1006/jsvi.2001.3905.

Aeroacoustics of large wind turbines – Hubbard & Shepherd (1991) “This paper reviews published information on aerodynamically generated noise from large horizontal axis wind turbines operated for electric power generation. Methods are presented for predicting both the discrete frequency rotational noise components and the broadband noise components, and results are compared with measurements. Refraction effects that result in the formation of high-frequency shadow zones in the upwind direction and channeling effects for the low frequencies in the downwind direction are illustrated. Special topics such as distributed source effects in prediction and the role of building dynamics in perception are also included. © 1991 Acoustical Society of America.” Harvey H. Hubbard and Kevin P. Shepherd, J. Acoust. Soc. Am. Volume 89, Issue 6, pp. 2495-2508 (1991), http://dx.doi.org/10.1121/1.401021.

Noise characteristics of large wind turbine generators – Hubbard et al. (1983) “Data on wind turbine noise taken from the large wind turbines, the Mod-OA, Mod-1, and Mod-2, are examined for guides to developing a predictive model for wind turbine noise. Data were taken on the pressure time histories, the narrowband spectra, the one-third octave band spectra, and the overall linear and A-weighted noise levels. A thumping noise recorded upstream from the Mod-1 was due to the encounter of the downwind turning blades with the tower wake. The upwind Mod-2 caused broadband noise with peaks at 800 Hz, caused by interactions of turbulent boundary layers with the blade trailing edges. Amplitude modulation of the overall pressure time history was associated with a periodic swishing noise. Some noises were machine specific; however, the low frequency loading was directed upwind and downwind from the rotors in all machines, while the broadband noise was nondirectional. The wind velocity gradient elongated the noise downwind and shortened it upwind. Wake acoustic measurements of two of the Mod-2 machines indicated that the wake does not affect the acoustic output of one Mod-2 downwind from the other. Finally, evidence was found for random phase adding of broadband noise five rotors downstream.” Hubbard, H H, Grosveld, F W, Shepherd, K P, Noise Control Engineering Journal (ISSN 0736-2501), vol. 21, July-Aug. 1983, p. 21-29.

Posted in Adaptation & Mitigation | 4 Comments »

New research from last week 44/2012

Posted by Ari Jokimäki on November 5, 2012

In this week’s edition we see that mankind has warmed climate in Tibet, Greenland west coast, upper troposphere, and in oceans. Sea levels have been rising since 1920’s, and the rise seems to continue into the future. Climate warming melts sea ice which fools ocean life temporally. Also Chinese vegetation has got fooled by warming. We continue emitting greenhouse gases such as nitrous oxide. We also find out that scientists are not alarmists, but why do I always feel like an alarmist when I just report what their studies say?


When did modern rates of sea-level rise start?

When did modern rates of sea-level rise start? – Gehrels & Woodworth (2012)

Abstract: “Accelerations and inflexions in recent sea-level records are known from instrumental (tidegauge) datasets, but such records are generally too short to shed light on the question when modern rapid rates of sea-level rise commenced. Proxy sea-level records should therefore also be considered. In this review we compare recent proxy and instrumental sea-level records from the North Atlantic, Australia and New Zealand with the long-term (linear) rate of relative sea-level change that prevailed in the centuries and millennia before the 19th century. We re-evaluate dating models that underpin many of the proxy records and only consider published sea-level index points for which a reliable age can be firmly established. For seven coastal sites we determine the start of recent rapid sea-level rise by identifying the time when sea-level rise first departed from the long-term background rate. We find that within a 40 year period, centred around 1925, sea-level rise in all sites started to exceed the late Holocene background rate. This is consistent with local tide-gauge records and also with global and regional tide-gauge compilations. We conclude that proxy and instrumental sea-level datasets record a similar 20th century inflexion. Possible mismatches identified in published literature are therefore reconciled. We suggest that northern hemisphere ice melt, primarily from the Greenland Ice Sheet and small Arctic glaciers, is the main driving mechanism of early 20th century sea-level rise.”

Citation: W. Roland Gehrels, Philip L. Woodworth, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.10.020.


Spring vegetation green-up onset date has advanced in China

Changes in satellite-derived spring vegetation green-up date and its linkage to climate in China from 1982 to 2010: a multi-method analysis – Cong et al. (2012)

Abstract: “The change in spring phenology is recognized to exert a major influence on carbon balance dynamics in temperate ecosystems. Over the past several decades, several studies focused on shifts in spring phenology; however, large uncertainties still exist, and one under-studied source could be the method implemented in retrieving satellite-derived spring phenology. To account for this potential uncertainty, we conducted a multi-method investigation to quantify changes in vegetation green-up date from 1982 to 2010 over temperate China, and to characterize climatic controls on spring phenology. Over temperate China, the five methods estimated that the vegetation green-up onset date advanced, on average, at a rate of 1.3 ± 0.6 days per decade (ranging from 0.4 to 1.9 days per decade) over the last 29 years. Moreover, the sign of the trends in vegetation green-up date derived from the five methods were broadly consistent spatially and for different vegetation types, but with large differences in the magnitude of the trend. The large inter-method variance was notably observed in arid and semi-arid vegetation types. Our results also showed that change in vegetation green-up date is more closely correlated with temperature than with precipitation. However, the temperature sensitivity of spring vegetation green-up date became higher as precipitation increased, implying that precipitation is an important regulator of the response of vegetation spring phenology to change in temperature. This intricate linkage between spring phenology and precipitation must be taken into account in current phenological models which are mostly driven by temperature.”

Citation: Nan Cong, Tao Wang, Huijuan Nan, Yuecun Ma, Xuhui Wang, Ranga B. Myneni, Shilong Piao, Global Change Biology, DOI: 10.1111/gcb.12077.


Sea ice phenology affects biological phenology in the ocean

Sea ice phenology and timing of primary production pulses in the Arctic Ocean – Ji et al. (2012)

Abstract: “Arctic organisms are adapted to the strong seasonality of environmental forcing. A small timing mismatch between biological processes and the environment could potentially have significant consequences for the entire food web. Climate warming causes shrinking ice coverage and earlier ice retreat in the Arctic, which is likely to change the timing of primary production. In this study, we test predictions on the interactions among sea ice phenology and production timing of ice algae and pelagic phytoplankton. We do so using 1) a synthesis of available satellite observation data; and 2) the application of a coupled ice-ocean ecosystem model. The data and model results suggest that, over a large portion of the Arctic marginal seas, the timing variability of ice retreat at a specific location has a strong impact on the timing variability of pelagic phytoplankton peaks but weak or no impact on the timing of ice-algae blooms in those regions. The model predicts latitudinal and regional differences in the timing of ice algae biomass peak (varying from April to May) and the time lags between ice algae and pelagic phytoplankton peaks (varying from 45 to 90 days). The correlation between the time lag and ice retreat is significant in areas where ice retreat has no significant impact on ice-algae peak timing, suggesting that changes in pelagic phytoplankton peak timing control the variability of time lags. Phenological variability of primary production is likely to have consequences for higher trophic levels, particularly for the zooplankton grazers, whose main food source is composed of the dually pulsed algae production of the Arctic.”

Citation: Rubao Ji, Meibing Jin, Øystein Varpe, Global Change Biology, DOI: 10.1111/gcb.12074.


There is a human fingerprint in ocean’s salinity and temperature fields

The fingerprint of human-induced changes in the ocean’s salinity and temperature fields – Pierce et al. (2012)

Highlights: •Climate change has altered the salinity field of the world’s oceans. •Changes match model predictions over the top 125 m. •The signal is even stronger when salinity is taken jointly with temperature.

Abstract: “The ocean’s salinity field is driven primarily by evaporation, precipitation, and river discharge, all key elements of the Earth’s hydrological cycle. Observations show the salinity field has been changing in recent decades. We perform a formal fingerprint-based detection and attribution analysis of these changes between 1955–2004, 60°S and 60°N, and in the top 700 m of the water column. We find that observed changes are inconsistent with the effects of natural climate variability, either internal to the climate system (such as El Niño and the Pacific Decadal Oscillation) or external (solar fluctuations and volcanic eruptions). However, the observed changes are consistent with the changes expected due to human forcing of the climate system. Joint changes in salinity and temperature yield a stronger signal of human effects on climate than either salinity or temperature alone. When examining individual depth levels, observed salinity changes are unlikely (p < 0.05) to have arisen from natural causes over the top 125 m of the water column, while temperature changes (and joint salinity/temperature changes) are distinct from natural variability over the top 250 m.”

Citation: Pierce, D. W., P. J. Gleckler, T. P. Barnett, B. D. Santer, and P. J. Durack (2012), The fingerprint of human-induced changes in the ocean’s salinity and temperature fields, Geophys. Res. Lett., 39, L21704, doi:10.1029/2012GL053389.


A half-million-year record of paleoclimate from Lake Manix, California

A half-million-year record of paleoclimate from the Lake Manix Core, Mojave Desert, California – Reheis et al. (2012)

Highlights: ► We obtained a 45-m core from Lake Manix, former terminus of the Mojave River ~ 475–25 ka. ► Lake Manix persisted from OIS 12 through early OIS 2, except during interglacial OIS 11. ► Ostracode faunas record a surprising summer-dominated hydrology only during OIS 12. ► Highly variable stable isotopes buffered by evaporation persist in interglacials and glacials. ► Internal drainage-basin changes also affected the isotopic record.

Abstract: “Pluvial lakes in the southwestern U.S. responded sensitively to past climate through effects on rainfall, runoff, and evaporation. Although most studies agree that pluvial lakes in the southwestern U.S. reached their highest levels coeval with glacial stages, the specific timing of increased effective moisture and lake-level rise is debated, particularly for the southwesternmost lakes. We obtained a 45-m core of lacustrine sediment from Lake Manix, the former terminus of the Mojave River prior to about 25 ka, and supplemented data from the core with outcrop studies. These sediments provide a robust record of Mojave River discharge over the last half-million years. Lake Manix persisted from OIS 12 through early OIS 2, including during interstadial OIS 3 and interglacials OIS 5, 7, and 9. The ostracode faunal record displays a shift from an unexpectedly warm, summer-dominated lake hydrology during OIS 12 to predominantly colder, winter-dominated conditions afterwards. The ostracode-based stable isotope record displays a large degree of intra-sample variability and does not mimic other well-known isotopic records of climate change. Evaporation likely buffered the Manix δ18O record from most of the expected isotopic differences between interglacial and glacial-interval discharge. Isotopically depleted and stable lakes occurred only four to six times, most notably during OIS 7 and OIS 9. Internal drainage-basin changes also affected the isotopic record. Persistence of lakes in the Manix basin during interglacials requires atmospheric or oceanic circulation controls on the mean position of the Pacific storm track other than large ice sheets. We propose that the relative strength and sign of the Northern Annular Mode (NAM) and its influence on atmospheric river-derived precipitation is a potential explanation.”

Citation: Marith C. Reheis, Jordon Bright, Steve P. Lund, David M. Miller, Gary Skipp, Robert J. Fleck, Palaeogeography, Palaeoclimatology, Palaeoecology, Volumes 365–366, 1 December 2012, Pages 11–37, http://dx.doi.org/10.1016/j.palaeo.2012.09.002.


Climate scientists are not alarmists but have underestimated recent climate changes

Climate change prediction: Erring on the side of least drama? – Brysse et al. (2012)

Highlights: ► Climate scientists are not alarmists but have underestimated recent climate changes. ► We identify a directional bias toward erring on the side of least drama (ESLD). ► ESLD is an internal pressure arising from norms of objectivity, restraint, etc. ► ESLD may cause scientists to underpredict or downplay future climate changes.

Abstract: “Over the past two decades, skeptics of the reality and significance of anthropogenic climate change have frequently accused climate scientists of “alarmism”: of over-interpreting or overreacting to evidence of human impacts on the climate system. However, the available evidence suggests that scientists have in fact been conservative in their projections of the impacts of climate change. In particular, we discuss recent studies showing that at least some of the key attributes of global warming from increased atmospheric greenhouse gases have been under-predicted, particularly in IPCC assessments of the physical science, by Working Group I. We also note the less frequent manifestation of over-prediction of key characteristics of climate in such assessments. We suggest, therefore, that scientists are biased not toward alarmism but rather the reverse: toward cautious estimates, where we define caution as erring on the side of less rather than more alarming predictions. We call this tendency “erring on the side of least drama (ESLD).” We explore some cases of ESLD at work, including predictions of Arctic ozone depletion and the possible disintegration of the West Antarctic ice sheet, and suggest some possible causes of this directional bias, including adherence to the scientific norms of restraint, objectivity, skepticism, rationality, dispassion, and moderation. We conclude with suggestions for further work to identify and explore ESLD.”

Citation: Hou Guangliang, E Chongyi, Liu Xiangjun, Zeng Fangming, Theoretical and Applied Climatology, October 2012, DOI: 10.1007/s00704-012-0783-y.


Late 20th century temperatures highest of last 2000 years in Tibetan Plateau

Reconstruction of integrated temperature series of the past 2,000 years on the Tibetan plateau with 10-year intervals – Guangliang et al. (2012) [FULL TEXT]

Abstract: “Using 1,981 pieces of temperature records extracted from a selection of tree rings, ice cores, sediments, and other materials with high-resolution historical temperature proxy data, a temperature series of the past 2,000 years on the Tibetan Plateau (TP) with 10-year intervals was reconstructed by the method of single sample correction—multi-sample average integration equations. This series shows that the warm periods mainly appeared before 235 A.D., 775–1275 A.D. and 1845–2000 A.D., while the cold periods occurred 245–765 A.D., 1045–1145 A.D., and 1285–1835 A.D. The Little Ice Age left clear evidence on the TP and its coldest period was between 1635 and 1675 A.D. The Medieval Warm Period on the TP was not as warm as that in the late twentieth century. During the nineteenth century, overall temperature tends to be warmer with a clear rising trend, and in the late twentieth century new highs broke the record of the past 2,000 years. Power spectrum analysis shows that temperature on the TP changes consistently and evidently in a 150-year cycle. This integrated series also shows clear correlations with sunspot activity and solar radiation, as high sunspot activities generally led to warmer periods, and vice versa. Solar activities and intense radiation of recent years are naturally conducive to the global warming since the nineteenth century. The combination of greenhouse gases and natural fluctuations in climate has been the main culprit behind the global warming in the twentieth century.”

Citation: Hou Guangliang, E Chongyi, Liu Xiangjun, Zeng Fangming, Theoretical and Applied Climatology, October 2012, DOI: 10.1007/s00704-012-0783-y.


Model-observational difference for tropical upper tropospheric warming – biases in GCMs, observational datasets, or both?

Discrepancies in tropical upper tropospheric warming between atmospheric circulation models and satellites – Po-Chedley & Fu (2012) [FULL TEXT]

Abstract: “Recent studies have examined tropical upper tropospheric warming by comparing coupled atmosphere–ocean global circulation model (GCM) simulations from Phase 3 of the Coupled Model Intercomparison Project (CMIP3) with satellite and radiosonde observations of warming in the tropical upper troposphere relative to the lower-middle troposphere. These studies showed that models tended to overestimate increases in static stability between the upper and lower-middle troposphere. We revisit this issue using atmospheric GCMs with prescribed historical sea surface temperatures (SSTs) and coupled atmosphere–ocean GCMs that participated in the latest model intercomparison project, CMIP5. It is demonstrated that even with historical SSTs as a boundary condition, most atmospheric models exhibit excessive tropical upper tropospheric warming relative to the lower-middle troposphere as compared with satellite-borne microwave sounding unit measurements. It is also shown that the results from CMIP5 coupled atmosphere–ocean GCMs are similar to findings from CMIP3 coupled GCMs. The apparent model-observational difference for tropical upper tropospheric warming represents an important problem, but it is not clear whether the difference is a result of common biases in GCMs, biases in observational datasets, or both.”

Citation: Stephen Po-Chedley and Qiang Fu 2012 Environ. Res. Lett. 7 044018 doi:10.1088/1748-9326/7/4/044018.


Nitrous oxide emissions from the global agricultural nitrogen cycle

N2O emissions from the global agricultural nitrogen cycle – current state and future scenarios – Bodirsky et al. (2012) [FULL TEXT]

Abstract: “Reactive nitrogen (Nr) is not only an important nutrient for plant growth, thereby safeguarding human alimentation, but it also heavily disturbs natural systems. To mitigate air, land, aquatic, and atmospheric pollution caused by the excessive availability of Nr, it is crucial to understand the long-term development of the global agricultural Nr cycle. For our analysis, we combine a material flow model with a land-use optimization model. In a first step we estimate the state of the Nrcycle in 1995. In a second step we create four scenarios for the 21st century in line with the SRES storylines. Our results indicate that in 1995 only half of the Nr applied to croplands was incorporated into plant biomass. Moreover, less than 10 per cent of all Nr in cropland plant biomass and grazed pasture was consumed by humans. In our scenarios a strong surge of the Nr cycle occurs in the first half of the 21st century, even in the environmentally oriented scenarios. Nitrous oxide (N2O) emissions rise from 3 Tg N2O-N in 1995 to 7–9 in 2045 and 5–12 Tg in 2095. Reinforced Nr pollution mitigation efforts are therefore required.”

Citation: Bodirsky, B. L., Popp, A., Weindl, I., Dietrich, J. P., Rolinski, S., Scheiffele, L., Schmitz, C., and Lotze-Campen, H.: N2O emissions from the global agricultural nitrogen cycle – current state and future scenarios, Biogeosciences, 9, 4169-4197, doi:10.5194/bg-9-4169-2012, 2012.


Study finds very strong recent warming along the west coast of Greenland

Recent warming in Greenland in a long-term instrumental (1881–2012) climatic context: I. Evaluation of surface air temperature records – Hanna et al. (2012) [FULL TEXT]

Abstract: “We present an updated analysis of monthly means of daily mean, minimum and maximum surface air temperature (SAT) data from Greenland coastal weather stations and from a long-running site on the Greenland ice sheet, and analyse these data for evidence of climate change, especially focusing on the last 20 years but using the whole periods of available records (some since 1873). We demonstrate very strong recent warming along the west coast of Greenland, especially during winter (locally >10 °C since 1991), and rather weaker warming on the east Greenland coast, which is influenced by different oceanographic/sea-ice and meteorological synoptic forcing conditions to the rest of Greenland. Coastal Greenland seasonal mean SAT trends were generally 2–6 °C, strongest in winter (5.7 °C) and least in summer and autumn (both 2.2 °C), during 1981–2011/12. Since 2001 Greenland mean coastal SAT increased significantly by 2.9 °C in winter and 0.8 °C in summer but decreased insignificantly by 1.1 °C in autumn and 0.2 °C in spring, during a period when there was little net change (≤ ± 0.1 °C) in northern hemisphere temperatures. SAT means for the latest 2001–11/12 decade were significantly in excess of those for peak decadal periods during the Early Twentieth Century Warm Period only in summer and winter, and not significantly greater in spring and autumn. Summer SAT increases in southern Greenland for the last 20 years were generally greater for maximum than minimum temperatures. By contrast, in winter, the recent warming was greater for minimum than maximum temperatures. The greatest SAT changes in all seasons are seen on Greenland’s west coast. SAT changes on the ice sheet and a key marginal glacier closely followed nearby coastal temperatures over the last 20 years.”

Citation: Edward Hanna et al 2012 Environ. Res. Lett. 7 045404 doi:10.1088/1748-9326/7/4/045404.


New projections: higher sea level and more melting from glaciers by 2100 than in previous projections

Potential for bias in 21st century semiempirical sea level projections – Jevrejeva et al. (2012)

Abstract: “We examine the limitations of a semiempirical model characterized by a sea level projection of 73 cm with RCP4.5 scenario by 2100. Calibrating the model with data to 1990 and then simulating the period 1993–2009 produces sea level in close agreement with acceleration in sea level rise observed by satellite altimetry. Nonradiative forcing contributors, such as long-term adjustment of Greenland and Antarctica ice sheets since Last Glacial Maximum, abyssal ocean warming, and terrestrial water storage, may bias model calibration which, if corrected for, tend to reduce median sea level projections at 2100 by 2–10 cm, though this is within the confidence interval. We apply the semiempirical approach to simulate individual contributions from thermal expansion and small glacier melting. Steric sea level projections agree within 3 cm of output from process-based climate models. In contrast, semiempirical simulation of melting from glaciers is 26 cm, which is twice large as estimates from some process-based models; however, all process models lack simulation of calving, which likely accounts for 50% of small glacier mass loss worldwide. Furthermore, we suggest that changes in surface mass balance and dynamics of Greenland ice sheet made contributions to the sea level rise in the early 20th century and therefore are included within the semiempirical model calibration period and hence are included in semiempirical sea level projections by 2100. Antarctic response is probably absent from semiempirical models, which will lead to a underestimate in sea level rise if, as is probable, Antarctica loses mass by 2100.”

Citation: Jevrejeva, S., J. C. Moore, and A. Grinsted (2012), Potential for bias in 21st century semiempirical sea level projections, J. Geophys. Res., 117, D20116, doi:10.1029/2012JD017704.


Improving sea level reconstructions using non-sea level measurements

Improving sea level reconstructions using non-sea level measurements – Hamlington et al. (2012)

Abstract: “We present a new method for reconstructing sea level involving cyclostationary empirical orthogonal functions (CSEOFs). While we show results from a CSEOF reconstruction using basis functions computed from satellite altimetry and subsequently fit to tide gauge data, our focus is on how other ocean observations such as sea surface temperature can be leveraged to create an improved reconstructed sea level data set spanning the time period from 1900 to present. Basis functions are computed using satellite measurements of sea surface temperature, and using a simple regression technique, these basis functions are transformed to represent a similar temporal evolution to corresponding satellite altimeter-derived sea level basis functions. The resulting sea level and sea surface temperature basis functions are fit to tide gauge data and historical sea surface temperature data, respectively, to produce a reconstructed sea level data set spanning the period from 1900 to present. We demonstrate the use of this reconstructed data set for climate monitoring, focusing primarily on climate signals in the Pacific Ocean. The CSEOF reconstruction technique can be used to create indices computed solely from sea level measurements for monitoring signals such as the eastern Pacific (EP) El Niño–Southern Oscillation (ENSO), central Pacific (CP) ENSO, and Pacific Decadal Oscillation (PDO). The EP ENSO, CP ENSO, and PDO signals are all well represented in the CSEOF reconstruction relying solely on sea level measurements from 1950 to present; however, significant improvement can be made in reconstructing these signals during the first half of the twentieth century by including sea surface temperature measurements in the sea level reconstruction procedure.”

Citation: Hamlington, B. D., R. R. Leben, and K.-Y. Kim (2012), Improving sea level reconstructions using non-sea level measurements, J. Geophys. Res., 117, C10025, doi:10.1029/2012JC008277.


Other studies from last week

Milankovitch tuning of deep-sea records: Implications for maximum rates of change of sea level – Berger (2012)

The early twentieth century warming and winter Arctic sea ice – Semenov & Latif (2012) [FULL TEXT]

Increasing influence of heat stress on French maize yields from the 1960s to the 2030s – Hawkins et al. (2012)

Oxygen trends over five decades in the North Atlantic – Stendardo & Gruber (2012)

Homogenization of mean monthly temperature time series of Greece – Mamara et al. (2012)

Spatial and temporal variations in air temperature and precipitation in the Chinese Himalayas during the 1971–2007 – Yang et al. (2012)

Heat-related mortality in Moldova: the summer of 2007 – Corobov et al. (2012)

Above- and belowground linkages in Sphagnum-peatland: climate warming affects plant-microbial interactions – Jassey et al. (2012)

How did the hydrologic cycle respond to the two-phase mystery interval? – Broecker & Putnam (2012)

Climatic fluctuations as a significant contributing factor for volcanic collapses. Evidence from Mexico during the Late Pleistocene – Capra et al. (2012)

Climate Warming and Permafrost Dynamics in the Antarctic Peninsula Region – Bockheim et al. (2012)

BVOC-aerosol-climate interactions in the global aerosol-climate model ECHAM5.5-HAM2 – Makkonen et al. (2012) [FULL TEXT]

The ‘too few, too bright’ tropical low-cloud problem in CMIP5 models – Nam et al. (2012)

Decadal variability of the NAO: Introducing an augmented NAO index – Wang et al. (2012)

Snowfall-driven mass change on the East Antarctic ice sheet – Boening et al. (2012)

Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns? – Drijfhout et al. (2012)

Intensification of North American megadroughts through surface and dust aerosol forcing – Cook et al. (2012)

Evaluation and response of winter cold spells over Western Europe in CMIP5 models – Peings et al. (2012) [FULL TEXT]

A comprehensive review of climate adaptation in the United States: more than before, but less than needed – Bierbaum et al. (2012) [FULL TEXT]

Sea level trends, interannual and decadal variability in the Pacific Ocean – Zhang & Church (2012)

Atmospheric carbon dioxide retrieved from the Greenhouse gases Observing SATellite (GOSAT): Comparison with ground-based TCCON observations and GEOS-Chem model calculations – Cogan et al. (2012)

Should the United Nations Framework Convention on Climate Change recognize climate migrants? – Gibb & Ford (2012) [FULL TEXT]

Food benefit and climate warming potential of nitrogen fertilizer uses in China – Tian et al. (2012) [FULL TEXT]

Bunker Cave stalagmites: an archive for central European Holocene climate variability – Fohlmeister et al. (2012) [FULL TEXT]

Human impacts on terrestrial hydrology: climate change versus pumping and irrigation – Ferguson & Maxwell (2012) [FULL TEXT]

Optimal growth with adaptation to climate change – Dumas & Ha-Duong (2012) [FULL TEXT]

Recent changes in the dynamic properties of declining Arctic sea ice: A model study – Zhang et al. (2012)


CLASSIC OF THE WEEK: Crowe (1963)

Recent Temperature and Precipitation Fluctuations along the British Columbia Coast – Crowe (1963) [FULL TEXT]

Abstract: “Five-year running averages of mean annual temperature and total annual precipitation are shown for selected British Columbia coast stations. Similar averages of mean seasonal and annual temperature and total seasonal and annual precipitation are also shown for Agassiz, British Columbia. A general rising trend in mean annual temperature of not more than 2F over the 50-year period beginning about 1900 is found for the British Columbia coast. This rising trend is most pronounced in autumn and winter and least evident in spring and summer. There is some evidence that the trend may recently have begun to level off or way have ended. No significant decrease or increase in total annual precipitation has occurred over the British Columbia coast during the past half-century, although summer precipitation along the southern section seems to have been somewhat lower during the second quarter of this century than it was during the first.”

Citation: Crowe, R. B., 1963: Recent Temperature and Precipitation Fluctuations along the British Columbia Coast. J. Appl. Meteor., 2, 114–118. doi: http://dx.doi.org/10.1175/1520-0450(1963)0022.0.CO;2.


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 3 Comments »

Papers on hurricanes and global warming

Posted by Ari Jokimäki on November 1, 2012

This is a list of papers on hurricanes and global warming. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Homogeneous record of Atlantic hurricane surge threat since 1923 – Grinsted et al. (2012) “Detection and attribution of past changes in cyclone activity are hampered by biased cyclone records due to changes in observational capabilities. Here we construct an independent record of Atlantic tropical cyclone activity on the basis of storm surge statistics from tide gauges. We demonstrate that the major events in our surge index record can be attributed to landfalling tropical cyclones; these events also correspond with the most economically damaging Atlantic cyclones. We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years (P < 0.02).” Aslak Grinsted, John C. Moore, and Svetlana Jevrejeva, PNAS October 15, 2012, doi: 10.1073/pnas.1209542109. [FULL TEXT]

Consensus on climate trends in western North Pacific tropical cyclones – Kang & Elsner (2012) “Research on trends in western North Pacific tropical cyclone (TC) activity is limited by problems associated with different wind speed conversions used by the various meteorological agencies. This paper uses a quantile method to effectively overcome this conversion problem. Following the assumption that the intensity ranks of TCs are the same among agencies, quantiles at the same probability level in different data sources are regarded as having the same wind speed level. Tropical cyclone data from the Joint Typhoon Warning Center (JTWC) and Japan Meteorological Agency (JMA) are chosen for research and comparison. Trends are diagnosed for the upper 45% of the strongest TCs annually. The 27-year period beginning with 1984, when the JMA began using the Dvorak (1982) technique, is determined to be the most reliable for achieving consensus among the two agencies regarding these trends. The start year is a compromise between including as many years in the data as possible, but not too many that the period includes observations that result in inconsistent trend estimates. Consensus of TC trends between the two agencies over the period is interpreted as fewer, but stronger events since 1984, even with the lower Power Dissipation Index (PDI) in the western North Pacific in recent years.” Nam-Young Kang and James B. Elsner, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00735.1.

Physically based assessment of hurricane surge threat under climate change – Lin et al. (2012) “Storm surges are responsible for much of the damage and loss of life associated with landfalling hurricanes. Understanding how global warming will affect hurricane surges thus holds great interest. As general circulation models (GCMs) cannot simulate hurricane surges directly, we couple a GCM-driven hurricane model with hydrodynamic models to simulate large numbers of synthetic surge events under projected climates and assess surge threat, as an example, for New York City (NYC). Struck by many intense hurricanes in recorded history and prehistory, NYC is highly vulnerable to storm surges. We show that the change of storm climatology will probably increase the surge risk for NYC; results based on two GCMs show the distribution of surge levels shifting to higher values by a magnitude comparable to the projected sea-level rise (SLR). The combined effects of storm climatology change and a 1 m SLR may cause the present NYC 100-yr surge flooding to occur every 3–20 yr and the present 500-yr flooding to occur every 25–240 yr by the end of the century.” Ning Lin, Kerry Emanuel, Michael Oppenheimer & Erik Vanmarcke, Nature Climate Change 2, 462–467(2012), doi:10.1038/nclimate1389. [FULL TEXT]

Hurricanes and Global Warming: Results from Downscaling IPCC AR4 Simulations – Emanuel et al. (2011) “Changes in tropical cyclone activity are among the more potentially consequential results of global climate change, and it is therefore of considerable interest to understand how anthropogenic climate change may affect such storms. Global climate models are currently used to estimate future climate change, but the current generation of models lacks the horizontal resolution necessary to resolve the intense inner core of tropical cyclones. Here we review a new technique for inferring tropical cyclone climatology from the output of global models, extend it to predict genesis climatologies (rather than relying on historical climatology), and apply it to current and future climate states simulated by a suite of global models developed in support of the most recent Intergovernmental Panel on Climate Change report. This new technique attacks the horizontal resolution problem by using a specialized, coupled ocean–atmosphere hurricane model phrased in angular momentum coordinates, which provide a high resolution of the core at low cost. This model is run along each of 2,000 storm tracks generated using an advection-and-beta model, which is, in turn, driven by large-scale winds derived from the global models. In an extension to this method, tracks are initiated by randomly seeding large areas of the tropics with weak vortices and then allowing the intensity model to determine their survival, based on large-scale environmental conditions. We show that this method is largely successful in reproducing the observed seasonal cycle and interannual variability of tropical cyclones in the present climate, and that it is more modestly successful in simulating their spatial distribution. When applied to simulations of global climate with double the present concentration of carbon dioxide, this method predicts substantial changes and geographic shifts in tropical cyclone activity, but with much variation among the global climate models used. Basinwide power dissipation and storm intensity generally increase with global warming, but the results vary from model to model and from basin to basin. Storm frequency decreases in the Southern Hemisphere and north Indian Ocean, increases in the western North Pacific, and is indeterminate elsewhere. We demonstrate that in these simulations, the change in tropical cyclone activity is greatly influenced by the increasing difference between the moist entropy of the boundary layer and that of the middle troposphere as the climate warms.” Emanuel, Kerry, Ragoth Sundararajan, John Williams, 2008: Hurricanes and Global Warming: Results from Downscaling IPCC AR4 Simulations. Bull. Amer. Meteor. Soc., 89, 347–367. doi: http://dx.doi.org/10.1175/BAMS-89-3-347. [FULL TEXT]

Tropical cyclones and climate change – Knutson et al. (2010) “Whether the characteristics of tropical cyclones have changed or will change in a warming climate — and if so, how — has been the subject of considerable investigation, often with conflicting results. Large amplitude fluctuations in the frequency and intensity of tropical cyclones greatly complicate both the detection of long-term trends and their attribution to rising levels of atmospheric greenhouse gases. Trend detection is further impeded by substantial limitations in the availability and quality of global historical records of tropical cyclones. Therefore, it remains uncertain whether past changes in tropical cyclone activity have exceeded the variability expected from natural causes. However, future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6–34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre. For all cyclone parameters, projected changes for individual basins show large variations between different modelling studies.” Thomas R. Knutson, John L. McBride, Johnny Chan, Kerry Emanuel, Greg Holland, Chris Landsea, Isaac Held, James P. Kossin, A. K. Srivastava & Masato Sugi, Nature Geoscience 3, 157 – 163 (2010), doi:10.1038/ngeo779. [FULL TEXT]

Modeling the Dependence of Tropical Storm Counts in the North Atlantic Basin on Climate Indices – Villarini et al. (2010) “The authors analyze and model time series of annual counts of tropical storms lasting more than 2 days in the North Atlantic basin and U.S. landfalling tropical storms over the period 1878–2008 in relation to different climate indices. The climate indices considered are the tropical Atlantic sea surface temperature (SST), tropical mean SST, the North Atlantic Oscillation (NAO), and the Southern Oscillation index (SOI). Given the uncertainties associated with a possible tropical storm undercount in the presatellite era, two different time series of counts for the North Atlantic basin are employed: one is the original (uncorrected) tropical storm record maintained by the National Hurricane Center and the other one is with a correction for the estimated undercount associated with a changing observation network. Two different SST time series are considered: the Met Office’s HadISSTv1 and NOAA’s Extended Reconstructed SST. Given the nature of the data (counts), a Poisson regression model is adopted. The selection of statistically significant covariates is performed by penalizing models for adding extra parameters and two penalty functions are used. Depending on the penalty function, slightly different models, both in terms of covariates and dependence of the model’s parameter, are obtained, showing that there is not a “single best” model. Moreover, results are sensitive to the undercount correction and the SST time series. Suggestions concerning the model to use are provided, driven by both the outcomes of the statistical analyses and the current understanding of the underlying physical processes responsible for the genesis, development, and tracks of tropical storms in the North Atlantic basin. Although no single model is unequivocally superior to the others, the authors suggest a very parsimonious family of models using as covariates tropical Atlantic and tropical mean SSTs.” Villarini, Gabriele, Gabriel A. Vecchi, James A. Smith, 2010: Modeling the Dependence of Tropical Storm Counts in the North Atlantic Basin on Climate Indices. Mon. Wea. Rev., 138, 2681–2705. doi: http://dx.doi.org/10.1175/2010MWR3315.1. [FULL TEXT]

Atlantic hurricanes and climate over the past 1,500 years – Mann et al. (2009) “Atlantic tropical cyclone activity, as measured by annual storm counts, reached anomalous levels over the past decade1. The short nature of the historical record and potential issues with its reliability in earlier decades, however, has prompted an ongoing debate regarding the reality and significance of the recent rise. Here we place recent activity in a longer-term context by comparing two independent estimates of tropical cyclone activity over the past 1,500 years. The first estimate is based on a composite of regional sedimentary evidence of landfalling hurricanes, while the second estimate uses a previously published statistical model of Atlantic tropical cyclone activity driven by proxy reconstructions of past climate changes. Both approaches yield consistent evidence of a peak in Atlantic tropical cyclone activity during medieval times (around ad 1000) followed by a subsequent lull in activity. The statistical model indicates that the medieval peak, which rivals or even exceeds (within uncertainties) recent levels of activity, results from the reinforcing effects of La-Niña-like climate conditions and relative tropical Atlantic warmth.” Michael E. Mann, Jonathan D. Woodruff, Jeffrey P. Donnelly & Zhihua Zhang, Nature 460, 880-883 (13 August 2009) | doi:10.1038/nature08219. [FULL TEXT]

Gulf Stream and ENSO Increase the Temperature Sensitivity of Atlantic Tropical Cyclones – Moore et al. (2008) “Controversy exists over the role of the recent rise in sea surface temperatures (SST) and the frequency of tropical cyclones or hurricanes. Here, 135 yr of observational records are used to demonstrate how sea surface temperature, sea level pressure, and cyclone numbers are linked. A novel wavelet-lag coherence method is used to study cause and effect relations over a large space of time scales, phase lags, and periods. It is found that SST and cyclones are not merely correlated, but are in a negative feedback loop, where rising SST causes increased numbers of cyclones, which reduce SST. This is statistically most significant at decadal and not at longer periods, which is contrary to expectations if long-period natural cycles are important in driving cyclone numbers. Spatial relationships are examined using phase-aware teleconnections, which at the dominant decadal period show the in-phase behavior of the Atlantic SST in the Gulf Stream region, reflecting the role of the transportion of heat northward from the tropical Atlantic. At 5-yr periods there is significant coherence when SST leads cyclones by 2 yr, and this is associated with tropical ENSO activity such that, as predicted, increasing numbers of El Niños cause fewer Atlantic cyclones. The pattern of coherence existing since 1970 strongly favors the decadal coherence band, and despite growing coherence at higher frequencies, there is none at the 5-yr band, perhaps explaining why the observed sensitivity between SST and cyclones is larger than that from general circulation model (GCM) predictions and becoming greater.” Moore, J. C., A. Grinsted, S. Jevrejeva, 2008: Gulf Stream and ENSO Increase the Temperature Sensitivity of Atlantic Tropical Cyclones. J. Climate, 21, 1523–1531. doi: http://dx.doi.org/10.1175/2007JCLI1752.1. [FULL TEXT]

Whither Hurricane Activity? – Vecchi et al. (2008) “Alternative interpretations of the relationship between sea surface temperature and hurricane activity imply vastly different future Atlantic hurricane activity.” Gabriel A. Vecchi, Kyle L. Swanson and Brian J. Soden, Science 31 October 2008: Vol. 322 no. 5902 pp. 687-689, DOI: 10.1126/science.1164396. [FULL TEXT]

Counting Atlantic tropical cyclones back to 1900 – Landsea (2007) “Climate variability and any resulting change in the characteristics of tropical cyclones (tropical storms, subtropical storms, and hurricanes) have become topics of great interest and research within the past 2 years [International Workshop on Tropical Cyclones, 2006].An emerging focus is how the frequency of tropical cyclones has changed over time and whether any changes could be linked to anthropogenic global warming.” Landsea, C. (2007), Counting Atlantic tropical cyclones back to 1900, Eos Trans. AGU, 88(18), 197, doi:10.1029/2007EO180001. [FULL TEXT]

Estimated return periods for Hurricane Katrina – Elsner et al. (2006) “Hurricane Katrina is one of the most destructive natural disaster in U.S. history. The infrequency of severe coastal hurricanes implies that empirical probability estimates of the next big one will be unreliable. Here we use an extreme-value model together with interpolated best-track (HURDAT) records to show that a hurricane of Katrina’s intensity or stronger can be expected to occur, on average, once every 21 years somewhere along the Gulf coast from Texas through Alabama and once every 14 years somewhere along the entire coast from Texas through Maine. The model predicts a 100-year return level of 83 ms−1 (186 mph) during globally warm years and 75 ms−1 (168 mph) during globally cool years. This difference is consistent with models predicting an increase in hurricane intensity with increasing greenhouse warming.” Elsner, J. B., T. H. Jagger, and A. A. Tsonis (2006), Estimated return periods for Hurricane Katrina, Geophys. Res. Lett., 33, L08704, doi:10.1029/2005GL025452. [FULL TEXT]

Climatology Models for Extreme Hurricane Winds near the United States – Jagger & Elsner (2006) “The rarity of severe coastal hurricanes implies that empirical estimates of extreme wind speed return levels will be unreliable. Here climatology models derived from extreme value theory are estimated using data from the best-track [Hurricane Database (HURDAT)] record. The occurrence of a hurricane above a specified threshold intensity level is assumed to follow a Poisson distribution, and the distribution of the maximum wind is assumed to follow a generalized Pareto distribution. The likelihood function is the product of the generalized Pareto probabilities for each wind speed estimate. A geographic region encompassing the entire U.S. coast vulnerable to Atlantic hurricanes is of primary interest, but the Gulf Coast, Florida, and the East Coast regions are also considered. Model parameters are first estimated using a maximum likelihood (ML) procedure. Results estimate the 100-yr return level for the entire coast at 157 kt (±10 kt), but at 117 kt (±4 kt) for the East Coast region (1 kt = 0.514 m s−1). Highest wind speed return levels are noted along the Gulf Coast from Texas to Alabama. The study also examines how the extreme wind return levels change depending on climate conditions including El Niño–Southern Oscillation, the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, and global temperature. The mean 5-yr return level during La Niña (El Niño) conditions is 125 (116) kt, but is 140 (164) kt for the 100-yr return level. This indicates that La Niña years are the most active for the occurrence of strong hurricanes, but that extreme hurricanes are more likely during El Niño years. Although El Niño inhibits hurricane formation in part through wind shear, the accompanying cooler lower stratosphere appears to increase the potential intensity of hurricanes that do form. To take advantage of older, less reliable data, the models are reformulated using Bayesian methods. Gibbs sampling is used to integrate the prior over the likelihood to obtain the posterior distributions for the model parameters conditional on global temperature. Higher temperatures are conditionally associated with more strong hurricanes and higher return levels for the strongest hurricane winds. Results compare favorably with an ML approach as well as with recent modeling and observational studies. The maximum possible near-coastal wind speed is estimated to be 208 kt (183 kt) using the Bayesian (ML) approach.” Jagger, Thomas H., James B. Elsner, 2006: Climatology Models for Extreme Hurricane Winds near the United States. J. Climate, 19, 3220–3236. doi: http://dx.doi.org/10.1175/JCLI3913.1. [FULL TEXT]

Increasing destructiveness of tropical cyclones over the past 30 years – Emanuel (2005) “Theory and modelling predict that hurricane intensity should increase with increasing global mean temperatures, but work on the detection of trends in hurricane activity has focused mostly on their frequency and shows no trend. Here I define an index of the potential destructiveness of hurricanes based on the total dissipation of power, integrated over the lifetime of the cyclone, and show that this index has increased markedly since the mid-1970s. This trend is due to both longer storm lifetimes and greater storm intensities. I find that the record of net hurricane power dissipation is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multi-decadal oscillations in the North Atlantic and North Pacific, and global warming. My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential, and—taking into account an increasing coastal population—a substantial increase in hurricane-related losses in the twenty-first century.” Kerry Emanuel, Nature 436, 686-688 (4 August 2005), doi:10.1038/nature03906. [FULL TEXT, Landsea comment, Emanuel reply]

Impact of CO2-Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization – Knutson & Tuleya (2004) “Previous studies have found that idealized hurricanes, simulated under warmer, high-CO2 conditions, are more intense and have higher precipitation rates than under present-day conditions. The present study explores the sensitivity of this result to the choice of climate model used to define the CO2-warmed environment and to the choice of convective parameterization used in the nested regional model that simulates the hurricanes. Approximately 1300 five-day idealized simulations are performed using a higher-resolution version of the GFDL hurricane prediction system (grid spacing as fine as 9 km, with 42 levels). All storms were embedded in a uniform 5 m s−1 easterly background flow. The large-scale thermodynamic boundary conditions for the experiments— atmospheric temperature and moisture profiles and SSTs—are derived from nine different Coupled Model Intercomparison Project (CMIP2+) climate models. The CO2-induced SST changes from the global climate models, based on 80-yr linear trends from +1% yr−1 CO2 increase experiments, range from about +0.8° to +2.4°C in the three tropical storm basins studied. Four different moist convection parameterizations are tested in the hurricane model, including the use of no convective parameterization in the highest resolution inner grid. Nearly all combinations of climate model boundary conditions and hurricane model convection schemes show a CO2-induced increase in both storm intensity and near-storm precipitation rates. The aggregate results, averaged across all experiments, indicate a 14% increase in central pressure fall, a 6% increase in maximum surface wind speed, and an 18% increase in average precipitation rate within 100 km of the storm center. The fractional change in precipitation is more sensitive to the choice of convective parameterization than is the fractional change of intensity. Current hurricane potential intensity theories, applied to the climate model environments, yield an average increase of intensity (pressure fall) of 8% (Emanuel) to 16% (Holland) for the high-CO2 environments. Convective available potential energy (CAPE) is 21% higher on average in the high-CO2 environments. One implication of the results is that if the frequency of tropical cyclones remains the same over the coming century, a greenhouse gas–induced warming may lead to a gradually increasing risk in the occurrence of highly destructive category-5 storms.” Knutson, Thomas R., Robert E. Tuleya, 2004: Impact of CO2-Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization. J. Climate, 17, 3477–3495. doi: http://dx.doi.org/10.1175/1520-0442(2004)0172.0.CO;2. [FULL TEXT]

Impact of CO2-Induced Warming on Hurricane Intensities as Simulated in a Hurricane Model with Ocean Coupling – Knutson et al. (2001) “This study explores how a carbon dioxide (CO2) warming–induced enhancement of hurricane intensity could be altered by the inclusion of hurricane–ocean coupling. Simulations are performed using a coupled version of the Geophysical Fluid Dynamics Laboratory hurricane prediction system in an idealized setting with highly simplified background flow fields. The large-scale atmospheric boundary conditions for these high-resolution experiments (atmospheric temperature and moisture profiles and SSTs) are derived from control and high-CO2 climatologies obtained from a low-resolution (R30) global coupled ocean–atmosphere climate model. The high-CO2 conditions are obtained from years 71–120 of a transient +1% yr−1 CO2-increase experiment with the global model. The CO2-induced SST changes from the global climate model range from +2.2° to +2.7°C in the six tropical storm basins studied. In the storm simulations, ocean coupling significantly reduces the intensity of simulated tropical cyclones, in accord with previous studies. However, the net impact of ocean coupling on the simulated CO2 warming–induced intensification of tropical cyclones is relatively minor. For both coupled and uncoupled simulations, the percentage increase in maximum surface wind speeds averages about 5%–6% over the six basins and varies from about 3% to 10% across the different basins. Both coupled and uncoupled simulations also show strong increases of near-storm precipitation under high-CO2 climate conditions, relative to control (present day) conditions.” Knutson, Thomas R., Robert E. Tuleya, Weixing Shen, Isaac Ginis, 2001: Impact of CO2-Induced Warming on Hurricane Intensities as Simulated in a Hurricane Model with Ocean Coupling. J. Climate, 14, 2458–2468. doi: http://dx.doi.org/10.1175/1520-0442(2001)0142.0.CO;2. [FULL TEXT]

The Recent Increase in Atlantic Hurricane Activity: Causes and Implications – Goldenberg et al. (2001) “The years 1995 to 2000 experienced the highest level of North Atlantic hurricane activity in the reliable record. Compared with the generally low activity of the previous 24 years (1971 to 1994), the past 6 years have seen a doubling of overall activity for the whole basin, a 2.5-fold increase in major hurricanes (≥50 meters per second), and a fivefold increase in hurricanes affecting the Caribbean. The greater activity results from simultaneous increases in North Atlantic sea-surface temperatures and decreases in vertical wind shear. Because these changes exhibit a multidecadal time scale, the present high level of hurricane activity is likely to persist for an additional ∼10 to 40 years. The shift in climate calls for a reevaluation of preparedness and mitigation strategies.” Stanley B. Goldenberg, Christopher W. Landsea, Alberto M. Mestas-Nuñez, William M. Gray, Science 20 July 2001: Vol. 293 no. 5529 pp. 474-479, DOI: 10.1126/science.1060040. [FULL TEXT]

Increased hurricane intensities with CO2-induced warming as simulated using the GFDL hurricane prediction system – Knutson & Tuleya (1999) “The impact of CO2-induced global warming on the intensities of strong hurricanes is investigated using the GFDL regional high-resolution hurricane prediction system. The large-scale initial conditions and boundary conditions for the regional model experiments, including SSTs, are derived from control and transient CO2 increase experiments with the GFDL R30-resolution global coupled climate model. In a case study approach, 51 northwest Pacific storm cases derived from the global model under present-day climate conditions are simulated with the regional model, along with 51 storm cases for high CO2 conditions. For each case, the regional model is integrated forward for five days without ocean coupling. The high CO2 storms, with SSTs warmer by about 2.2 °C on average and higher environmental convective available potential energy (CAPE), are more intense than the control storms by about 3–7 m/s (5%–11%) for surface wind speed and 7 to 24 hPa for central surface pressure. The simulated intensity increases are statistically significant according to most of the statistical tests conducted and are robust to changes in storm initialization methods. Near-storm precipitation is 28% greater in the high CO2 sample. In terms of storm tracks, the high CO2 sample is quite similar to the control. The mean radius of hurricane force winds is 2 to 3% greater for the composite high CO2 storm than for the control, and the high CO2 storms penetrate slightly higher into the upper troposphere. More idealized experiments were also performed in which an initial storm disturbance was embedded in highly simplified flow fields using time mean temperature and moisture conditions from the global climate model. These idealized experiments support the case study results and suggest that, in terms of thermodynamic influences, the results for the NW Pacific basin are qualitatively applicable to other tropical storm basins.” T. R. Knutson, R. E. Tuleya, Climate Dynamics, July 1999, Volume 15, Issue 7, pp 503-519. [FULL TEXT]

Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment – Henderson-Sellers et al. (1998) “The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but there is no clear evidence of long-term trends. Efforts have been initiated to use geological and geomorphological records and analysis of oxygen isotope ratios in rainfall recorded in cave stalactites to establish a paleoclimate of tropical cyclones, but these have not yet produced definitive results. Recent thermodynamical estimation of the maximum potential intensities (MPI) of tropical cyclones shows good agreement with observations. Although there are some uncertainties in these MPI approaches, such as their sensitivity to variations in parameters and failure to include some potentially important interactions such as ocean spray feedbacks, the response of upper-oceanic thermal structure, and eye and eyewall dynamics, they do appear to be an objective tool with which to predict present and future maxima of tropical cyclone intensity. Recent studies indicate the MPI of cyclones will remain the same or undergo a modest increase of up to 10%–20%. These predicted changes are small compared with the observed natural variations and fall within the uncertainty range in current studies. Furthermore, the known omissions (ocean spray, momentum restriction, and possibly also surface to 300-hPa lapse rate changes) could all operate to mitigate the predicted intensification. A strong caveat must be placed on analysis of results from current GCM simulations of the “tropical-cyclone-like” vortices. Their realism, and hence prediction skill (and also that of “embedded” mesoscale models), is greatly limited by the coarse resolution of current GCMs and the failure to capture environmental factors that govern cyclone intensity. Little, therefore, can be said about the potential changes of the distribution of intensities as opposed to maximum achievable intensity. Current knowledge and available techniques are too rudimentary for quantitative indications of potential changes in tropical cyclone frequency. The broad geographic regions of cyclogenesis and therefore also the regions affected by tropical cyclones are not expected to change significantly. It is emphasized that the popular belief that the region of cyclogenesis will expand with the 26°C SST isotherm is a fallacy. The very modest available evidence points to an expectation of little or no change in global frequency. Regional and local frequencies could change substantially in either direction, because of the dependence of cyclone genesis and track on other phenomena (e.g., ENSO) that are not yet predictable. Greatly improved skills from coupled global ocean–atmosphere models are required before improved predictions are possible.” Henderson-Sellers, A., and Coauthors, 1998: Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment. Bull. Amer. Meteor. Soc., 79, 19–38. doi: http://dx.doi.org/10.1175/1520-0477(1998)0792.0.CO;2. [FULL TEXT]

Simulated Increase of Hurricane Intensities in a CO2-Warmed Climate – Knutson et al. (1998) “Hurricanes can inflict catastrophic property damage and loss of human life. Thus, it is important to determine how the character of these powerful storms could change in response to greenhouse gas–induced global warming. The impact of climate warming on hurricane intensities was investigated with a regional, high-resolution, hurricane prediction model. In a case study, 51 western Pacific storm cases under present-day climate conditions were compared with 51 storm cases under high-CO2 conditions. More idealized experiments were also performed. The large-scale initial conditions were derived from a global climate model. For a sea surface temperature warming of about 2.2°C, the simulations yielded hurricanes that were more intense by 3 to 7 meters per second (5 to 12 percent) for wind speed and 7 to 20 millibars for central surface pressure.” Thomas R. Knutson, Robert E. Tuleya, Yoshio Kurihara, Science 13 February 1998: Vol. 279 no. 5353 pp. 1018-1021, DOI: 10.1126/science.279.5353.1018. [FULL TEXT]

The Maximum Potential Intensity of Tropical Cyclones – Holland (1997) “A thermodynamic approach to estimating maximum potential intensity (MPI) of tropical cyclones is described and compared with observations and previous studies. The approach requires an atmospheric temperature sounding, SST, and surface pressure; includes the oceanic feedback of increasing moist entropy associated with falling surface pressure over a steady SST; and explicitly incorporates a cloudy eyewall and a clear eye. Energetically consistent, analytic solutions exist for all known atmospheric conditions. The method is straightforward to apply and is applicable to operational analyses and numerical model forecasts, including climate model simulations. The derived MPI is highly sensitive to the surface relative humidity under the eyewall, to the height of the warm core, and to transient changes of ocean surface temperature. The role of the ocean is to initially contribute to the establishment of the ambient environment suitable for cyclone development, then to provide the additional energy required for development of an intense cyclone. The major limiting factor on cyclone intensity is the height and amplitude of the warm core that can develop; this is closely linked to the height to which eyewall clouds can reach, which is related to the level of moist entropy that can be achieved from ocean interactions under the eyewall. Moist ascent provides almost all the warming above 200 hPa throughout the cyclone core, including the eye, where warm temperatures are derived by inward advection and detrainment mixing from the eyewall. The clear eye contributes roughly half the total warming below 300 hPa and produces a less intense cyclone than could be achieved by purely saturated moist processes. There are necessarily several simplifications incorporated to arrive at a tractable solution, the consequences of which are discussed in detail. Nevertheless, application of the method indicates very close agreement with observations. For SST < 26°C there is generally insufficient energy for development. From 26° to 28°C SST the ambient atmosphere warms sharply in the lower troposphere and cools near the tropopause, but with little change in midlevels. The result is a rapid increase of MPI of about 30 hPa °C−1. At higher SST, the atmospheric destabilization ceases and the rate of increase of MPI is reduced.” Holland, Greg J., 1997: The Maximum Potential Intensity of Tropical Cyclones. J. Atmos. Sci., 54, 2519–2541. doi: http://dx.doi.org/10.1175/1520-0469(1997)0542.0.CO;2. [FULL TEXT]

Predicting Atlantic Basin Seasonal Tropical Cyclone Activity by 1 June – Gray et al. (1994) “This is the third in a series of papers describing the potential for the seasonal forecasting of Atlantic basin tropical cyclone activity. Earlier papers by the authors describe seasonal prediction from 1 December of the previous year and from 1 August of the current year; this work demonstrates the degree of predictability by 1 June, the “official” beginning of the hurricane season. Through three groupings consisting of 13 separate predictors, hindcasts are made that explain 51%–72% of the variability as measured by cross-validated agreement coefficients for eight measures of seasonal tropical cyclone activity. The three groupings of predictors include 1) an extrapolation of quasi-biennial oscillation of 50- and 30-mb zonal winds and the vertical shear between the 50- and 30-mb zonal winds (three predictors); 2) West African rainfall, sea level pressure, and temperature data (four predictors); and 3) Caribbean basin and El Niño–Southern Oscillation information including Caribbean 200-mb zonal winds and sea level pressures, equatorial eastern Pacific sea surface temperatures and Southern Oscillation index values, and their changes in time (six predictors). The cross validation is carried out using least sum of absolute deviations regression that provides an efficient procedure for the maximum agreement measure criterion. Corrected intense hurricane data for the 1950s and 1960s have been incorporated into the forecasts. Comparisons of these 1 June forecast results with forecast results from 1 December of the year previous and 1 August of the current year are also given.” Gray, William M., Christopher W. Landsea, Paul W. Mielke, Kenneth J. Berry, 1994: Predicting Atlantic Basin Seasonal Tropical Cyclone Activity by 1 June. Wea. Forecasting, 9, 103–115. doi: http://dx.doi.org/10.1175/1520-0434(1994)0092.0.CO;2 . [FULL TEXT]

Strong Association Between West African Rainfall and U.S. Landfall of Intense Hurricanes – Gray (1990) “Intense hurricanes occurred much more frequently during the period spanning the late 1940s through the late 1960s than during the 1970s and 1980s, except for 1988 and 1989. Seasonal and multidecadal variations of intense hurricane activity are closely linked to seasonal and multidecadal variations of summer rainfall amounts in the Western Sahel region of West Africa. The multidecadal nature of West African precipitation variations and their association with variations of intense Atlantic hurricane activity can be observed in data going back nearly a century. The apparent recent breaking of the 18-year Sahel drought during 1988 and 1989 suggests that the incidence of intense hurricanes making landfall on the U.S. coast and in the Caribbean basin will likely increase during the 1990s and early years of the 21st century to levels of activity notably greater than were observed during the 1970s and 1980s.” William M. Gray, Science, New Series, Vol. 249, No. 4974 (Sep. 14, 1990), pp. 1251-1256, DOI: 10.2307/2877855.

The dependence of hurricane intensity on climate – Emanuel (1987) “Tropical cyclones rank with earthquakes as the major geophysical causes of loss of life and property. It is therefore of practical as well as scientific interest to estimate the changes in tropical cyclone frequency and intensity that might result from short-term man-induced alterations of the climate. In this spirit we use a simple Carnot cycle model to estimate the maximum intensity of tropical cyclones under the somewhat warmer conditions expected to result from increased atmospheric CO2 content. Estimates based on August mean conditions over the tropical oceans predicted by a general circulation model with twice the present CO2 content yield a 40–50% increase in the destructive potential of hurricanes.” Kerry A. Emanuel, Nature 326, 483 – 485 (08 April 1987); doi:10.1038/326483a0. [FULL TEXT]

Atlantic Seasonal Hurricane Frequency. Part I: El Niño and 30 mb Quasi-Biennial Oscillation Influences – Gray (1984) “This is the first of two papers on Atlantic seasonal hurricane frequency. In this paper, seasonal hurricane frequency as related to E1 Niño events during 1900–82 and to the equatorial Quasi-Biennial Oscillation (QBO) of stratospheric zonal wind from 1950 to 1982 is discussed. It is shown that a substantial negative correlation is typically present between the seasonal number of hurricanes, hurricane days and tropical storms, and moderate or strong (15 cases) El Niñ off the South American west coast. A similar negative anomaly in hurricane activity occurs when equatorial winds at 30 mb are from an easterly direction and/or are becoming more easterly with time during the hurricane season. This association of Atlantic hurricane activity with El Niño can also be made with the Southern Oscillation Index. By contrast, seasonal hurricane frequency is slightly above normal in non-El Niño years and substantially above normal when equatorial stratospheric winds blow from a westerly direction and/or are becoming more westerly with time during the storm season. El Niño events are shown to be related to an anomalous increase in upper tropospheric westerly winds over the Caribbean basin and the equatorial Atlantic. Such anomalous westerly winds inhibit tropical cyclone activity by increasing tropospheric vertical wind shear and giving rise to a regional upper-level environment which is less anticyclonic and consequently less conductive to cyclone development and maintenance. The seasonal frequency of hurricane activity in storm basis elsewhere is much less affected by El Niño events and the QBO. Seasonal hurricane frequency in the Atlantic and the stratospheric QBO is hypothesized to be associated with the trade-wind nature of Atlantic cyclone formation. Tropical cyclone formation in the other storm basins is primarily associated with monsoon trough conditions which are absent in the Atlantic. Quasi-Biennial Oscillation-induced influences do not positively enhance monsoon trough region vorticity fields as they apparently do with cyclone formations within the trade winds. Part II discusses the utilization of the information in this paper for the development of a forecast scheme for seasonal hurricane activity variations.” Gray, William M., 1984: Atlantic Seasonal Hurricane Frequency. Part I: El Niño and 30 mb Quasi-Biennial Oscillation Influences. Mon. Wea. Rev., 112, 1649–1668. doi: http://dx.doi.org/10.1175/1520-0493(1984)1122.0.CO;2. [FULL TEXT]

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