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Observations of anthropogenic global warming

Archive for April, 2012

New research from last week 17/2012

Posted by Ari Jokimäki on April 30, 2012

Is it something that is happening in the Sun,
or are atmospheric GHG’s the smoking gun?

Temperature is rising on the surface of the sea.
Did we do it, or did nature do it for free?

Cryospheric presence in Arctic is very nice.
After mankind’s tricks, does anybody see there any ice?

What causes changes in avalanches of snow,
or in floods, does anyone know?

When wetlands are all gone, rotten and stink,
what can carbon do after that, where does it sink?

Migration is something that trees and butterflies have to face.
I just wonder if they’ll end up in same place?

The move from MWP to LIA is a big change,
but weather can do it with same regime, isn’t that strange?

Subtropical clouds are difficult things to simulate.
Can’t climate models ever do it, or is it their fate?


Impact of anthropogenic climate change is observable in Arctic sea ice already today

Observations reveal external driver for Arctic sea-ice retreat – Notz & Marotzke (2012)

Abstract: “The very low summer extent of Arctic sea ice that has been observed in recent years is often casually interpreted as an early-warning sign of anthropogenic global warming. For examining the validity of this claim, previously IPCC model simulations have been used. Here, we focus on the available observational record to examine if this record allows us to identify either internal variability, self-acceleration, or a specific external forcing as the main driver for the observed sea-ice retreat. We find that the available observations are sufficient to virtually exclude internal variability and self-acceleration as an explanation for the observed long-term trend, clustering, and magnitude of recent sea-ice minima. Instead, the recent retreat is well described by the superposition of an externally forced linear trend and internal variability. For the externally forced trend, we find a physically plausible strong correlation only with increasing atmospheric CO2 concentration. Our results hence show that the observed evolution of Arctic sea-ice extent is consistent with the claim that virtually certainly the impact of an anthropogenic climate change is observable in Arctic sea ice already today.”

Citation: Notz, D. and J. Marotzke (2012), Observations reveal external driver for Arctic sea-ice retreat, Geophys. Res. Lett., 39, L08502, doi:10.1029/2012GL051094.


Coastal vegetated wetlands are rapidly vanishing carbon sinks

Carbon sequestration in wetland dominated coastal systems — a global sink of rapidly diminishing magnitude – Hopkinson et al. (2012)

Abstract: “Coastal vegetated wetlands have recently been identified as very important global C sinks but vulnerable to degradation by direct human alteration of their habitats. While their expanse is small globally, areal rates of C burial, or sequestration, are among the highest of Earth’s ecosystems. There is considerable uncertainty in the magnitude of total global sequestration in these systems for two reasons: poor estimates of their global areas and high variability and uncertainty in areal rates of burial between systems. The magnitude of C burial in vegetated coastal systems has been decreasing rapidly over the past century due primarily to human disturbances such as dredging, filling, eutrophication, and timber harvest. These systems continue to be lost globally at rates ranging from 1% to 7% annually. We find that climate change including global warming, human engineering of river systems, continued agricultural expansion, and sea level rise will also negatively impact C burial of coastal vegetated wetlands. A decrease in global C burial in these systems will ultimately exacerbate CO2 emissions, and further contribute to climate change in the future.”

Citation: Charles S Hopkinson, Wei-Jun Cai, Xinping Hu, Current Opinion in Environmental Sustainability, http://dx.doi.org/10.1016/j.cosust.2012.03.005.


Ranges of British butterflies have been thinning as they have expanded northwards

Temporal variation in responses of species to four decades of climate warming – Mair et al. (2012)

Abstract: “Many species are expanding at their leading-edge range boundaries in response to climate warming. Species are known to respond individualistically to climate change, but there has been little consideration of whether responses are consistent over time. We compared responses of 37 southerly-distributed British butterflies over two study periods, first between 1970-82 and 1995-99 and then between 1995-99 and 2005-09, when mean annual temperature increased regionally by 0.03 ⁰C yr−1 (a significant rate of increase) and 0.01 ⁰C yr−1(a non-significant increase), respectively. Our study species might be expected to benefit from climate warming. We measured three responses to climate to investigate this; changes in range margin, distribution area and abundance. In general, the responses of species were inconsistent over time. Species that increased their distribution areas during the first period tended to do so again during the second period, but the relationship was weak. Change in range margins and abundance were not consistent. In addition, only 5/37 species showed qualitatively similar responses in all three response variables over time (three species increased and two species declined in all variables in both periods). Overall rates of range expansion and distribution area change were significantly greater in the second study period, despite the lower rate of warming, perhaps due to species exploiting climate-distribution lags remaining from the earlier, warmer period. However, there was a significantly greater decline in abundance during the second study period, so range expansions northwards were not necessarily accompanied by increases in distribution area and/or abundance. Hence species ranges have been thinning as they have expanded northwards. The idiosyncratic responses of these species likely reflect the balance of climatic and habitat drivers of species distribution and abundance changes.”

Citation: Louise Mair, Chris D Thomas, Barbara J Anderson, Richard Fox, Marc Botham, Jane K Hill, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02730.x.


Snow avalanche activity has increased in French Alps with temperature

Snow and weather climatic control on snow avalanche occurrence fluctuations over 50 yr in the French Alps – Castebrunet et al. (2012) [FULL TEXT]

Abstract: “Snow avalanche activity is controlled to a large extent by snow and weather patterns. However, its response to climate fluctuations remains poorly documented. Previous studies have focused on direct extraction of trends in avalanche and winter climate data, and this study employs a time-implicit method to model annual avalanche activity in the French Alps during the 1958–2009 period from its most representative climatic drivers. Modelled snow and weather data for different elevations and aspects are considered as covariates that explain actual observed avalanche counts, modelled instability indexes, and a combination of both avalanche activity indicators. These three series present relatively similar fluctuations over the period and good consistency with historically harsh winters. A stepwise procedure is used to obtain regression models that accurately represent trends as well as high and low peaks with a small number of physically meaningful covariates, showing their climatic relevance. The activity indicators and their regression models seen as time series show, within a high interannual variability, a predominant bell-shaped pattern presumably related to a short period of colder and snowier winters around 1980, as well as a very slight but continuous increase between 1975 and 2000 concomitant with warming. Furthermore, the regression models quantify the respective weight of the different covariates, mostly temperature anomalies and south-facing snowpack characteristics to explain the trends and most of the exceptional winters. Regional differences are discussed as well as seasonal variations between winter and spring activity and confirm rather different snow and weather regimes influencing avalanche activity over the Northern and Southern Alps, depending on the season.”

Citation: Castebrunet, H., Eckert, N., and Giraud, G.: Snow and weather climatic control on snow avalanche occurrence fluctuations over 50 yr in the French Alps, Clim. Past, 8, 855-875, doi:10.5194/cp-8-855-2012, 2012.


Does natural variability dominate global sea surface temperature changes since 1984?

On the Observed Trends and Changes in Global Sea Surface Temperature and Air-Sea Heat Fluxes (1984-2006) – Large & Yeager (2012)

Abstract: “Global satellite observations show the sea surface temperature (SST) increasing since the 1970s in all ocean basins, while the net air-sea heat flux, Q, decreases. Over the period 1984-2006 the global changes are 0.28°C in SST and -9.1 W/m2 in Q, giving an effective air-sea coupling coefficient of -32 W/m2/°C. The global response in Q expected from SST alone is determined to be -12.9 W/m2, and the global distribution of the associated coupling coefficient is shown. Typically, about one-half (6.8 W/m2) of this SST effect on heat flux is compensated by changes in the overlying near surface atmosphere. Slab Ocean Models (SOMs) assume that ocean heating processes do not change from year to year, so that a constant annual heat flux would maintain a linear trend in annual SST. However, the necessary 6.1 W/m2 increase is not found in the downwelling longwave and shortwave fluxes, which combined show a -3 W/m2 decrease. The SOM assumptions are revisited to determine the most likely source of the inconsistency with observations. The indirect inference is that diminished ocean cooling due to vertical ocean processes played an important role in sustaining the observed positive trend in global SST from 1984 through 2006, despite the decrease in global surface heat flux. A similar situation is found in the individual basins, though magnitudes differ. A conclusion is that natural variability, rather than long term climate change, dominates the SST and heat flux changes over this 23 year period. On shorter time scales the relationship between SST and heat flux exhibits a variety of behaviors.”

Citation: W. G. Large and S. G. Yeager, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00148.1.


Climate determines where trees live

How are tree species distributed in climatic space? A simple and general pattern – Boucher Lalonde et al. (2012)

Abstract: “Aim: Although many factors undoubtedly affect species geographic distributions, can a single, simple model nonetheless capture most of the spatial variation in the probability of presence/absence in a large set of species? For 482 North American tree species that occur east of the Rocky Mountains, we investigated the shape(s) of the relationship between the probability of occupancy of a given location and macroclimate, and its consistency among species and regions. Location: North America. Methods: Using Little’s tree range maps, we tested four hypothetical shapes of response relating occupancy to climate: (1) high occupancy of all suitable climates; (2) threshold response (i.e. unsuitable climates exclude species, but within the thresholds, species presence is independent of climate); (3) occupancy is a bivariate normal function of annual temperature and precipitation; and (4) asymmetric limitation (i.e. abiotic factors set abrupt range limits in stressful climates only). Finally, we compared observed climatic niches with the occupancy of similar climates on off-shore islands as well as west of the Rockies. Results: (a) Species’ distributions in climatic space do not have strong thresholds, nor are they systematically skewed towards less stressful climates. (b) Occupancy can generally be described by a bivariate normal function of temperature and precipitation, with little or no interaction between the two variables. This model, averaged over all species, accounts for 82% of the spatial variation in the probability of occupancy of a given area. (c) Occupied geographic ranges are typically ringed by unoccupied, but climatically suitable areas. (d) Observed climatic niche positions are largely conserved between regions. Main conclusions: We conclude that, despite the complexities of species histories and biologies, to a first approximation most of the variation in their geographic distributions relates to climate, in similar ways for nearly all species.”

Citation: Véronique Boucher Lalonde, Antoine Morin, David J. Currie, Global Ecology and Biogeography, DOI: 10.1111/j.1466-8238.2012.00764.x.


Transition from Medieval Warm Period to Little Ice Age in North Atlantic does not imply changes in weather regimes

Stability of weather regimes during the last millennium from climate simulations – Yiou et al. (2012)

Abstract: “The variability of the extra-tropical atmospheric circulation and its potential dependence on external forcings have been debated topics in climate modeling and observation communities. A recent reconstruction of the North Atlantic Oscillation Index has argued that the Medieval Warm Period period yielded a persistent positive phase of this index in contrast with an oscillating mode during the Little Ice Age. This paper tests whether this feature can be obtained, in millennium simulations from three different climate models. We examine the daily atmospheric dynamics that drives the main modes of extra-tropical variability. We find that the transition from a Medieval Warm Period to a Little Ice Age in the North Atlantic does not imply changes in patterns or frequency of weather regimes, although the mean surface temperature change is significant. This implies that the interpretation of proxy records in terms of atmospheric variability should be revised in order to take into account the structure of daily meteorological patterns, and/or climate models are too constrained to infer large changes of atmospheric variability.”

Citation: Yiou, P., J. Servonnat, M. Yoshimori, D. Swingedouw, M. Khodri, and A. Abe-Ouchi (2012), Stability of weather regimes during the last millennium from climate simulations, Geophys. Res. Lett., 39, L08703, doi:10.1029/2012GL051310.


Comparison of climate response to solar and GHG forcings

Robustness of Dynamical Feedbacks from Radiative Forcing: 2% Solar versus 2xCO2 Experiments in an Idealized GCM – Cai & Tung (2012)

Abstract: “Despite the differences in the spatial patterns of the external forcing associated with a doubling CO2 and with a 2% solar variability, the final responses in the troposphere and at the surface in a three-dimensional general circulation model appear remarkably similar. Various feedback processes are diagnosed and compared using the Climate Feedback-Response Analysis Method (CFRAM) to understand the mechanisms responsible. At the surface, solar radiative forcing is stronger in the tropics than at the high latitudes, while greenhouse radiative forcing is stronger at high latitudes compared to the tropics. Also solar forcing is positive everywhere in the troposphere and greenhouse radiative forcing is positive mainly in lower troposphere. The water vapor feedback strengthens the upward decreasing radiative heating profile in the tropics and the poleward decreasing radiative heating profile in the lower troposphere. The “evaporative” and convective feedbacks play an important role only in the tropics where they act to reduce the warming at the surface and lower troposphere in favor of upper troposphere warming. Both water vapor feedback and enhancement of convection in the tropics further strengthen the initial poleward decreasing profile of energy flux convergence perturbations throughout the troposphere. As a result, the large-scale dynamical poleward energy transport, which acts on the negative temperature gradient, is enhanced in both cases, contributing to a polar amplification of warming aloft and a warming reduction in the tropics. The dynamical amplification of polar atmospheric warming also contributes additional warming to the surface below via downward thermal radiation.”

Citation: Ming Cai and Ka-Kit Tung, Journal of the Atmospheric Sciences 2012, doi: http://dx.doi.org/10.1175/JAS-D-11-0117.1.


Queensland 2011 flood as PDO indicator

The 2011 southeast Queensland extreme summer rainfall: A confirmation of a negative Pacific Decadal Oscillation phase? – Cai & Rensch (2012)

Abstract: “The devastating southeast Queensland (SEQ) flood and the associated extreme rainfall in January 2011 were accompanied by an extraordinarily strong La Niña. The regional summer rainfall is affected by the El Niño-Southern Oscillation (ENSO) cycle, but modulated by the Pacific Decadal Oscillation (PDO) or the Interdecadal Pacific Oscillation (IPO). What does the recent flood tell about the status of the PDO-IPO? Using three lines of supporting evidence it is proposed that the SEQ 2011 austral summer rain constitutes a confirmation of a transition to a negative phase of the PDO-IPO. Firstly, the 2011 summer saw large SEQ rainfall and SOI values that historically occur only in a negative PDO-IPO phase; secondly, there was an associated re-establishment of an ENSO-SEQ rainfall teleconnection; and finally, the decadal-circulation state, particularly the tropical convection, has developed toward a state similar to that during other negative PDO-IPO periods. The results imply an increased chance of high summer rainfall events over the region during La Niña in the upcoming decade or so.”

Citation: Cai, W. and P. van Rensch (2012), The 2011 southeast Queensland extreme summer rainfall: A confirmation of a negative Pacific Decadal Oscillation phase?, Geophys. Res. Lett., 39, L08702, doi:10.1029/2011GL050820.


Improvements are needed for climate model simulations of cloud forcing in subtropics

Origins of differences in climate sensitivity, forcing and feedback in climate models – Webb et al. (2012)

Abstract: “We diagnose climate feedback parameters and CO2 forcing including rapid adjustment in twelve atmosphere/mixed-layer-ocean (“slab”) climate models from the CMIP3/CFMIP-1 project (the AR4 ensemble) and fifteen parameter-perturbed versions of the HadSM3 slab model (the PPE). In both ensembles, differences in climate feedbacks can account for approximately twice as much of the range in climate sensitivity as differences in CO2 forcing. In the AR4 ensemble, cloud effects can explain the full range of climate sensitivities, and cloud feedback components contribute four times as much as cloud components of CO2 forcing to the range. Non-cloud feedbacks are required to fully account for the high sensitivities of some models however. The largest contribution to the high sensitivity of HadGEM1 is from a high latitude clear-sky shortwave feedback, and clear-sky longwave feedbacks contribute substantially to the highest sensitivity members of the PPE. Differences in low latitude ocean regions (30°N/S) contribute more to the range than those in mid-latitude oceans (30–55°N/S), low/mid latitude land (55°N/S) or high latitude ocean/land (55–90°N/S), but contributions from these other regions are required to account fully for the higher model sensitivities, for example from land areas in IPSL CM4. Net cloud feedback components over the low latitude oceans sorted into percentile ranges of lower tropospheric stability (LTS) show largest differences among models in stable regions, mainly due to their shortwave components, most of which are positive in spite of increasing LTS. Differences in the mid-stability range are smaller, but cover a larger area, contributing a comparable amount to the range in climate sensitivity. These are strongly anti-correlated with changes in subsidence. Cloud components of CO2 forcing also show the largest differences in stable regions, and are strongly anticorrelated with changes in estimated inversion strength (EIS). This is qualitatively consistent with what would be expected from observed relationships between EIS and low-level cloud fraction. We identify a number of cases where individual models show unusually strong forcings and feedbacks compared to other members of the ensemble. We encourage modelling groups to investigate unusual model behaviours further with sensitivity experiments. Most of the models fail to correctly reproduce the observed relationships between stability and cloud radiative effect in the subtropics, indicating that there remains considerable room for model improvements in the future.”

Citation: Mark J. Webb, F. Hugo Lambert and Jonathan M. Gregory, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1336-x.


CLASSIC OF THE WEEK: Anders (1882)

Forests-Their Influence Upon Climate and Rainfall – Anders (1882) [FULL TEXT]

Abstract: No abstract. Quote from the beginning of the article: “That there exists some sort of relation betwixt forests and conditions of climate, perhaps most observers would be ready to concede. Many attempts have been made to explain how forests affect atmospheric states, but there is great diversity of opinion on the subject, and, indeed, the question to-day remains somewhat involved in obscurity. As every one knows,…”

Citation: Anders, J. M., The American Naturalist, Vol. 16, No. 1 (Jan., 1882) (pp. 19-30).


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 16/2012

Posted by Ari Jokimäki on April 23, 2012

I’m sick and tired of coming up something witty and funny week after week for these introductions, so now I’ll just write this boring summary: Themes of this week are mapping, Arctic sea ice, non-Arctic air traffic, greenhouse gases (which by the way has nothing to do with gardener’s stomach problems), paleoclimate, biosphere, groundwater, seawater, groundweather, seaweather, and what else? Oh yes, and climate, of course. All this in just 15 little studies plus one classic.


Using computer tomography for measuring tree rings

DendroCT – Dendrochronology without damage – Bill et al. (2012)

Abstract: “The paper describes an evaluation of the applicability of computer tomography in archaeological dendrochronology. Two different computer tomographs were tested, a Siemens Somatom Emotion single slice scanner developed for medical use, and a Nikon Metrology model XT H 225 LC, which is an industrial type scanner. Both scanners were tested against air-dried, archaeological oak wood, and more limited experiments were made with waterlogged archaeological oak wood and archaeological oak wood which had been treated with high-molecular polyethyleneglycol as a conservation treatment. After scanning the resulting imagery were measured and analysed for dendrochronology using off-the-shelf software for handling and measuring on the images and the specialist programme DENDRO for the dendrochronological analyses. The results showed that only the industrial scanner produced sufficiently clear imagery to allow for dendrochronological analyses. In the scans it was possible to separate tree-rings down to 0.2 mm width, and it was possible to identify the sapwood–heartwood border when sufficient sapwood rings were present. It was found, however, that a visual inspection of the object was required to distinguish between sapwood and decayed wood. Comparisons between direct measurements of tree-rings and measurements based on CT-imagery revealed no significant differences. The scanning and subsequent dating of more than 90 objects showed that dendrochronological dating based on CT-scanning has a success rate equal to conventional dating, albeit more time consuming. The attempts to scan waterlogged and PEG-impregnated archaeological oak wood were unsuccessful, due to a low degree of contrast between the water/PEG and the preserved wood. The experiments were too limited to exclude, however, that a successful protocol can be developed also for these types of materials.”

Citation: Jan Bill, Aoife Daly, Øistein Johnsen, Knut S. Dalen, Dendrochronologia, http://dx.doi.org/10.1016/j.dendro.2011.11.002.


Satellite measurements of global carbon dioxide distribution

Global CO2 distributions over land from the Greenhouse Gases Observing Satellite (GOSAT) – Hammerling et al. (2012)

Abstract: “January 2009 saw the successful launch of the first space-based mission specifically designed for measuring greenhouse gases, the Japanese Greenhouse gases Observing SATellite (GOSAT). We present global land maps (Level 3 data) of column-averaged CO2 concentrations (XCO2) derived using observations from the GOSAT ACOS retrieval algorithm, for July through December 2009. The applied geostatistical mapping approach makes it possible to generate maps at high spatial and temporal resolutions that include uncertainty measures and that are derived directly from the Level 2 observations, without invoking an atmospheric transport model or estimates of CO2 uptake and emissions. As such, they are particularly well suited for comparison studies. Results show that the Level 3 maps for July to December 2009 on a 1° × 1.25° grid, at six-day resolution capture much of the synoptic scale and regional variability of XCO2, in addition to its overall seasonality. The uncertainty estimates, which reflect local data coverage, XCO2 variability, and retrieval errors, indicate that the Southern latitudes are relatively well-constrained, while the Sahara Desert and the high Northern latitudes are weakly-constrained. A probabilistic comparison to the PCTM/GEOS-5/CASA-GFED model reveals that the most statistically significant discrepancies occur in South America in July and August, and central Asia in September to December. While still preliminary, these results illustrate the usefulness of a high spatiotemporal resolution, data-driven Level 3 data product for direct interpretation and comparison of satellite observations of highly dynamic parameters such as atmospheric CO2.”

Citation: Hammerling, D. M., A. M. Michalak, C. O’Dell, and S. R. Kawa (2012), Global CO2 distributions over land from the Greenhouse Gases Observing Satellite (GOSAT), Geophys. Res. Lett., 39, L08804, doi:10.1029/2012GL051203.


Phytoplankton production from melting ponds on Arctic sea ice less than 1% of total Arctic Ocean production

Phytoplankton production from melting ponds on Arctic sea ice – Lee et al. (2012)

Abstract: “Recently, the areal extent of melt ponds within sea ice has rapidly increased during the Arctic Ocean summer. However, the biological impacts of melt ponds on the Arctic marine ecosystem have rarely been studied. Carbon and nitrogen uptake rates of phytoplankton were measured at 26 different melt ponds in 2005 and 2008, using a 13C-15N dual stable isotope tracer technique. Generally, the open ponds had relatively higher nutrients than closed ponds, but the nutrient concentrations in the open ponds were within a range similar to those in surrounding surface seawaters. Chlorophyll a (Chl a) concentrations in melt ponds ranged from 0.1 to 2.9 mg Chl a m−3 with a mean of 0.6 mg Chl a m−3 (SD = ±0.8 mg Chl a m−3) in the Canada Basin in 2005, whereas the range of the Chl a concentrations was from 0.1 to 0.3 mg Chl a m−3 with a mean of 0.2 mg Chl a m−3 (SD = ±0.1 mg Chl a m−3) in the central Arctic Ocean in 2008. The average annual carbon production in sea ice melt ponds was 0.67 g C m−3 (SD = ±1.03 g C m−3) in the Arctic Ocean. Based on this study, recent annual carbon production of all melt ponds was roughly estimated to be approximately 2.6 Tg C, which is less than 1% of the total production in the Arctic Ocean.”

Citation: Lee, S. H., D. A. Stockwell, H.-M. Joo, Y. B. Son, C.-K. Kang, and T. E. Whitledge (2012), Phytoplankton production from melting ponds on Arctic sea ice, J. Geophys. Res., 117, C04030, doi:10.1029/2011JC007717.


The greenhouse gas that mankind stopped emitting

Emissions halted of the potent greenhouse gas SF5CF3 – Sturges et al. (2012) [FULL TEXT]

Abstract: “Long term measurements in background air (Cape Grim, Tasmania) and firn air (NEEM, Greenland) of the potent long-lived greenhouse gas SF5CF3show that emissions declined after the late 1990s, having grown since the 1950s, and became indistinguishable from zero after 2003. The timing of this decline suggests that emissions of this gas may have been related to the production of certain fluorochemicals; production of which have been recently phased out. An earlier observation of closely correlated atmospheric abundances of SF5CF3 and SF6 are shown here to have likely been purely coincidental, as their respective trends diverged after 2002. Due to its long lifetime (ca. 900 yr), atmospheric concentrations of SF5CF3 have not declined, and it is now well mixed between hemispheres, as is also shown here from interhemispheric aircraft measurements. Total cumulative emissions of SF5CF3 amount to around 5 kT.”

Citation: Sturges, W. T., Oram, D. E., Laube, J. C., Reeves, C. E., Newland, M. J., Hogan, C., Martinerie, P., Witrant, E., Brenninkmeijer, C. A. M., Schuck, T. J., and Fraser, P. J.: Emissions halted of the potent greenhouse gas SF5CF3, Atmos. Chem. Phys., 12, 3653-3658, doi:10.5194/acp-12-3653-2012, 2012.


What Atlantic Multidecadal Oscillation was like during the Holocene?

Simulated Atlantic Multidecadal Oscillation during the Holocene – Wei & Lohmann (2012)

Abstract: “The Atlantic Multidecadal Oscillation (AMO) and its possible change during the Holocene are examined in this study, using long-term simulations of the Earth system model COSMOS. A quasi-persistent ~55- to 80-year cycle characterizing in the North Atlantic sea surface temperature, is highly associated with the multidecadal variability of the Atlantic Meridional Overturning Circulation (AMOC) during the Holocene. This mode can be found throughout the Holocene, indicating that the AMO is dominated by internal climate variability. Stronger-than-normal AMOC results in warmer-than-normal surface temperature, spreading over almost the whole North Hemisphere, in particular the North Atlantic Ocean. During the warm phase of the AMO, more precipitation is detected in the North Atlantic low and high latitudes. It also generates a dipolar seesaw pattern in the sea ice anomaly. Our results reveal that the influence of the AMO can be amplified by a more vigorous AMOC variability during the early Holocene in the presence of a remnant of the Laurentide Ice Sheet and when freshwater entered the North Atlantic Ocean. This conclusion might be applicable to the past AMO reconstruction and the future AMO estimation.”

Citation: Wei Wei and Gerrit Lohmann, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00667.1.


Flooding of wet tundra can lead to increased carbon dioxide loss

Increased CO2 loss from vegetated drained lake tundra ecosystems due to flooding – Zona et al. (2012)

Abstract: “Tundra ecosystems are especially sensitive to climate change, which is particularly rapid in high northern latitudes resulting in significant alterations in temperature and soil moisture. Numerous studies have demonstrated that soil drying increases the respiration loss from wet Arctic tundra. And, warming and drying of tundra soils are assumed to increase CO2 emissions from the Arctic. However, in this water table manipulation experiment (i.e., flooding experiment), we show that flooding of wet tundra can also lead to increased CO2 loss. Standing water increased heat conduction into the soil, leading to higher soil temperature, deeper thaw and, surprisingly, to higher CO2 loss in the most anaerobic of the experimental areas. The study site is located in a drained lake basin, and the soils are characterized by wetter conditions than upland tundra. In experimentally flooded areas, high wind speeds (greater than ∼4 m s−1) increased CO2 emission rates, sometimes overwhelming the photosynthetic uptake, even during daytime. This suggests that CO2 efflux from C rich soils and surface waters can be limited by surface exchange processes. The comparison of the CO2 and CH4 emission in an anaerobic soil incubation experiment showed that in this ecosystem, CO2 production is an order of magnitude higher than CH4 production. Future increases in surface water ponding, linked to surface subsidence and thermokarst erosion, and concomitant increases in soil warming, can increase net C efflux from these arctic ecosystems.”

Citation: Zona, D., D. A. Lipson, K. T. Paw U, S. F. Oberbauer, P. Olivas, B. Gioli, and W. C. Oechel (2012), Increased CO2 loss from vegetated drained lake tundra ecosystems due to flooding, Global Biogeochem. Cycles, 26, GB2004, doi:10.1029/2011GB004037.


Where to build wells in Africa

Quantitative maps of groundwater resources in Africa – MacDonald et al. (2012) [FULL TEXT]

Abstract: “In Africa, groundwater is the major source of drinking water and its use for irrigation is forecast to increase substantially to combat growing food insecurity. Despite this, there is little quantitative information on groundwater resources in Africa, and groundwater storage is consequently omitted from assessments of freshwater availability. Here we present the first quantitative continent-wide maps of aquifer storage and potential borehole yields in Africa based on an extensive review of available maps, publications and data. We estimate total groundwater storage in Africa to be 0.66 million km3 (0.36–1.75 million km3). Not all of this groundwater storage is available for abstraction, but the estimated volume is more than 100 times estimates of annual renewable freshwater resources on Africa. Groundwater resources are unevenly distributed: the largest groundwater volumes are found in the large sedimentary aquifers in the North African countries Libya, Algeria, Egypt and Sudan. Nevertheless, for many African countries appropriately sited and constructed boreholes can support handpump abstraction (yields of 0.1–0.3 l s−1), and contain sufficient storage to sustain abstraction through inter-annual variations in recharge. The maps show further that the potential for higher yielding boreholes ( > 5 l s−1) is much more limited. Therefore, strategies for increasing irrigation or supplying water to rapidly urbanizing cities that are predicated on the widespread drilling of high yielding boreholes are likely to be unsuccessful. As groundwater is the largest and most widely distributed store of freshwater in Africa, the quantitative maps are intended to lead to more realistic assessments of water security and water stress, and to promote a more quantitative approach to mapping of groundwater resources at national and regional level.”

Citation: A M MacDonald et al 2012 Environ. Res. Lett. 7 024009 doi:10.1088/1748-9326/7/2/024009.


Climate change might lead to more frequent environments favorable for severe thunderstorms

Severe thunderstorms and climate change – Brooks (2012) [FULL TEXT]

Abstract: “As the planet warms, it is important to consider possible impacts of climate change on severe thunderstorms and tornadoes. To further that discussion, the current distribution of severe thunderstorms as a function of large-scale environmental conditions is presented. Severe thunderstorms are much more likely to form in environments with large values of convective available potential energy (CAPE) and deep-tropospheric wind shear. Tornadoes and large hail are preferred in high-shear environments and non-tornadic wind events in low shear. Further, the intensity of tornadoes and hail, given that they occur, tends to be almost entirely a function of the shear and only weakly depends on the thermodynamics. Climate model simulations suggest that CAPE will increase in the future and the wind shear will decrease. Detailed analysis has suggested that the CAPE change will lead to more frequent environments favorable for severe thunderstorms, but the strong dependence on shear for tornadoes, particularly the strongest ones, and hail means that the interpretation of how individual hazards will change is open to question. The recent development of techniques to use higher-resolution models to estimate the occurrence of storms of various kinds is discussed. Given the large interannual variability in environments and occurrence of events, caution is urged in interpreting the observational record as evidence of climate change.”

Citation: H.E. Brooks, Atmospheric Research, http://dx.doi.org/10.1016/j.atmosres.2012.04.002.


Arctic seasonal sea ice has smaller albedo than multiyear ice

Albedo evolution of seasonal Arctic sea ice – Perovich & Polashenski (2012)

Abstract: “There is an ongoing shift in the Arctic sea ice cover from multiyear ice to seasonal ice. Here we examine the impact of this shift on sea ice albedo. Our analysis of observations from four years of field experiments indicates that seasonal ice undergoes an albedo evolution with seven phases; cold snow, melting snow, pond formation, pond drainage, pond evolution, open water, and freezeup. Once surface ice melt begins, seasonal ice albedos are consistently less than albedos for multiyear ice resulting in more solar heat absorbed in the ice and transmitted to the ocean. The shift from a multiyear to seasonal ice cover has significant implications for the heat and mass budget of the ice and for primary productivity in the upper ocean. There will be enhanced melting of the ice cover and an increase in the amount of sunlight available in the upper ocean.”

Citation: Perovich, D. K. and C. Polashenski (2012), Albedo evolution of seasonal Arctic sea ice, Geophys. Res. Lett., 39, L08501, doi:10.1029/2012GL051432.


Recent sea level trend fluctuations in tropical Pacific are dominated by natural variability

Tropical Pacific spatial trend patterns in observed sea level: internal variability and/or anthropogenic signature? – Meyssignac et al. (2012) [FULL TEXT]

Abstract: “In this study we focus on the sea level trend pattern observed by satellite altimetry in the tropical Pacific over the 1993–2009 time span (i.e. 17 yr). Our objective is to investigate whether this 17-yr-long trend pattern was different before the altimetry era, what was its spatio-temporal variability and what have been its main drivers. We try to discriminate the respective roles of the internal variability of the climate system and of external forcing factors, in particular anthropogenic emissions (greenhouse gases and aerosols). On the basis of a 2-D past sea level reconstruction over 1950–2009 (based on a combination of observations and ocean modelling) and multi-century control runs (i.e. with constant, preindustrial external forcing) from eight coupled climate models, we have investigated how the observed 17-yr sea level trend pattern evolved during the last decades and centuries, and try to estimate the characteristic time scales of its variability. For that purpose, we have computed sea level trend patterns over successive 17-yr windows (i.e. the length of the altimetry record), both for the 60-yr long reconstructed sea level and the model runs. We find that the 2-D sea level reconstruction shows spatial trend patterns similar to the one observed during the altimetry era. The pattern appears to have fluctuated with time with a characteristic time scale of the order of 25–30 yr. The same behaviour is found in multi-centennial control runs of the coupled climate models. A similar analysis is performed with 20th century coupled climate model runs with complete external forcing (i.e. solar plus volcanic variability and changes in anthropogenic forcing). Results suggest that in the tropical Pacific, sea level trend fluctuations are dominated by the internal variability of the ocean–atmosphere coupled system. While our analysis cannot rule out any influence of anthropogenic forcing, it concludes that the latter effect in that particular region is stillhardly detectable.”

Citation: Meyssignac, B., Salas y Melia, D., Becker, M., Llovel, W., and Cazenave, A.: Tropical Pacific spatial trend patterns in observed sea level: internal variability and/or anthropogenic signature?, Clim. Past, 8, 787-802, doi:10.5194/cp-8-787-2012, 2012.


Recent sea ice loss is largely caused by Atlantification of the Barents Sea

Quantifying the influence of Atlantic heat on Barents Sea ice variability and retreat – Årthun et al. (2012)

Abstract: “The recent Arctic winter sea ice retreat is most pronounced in the Barents Sea. Using available observations of the Atlantic inflow to the Barents Sea and results from a regional ice-ocean model we assess and quantify the role of inflowing heat anomalies on sea ice variability. The interannual variability and longer term decrease in sea ice area reflect the variability of the Atlantic inflow, both in observations and model simulations. The last decade (1998-2008) the reduction in annual (July-June) sea ice area was 218·103 km2, or close to 50%. This reduction has occurred concurrent to an increase in observed Atlantic heat transport, due to both strengthening and warming of the inflow. Modelled interannual variations in sea ice area between 1948 and 2007 are associated with anomalous heat transport (r = −0.63) with a 70·103 km2 decrease per 10 TW input of heat. Based on the simulated ocean heat budget we find that the heat transport into the western Barents Sea sets the boundary of the ice-free Atlantic domain and, hence, the sea ice extent. The regional heat content and heat loss to the atmosphere scale with the area of open ocean as a consequence. Recent sea ice loss is thus largely caused by an increasing “Atlantification” of the Barents Sea.”

Citation: M. Årthun, T. Eldevik, L. H. Smedsrud, Ø. Skagseth and R. B. Ingvaldsen, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00466.1.


Foraminifera species cannot maintain populations under next century carbon dioxide levels

Productivity gains do not compensate for reduced calcification under near-future ocean acidification in the photosynthetic benthic foraminifera Marginopora vertebralis – Uthicke & Fabricius (2012)

Abstract: “Changes in the seawater carbonate chemistry (ocean acidification) from increasing atmospheric carbon dioxide (CO2) concentrations negatively affect many marine calcifying organisms, but may benefit primary producers under dissolved inorganic carbon (DIC) limitation. To improve predictions of the ecological effects of ocean acidification, the net gains and losses between the processes of photosynthesis and calcification need to be studied jointly on physiological and population levels. We studied productivity, respiration, and abundances of the symbiont-bearing foraminifera Marginopora vertebralis on natural CO2 seeps in Papua New Guinea and conducted additional studies on production and calcification on the Great Barrier Reef (GBR) using artificially enhanced pCO2. Net oxygen production increased up to 90% with increasing pCO2, with temperature, light and pH together explaining 61% of the variance in production. Production increased with increasing light and increasing pCO2, and declined at higher temperatures. Respiration was also significantly elevated (~25%), while calcification was reduced (16-39%) at low pH/high pCO2 compared to present day conditions. In the field, M. vertebralis was absent at three CO2 seep sites at pHTotal levels below ~7.9 (pCO2 ~700 μatm), but it was found in densities of over 1000 m−2 at all three control sites. The study showed that endosymbiotic algae in foraminifera benefit from increased DIC availability, and may be naturally carbon limited. The observed reduction in calcification may have been caused either by increased energy demands for proton pumping (measured as elevated rates of respiration), or by stronger competition for DIC from the more productive symbionts. The net outcome of these two competing processes is that M. vertebralis cannot maintain populations under pCO2 exceeding 700 μatm, thus are likely to be extinct in the next century.”

Citation: S. Uthicke, K. Fabricius, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02715.x.


Role of climate in medieval Norway population might have been underestimated

Climate and demographic crises in Norway in medieval and early modern times – Dybdahl (2012)

Abstract: “The topic of this paper is the importance of climate for the population and settlement in medieval and early modern times. Were the demographic crises caused by crop failure and famine or by disease? I begin by reviewing European research (particularly English) relating to the issue. The views of Norwegian historians regarding the causes of the agrarian crisis in the late Middle Ages are then examined. Hasund (Hasund S, 1919, 1944, Den store mannedauden. Or Noregs bondesoge. Glytt og granskingar II, Oslo, pp. 82–161. First printed in Beretning om Norges Landbrukshøiskoles virksomhet 1918–1919) claimed it was the plagues, not the climate, that held the population at a low level to the end of the Middle Ages, a view that has been repeated in recent years by such researchers as Lunden (Lunden K, 2002, Norges landbrukshistorie II, 1350–1814. Frå svartedauden til 17. mai. Oslo) and Moseng (Moseng OG, 2006, Den flyktige pesten. Vilkårene for epidemier i Norge i seinmiddelalder og tidlig nytid. Oslo). This paper claims that the role of the climate has been underestimated, in particular that the climatic shock of several bad years in a row directly and indirectly brought appreciable excess mortality in a country situated so far north. ‘Bad’ years demonstrated through dendrochronology are in many cases reflected in documentary evidence concerning poor corn harvests and high mortality.”

Citation: Audun Dybdahl, The Holocene April 16, 2012 0959683612441843, doi: 10.1177/0959683612441843.


Amazonian diversity depends primarily on ability of species to tolerate rising temperatures

The relative importance of deforestation, precipitation change, and temperature sensitivity in determining the future distributions and diversity of Amazonian plant species – Feeley et al. (2012)

Abstract: “Tropical forests are threatened by many human disturbances – two of the most important of which are deforestation and climate change. In order to mitigate the impacts of these disturbances, it is important to understand their potential effects on the distributions of species. In the tropics, such understanding has been hindered by poor knowledge of the current distributions and range limits of most species. Here we use herbarium collection records to model the current and future distributions of ca 3000 Amazonian plant species. We project these distributions into the future under a range of different scenarios related to the magnitude and extent of disturbance as well as the response of species to changes in temperature, precipitation and atmospheric concentrations of CO2. We find that the future of Amazonian diversity will be dependant primarily on the ability of species to tolerate or adapt to rising temperatures. If the thermal niches of tropical plants are fixed and incapable of expanding under rapid warming, then the negative effects of climate change will overshadow the effects of deforestation, greatly reducing the area of suitable habitat available to most species and potentially leading to massive losses of biodiversity throughout the Amazon. If tropical species are generally capable of tolerating warmer temperatures, rates of habitat loss will be greatly reduced but many parts of Amazonia may still experience rapid losses of diversity, with the effects of enhanced seasonal water stress being similar in magnitude to the effects of deforestation.”

Citation: Kenneth J. Feeley, Yadvinder Malhi, Przemyslaw Zelazowski, Miles R. Silman, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02719.x.


Rerouting Arctic cross-polar flights might be a good idea

The effects of rerouting aircraft around the arctic circle on arctic and global climate – Jacobson et al. (2012)

Abstract: “Climate data suggest greater warming over the Arctic than lower latitudes, and the most abundant direct source of black carbon and other climate-relevant pollutants over the Arctic is cross-polar flights by international aviation. A relevant question is whether rerouting cross-polar flights to circumnavigate the Arctic Circle reduces or enhances such warming. To study this issue, a model accounting for subgrid exhaust plumes from each individual commercial flight worldwide was used with 2006 global aircraft emission inventories that treated cross-polar flights and flights rerouted around the Arctic Circle (66.56083 °N), respectively. Rerouting increased fuel use by 0.056 % in the global average, mostly right outside the Arctic Circle, but most of the associated black carbon and other emissions were removed faster because they were now over latitudes of greater precipitation and lesser stability. Rerouting also reduced fuel use and emissions within the Arctic Circle by 83 % and delayed pollutant transport to the Arctic. The Arctic reduction in pollutants, particularly of black carbon, decreased Arctic and global temperature and increased Arctic sea ice over 22 years. Although the slight increase in total CO2 emissions due to rerouting may dampen the benefit of rerouting over more decades, rerouting or even partial rerouting (allowing cross-polar flights during polar night only) may delay the elimination of Arctic sea ice, which will otherwise likely occur within the next 2–3 decades due to global warming in general. Rerouting may increase worldwide fuel plus operational costs by only ~$99 million/yr, 47–55 times less than an estimated 2025 U.S.-alone cost savings due to the global warming reduction from rerouting.”

Citation: Mark Z. Jacobson, Jordan T. Wilkerson, Sathya Balasubramanian, Wayne W. Cooper and Nina Mohleji, Climatic Change, DOI: 10.1007/s10584-012-0462-0.


CLASSIC OF THE WEEK: Palmer (1910)

The Influence of Sun-Spots Upon Climate – Palmer (1910) [FULL TEXT]

Abstract: No abstract. Quote from the beginning of the paper: “Considerable speculation has been indulged in within recent years as to the terrestrial influence of sun-spots. While few investigations have been made attempting to measure this relation, if such exists, many conjectures of various kinds have been offered from time to time. Certain influences of these solar activities upon the Earth have been perfectly demonstrated. For example,…”

Citation: Palmer, Andrew H., 1910, Popular Astronomy, vol. 18, pp.8-12.


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 15/2012

Posted by Ari Jokimäki on April 16, 2012

This week’s shocker is the climate change 4000 years ago that wiped out most of Chinese Neolithic cultures. However, several thousands of years earlier Chinese had it better; climate change back then (known as Younger Dryas event) was much milder in China than in Greenland. I wonder if Greenland was actually green during the YD event, or was it even a “land”. They might have called it Whiteice back then.

By the way, we do have a study on Greenland this week. This one studies supraglacial lakes in West Greenland. You might think that melting is a good thing for lakes as it increases their water amount, but strangely enough, in this case the meltwater apparently drains the lakes. Another study this week studies glacial lakes in Himalaya. There the lakes are quite nasty, as they produce outburst floods. There’s also another study that has mapped all the glacial lakes there. As you can see, in the world of scientists, lakes aren’t just those watery things that lie there without actually doing anything. No, in their world lakes are things that go out in a burst. And some say that science isn’t interesting…

Each week, we usually have many studies concerning biosphere, but this week we only have one study. Gladly that one is a stellar study – it is about a sea star. Well ok, we do have a study on land carbon cycle which largely is about biosphere. We also have a tree ring study which can be considered as biosphere related study. So, perhaps we should just conclude that we have lot of biosphere studies this week. How many Arctic studies we have? There was the Greenland paper (I wonder if in the future paper will actually be important export of Greenland), and then we have the upwelling paper, positive cloud feedback paper, and perhaps even the NAO paper. That would make four papers. We only have one paper from Antarctica – the one on temperature trends. This uneven spatial distibution of papers might be due to my northern bias. After all, part of my home country is in Arctic region.

Two other not yet mentioned studies in this week have been studying urban issues. You will find out how modification of urban surface albedos affects global climate and how methane isotopes in Los Angeles reveal fossil fuel leaks. Hmm… Los Angeles isotopes. That doesn’t sound right. Shouldn’t they have made their study in Springfield?


YD event was more gradual and had smaller amplitude in northern China than in Greenland

Timing and structure of the Younger Dryas event in northern China – Ma et al. (2012)

Abstract: “A high-resolution and absolute-dated stalagmite record from Kulishu Cave, Beijing characterizes Asian Monsoon (AM) history in northern China between ca 14 and 10.5 ka BP (thousand yrs before present, present = 1950), including the entire Younger Dryas (YD) event. Using 230Th dates and counting of annual-layers, the shift into the YD began at 12,850 ± 40 yr BP and took ∼340 yrs and the shift out of the YD began at 11,560 ± 40 yr BP and took <38 yrs (best estimate ∼20 yrs), broadly similar to previously reported AM records from central and southeastern China. The more gradual nature of the start of the YD event as observed in the AM records appears to contrast with the more abrupt beginning observed in the Greenland ice records. The total amplitude of the AM YD event is also smaller than the amplitude of the AM Heinrich Stadial 1 event. In addition, the general rising trend of the AM during the Bølling-Allerød period contrasts with the general cooling trend in Greenland temperature during that time. The influence of rising insolation on the AM may explain this observation."

Citation: Zhi-Bang Ma, Hai Cheng, Ming Tan, R. Lawrence Edwards, Hong-Chun Li, Chen-Feng You, Wu-Hui Duan, Xu Wang, Megan J. Kelly, Quaternary Science Reviews, Volume 41, 18 May 2012, Pages 83–93, http://dx.doi.org/10.1016/j.quascirev.2012.03.006.


Exceptional years in tree ring records reveal climate events and volcanic eruptions

Extreme pointer years in tree-ring records of Central Spain as evidence of climatic events and the eruption of the Huaynaputina Volcano (Peru, 1600 AD) – Génova (2012) [FULL TEXT]

Abstract: “The study of pointer years of numerous tree-ring chronologies of the central Iberian Peninsula (Sierra de Guadarrama) could provide complementary information about climate variability over the last 405 yr. In total, 64 pointer years have been identified: 30 negative (representing minimum growths) and 34 positive (representing maximum growths), the most significant of these being 1601, 1963 and 1996 for the negative ones, and 1734 and 1737 for the positive ones. Given that summer precipitation was found to be the most limiting factor for the growth of Pinus in the Sierra de Guadarrama in the second half of the 20th century, it is also an explanatory factor in almost 50% of the extreme growths. Furthermore, these pointer years and intervals are not evenly distributed throughout time. Both in the first half of the 17th and in the second half of 20th, they were more frequent and more extreme and these periods are the most notable for the frequency of negative pointer years in Central Spain. The interval 1600–1602 is of special significance, being one of the most unfavourable for tree growth in the centre of Spain, with 1601 representing the minimum index in the regional chronology. We infer that this special minimum annual increase was the effect of the eruption of Huaynaputina, which occurred in Peru at the beginning of 1600 AD. This is the first time that the effects of this eruption in the tree-ring records of Southern Europe have been demonstrated.”

Citation: Génova, M.: Extreme pointer years in tree-ring records of Central Spain as evidence of climatic events and the eruption of the Huaynaputina Volcano (Peru, 1600 AD), Clim. Past, 8, 751-764, doi:10.5194/cp-8-751-2012, 2012.


Most of Chinese Neolithic cultures were destroyed in a climate event 4000 years ago

A dramatic climatic transition at ~4000 cal. yr BP and its cultural responses in Chinese cultural domains – Liu & Feng (2012)

Abstract: “Our review of recently published climatic proxy sequences shows that the most dramatic climate tranistion of the mid Holocene (~8500–~3500 cal. yr BP) occurred at the middle- to late-Holocene transition at ~4000 cal. yr BP. In northern China, an abrupt climatic shift at ~4000 cal. yr BP was recorded in the eastern margin of the Tibetan Plateau, in the western part of the Chinese Loess Plateau and in the vast Inner Mongolian Plateau. In southern China, the ~4000 cal. yr BP event was also abrupt, but it is expressed as one of several quasi-cyclic events in most of the records. We propose that the cumulative effects of insolation-dictated declining trend in tropical SST and the geologically documented increasing trend of ENSO activity were the first-order causes of the cooling and the associated drying during the past 6000 years. Superimposed on the first-order causes were the second-order causes, i.e. the additive effects of the ‘Bond Event 3’-associated lower insolation and the increasingly drying-resulted negative feedback of ‘air–land interactions’. The second-order causes made ~4000 cal. yr BP the tipping point when the resultant drying had destroyed many Chinese Neolithic cultures. Our review of published archaeological literature shows that six of the seven well-documented Chinese Neolithic cultures collapsed at ~4000 cal. yr BP with the exception of the Henan Longshan Culture that evolved to the more advanced Erlitou Culture. The indicators of the cultural collapse include (1) the number of archaeological sites was significantly reduced, (2) the quality of the archaeological artifacts of the succeeding culture is lower than that of the preceding culture, (3) more sophisticated architectures disappeared, and (4) agricultural cultures were replaced by pastoralism or by agro-pastoralism in northern China.”

Citation: Fenggui Liu, Zhaodong Feng, The Holocene April 12, 2012 0959683612441839, doi: 10.1177/0959683612441839.


Warming produced meltwater might enhance supraglacial lake drainage events in West Greenland

A decadal investigation of supraglacial lakes in West Greenland using a fully automatic detection and tracking algorithm – Liang et al. (2012) [FULL TEXT]

Abstract: “The sudden drainage of supraglacial lakes has been previously observed to initiate surface-to-bed hydrologic connections, which are capable of enhancing basal sliding, in regions of the Greenland Ice Sheet where ice thickness approaches 1 km. In this study, we develop a robust algorithm, which automatically detects and tracks individual supraglacial lakes using visible satellite imagery, to document the evolution of a population of West Greenland supraglacial lakes over ten consecutive melt seasons. Validation tests indicate that the algorithm is highly accurate: 99.0% of supraglacial lakes can be detected and tracked and 96.3% of reported lakes are true supraglacial lakes with accurate lake properties, such as lake area, and timing of formation and drainage. Investigation of the interannual evolution of supraglacial lakes in the context of annual melt intensity reveals that during more intense melt years, supraglacial lakes drain more frequently and earlier in the melt season. Additionally, the lake population extends to higher elevations during more intense melt years, exposing an increased inland area of the ice sheet to sudden lake drainage events. These observations suggest that increased surface meltwater production due to climate change will enhance the spatial extent and temporal frequency of lake drainage events. It is unclear whether this will ultimately increase or decrease the basal sliding sensitivity of interior regions of the Greenland Ice Sheet.”

Citation: Yu-Li Lianga, William Colganb, Qin Lva, Konrad Steffenb, Waleed Abdalatib, Julienne Stroeveb, David Gallaherb, Nicolas Bayou, Remote Sensing of Environment, Volume 123, August 2012, Pages 127–138, http://dx.doi.org/10.1016/j.rse.2012.03.020.


Isotopic measurements show that major source of atmospheric methane in Los Angeles is leakage of fossil fuels

Isotopic measurements of atmospheric methane in Los Angeles, California, USA: Influence of “fugitive” fossil fuel emissions – Townsend-Small et al. (2012)

Abstract: “Recent studies have suggested that CH4 emissions in Los Angeles and other large cities may be underestimated. We utilized stable isotopes (13C and D) and radiocarbon (14C) to investigate sources of CH4 in Los Angeles, California. First, we made measurements of δ13C and δD of various CH4 sources in urban areas. Fossil fuel CH4 sources (oil refineries, power plants, traffic, and oil drilling fields) had δ13C values between −45 and −30‰ and dD values between −275 and −100‰, whereas biological CH4 (cows, biofuels, landfills, sewage treatment plants, and cattle feedlots) had δ13C values between −65 and −45‰ and δD values between −350 and −275‰. We made high-altitude observations of CH4 concentration using continuous tunable laser spectroscopy measurements combined with isotope analyses (13C, 14C, and D) of discrete samples to constrain urban CH4 sources. Our data indicate that the dominant source of CH4 in Los Angeles has a δ13C value of approximately −41.5‰ and a δD value between −229 and −208‰. Δ14C of CH4 in urban air samples ranged from +262 to +344‰ (127.1 to 134.9 pMC), depleted with respect to average global background CH4. We conclude that the major source of CH4 in Los Angeles is leakage of fossil fuels, such as from geologic formations, natural gas pipelines, oil refining, and/or power plants. More research is needed to constrain fluxes of CH4 from natural gas distribution and refining, as this flux may increase with greater reliance on natural gas and biogas for energy needs.”

Citation: Townsend-Small, A., S. C. Tyler, D. E. Pataki, X. Xu, and L. E. Christensen (2012), Isotopic measurements of atmospheric methane in Los Angeles, California, USA: Influence of “fugitive” fossil fuel emissions, J. Geophys. Res., 117, D07308, doi:10.1029/2011JD016826.


Increasing urban surface albedos could cause global cooling of 0.01-0.07K

The long-term effect of increasing the albedo of urban areas – Akbari et al. (2012) [FULL TEXT]

Abstract: “Solar reflective urban surfaces (white rooftops and light-colored pavements) can increase the albedo of an urban area by about 0.1. Increasing the albedo of urban and human settlement areas can in turn decrease atmospheric temperature and could potentially offset some of the anticipated temperature increase caused by global warming. We have simulated the long-term (decadal to centennial) effect of increasing urban surface albedos using a spatially explicit global climate model of intermediate complexity. We first carried out two sets of simulations in which we increased the albedo of all land areas between ±20° and ±45° latitude respectively. The results of these simulations indicate a long-term global cooling effect of 3 × 10−15 K for each 1 m2 of a surface with an albedo increase of 0.01. This temperature reduction corresponds to an equivalent CO2 emission reduction of about 7 kg, based on recent estimates of the amount of global warming per unit CO2 emission. In a series of additional simulations, we increased the albedo of urban locations only, on the basis of two independent estimates of the spatial extent of urban areas. In these simulations, global cooling ranged from 0.01 to 0.07 K, which corresponds to a CO2 equivalent emission reduction of 25–150 billion tonnes of CO2.”

Citation: Hashem Akbari et al 2012 Environ. Res. Lett. 7 024004 doi:10.1088/1748-9326/7/2/024004.


Magnitude of extremely cold temperatures has reduced in Antarctic Peninsula

Significant reduction of cold temperature extremes at Faraday/Vernadsky station in the Antarctic Peninsula – Franzke (2012)

Abstract: “This study examines the daily observed temperature at the Faraday/Vernadsky station in the Antarctic Peninsula for the period February 1947 through January 2011. Faraday/Vernadsky is experiencing a significant warming trend of about 0.6 °C/decade over the last few decades. Concurrently, the magnitude of extremely cold temperatures has reduced while there is no evidence for an increase of the annual maximum temperature. An empirical mode decomposition reveals that most of the temperature variability occurs on intraannual time scales and that changes in the magnitude of the annual cycle can be explained by a simple periodic stochastic process. Extremely cold temperatures below a threshold follow a generalised Pareto distribution (GPD) with a negative shape parameter and thus are bounded. We find that the extremely cold behaviour in the first half of the record is significantly different from the second half. At the same time there is no evident increase of warm temperatures or in the location of the maximum of the temperature probability distribution. These findings provide evidence that at Faraday/Vernadsky, it is the change in the shape of the temperature distribution that has substantially contributed to the observed warming over the last few decades. Furthermore, we find evidence for clustering of extreme cold events and show that they are predictable a few days in advance using a precursor-based prediction scheme.”

Citation: Christian Franzke, International Journal of Climatology, DOI: 10.1002/joc.3490.


Temperature sensitivity of photosynthetic metabolism is most important uncertainty in land carbon cycle

High sensitivity of future global warming to land carbon cycle processes – Booth et al. (2012) [FULL TEXT]

Abstract: “Unknowns in future global warming are usually assumed to arise from uncertainties either in the amount of anthropogenic greenhouse gas emissions or in the sensitivity of the climate to changes in greenhouse gas concentrations. Characterizing the additional uncertainty in relating CO2 emissions to atmospheric concentrations has relied on either a small number of complex models with diversity in process representations, or simple models. To date, these models indicate that the relevant carbon cycle uncertainties are smaller than the uncertainties in physical climate feedbacks and emissions. Here, for a single emissions scenario, we use a full coupled climate–carbon cycle model and a systematic method to explore uncertainties in the land carbon cycle feedback. We find a plausible range of climate–carbon cycle feedbacks significantly larger than previously estimated. Indeed the range of CO2 concentrations arising from our single emissions scenario is greater than that previously estimated across the full range of IPCC SRES emissions scenarios with carbon cycle uncertainties ignored. The sensitivity of photosynthetic metabolism to temperature emerges as the most important uncertainty. This highlights an aspect of current land carbon modelling where there are open questions about the potential role of plant acclimation to increasing temperatures. There is an urgent need for better understanding of plant photosynthetic responses to high temperature, as these responses are shown here to be key contributors to the magnitude of future change.”

Citation: Ben B B Booth et al 2012 Environ. Res. Lett. 7 024002 doi:10.1088/1748-9326/7/2/024002.


Observed low cloud increase in Arctic is positive feedback to warming through sea ice loss

Arctic low cloud changes as observed by MISR and CALIOP: Implication for the enhanced autumnal warming and sea ice loss – Wu & Lee (2012)

Abstract: “Retreat of Arctic sea ice extent has led to more evaporation over open water in summer and subsequent cloud changes in autumn. Studying recent satellite cloud data over the Arctic Ocean, we find that low (0.5–2 km) cloud cover in October has been increasing significantly during 2000–2010 over the Beaufort and East Siberian Sea (BESS). This change is consistent with the expected boundary layer cloud response to the increasing Arctic evaporation accumulated during summer. Because low clouds have a net warming effect at the surface, October cloud increases may be responsible for the enhanced autumnal warming in surface air temperature, which effectively prolong the melt season and lead to a positive feedback to Arctic sea ice loss. Thus, the new satellite observations provide a critical support for the hypothesized positive feedback involving interactions between boundary layer cloud, water vapor, temperature, and sea ice in the Arctic Ocean.”

Citation: Wu, D. L., and J. N. Lee (2012), Arctic low cloud changes as observed by MISR and CALIOP: Implication for the enhanced autumnal warming and sea ice loss, J. Geophys. Res., 117, D07107, doi:10.1029/2011JD017050.


Possible link between sunspots and North Atlantic Oscillation

Trends in sunspots and North Atlantic sea level pressure – van Loon et al. (2012)

Abstract: “We analyze the periods 1878–1944 and 1944–2008. The quasi-stationary wave in the North Atlantic region was stronger and the baroclinity steeper in 1878–1944 than in 1944–2008. The North Atlantic Oscillation Index—as defined by the Climate Research Unit, University of East Anglia—was higher in the former period too. We illustrate these statements by maps of sea level pressure and air temperature at the surface. The long-term trends in the North Atlantic Oscillation Index are linked to the trend in sunspot number such that when, in the mean, the sunspot numbers were high (Gleissberg maxima) the trends in the two quantities were parallel; and when the mean sunspot numbers were low (Gleissberg minima) the trends in the North Atlantic Oscillation Index and sunspots were opposite. We find the connections between the trends statistically significant, and we infer that the level of solar activity played a role in the trends of the past two centuries in the North Atlantic region. However, we cannot as yet provide a mechanism linking the solar trends to those in the atmosphere and ocean, but as a step toward an explanation, the equator to pole temperature gradient is steeper in a Gleissberg minimum than in a maximum.”

Citation: van Loon, H., J. Brown, and R. F. Milliff (2012), Trends in sunspots and North Atlantic sea level pressure, J. Geophys. Res., 117, D07106, doi:10.1029/2012JD017502.


Disappearing sea ice causes unexpected upwelling events of CO2-rich waters in Arctic

Storm-induced upwelling of high pCO2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states – Mathis et al. (2012)

Abstract: “The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat from multiple stressors. In October 2011, persistent wind-driven upwelling occurred in open water along the continental shelf of the Beaufort Sea in the western Arctic Ocean. During this time, cold (<−1.2°C), salty (>32.4) halocline water—supersaturated with respect to atmospheric CO2 (pCO2 > 550 μatm) and undersaturated in aragonite (Ωaragonite < 1.0) was transported onto the Beaufort shelf. A single 10-day event led to the outgassing of 0.18–0.54 Tg-C and caused aragonite undersaturations throughout the water column over the shelf. If we assume a conservative estimate of four such upwelling events each year, then the annual flux to the atmosphere would be 0.72–2.16 Tg-C, which is approximately the total annual sink of CO2 in the Beaufort Sea from primary production. Although a natural process, these upwelling events have likely been exacerbated in recent years by declining sea ice cover and changing atmospheric conditions in the region, and could have significant impacts on regional carbon budgets. As sea ice retreat continues and storms increase in frequency and intensity, further outgassing events and the expansion of waters that are undersaturated in carbonate minerals over the shelf are probable.”

Citation: Mathis, J. T., et al. (2012), Storm-induced upwelling of high pCO2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states, Geophys. Res. Lett., 39, L07606, doi:10.1029/2012GL051574.


Melting glaciers in Mount Everest region cause a risk of glacier lake outburst floods

Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards – Benn et al. (2012)

Abstract: “In areas of high relief, many glaciers have extensive covers of supraglacial debris in their ablation zones, which alters both rates and spatial patterns of melting, with important consequences for glacier response to climate change. Wastage of debris-covered glaciers can be associated with the formation of large moraine-dammed lakes, posing risk of glacier lake outburst floods (GLOFs). In this paper, use observations of glaciers in the Mount Everest region to present an integrated view of debris-covered glacier response to climate change, which helps provide a long-term perspective on evolving GLOF risks. In recent decades, debris-covered glaciers in the Everest region have been losing mass at a mean rate of ~ 0.32 m yr-1, although in most cases there has been little or no change in terminus position. Mass loss occurs by 4 main processes: (1) melting of clean ice close to glacier ELAs; (2) melting beneath surface debris; (3) melting of ice cliffs and calving around the margins of supraglacial ponds; and (4) calving into deep proglacial lakes. Modelling of processes (1) and (2) shows that Everest-region glaciers typically have an inverted ablation gradient in their lower reaches, due to the effects of a down-glacier increase in debris thickness. Mass loss is therefore focused in the mid parts of glacier ablation zones, causing localized surface lowering and a reduction in downglacier surface gradient, which in turn reduce driving stress and glacier velocity, so the lower ablation zones of many glaciers are now stagnant. Model results also indicate that increased summer temperatures have raised the altitude of the rain-snow transition during the summer monsoon period, reducing snow accumulation and ice flux to lower elevations. As downwasting proceeds, formerly efficient supraglacial and englacial drainage networks are broken up, and supraglacial lakes form in hollows on the glacier surface. Ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub-debris melt rates, so extensive lake formation accelerates overall rates of ice loss. Most supraglacial lakes are ‘perched’ above hydrological base level, and are susceptible to drainage if they become connected to the englacial drainage system. Speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre-existing weaknesses in the ice. Roof collapses can open these voids up to the surface, and commonly provide the nuclei of new lakes. Thus, by influencing both lake drainage and formation, englacial conduits exert a strong control on surface ablation rates. An important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier. Base-level lakes formed behind intact moraine dams can grow monotonically, and in some cases can pose serious GLOF hazards. Glacier termini can evolve in different ways in response to the same climatic forcing, so that potentially hazardous lakes will form in some situations but not others. Additionally, the probability of a flood not simply a function of lake volume, but depend on the geometry and structure of the dam, and possible trigger mechanisms such as ice- or rockfalls into the lake. Satellite-based measurements of glacier surface gradient and ice velocities allow probable future locations of base-level lakes to be identified. A base-level lake has begun to grow rapidly on Ngozumpa Glacier west of Mount Everest, and could attain a volume of ~ 108 m3 within the next 2 or 3 decades. Unless mitigation efforts are undertaken, this lake could pose considerable GLOF hazard potential.”

Citation: D.I. Benn, T. Benn, K. Hands, J. Gulley, A. Luckman, L.I. Nicholson, D. Quincey, S. Thompson, R. Toumi, S. Wiseman, Earth-Science Reviews, http://dx.doi.org/10.1016/j.earscirev.2012.03.008.

See also another last week study, Salerno et al. (2012), who mapped glacial lakes of Mount Everest region.


For a sea star species future warming is worse than acidification

Non-calcifying larvae in a changing ocean: warming, not acidification/hypercapnia, is the dominant stressor on development of the sea star Meridiastra calcar – Nguyen et al. (2012)

Abstract: “Climate change driven ocean warming and acidification is potentially detrimental to the sensitive planktonic life stages of benthic marine invertebrates. Research has focused on the effects of acidification on calcifying larvae with a paucity of data on species with alternate developmental strategies and on the interactive effects of warming and acidification. To determine the impact of climate change on a conspicuous component of the intertidal fauna of southeast Australia, the development of the non-calcifying lecithotrophic larvae of the sea star Meridiastra calcar was investigated in the setting of predicted ocean warming (+2-4°C) and acidification (-0.4-0.6 pH units) for 2100 and beyond in all combinations of stressors. Temperature and pH were monitored in the habitat of M. calcar to place experiments in context with current environmental conditions. There was no effect of temperature or pH on cleavage stage embryos but later development (gastrula-larvae) was negatively effected by a +2°-4°C warming and there was a negative effect of -0.6 pH units on embryos reaching the hatched gastrula stage. Mortality and abnormal development in larvae increased significantly even with +2°C warming and larval growth was impaired at +4°C. For the range of temperature and pH conditions tested, there were no interactive effects of stressors across all stages monitored. For M. calcar, warming not acidification was the dominant stressor. A regression model incorporating data from this study and projected increasing SST for the region suggests an increase in larval mortality to 70% for M. calcar by 2100 in the absence of acclimation and adaptation. The broad distribution of this species in eastern Australia encompassing subtropical to cold temperate thermal regimes provides the possibility that local M. calcar populations may be sustained in a warming world through poleward migration of thermotolerant propagules, facilitated by the strong southward flow of the East Australian Current.”

Citation: Hong D. Nguyen, Steve S. Doo, Natalie A. Soars, Maria Byrne, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02714.x.


CLASSIC OF THE WEEK: Stupart (1917)

Is the Climate Changing? – Stupart (1917) [FULL TEXT]

Abstract: No abstract. A quote from the paper: “The purpose of this paper is to show what indications there may be, if any, that the climate of Canada is gradually changing; whether there is a tendency towards greater warmth or greater cold, or whether the rainfall is increasing or decreasing. Before proceeding, however, I would draw your attention to certain conclusions by recent writers regarding the climate of the past 3,000 years.”

Citation: Stupart, Frederic, Sir, 1917, Journal of the Royal Astronomical Society of Canada, Vol. 11, p.197.


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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Papers on Russia 2010 heatwave

Posted by Ari Jokimäki on April 11, 2012

This is a list of papers on Russia 2010 heatwave with an emphasis on the causes of the event. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

UPDATE (May 16, 2012): Huijnen et al. (2012) added.

Hindcast experiments of tropospheric composition during the summer 2010 fires over western Russia – Huijnen et al. (2012) “The severe wildfires in western Russia during July–August 2010 coincided with a strong heat wave and led to large emissions of aerosols and trace gases such as carbon monoxide (CO), hydrocarbons and nitrogen oxides into the troposphere. This extreme event is used to evaluate the ability of the global MACC (Monitoring Atmospheric Composition and Climate) atmospheric composition forecasting system to provide analyses of large-scale pollution episodes and to test the respective influence of a priori emission information and data assimilation on the results. Daily 4-day hindcasts were conducted using assimilated aerosol optical depth (AOD), CO, nitrogen dioxide (NO2) and ozone (O3) data from a range of satellite instruments. Daily fire emissions were used from the Global Fire Assimilation System (GFAS) version 1.0, derived from satellite fire radiative power retrievals. The impact of accurate wildfire emissions is dominant on the composition in the boundary layer, whereas the assimilation system influences concentrations throughout the troposphere, reflecting the vertical sensitivity of the satellite instruments. The application of the daily fire emissions reduces the area-average mean bias by 63% (for CO), 60% (O3) and 75% (NO2) during the first 24 h with respect to independent satellite observations, compared to a reference simulation with a multi-annual mean climatology of biomass burning emissions. When initial tracer concentrations are further constrained by data assimilation, biases are reduced by 87, 67 and 90%. The forecast accuracy, quantified by the mean bias up to 96 h lead time, was best for all compounds when using both the GFAS emissions and assimilation. The model simulations suggest an indirect positive impact of O3 and CO assimilation on hindcasts of NO2 via changes in the oxidizing capacity. However, the quality of local hindcasts was strongly dependent on the assumptions made for forecasted fire emissions. This was well visible from a relatively poor forecast accuracy quantified by the root mean square error, as well as the temporal correlation with respect to ground-based CO total column data and AOD. This calls for a more advanced method to forecast fire emissions than the currently adopted persistency approach. The combined analysis of fire radiative power observations, multiple trace gas and aerosol satellite observations, as provided by the MACC system, results in a detailed quantitative description of the impact of major fires on atmospheric composition, and demonstrate the capabilities for the real-time analysis and forecasts of large-scale fire events.” Huijnen, V., Flemming, J., Kaiser, J. W., Inness, A., Leitão, J., Heil, A., Eskes, H. J., Schultz, M. G., Benedetti, A., Hadji-Lazaro, J., Dufour, G., and Eremenko, M.: Hindcast experiments of tropospheric composition during the summer 2010 fires over western Russia, Atmos. Chem. Phys., 12, 4341-4364, doi:10.5194/acp-12-4341-2012, 2012. [Full text]

Reconciling two approaches to attribution of the 2010 Russian heat wave – Otto et al. (2012) “In the summer 2010 Western Russia was hit by an extraordinary heat wave, with the region experiencing by far the warmest July since records began. Whether and to what extent this event is attributable to anthropogenic climate change is controversial. Dole et al. (2011) report the 2010 Russian heat wave was “mainly natural in origin” whereas Rahmstorf and Coumou (2011) write that with a probability of 80% “the 2010 July heat record would not have occurred” without the large-scale climate warming since 1980, most of which has been attributed to the anthropogenic increase in greenhouse gas concentrations. The latter explicitly state that their results “contradict those of Dole et al. (2011).” Here we use the results from a large ensemble simulation experiment with an atmospheric general circulation model to show that there is no substantive contradiction between these two papers, in that the same event can be both mostly internally-generated in terms of magnitude and mostly externally-driven in terms of occurrence-probability. The difference in conclusion between these two papers illustrates the importance of specifying precisely what question is being asked in addressing the issue of attribution of individual weather events to external drivers of climate.” Otto, F. E. L., N. Massey, G. J. van Oldenborgh, R. G. Jones, and M. R. Allen (2012), Reconciling two approaches to attribution of the 2010 Russian heat wave, Geophys. Res. Lett., 39, L04702, doi:10.1029/2011GL050422. [Full text]

The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorological Extremes – Lau & Kim (2012) “In this paper, preliminary results are presented showing that the two record-setting extreme events during 2010 summer (i.e., the Russian heat wave–wildfires and Pakistan flood) were physically connected. It is found that the Russian heat wave was associated with the development of an extraordinarily strong and prolonged extratropical atmospheric blocking event in association with the excitation of a large-scale atmospheric Rossby wave train spanning western Russia, Kazakhstan, and the northwestern China–Tibetan Plateau region. The southward penetration of upper-level vorticity perturbations in the leading trough of the Rossby wave was instrumental in triggering anomalously heavy rain events over northern Pakistan and vicinity in mid- to late July. Also shown are evidences that the Russian heat wave was amplified by a positive feedback through changes in surface energy fluxes between the atmospheric blocking pattern and an underlying extensive land region with below-normal soil moisture. The Pakistan heavy rain events were amplified and sustained by strong anomalous southeasterly flow along the Himalayan foothills and abundant moisture transport from the Bay of Bengal in connection with the northward propagation of the monsoonal intraseasonal oscillation.” Lau, William K. M., Kyu-Myong Kim, 2012: The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorological Extremes. J. Hydrometeor, 13, 392–403.

Increase of extreme events in a warming world – Rahmstorf & Coumou (2011) “We develop a theoretical approach to quantify the effect of long-term trends on the expected number of extremes in generic time series, using analytical solutions and Monte Carlo simulations. We apply our method to study the effect of warming trends on heat records. We find that the number of record-breaking events increases approximately in proportion to the ratio of warming trend to short-term standard deviation. Short-term variability thus decreases the number of heat extremes, whereas a climatic warming increases it. For extremes exceeding a predefined threshold, the dependence on the warming trend is highly nonlinear. We further find that the sum of warm plus cold extremes increases with any climate change, whether warming or cooling. We estimate that climatic warming has increased the number of new global-mean temperature records expected in the last decade from 0.1 to 2.8. For July temperature in Moscow, we estimate that the local warming trend has increased the number of records expected in the past decade fivefold, which implies an approximate 80% probability that the 2010 July heat record would not have occurred without climate warming.” Stefan Rahmstorf and Dim Coumou, PNAS November 1, 2011 vol. 108 no. 44 17905-17909, doi: 10.1073/pnas.1101766108. [Full text]

Was there a basis for anticipating the 2010 Russian heat wave? – Dole et al. (2011) “The 2010 summer heat wave in western Russia was extraordinary, with the region experiencing the warmest July since at least 1880 and numerous locations setting all-time maximum temperature records. This study explores whether early warning could have been provided through knowledge of natural and human-caused climate forcings. Model simulations and observational data are used to determine the impact of observed sea surface temperatures (SSTs), sea ice conditions and greenhouse gas concentrations. Analysis of forced model simulations indicates that neither human influences nor other slowly evolving ocean boundary conditions contributed substantially to the magnitude of this heat wave. They also provide evidence that such an intense event could be produced through natural variability alone. Analysis of observations indicate that this heat wave was mainly due to internal atmospheric dynamical processes that produced and maintained a strong and long-lived blocking event, and that similar atmospheric patterns have occurred with prior heat waves in this region. We conclude that the intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability. Slowly varying boundary conditions that could have provided predictability and the potential for early warning did not appear to play an appreciable role in this event.” Dole, R., M. Hoerling, J. Perlwitz, J. Eischeid, P. Pegion, T. Zhang, X.-W. Quan, T. Xu, and D. Murray (2011), Was there a basis for anticipating the 2010 Russian heat wave?, Geophys. Res. Lett., 38, L06702, doi:10.1029/2010GL046582. [Full text]

Influence of subtropical and polar sea-surface temperature anomalies on temperatures in Eurasia – Sedláček et al. (2011) “In summer 2010 an exceptional heatwave occurred over western Russia. At the same time sea-surface temperatures (SSTs) were anomalously warm in the Barents Sea and the Arabian Sea. We investigate a possible link between these two SST anomalies by prescribing SST anomalies separately and combined in an ensemble of climate model simulations. The positive surface air temperature response over western Russia is strengthened if both SST forcings are combined. While the SST anomalies in the Arabian Sea are likely due to natural variability the sea surface in the Barents Sea is expected to warm in future and the sea-ice cover to decline enhancing the warming. Thus, we hypothesize that heatwaves over Europe and Russia will likely become more frequent as a result of the dynamic response of the atmosphere in addition to what is expected from the change in mean temperature.” Sedláček, J., O. Martius, and R. Knutti (2011), Influence of subtropical and polar sea-surface temperature anomalies on temperatures in Eurasia, Geophys. Res. Lett., 38, L12803, doi:10.1029/2011GL047764. [Full text]

The Hot Summer of 2010: Redrawing the Temperature Record Map of Europe – Barriopedro et al. (2011) “The summer of 2010 was exceptionally warm in eastern Europe and large parts of Russia. We provide evidence that the anomalous 2010 warmth that caused adverse impacts exceeded the amplitude and spatial extent of the previous hottest summer of 2003. “Mega-heatwaves” such as the 2003 and 2010 events likely broke the 500-year-long seasonal temperature records over approximately 50% of Europe. According to regional multi-model experiments, the probability of a summer experiencing mega-heatwaves will increase by a factor of 5 to 10 within the next 40 years. However, the magnitude of the 2010 event was so extreme that despite this increase, the likelihood of an analog over the same region remains fairly low until the second half of the 21st century.” David Barriopedro, Erich M. Fischer, Jürg Luterbacher, Ricardo M. Trigo, and Ricardo García-Herrera, Science 8 April 2011: Vol. 332 no. 6026 pp. 220-224, DOI: 10.1126/science.1201224. [Full text]

Satellite monitoring of wildfires during the anomalous heat wave of 2010 in Russia – Bondur (2011) “We describe the specific features of the summer 2010 emergency conditions in the European part of the Russian Federation, when an anomalous heat wave (the monthly mean temperatures in the summer months were 5–9°C higher than those for 2002–2009) and prolonged blocking anticyclones led to large wildfires. We analyze their causes and consequences. The features of the satellite system for operational fire monitoring (constructed at the Aerospace Scientific Center) and examples of its application in summer 2010 are presented. On the basis of the results of processing of satellite images of low (250–1000 m), medium (∼30–50 m), and high (∼6 m) resolutions, we found that the total area covered by fire from March to November of 2010 amounted to approximately 10.9 million hectares for the entire territory of the country and and 2.2 million hectares for its European part. Daily histograms of areas covered by fire in the summer months of 2010 were constructed. On the basis of these data and empirical models, we estimate the daily emissions of carbon monoxide (CO) from wildfires in the summer months of 2010 for the European part of Russia and Moscow oblast. On some days in August 2010, these emissions reached 15000–27000 t for the European part of Russia and 3000–7500 t for Moscow oblast. On the basis of analysis of data from the AIRS spectrometer (Aqua satellite), we derived the spatial distribution of CO concentrations at heights of 2 to 10 km above the territory of the Eastern and Central Europe. Moscow was shown to have been most severely affected by smoke from wildfires occurring on August 6–9, 2010, when the concentrations of harmful gases (CO2, CO, CH4, and O3) and aerosols in the air significantly exceeded both the daily and the one-hour maximum allowable concentrations.” V. G. Bondur, Izvestiya Atmospheric and Oceanic Physics, Volume 47, Number 9, 1039-1048, DOI: 10.1134/S0001433811090040.

Anomalies of trace gases in the air of the European part of Russia and Ukraine in summer 2010 – Zvyagintsev et al. (2011) “Time series of concentrations of some trace gases in the Moscow and Kirov Regions, Kyiv and the Crimea under conditions of the abnormally hot summer of 2010 have been analyzed. Concentrations of ozone, particulate matter (PM10), carbon monoxide, and nitrogen oxides, almost continuously exceeded national standards of maximum permissible levels in July–August 2010 in the Moscow Region. The highest pollution was observed on August 2–11, when some heavy plumes of forest and peatbog fires covered the region, as in 2002. Concentrations of pollutants, first, ozone, exceeded the levels usually observed in Western Europe during periods of high photochemical air pollution. This air pollution event adversely affected human health, and finally resulted in an increase in mortality due to, first of all, increased PM10 and ozone concentrations. Air quality in the Kirov Region, Kyiv, and the Crimea, not affected by the fire plumes, was quite satisfactory despite weather conditions similar to those in Moscow.” A. M. Zvyagintsev, O. B. Blum, A. A. Glazkova, S. N. Kotel’nikov, I. N. Kuznetsova, V. A. Lapchenko, E. A. Lezina, E. A. Miller, V. A. Milyaev and A. P. Popikov, et al., Atmospheric and Oceanic Optics, Volume 24, Number 6, 536-542, DOI: 10.1134/S1024856011060145.

Predictability of Euro-Russian blocking in summer of 2010 – Matsueda (2011) “Eastern Europe and Western Russia experienced a strong heat wave during the summer of 2010. Maximum temperatures exceeded 40°C in early August, resulting in over 15,000 deaths and many wildfires, inflicting large economic losses on Russia. The heat wave resulted from strong atmospheric blocking that persisted over the Euro-Russian region from late June to early August. This study investigates the predictabilities of extreme Euro-Russian blocking and of the blocking-induced extreme surface temperatures in the summer of 2010, using medium-range ensemble forecasts. The results show that the blocking in June–August (JJA) of 2010 was easily predictable, even for a lead time of +216 hr; however, the blocking that occurred from 30th July to 9th August showed a lower predictability in forecasts over +144 hr compared with other blocking occurrences in JJA of 2010. This low predictability resulted in the failure to predict the extreme temperatures associated with the mature blocking in early August. Most of the forecasts predicted a decay of the blocking earlier than that observed.” Matsueda, M. (2011), Predictability of Euro-Russian blocking in summer of 2010, Geophys. Res. Lett., 38, L06801, doi:10.1029/2010GL046557.

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New research from last week 14/2012

Posted by Ari Jokimäki on April 9, 2012

We only have 10 new papers this week but they are diverse. Himalayan glaciers, global temperature record, European growing season, bioenergy, Australia snow cover, ancient ocean acidification, marine boundary layer cloud feedbacks, ocean temperature measurements, stratospheric air, and solar activity proxies are all subjects that get treated with new research articles this week. Remember that 1960 Keeling paper where he announced that atmospheric carbon dioxide concentration is increasing? As the classic of the week we bring you a paper from that same issue of Tellus, where it is estimated based on ocean carbon dioxide uptake that carbon dioxide from fossil fuel burning should increase the atmospheric concentration.


Potential solar activity proxy from 10Be in lake sediments

10Be in lacustrine sediments – a record of solar activity? – Mann et al. (2012)

Abstract: “Concentrations and fluxes of cosmogenic 10Be in three varved lake sediments covering the last 100 years were determined to investigate their suitability to record past solar activity. The 10Be signal in lake sediments is composed of a component reflecting the radionuclide production in the atmosphere and a component related to the subsequent transport into the sediment. In order to separate these two components we applied singular-spectrum analysis (SSA). The extracted patterns in concentrations and depositional fluxes were compared to 10Be records from polar ice cores and to the solar modulation potential derived from neutron monitor data. In the transport component we discovered the existence of a long-term trend in the 10Be concentrations, which can be attributed to the redox cycle of both lakes. In the production component we found a similar pattern as in the NGrip ice core. A cross correlation analysis yielded a significant negative correlation between the 10Be production component and the solar modulation potential. 10Be lags the production on average by 1.5 years which corresponds to the expected transport time from the atmosphere to the Earth’s surface. Hence, we conclude that varved lake sediments are potentially suitable to study the solar activity of the past. However, one should be aware that various mechanisms may mask the 10Be signal in the sediment.”

Citation: M. Mann, J. Beer, F. Steinhilber, M. Christl, Journal of Atmospheric and Solar-Terrestrial Physics, http://dx.doi.org/10.1016/j.jastp.2012.03.011.


How old is stratospheric air?

Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period – Stiller et al. (2012) [FULL TEXT]

Abstract: “An extensive observational data set, consisting of more than 106 SF6 vertical profiles from MIPAS measurements distributed over the whole globe has been condensed into monthly zonal means of mean age of air for the period September 2002 to January 2010, binned at 10° latitude and 1–2 km altitude. The data were analysed with respect to their temporal variation by fitting a regression model consisting of a constant and a linear increase term, 2 proxies for the QBO variation, sinusoidal terms for the seasonal and semi-annual variation and overtones for the correction of the shapes to the observed data set. The impact of subsidence of mesospheric SF6-depleted air and in-mixing into non-polar latitudes on mid-latitudinal absolute age of air and its linear increase was assessed and found to be small. The linear increase of mean age of stratospheric air was found to be positive and partly larger than the trend derived by Engel et al. (2009) for most of the Northern mid-latitudes, the middle stratosphere in the tropics, and parts of the Southern mid-latitudes, as well as for the Southern polar upper stratosphere. Multi-year decrease of age of air was found for the lowermost and the upper stratospheric tropics, for parts of Southern mid-latitudes, and for the Northern polar regions. Analysis of the amplitudes and phases of the seasonal variation shed light on the coupling of stratospheric regions to each other. In particular, the Northern mid-latitude stratosphereis well coupled to the tropics, while the Northern lowermost mid-latitudinal stratosphere is decoupled, confirming the separation of the shallow branch of the Brewer-Dobson circulation from the deep branch. We suggest an overall increased tropical upwelling, together with weakening of mixing barriers, especially in the Northern Hemisphere, as a hypothetical model to explain the observed pattern of linear multi-year increase/decrease, and amplitudes and phase shifts of the seasonal variation.”

Citation: Stiller, G. P., von Clarmann, T., Haenel, F., Funke, B., Glatthor, N., Grabowski, U., Kellmann, S., Kiefer, M., Linden, A., Lossow, S., and López-Puertas, M.: Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period, Atmos. Chem. Phys., 12, 3311-3331, doi:10.5194/acp-12-3311-2012, 2012.


Correcting biases in XBT based ocean temperature measurements

Empirical correction of XBT data – Hamon et al. (2012) [FULL TEXT]

Abstract: “We use a collocation method between XBT and CTD/OSD (Ocean Station Data including bottle cast and low resolution CTD) from WOD2005 to statistically correct the XBT fall rate. An analysis of the annual median bias on depth shows that it is necessary to apply a thermal correction, a second order correction on the depth as well as a depth offset representing measurement errors during XBT deployment. We separated data in several categories: shallow and deep XBTs and below or above 10°C of vertically averaged ocean temperatures (in the top 400m). We also processed separately XBT measurements in the western Pacific between 1968 and 1985 due to large regional biases. The estimated corrections deviate from other published estimates with some large variations in time of both linear and curvature terms in the depth corrections, and less time variation of the temperature correction for the deep XBTs. This analysis of heat content derived from corrected XBTs provides at first order a similar variability to other estimates from corrected XBTs and MBTs. It shows a fairly prominent trend in 0-700m ocean heat content of 0.39.1022J/year between 1970 and 2008.”

Citation: M. Hamon, G. Reverdin, and P.-Y. Le Traon, Journal of Atmospheric and Oceanic Technology 2012, doi: http://dx.doi.org/10.1175/JTECH-D-11-00129.1.


Negative feedback from cloud water amount and positive feedback from cloudiness reduction in marine boundary layer

Marine boundary-layer cloud feedbacks in a constant relative humidity atmosphere – Rieck et al. (2012)

Abstract: “The mechanisms that govern the response of shallow cumulus, such as found in the trade-wind regions, to a warming of the atmosphere in which large-scale atmospheric processes act to keep relative humidity constant are explored. Two robust effects are identified. First, and as is well known, the liquid-water lapse-rate increases with temperature and tends to increase the amount of water in clouds, making clouds more reflective of solar radiation. Second, and less well appreciated, the surface fluxes increase with the saturation specific humidity which itself is a strong function of temperature. Using large-eddy simulations we show that the liquid-water lapse-rate acts as a negative feedback: a positive temperature increase driven by radiative forcing is reduced by the increase in cloud water and hence cloud albedo. However, this effect is more than compensated by a reduction of cloudiness associated with the deepening and relative drying of the boundary layer, driven by larger surface moisture fluxes. Because they are so robust these effects are thought to underlie changes in the structure of the marine boundary layer as a result of global warming.”

Citation: Malte Rieck, Louise Nuijens, and Bjorn Stevens, Journal of the Atmospheric Sciences 2012, doi: http://dx.doi.org/10.1175/JAS-D-11-0203.1.


Trying to detect ancient ocean acidification

Recognising ocean acidification in deep time: An evaluation of the evidence for acidification across the Triassic-Jurassic boundary – Greene et al. (2012)

Abstract: “While demonstrating ocean acidification in the modern is relatively straightforward (measure increase in atmospheric CO2 and corresponding ocean chemistry change), identifying palaeo-ocean acidification is problematic. The crux of this problem is that the rock record is a constructive archive while ocean acidification is essentially a destructive (and/or inhibitory) phenomenon. This is exacerbated in deep time without the benefit of a deep ocean record. Here, we discuss the feasibility of, and potential criteria for, identifying an acidification event in deep time. Furthermore, we investigate the evidence for ocean acidification during the Triassic-Jurassic (T-J) boundary interval, an excellent test case because 1) it occurs in deep time, beyond the reach of deep sea drilling coverage; 2) a potential trigger for acidification is known; and 3) it is associated with one of the ‘Big Five’ mass extinctions which disproportionately affected modern-style invertebrates. Three main criteria suggest that acidification may have occurred across the T-J transition. 1) The eruption of the Central Atlantic Magmatic Province (CAMP) and the associated massive and rapid release of CO2 coincident with the end-Triassic mass extinction provide a suitable trigger for an acidification event (full carbonate undersaturation in the surface ocean is possible but improbable). 2) Tentative evidence for a global paucity of carbonate across the end-Triassic mass extinction versus the adjacent stratigraphy is consistent with a predicted sedimentary response to acidification. 3) The end-Triassic mass extinction was particularly selective against acid-sensitive organisms (more so than perhaps any other extinction event) and temporarily eliminated coral reefs. Therefore multiple lines of evidence are consistent with a T-J ocean acidification event within our current resolution to recognise such events in deep time. The conclusion that the end-Triassic extinction was influenced by acidification implies that short-term acidification perturbations may have long-term effects on ecosystems, a repercussion that has previously not been established. Although anthropogenic emissions are more rapid than any event in the geologic record, events such as the T-J can serve as partial analogues for the present anthropogenic carbon release. Since the T-J was such a pronounced crisis for both modern-style marine invertebrates and scleractinian reefs, it is of particular interest in terms of informing projections about the effects of modern ocean acidification.”

Citation: Sarah E. Greene, Rowan C. Martindale, Kathleen A. Ritterbush, David J. Bottjer, Frank A. Corsetti, William M. Berelson, Earth Science Reviews, http://dx.doi.org/10.1016/j.earscirev.2012.03.009.


Observational record of Australia snow cover

Satellite based observations for seasonal snow cover detection and characterisation in Australia – Bormann et al. (2012)

Abstract: “A new daily snow cover dataset was developed using Moderate resolution Imaging Spectroradiometer (MODIS) Level-1B products for the Australian alpine region over the period 2000–2010 at 500 m resolution. The dataset has been evaluated during clear-sky conditions using snow detection estimates derived from Landsat Thematic Mapper (TM) data and has been compared to the MOD10_L2 snow cover products. The ability to customise the snow detection threshold is one of the benefits of developing the Melt Area Detection Index (MADI) approach for regional conditions. The dataset provides a new satellite based observational record that may be used to characterise spatial and temporal development of Australian snow cover extent and duration. The new snow cover observations provide insight into snow characteristics in this region where significant declines in snow cover extent, season duration and a shift towards earlier snow melt date are observed. Shifts towards early season melt dates are observed for snow at 1580 m and above. This includes areas which are pertinent to snow recreation activities in the region. Season length declines are attributed to earlier seasonal snowmelt rather than later season onset and may be linked to observed warming trends in the area. The MODIS based approach can be applied to other regions and other sensors to assist in evaluating snow modelling efforts and improve water resource management and snow hydrology based investigations.”

Citation: Kathryn J. Bormann, Matthew F. McCabe, Jason P. Evans, Remote Sensing of Environment, Volume 123, August 2012, Pages 57–71, http://dx.doi.org/10.1016/j.rse.2012.03.003.


Large-scale production of bioenergy from forest biomass is neither sustainable nor GHG neutral

Large-scale bioenergy from additional harvest of forest biomass is neither sustainable nor greenhouse gas neutral – Schulze et al. (2012)

Abstract: “Owing to the peculiarities of forest net primary production humans would appropriate ca. 60% of the global increment of woody biomass if forest biomass were to produce 20% of current global primary energy supply. We argue that such an increase in biomass harvest would result in younger forests, lower biomass pools, depleted soil nutrient stocks and a loss of other ecosystem functions. The proposed strategy is likely to miss its main objective, i.e. to reduce greenhouse gas (GHG) emissions, because it would result in a reduction of biomass pools that may take decades to centuries to be paid back by fossil fuel substitution, if paid back at all. Eventually, depleted soil fertility will make the production unsustainable and require fertilization, which in turn increases GHG emissions due to N2O emissions. Hence, large-scale production of bioenergy from forest biomass is neither sustainable nor GHG neutral.”

Citation: Ernst-Detlef Schulze, Christian Körner, Beverly E. Law, Helmut Haberl, Sebastiaan Luyssaert, GCB Bioenergy, DOI: 10.1111/j.1757-1707.2012.01169.x.


Changes in the timing in European growing season differ regionally

Combining satellite derived phenology with climate data for climate change impact assessment – Ivits et al. (2012)

Abstract: “The projected influence of climate change on the timing and volume of phytomass production is expected to affect a number of ecosystem services. In order to develop coherent and locally effective adaptation and mitigation strategies, spatially explicit information on the observed changes is needed. Long-term variations of the vegetative growing season in different environmental zones of Europe for 1982–2006 have been derived by analysing time series of GIMMS NDVI data. The associations of phenologically homogenous spatial clusters to time series of temperature and precipitation data were evaluated. North-East Europe showed a trend to an earlier and longer growing season, particularly in the northern Baltic areas. Despite the earlier greening up large areas of Europe exhibited rather stable season length indicating the shift of the entire growing season to an earlier period. The northern Mediterranean experience a growing season shift towards later dates while some agglomerations of earlier and shorter growing season were also seen. The correlation of phenological time series with climate data shows a cause-effect relationship over the semi natural areas consistent with results in literature. Managed ecosystems however appear to have heterogeneous change pattern with less or no correlation to climatic trends. Over these areas climatic trends seemed to overlap in a complex manner with more pronounced effects of local biophysical conditions and/or land management practices. Our results underline the importance of satellite derived phenological observations to explain local nonconformities to climatic trends for climate change impact assessment.”

Citation: E. Ivits, M. Cherlet, G. Toth, S. Sommer, W. Mehl, J. Vogt, F. Micale, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.03.010.


Analysis of quasiperiodic 50-80 year oscillation in global temperature record

Quasiperiodic climate variability with a period of 50–80 years: Fourier analysis of measurements and Earth System Model simulations – Henriksson et al. (2012)

Abstract: “We examine an oscillation of global mean temperature with a period of about two thirds of a century. We find evidence for the oscillation both in the instrumental temperature record and in an Earth System Model millennium simulation without external forcing. There is also evidence for the oscillation in the Central England Temperature record, the longest instrumental record available. Our method is based on a discrete Fourier transform with varying starting point and length of time window. This method allows us to make a quantitative estimate of the contribution of an oscillation to global mean temperature, to track the phase evolution of the oscillation and to compare measurement and model results. The multidecadal oscillation could provide part of the explanation both for near-constant global mean temperatures in recent years despite warming by rising concentrations of greenhouse gases and for declining global mean temperature in the 1950s and 1960s alongside with the explanation of aerosol cooling. Quantitative estimates of the contribution of the oscillation to global mean temperature vary between ±(0.03–0.17) K. For the instrumental temperature record, our results indicate an amplitude of 0.03 K presently if the IPCC model average represents the effect of external forcings well, and (0.08–0.17) K when using simple linear and quadratic fits for detrending. For the millennium simulation, the amplitude of the oscillation is (0.05–0.06) K, but could be underestimated as compared to reality if external forcing acts to globally synchronize multidecadal variability. The role of the Atlantic Multidecadal Oscillation (AMO) in the model is discussed. The AMO has a spatial temperature distribution similar to earlier literature results and is more correlated with the global oscillation when external forcing is included.”

Citation: S. V. Henriksson, P. Räisänen, J. Silén and A. Laaksonen, Climate Dynamics, DOI: 10.1007/s00382-012-1341-0.


Himalayan glaciers have gotten smaller and glacial lakes bigger

Responses of glaciers and glacial lakes to climate variation between 1975 and 2005 in the Rongxer basin of Tibet, China and Nepal – Wu et al. (2012)

Abstract: “This research presents an evaluation of glacier recession and glacial-lake expansion in the Rongxer basin in the Mount Qomolangma National Reserve of central Himalaya. Changes in glacier and glacial-lake surface areas in the Reserve between 1975, 1992 and 2005 have been estimated using remote sensing and GIS techniques that have integrated field data from 2009, 1:50,000 scale topographic maps, ASTER satellite data from 2009, and Landsat MSS/TM images in 1975, 1992 and 2005. By 2005, the glacier surface area had declined from 596.52 to 451.58 km2 with a total area loss of 144.94 km2, and glacial lakes had increased from 3.55 to 7.87 km2, an increase of 121.69 %. The volume of glaciers was reduced by 69.99 km3 from 1975 to 2005. The observed changes in the extent of glaciers are in line with the observed atmospheric warming in the Rongxer basin. Records from the Tingri station and Nyalam station have revealed warming during the ablation season since the 1970s at a rate of 0.03–0.04 °C a−1 in the northern and central Rongxer basin. At higher elevations in the study area, represented by the Tingri and Nyalam meteorological stations, the summer warming was accompanied by negative anomalies in annual precipitation since the 1970s, likely enhancing glacier retreat and glacial lake expansion.”

Citation: Shan-shan Wu, Zhi-jun Yao, He-qing Huang, Zhao-fei Liu and Gao-huan Liu, Regional Environmental Change, DOI: 10.1007/s10113-012-0302-9.


CLASSIC OF THE WEEK: Kanwisher (1960)

pCO2 in Sea Water and its Effect on the Movement of CO2 in Nature – Kanwisher (1960) [FULL TEXT]

Abstract:“A method is described for measuring pCO2 in sea water. A gas phase is analyzed continuously by infrared absorption for CO2 while it is equilibrated gently with the water in a countercurrent column. It has been used to determine the changes in pCO2 produced by variations of temperature and total CO2. Partial pressure shows large changes for small increments in these two independant variables. These properties of sea water are useful in estimating the movement of CO2 between the atmosphere and oceans. It appears, for instance, that most of the fossil fuel CO2 released by man has been effective in increasing the percentage of this gas in air.”

Citation: John Kanwisher, Tellus, Volume 12, Issue 2, pages 209–215, May 1960, DOI: 10.1111/j.2153-3490.1960.tb01302.x.


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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Papers on regional and local land temperature reconstructions

Posted by Ari Jokimäki on April 7, 2012

This is a list of papers on regional and local land temperature reconstructions. Only papers giving quantitative temperature reconstructions are included (qualitative climate and environment reconstructions are not included). The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

UPDATE (April 20, 2012): Few European studies added.
UPDATE (April 18, 2012): Viau et al. (2011) added. Thanks to Barry for pointing it out.

Africa: Powers et al. (2005) [abstract], Weijers et al. (2007) [abstract, full text], Tierney et al. (2008) [abstract, full text]

  • South Africa: Palmer et al. (2001) [abstract]

Antarctic: Schneider et al. (2006) [abstract, full text], Kawamura et al. (2007) [abstract]

Arctic: Overpeck et al. (1997) [abstract, full text], Kaufman et al. (2009) [abstract, full text]

Asia

Europe Briffa et al. (1988) [abstract], Davis et al. (2003) [abstract, full text], Luterbacher et al. (2004) [abstract, full text], Guiot et al. (2005) [abstract, full text], Casty et al. (2005) [abstract, full text], Frank & Esper (2005) [abstract, full text], Xoplaki et al. (2005) [abstract, full text], Glaser & Riemann (2009) [abstract], Bjune et al. (2009) [abstract], Lindholm et al. (2010) [abstract], Dobrovolný et al. (2010) [abstract, full text], Guiot et al. (2010) [abstract and full text], Büntgen et al. (2011) [abstract, full text]

Extra-tropics: Cook et al. (2004) [abstract], Christiansen & Ljungqvist (2011) [abstract, full text]

North America Jacoby & D’Arrigo (1989) [abstract], Briffa et al. (1992) [abstract, full text], Viau et al. (2006) [abstract], Viau et al. (2011) [abstract]

Oceania

South America Villalba et al. (2003) [abstract, full text], Bendle et al. (2010) [abstract]

  • Chile: von Gunten et al. (2009) [abstract]
  • United States: Graumlich & Brubaker (1986) [abstract], Graumlich (1993) [abstract]

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New research from last week 13/2012

Posted by Ari Jokimäki on April 2, 2012

Some new climate claims are introduced this week. For example, if you suggest that mankind is doing bad things to coral reefs, I answer: “So what? Mankind has done bad things to coral reefs before!” We also learn that things are well for those who grow thermals in China. In the Tibetan Plateau there’s no ocean, so the missing heat is hiding underground. There’s (at least) one strange thing in this week’s batch: They say that slow-flying bats reduce their activity in the presence of LED street lighting, but how that goes with the saying “blind as a bat”? Surely one of them must be wrong.

We also have studies on phenology, water vapor feedback, alpine tree growth, tundra vegetation, Granger causality, climate mode biases, GHCN daily, Greenland ice sheet, mitigating species’ vulnerability, coral calcification, cloud cover, glacier bacteria, and heat-related mortality.


Species that don’t advance their phenology tend to decline in performance with warming

Phenological tracking enables positive species responses to climate change – Cleland et al. (2012)

Abstract: “Earlier spring phenology observed in many plant species in recent decades provides compelling evidence that species are already responding to the rising global temperatures associated with anthropogenic climate change. There is great variability among species, however, in their phenological sensitivity to temperature. Species that do not phenologically “track” climate change may be at a disadvantage if their growth becomes limited by missed interactions with mutualists, or a shorter growing season relative to earlier-active competitors. Here, we set out to test the hypothesis that phenological sensitivity could be used to predict species performance in a warming climate, by synthesizing results across terrestrial warming experiments. We assembled data for 57 species across 24 studies where flowering or vegetative phenology was matched with a measure of species performance. Performance metrics included biomass, percent cover, number of flowers or individual growth. We found that species that advanced their phenology with warming also increased their performance while those that did not advance tended to decline in performance with warming. This indicates that species that cannot phenologically “track” climate may be at increased risk with future climate change, and suggests that phenological monitoring may provide an important tool for setting future conservation priorities.”

Citation: Cleland, Elsa E., Jenica M. Allen, Theresa M. Crimmins, Jennifer A. Dunne, Stephanie Pau, Steven Travers, Erika S. Zavaleta, and Elizabeth M. Wolkovich. In press. Phenological tracking enables positive species responses to climate change. Ecology. http://dx.doi.org/10.1890/11-1912.1.


Thermal growing season has extended by 14 days in temperate China since 1960

Specification of thermal growing season in temperate China from 1960 to 2009 – Shen et al. (2012)

Abstract: “A number of studies have reported an extension of the thermal growing season in response to the warming climate during recent decades. However, the magnitude of extension depends heavily on the threshold temperature used: for a given area, a small change in the threshold temperature results in significant differences in the calculated thermal growing season. Here, we specified the threshold temperature for determining the thermal growing season of local vegetation across 326 meteorological stations in temperate China by using vegetation phenology based on satellite imagery. We examined changes in the start, end, and length of the thermal growing season from 1960 to 2009. The threshold temperatures for determining the start and end increased strongly with increasing mean annual temperature. Averaged across temperate China, the start of the thermal growing season advanced by 8.4 days and the end was delayed by 5.7 days, resulting in a 14.1-day extension from 1960 to 2009. The thermal growing season was intensively prolonged (by 0.59 day/year) since the mid-1980s owing to accelerated warming during this period. This extension was similar to that determined by a spatially fixed threshold temperature of 5 °C, but the spatial patterns differed, owing to differences in the threshold temperature and to intra-annual heterogeneity in climate warming. This study highlights the importance of specifying the temperature threshold for local vegetation when assessing the influences of climate change on thermal growing season, and provides a method for determining the threshold temperature from satellite-derived vegetation phenology.”

Citation: Miaogen Shen, Yanhong Tang, Jin Chen and Wei Yang, Climatic Change, DOI: 10.1007/s10584-012-0434-4.


All the bad things mankind has done to coral reefs since 19th century

Anthropogenic mortality on coral reefs in Caribbean Panama predates coral disease and bleaching – Cramer et al. (2012) [FULL TEXT]

Abstract: “Caribbean reef corals have declined precipitously since the 1980s due to regional episodes of bleaching, disease and algal overgrowth, but the extent of earlier degradation due to localised historical disturbances such as land clearing and overfishing remains unresolved. We analysed coral and molluscan fossil assemblages from reefs near Bocas del Toro, Panama to construct a timeline of ecological change from the 19th century—present. We report large changes before 1960 in coastal lagoons coincident with extensive deforestation, and after 1960 on offshore reefs. Striking changes include the demise of previously dominant staghorn coral Acropora cervicornis and oyster Dendrostrea frons that lives attached to gorgonians and staghorn corals. Reductions in bivalve size and simplification of gastropod trophic structure further implicate increasing environmental stress on reefs. Our paleoecological data strongly support the hypothesis, from extensive qualitative data, that Caribbean reef degradation predates coral bleaching and disease outbreaks linked to anthropogenic climate change.”

Citation: Katie L. Cramer, Jeremy B. C. Jackson, Christopher V. Angioletti, Jill Leonard-Pingel, Thomas P. Guilderson, Ecology Letters, DOI: 10.1111/j.1461-0248.2012.01768.x.


Amplified water vapour feedback at high altitudes during winter

Amplified water vapour feedback at high altitudes during winter – Rangwala (2012)

Abstract: “During the last five decades, the Tibetan Plateau has experienced a warming trend of 0.4 °C/decade in winter, which is at least twice that of any other season. Some studies have suggested that this anomalous winter warming is caused, in part, by the observed increases in near-surface water vapour and its amplifying effect on the surface longwave downward radiation (LDR). This study uses observations of surface-specific humidity (q) and temperature as input to a one-dimensional radiative transfer model to assess the influence of lower atmospheric increases in water vapour on surface LDR, and the sensitivity of this process to different elevations and seasons on the Tibetan Plateau. The results from three idealized experiments are examined based on realistic atmospheric column profiles of temperature and moisture. They show that when an equal mass of water vapour is added into the atmospheric boundary layer during winter, a substantially greater increase (8×) in LDR is found at the high-elevation site relative to the low-elevation site. During summer, the LDR increases are much smaller as are the differences between the two sites. Experiments, where both q and temperature are increased, suggest that the influence of temperature changes on LDR is much greater than those caused by changes in q in all cases, except for the high-elevation-winter case when the opposite is true. These results provide further evidence for the possibility of a strong modulation of surface LDR caused by increases in atmospheric water vapour in high altitude regions (>3000 m) during the cold season.”

Citation: Imtiaz Rangwala, International Journal of Climatology, DOI: 10.1002/joc.3477.


Alpine tree growth has fading temperature sensitivity with decreasing latitude

Fading temperature sensitivity of Alpine tree growth at its Mediterranean margin and associated effects on large-scale climate reconstructions – Büntgen et al. (2012)

Abstract: “A millennium-long tree-ring width chronology of living and dead larch (Larix decidua Mill.) specimens from the Maritime French Alps was introduced 35 years ago. This record has been included in various large-scale temperature reconstructions, though recent analyses revealed only weak associations with regional summer temperatures. Calibration and verification trials against instrumental measurements were, however, limited by the original record’s early ending in 1974. Here we introduce an update of this widely considered chronology until 2007 and back into medieval times. A total of 297 new larch samples from high-elevation settings in the southern French Alps were included, and the combined 398 measurement series allowed effects of tree-ring detrending and chronology development to be explored. Comparisons with meteorological temperature, precipitation and drought indices revealed weak and temporally inconsistent climate sensitivity. To further place these local findings in a biogeographic context, we used >3,000 larch trees from 61 locations across the Alpine arc. This unique network approach confirmed fading temperature sensitivity with decreasing latitude, and thus questioned the overall reliability of ring width-based temperature reconstructions in the Mediterranean region. Our results further emphasize the pending need to develop chronologies from maximum latewood densities and stable isotope ratios across the lower latitudes, and to carefully evaluate ecological site conditions and methodological data restrictions prior to compiling local data into global networks.”

Citation: Ulf Büntgen, David Frank, Thomas Neuenschwander and Jan Esper, Climatic Change, DOI: 10.1007/s10584-012-0450-4.


Ground surface temperature has increased more than air temperature in Qinghai-Tibet Plateau

Recent ground surface warming and its effects on permafrost on the central Qinghai-Tibet Plateau – Wu et al. (2012)

Abstract: “In this study, the ground surface temperature (GST) records from 16 meteorological stations, which are located in or adjacent to permafrost regions on the central Qinghai-Tibet Plateau (QTP), are analysed using Mann–Kendal test and Sen’s slope estimate methods. We revealed that the GSTs have shown statistically significant warming. On average, mean annual ground surface temperature has increased at a rate of 0.60 °C decade−1 over the period of 1980–2007, which is more pronounced than the increase of mean annual air temperature on the plateau. The winter ground surface warming is especially prominent, which is similar to the seasonal trends in changes of air temperature. As important parameters to assess the changes of ground thermal regime in cold regions, surface freezing and thawing indices were also studied. The nonparametric statistic test and estimate indicate that surface freezing and thawing indices both show significant variations (−111.2 and 125.0 °C d decade−1, respectively) on the central QTP. The intensive ground surface warming is responsible for the concurrent increase in permafrost temperatures at the long-term observation sites on the plateau. The close correlations between ground surface and permafrost temperatures indicate that the dramatic ground surface warming could have significant influence on the change of permafrost thermal regime in the study region.”

Citation: Dr Tonghua Wu, Lin Zhao, Ren Li, Qinxue Wang, Changwei Xie, Qiangqiang Pang, International Journal of Climatology, DOI: 10.1002/joc.3479.


LED street lights cause a reduction in activity of slow-flying bats

Conserving energy at a cost to biodiversity? Impacts of LED lighting on bats – Stone et al. (2012)

Abstract: “Artificial lighting is a key biodiversity threat and produces 1900 million tonnes of CO2 emissions globally, more than three times that produced by aviation. The need to meet climate change targets has led to a global increase in energy-efficient light sources such as high-brightness light-emitting diodes (LEDs). Despite the energetic benefits of LEDs, their ecological impacts have not been tested. Using an experimental approach we show that LED street lights caused a reduction in activity of slow-flying bats (Rhinolophus hipposideros and Myotis spp.). Both R. hipposideros and Myotis spp. activity was significantly reduced even during low light levels of 3.6 lux. There was no effect of LED lighting on the relatively fast-flying Pipistrellus pipistrellus, P. pygmaeus and Nyctalus/Eptesicus spp. We provide the first evidence of the effects of LED lights on bats. Despite having considerable energy-saving benefits, LED lights can potentially fragment commuting routes for bats with associated negative conservation consequences. Our results add to the growing evidence of negative impacts of lighting on a wide range of taxa. We highlight the complexities involved in simultaneously meeting targets for reduction of greenhouse gas emissions and biodiversity loss. New lighting strategies should integrate climate change targets with the cultural, social, and ecological impacts of emerging lighting technologies.”

Citation: Emma Louise Stone, Gareth Jones, Stephen Harris, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02705.x.


Evidence for changes in tundra vegetation

Satellite-based evidence for shrub and graminoid tundra expansion in northern Quebec from 1986-2010 – McManus et al. (2012)

Abstract: “Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two scales of inference, we analyzed a 24-year (1986-2010) Landsat time series in a latitudinal transect across the boreal forest-tundra biome boundary in northern Quebec province, Canada. This region has experienced rapid warming during both winter and summer months during the last forty years. Using a per-pixel (30 m) trend analysis, 30% of the observable (cloud-free) land area experienced a significant (p < 0.05) positive trend in the Normalized Difference Vegetation Index (NDVI). However, greening trends were not evenly split among cover types. Low shrub and graminoid tundra contributed preferentially to the greening trend, while forested areas were less likely to show significant trends in NDVI. These trends reflect increasing leaf area, rather than an increase in growing season length, because Landsat data were restricted to peak-summer conditions. The average NDVI trend (0.007/yr) corresponds to a leaf-area index (LAI) increase of ~0.6 based on the regional relationship between LAI and NDVI from the Moderate Resolution Spectroradiometer (MODIS). Across the entire transect, the area-averaged LAI increase was ~0.2 during 1986-2010. A higher area-averaged LAI change (~0.3) within the shrub-tundra portion of the transect represents a 20-60% relative increase in LAI during the last two decades. Our Landsat-based analysis subdivides the overall high-latitude greening trend into changes in peak-summer greenness by cover type. Different responses within and among shrub, graminoid, and tree-dominated cover types in this study indicate important fine-scale heterogeneity in vegetation growth. Although our findings are consistent with community shifts in low-biomass vegetation types over multi-decadal time scales, the response in tundra and forest ecosystems to recent warming was not uniform.”

Citation: K.M. McManus, D.C. Morton, J.G. Masek, D. Wang, J.O. Sexton, J. Nagol, P. Ropars, S. Boudreau, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02708.x.


Detectable Granger causality from anthropogenic forcings to global temperature – not from natural forcings

Testing for linear Granger causality from natural/anthropogenic forcings to global temperature anomalies – Attanasio (2012)

Abstract: “In this paper, we analyze the Granger causality from natural or anthropogenic forcings to global temperature anomalies. The lag-augmented Wald test is performed, and its robustness is also evaluated considering bootstrap method. The results show there is no-evidence of Granger causality from natural forcings to global temperature. On the contrary, a detectable Granger causality is found from anthropogenic forcings to global temperature confirming that greenhouse gases have an important role on recent global warming.”

Citation: Alessandro Attanasio, Theoretical and Applied Climatology, DOI: 10.1007/s00704-012-0634-x.


Seasonal changes in climate model biases

Nonstationarities of regional climate model biases in European seasonal mean temperature and precipitation sums – Maraun (2012)

Abstract: “Bias correcting climate models implicitly assumes stationarity of the correction function. This assumption is assessed for regional climate models in a pseudo reality for seasonal mean temperature and precipitation sums. An ensemble of regional climate models for Europe is used, all driven with the same transient boundary conditions. Although this model-dependent approach does not assess all possible bias non-stationarities, conclusions can be drawn for the real world. Generally, biases are relatively stable, and bias correction on average improves climate scenarios. For winter temperature, bias changes occur in the Alps and ice covered oceans caused by a biased forcing sensitivity of surface albedo; for summer temperature, bias changes occur due to a biased sensitivity of cloud cover and soil moisture. Precipitation correction is generally successful, but affected by internal variability in arid climates. As model sensitivities vary considerably in some regions, multi model ensembles are needed even after bias correction.”

Citation: Maraun, D. (2012), Nonstationarities of regional climate model biases in European seasonal mean temperature and precipitation sums, Geophys. Res. Lett., 39, L06706, doi:10.1029/2012GL051210.


GHCN daily database with free public access

An Overview of the Global Historical Climatology Network-Daily Database – Menne et al. (2012) [FULL TEXT]

Abstract: “A database is described that has been designed to fulfill the need for daily climate data over global land areas. The dataset, known as Global Historical Climatology Network (GHCN) – Daily, was developed for a wide variety of potential applications including climate analysis and monitoring studies that require data at a daily time resolution (e.g., assessments of the frequency of heavy rainfall, heat wave duration, etc.). The dataset contains records from over 80000 stations in 180 countries and territories and its processing system produces the official archive for U.S. daily data. Variables include maximum and minimum temperature, total daily precipitation, snowfall, and snow depth; however, about two thirds of the stations report precipitation only. Quality assurance checks are routinely applied to the full dataset, but the data are not homogenized to account for artifacts associated with the various eras in reporting practice at any particular station (i.e., for changes in systematic bias). Daily updates are provided for many of the station records in GHCN-Daily. The dataset is also regularly reconstructed, usually once per week, from its 20-plus data source components, ensuring that the dataset is broadly synchronized with its growing list of constituent sources. The daily updates and weekly reprocessed versions of GHCN-Daily are assigned a unique version number and the most recent dataset version is provided on the GHCN-Daily web site for free public access. Each version of the dataset is also archived at NOAA’s National Climatic Data Center in perpetuity for future retrieval.”

Citation: Matthew J. Menne, Imke Durre, Russell S. Vose, Byron E. Gleason, and Tamara G. Houston, Journal of Atmospheric and Oceanic Technology 2012, doi: http://dx.doi.org/10.1175/JTECH-D-11-00103.1.


Rapid erosion beneath the Greenland ice sheet

Rapid erosion beneath the Greenland ice sheet – Cowton et al. (2012)

Abstract: “The Pleistocene ice sheets left a clear signature of erosion, but the rate at which ice sheets erode is difficult to determine from either paleolandscapes or observations of contemporary processes. Here we use two years of sediment flux data, derived from meltwaters emerging from an outlet glacier in west Greenland, to calculate an average rate of subglacial erosion across a catchment extending >50 km inland from the ice margin. Erosion in this zone occurs at 4.8 ± 2.6 mm a−1, a rate 1–2 orders of magnitude greater than previous estimates of erosion rate beneath the Greenland Ice Sheet. Our results suggest that where surface meltwaters are able to access the bed, the rate of erosion by ice sheets is in keeping with the rapid erosion observed at temperate alpine glaciers. During deglacial phases, when meltwater was abundant, ice sheet margins should therefore have acted as highly efficient agents of erosion.”

Citation: T. Cowton, P. Nienow, I. Bartholomew, A. Sole1 and D. Mair, Geology, v. 40 no. 4 p. 343-346, doi: 10.1130/G32687.1.


Mitigating sensitive species vulnerability to climate change can reduce representation of other species

Species vulnerability to climate change: impacts on spatial conservation priorities and species representation – Summers et al. (2012)

Abstract: “Climate change may shrink and/or shift plant species ranges thereby increasing their vulnerability and requiring targeted conservation to facilitate adaptation. We quantified the vulnerability to climate change of plant species based on exposure, sensitivity and adaptive capacity and assessed the effects of including these components in complementarity-based spatial conservation prioritisation. We modelled the vulnerability of 584 native plant species under three climate change scenarios in an 11.9 million hectare fragmented agricultural region in southern Australia. We represented exposure as species’ geographic range under each climate change scenario as quantified using species distribution models. We calculated sensitivity as a function of the impact of climate change on species’ geographic ranges. Using a dispersal kernel, we quantified adaptive capacity as species’ ability to migrate to new geographic ranges under each climate change scenario. Using Zonation, we assessed the impact of individual components of vulnerability (exposure, sensitivity and adaptive capacity) on spatial conservation priorities and levels of species representation in priority areas under each climate change scenario. The full vulnerability framework proved an effective basis for identifying spatial conservation priorities under climate change. Including different dimensions of vulnerability had significant implications for spatial conservation priorities. Incorporating adaptive capacity increased the level of representation of most species. However, prioritising sensitive species reduced the representation of other species. We conclude that whilst taking an integrated approach to mitigating species vulnerability to climate change can ensure sensitive species are well-represented in a conservation network, this can come at the cost of reduced representation of other species. Conservation planning decisions aimed at reducing species vulnerability to climate change need to be made in full cognisance of the sensitivity of spatial conservation priorities to individual components of vulnerability, and the trade-offs associated with focussing on sensitive species.”

Citation: David M. Summers, Brett A. Bryan, Neville D. Crossman, Wayne S. Meyer, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02700.x.


Coral community calcification might decline by 55% of its preindustrial value before 2100

Impacts of ocean acidification in naturally variable coral reef flat ecosystems – Shaw et al. (2012)

Abstract: “Ocean acidification leads to changes in marine carbonate chemistry that are predicted to cause a decline in future coral reef calcification. Several laboratory and mesocosm experiments have described calcification responses of species and communities to increasing CO2. The few in situ studies on natural coral reefs that have been carried out to date have shown a direct relationship between aragonite saturation state (Ωarag) and net community calcification (Gnet). However, these studies have been performed over a limited range of Ωarag values, where extrapolation outside the observational range is required to predict future changes in coral reef calcification. We measured extreme diurnal variability in carbonate chemistry within a reef flat in the southern Great Barrier Reef, Australia. Ωarag varied between 1.1 and 6.5, thus exceeding the magnitude of change expected this century in open ocean subtropical/tropical waters. The observed variability comes about through biological activity on the reef, where changes to the carbonate chemistry are enhanced at low tide when reef flat waters are isolated from open ocean water. We define a relationship between net community calcification and Ωarag, using our in situ measurements. We find net community calcification to be linearly related to Ωarag, while temperature and nutrients had no significant effect on Gnet. Using our relationship between Gnet and Ωarag, we predict that net community calcification will decline by 55% of its preindustrial value by the end of the century. It is not known at this stage whether exposure to large variability in carbonate chemistry will make reef flat organisms more or less vulnerable to the non-calcifying physiological effects of increasing ocean CO2 and future laboratory studies will need to incorporate this natural variability to address this question.”

Citation: Shaw, E. C., B. I. McNeil, and B. Tilbrook (2012), Impacts of ocean acidification in naturally variable coral reef flat ecosystems, J. Geophys. Res., 117, C03038, doi:10.1029/2011JC007655.


Cloud cover has decreased in China between 1954 and 2005

Significant decreasing cloud cover during 1954–2005 due to more clear-sky days and less overcast days in China and its relation to aerosol – Xia (2012) [FULL TEXT]

Abstract: “An updated analysis of cloud cover during 1954–2005 in China was performed using homogeneous cloud cover data from 314 stations. Long-term changes in frequencies of different cloud cover categories and their contributions to long-term changes in cloud cover were assessed. Furthermore, aerosol effects on cloud cover trends were discussed based on comparison of cloud cover trends in polluted and mildly polluted regions. Frequencies of clear sky (cloud cover 80%) were observed to increase by ~2.2 days and decrease by ~3.3 days per decade, respectively, which accounts for ~80% of cloud cover reduction. Larger decreasing trends in cloud cover due to larger increase in clear sky frequency and larger decreases in overcast frequency were observed at stations with lower aerosol optical depth. There is no significant difference in trends regarding cloud cover, clear sky frequency, and overcast frequency between mountain and plain stations. These results are inconsistent with our expectation that larger decreasing trends in cloud cover should have been observed in regions with higher aerosol loading where more aerosols could lead to stronger obscuring effect on ground observation of cloud cover and stronger radiative effect as compared with the mildly polluted regions. Aerosol effect on decreasing cloud cover in China appear not to be supported by this analysis and therefore, further study on this issue is required.”

Citation: Xia, X.: Significant decreasing cloud cover during 1954–2005 due to more clear-sky days and less overcast days in China and its relation to aerosol, Ann. Geophys., 30, 573-582, doi:10.5194/angeo-30-573-2012, 2012.


Positive outcome of global warming: glaciers retreat – more living space for bacteria

Bacterial diversity in the foreland of the Tianshan No. 1 glacier, China – Wu et al. (2012) [FULL TEXT]

Abstract: “There is compelling evidence that glaciers are retreating in many mountainous areas of the world due to global warming. With this glacier retreat, new habitats are being exposed that are colonized by microorganisms whose diversity and function are less well studied. Here, we characterized bacterial diversity along the chronosequences of the glacier No. 1 foreland that follows glacier retreat. An average of 10 000 sequences was obtained from each sample by 454 pyrosequencing. Using non-parametric and rarefaction estimated analysis, we found bacterial phylotype richness was high. The bacterial species turnover rate was especially high between sites exposed for 6 and 10 yr. Pyrosequencing showed tremendous bacterial diversity, among which the Acidobacteria, Actinobacteria, Bacteroidetes and Proteobacteria were found to be present at larger numbers at the study area. Meanwhile, the proportion of Bacteroidetes and Proteobacteria decreased and the proportion of Acidobacteria increased along the chronosequences. Some known functional bacterial genera were also detected and the sulfur- and sulfate-reducing bacteria were present in a lower proportion of sequences. These findings suggest that high-throughput pyrosequencing can comprehensively detect bacteria in the foreland, including rare groups, and give a deeper understanding of the bacterial community structure and variation along the chronosequences.”

Citation: Xiukun Wu et al 2012 Environ. Res. Lett. 7 014038 doi:10.1088/1748-9326/7/1/014038.


Major Californian urban centers could have large increase in heat-related mortality by the 2090s

Future heat vulnerability in California, Part II: projecting future heat-related mortality – Sheridan et al. (2012)

Abstract: “Through the 21st century, a significant increase in heat events is likely across California (USA). Beyond any climate change, the state will become more vulnerable through demographic changes resulting in a rapidly aging population. To assess these impacts, future heat-related mortality estimates are derived for nine metropolitan areas in the state for the remainder of the century. Heat-related mortality is first assessed by initially determining historical weather-type mortality relationships for each metropolitan area. These are then projected into the future based on predicted weather types created in Part I. Estimates account for several levels of uncertainty: for each metropolitan area, mortality values are produced for five different climate model-scenarios, three different population projections (along with a constant-population model), and with and without partial acclimatization. Major urban centers could have a greater than tenfold increase in short-term increases in heat-related mortality in the over 65 age group by the 2090s.”

Citation: Scott C. Sheridan, Michael J. Allen, Cameron C. Lee and Laurence S. Kalkstein, Climatic Change, DOI: 10.1007/s10584-012-0437-1.


CLASSIC OF THE WEEK: Searle (1888)

Atmospheric Economy of Solar Radiation – Searle (1888) [FULL TEXT]

Abstract: No abstract.

Citation: Arthur Searle, Proceedings of the American Academy of Arts and Sciences, Vol. 24, (May, 1888 – May, 1889) (pp. 26-29).


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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