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Archive for November, 2010

New research from last week 47/2010

Posted by Ari Jokimäki on November 29, 2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

CO2 uptake not the only thing causing ocean acidification

Seasonal and long-term changes in pH in the Dutch coastal zone – Provoost et al. (2010) “Recent observations and modelling studies suggest that biogeochemical changes can mask atmospheric CO2-induced pH decreases. Data collected by the Dutch monitoring authorities in different coastal systems (North Sea, Wadden Sea, Ems-Dollard, Eastern Scheldt and Scheldt estuary) since 1975 provide an excellent opportunity to test whether this is the case in the Dutch coastal zone. The time-series were analysed using Multi-Resolution Analysis (MRA) which resulted in the identification of system-dependent patterns on both seasonal and intra-annual time scales. The observed rates of pH change greatly exceed those expected from enhanced CO2 uptake, thus suggesting that other biogeochemical processes, possibly related to changes in nutrient loading, can play a dominant role in ocean acidification.” Provoost, P., van Heuven, S., Soetaert, K., Laane, R. W. P. M., and Middelburg, J. J.: Seasonal and long-term changes in pH in the Dutch coastal zone, Biogeosciences, 7, 3869-3878, doi:10.5194/bg-7-3869-2010, 2010. [full text]

Calcifying invertebrates survive in CO2-rich environment but might not in future

Calcifying invertebrates succeed in a naturally CO2-rich coastal habitat but are threatened by high levels of future acidification – Thomsen et al. (2010) “CO2 emissions are leading to an acidification of the oceans. Predicting marine community vulnerability towards acidification is difficult, as adaptation processes cannot be accounted for in most experimental studies. Naturally CO2 enriched sites thus can serve as valuable proxies for future changes in community structure. Here we describe a natural analogue site in the Western Baltic Sea. Seawater pCO2 in Kiel Fjord is elevated for large parts of the year due to upwelling of CO2 rich waters. Peak pCO2 values of >230 Pa (>2300 μatm) and pHNBS values of <7.5 are encountered during summer and autumn, average pCO2 values are ~70 Pa (~700 μatm). In contrast to previously described naturally CO2 enriched sites that have suggested a progressive displacement of calcifying auto- and heterotrophic species, the macrobenthic community in Kiel Fjord is dominated by calcifying invertebrates. We show that blue mussels from Kiel Fjord can maintain control rates of somatic and shell growth at a pCO2 of 142 Pa (1400 μatm, pHNBS = 7.7). Juvenile mussel recruitment peaks during the summer months, when high water pCO2 values of ~100 Pa (~1000 μatm) prevail. Our findings indicate that calcifying keystone species may be able to cope with surface ocean pHNBS values projected for the end of this century when food supply is sufficient. However, owing to non-linear synergistic effects of future acidification and upwelling of corrosive water, peak seawater pCO2 in Kiel Fjord and many other productive estuarine habitats could increase to values >400 Pa (>4000 μatm). These changes will most likely affect calcification and recruitment, and increase external shell dissolution.” Thomsen, J., Gutowska, M. A., Saphörster, J., Heinemann, A., Trübenbach, K., Fietzke, J., Hiebenthal, C., Eisenhauer, A., Körtzinger, A., Wahl, M., and Melzner, F.: Calcifying invertebrates succeed in a naturally CO2-rich coastal habitat but are threatened by high levels of future acidification, Biogeosciences, 7, 3879-3891, doi:10.5194/bg-7-3879-2010, 2010. [full text]

Study compares concepts of slave ownership and fossil fuel usage

Past connections and present similarities in slave ownership and fossil fuel usage – Mouhot (2010) “The first part of the paper demonstrates the connection between the abolition of slavery and the Industrial Revolution: steam power changed the perception of labour; new techniques facilitated diffusion of pro-abolition pamphlets; fewer threats to basic existence resulting from industrial advances fostered sensibilities and moral standards toward abolitionism; and, through industrial development, the North grasped victory in the American Civil War. The second part presents similarities between societies in the past that have used slave labour and those in the present that use fossil fuels. It argues that slaves and fossil-fuelled machines play(ed) similar economic and social roles: both slave societies and developed countries externalise(d) labour and both slaves and modern machines free(d) their owners from daily chores. Consequently, we are as dependent on fossil fuels as slave societies were dependent on bonded labour. It also suggests that, in differing ways, suffering resulting (directly) from slavery and (indirectly) from the excessive burning of fossil fuels are now morally comparable. When we emit carbon dioxide at a rate that exceeds what the ecosystem can absorb, when we deplete non-renewable resources, we indirectly cause suffering to other human beings. Similarly, cheap oil facilitates imports of goods from countries with little social protection and hence help externalise oppression. The conclusion draws on the lessons which may be learned by Climate Change campaigners from the campaigns to abolish slavery: environmental apathy can be opposed effectively if we learn from what worked in the fight against this inhuman institution.” Jean-François Mouhot, Climatic Change, DOI: 10.1007/s10584-010-9982-7.

Cosmic rays linked to rapid mid-latitude cloud changes

Cosmic rays linked to rapid mid-latitude cloud changes – Laken et al. (2010) “The effect of the Galactic Cosmic Ray (GCR) flux on Earth’s climate is highly uncertain. Using a novel sampling approach based around observing periods of significant cloud changes, a statistically robust relationship is identified between short-term GCR flux changes and the most rapid mid-latitude (60°–30° N/S) cloud decreases operating over daily timescales; this signal is verified in surface level air temperature (SLAT) reanalysis data. A General Circulation Model (GCM) experiment is used to test the causal relationship of the observed cloud changes to the detected SLAT anomalies. Results indicate that the anomalous cloud changes were responsible for producing the observed SLAT changes, implying that if there is a causal relationship between significant decreases in the rate of GCR flux (~0.79 GU, where GU denotes a change of 1% of the 11-year solar cycle amplitude in four days) and decreases in cloud cover (~1.9 CU, where CU denotes a change of 1% cloud cover in four days), an increase in SLAT (~0.05 KU, where KU denotes a temperature change of 1 K in four days) can be expected. The influence of GCRs is clearly distinguishable from changes in solar irradiance and the interplanetary magnetic field. However, the results of the GCM experiment are found to be somewhat limited by the ability of the model to successfully reproduce observed cloud cover. These results provide perhaps the most compelling evidence presented thus far of a GCR-climate relationship. From this analysis we conclude that a GCR-climate relationship is governed by both short-term GCR changes and internal atmospheric precursor conditions.” Laken, B. A., Kniveton, D. R., and Frogley, M. R.: Cosmic rays linked to rapid mid-latitude cloud changes, Atmos. Chem. Phys., 10, 10941-10948, doi:10.5194/acp-10-10941-2010, 2010. [full text]

Testing for the seasonality of sea surface temperature proxies

Disentangling seasonal signals in Holocene climate trends by satellite-model-proxy integration – Schneider et al. (2010) “Past sea surface temperatures (SSTs) are routinely estimated from organic and inorganic remains of fossil phytoplankton or zooplankton organisms, recovered from seafloor sediments. Potential seasonal biases of paleoproxies were intensely studied in the past; however, even for the two most commonly used paleoproxies for SST, U37K′ and Mg/Ca ratios, a clear global picture does not yet exist. In the present study we combine Holocene SST trends derived from U37K′ and Mg/Ca ratios with results from idealized climate model simulations forced by changes in the orbital configuration, which represents the major climate driver over the last 10 kyr. Such changes cause a spatiotemporal redistribution of incoming solar radiation, resulting in a modulation of amplitude and phasing of the seasonal cycle. Considering that the climate signal recorded by a plankton-based paleoproxy may be affected by the seasonal productivity cycle of the respective organism, we use the modern relationship between SST and marine net primary production, both obtained from satellite observations, to calculate a seasonality index (SI) as an independent constraint to link modeled SST trends with proxy data. Although the climate model systematically underestimates Holocene SST trends, we find that seasonal productivity peaks of the phytoplankton-based U37K′ result in a preferential registering of the warm (cold) season in high (low) latitudes, as it was expected from the SI distribution. The overall smoother trends from the zooplankton-derived Mg/Ca SSTs suggest a more integrated signal over longer time averages, which may also carry a seasonal bias, but the spatial pattern is less clear. Based on our findings, careful multiproxy approaches can actually go beyond the reconstruction of average climate trends, specifically allowing to resolve the evolution of seasonality.” Schneider, B., G. Leduc, and W. Park (2010), Paleoceanography, 25, PA4217, doi:10.1029/2009PA001893. [full text]

Lakes have warmed rapidly since 1985

Space observations of inland water bodies show rapid surface warming since 1985 – Schneider & Hook (2010) “Surface temperatures were extracted from nighttime thermal infrared imagery of 167 large inland water bodies distributed worldwide beginning in 1985 for the months July through September and January through March. Results indicate that the mean nighttime surface water temperature has been rapidly warming for the period 1985–2009 with an average rate of 0.045 ± 0.011°C yr−1 and rates as high as 0.10 ± 0.01°C yr−1. Worldwide the data show far greater warming in the mid- and high latitudes of the northern hemisphere than in low latitudes and the southern hemisphere. The analysis provides a new independent data source for assessing the impact of climate change throughout the world and indicates that water bodies in some regions warm faster than regional air temperature. The data have not been homogenized into a single unified inland water surface temperature dataset, instead the data from each satellite instrument have been treated separately and cross compared. Future work will focus on developing a single unified dataset which may improve uncertainties from any inter-satellite biases.” Schneider, P., and S. J. Hook (2010), Geophys. Res. Lett., 37, L22405, doi:10.1029/2010GL045059.

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Papers on diurnal temperature range

Posted by Ari Jokimäki on November 24, 2010

This is a list of papers on the diurnal temperature range (daily maximum and minimum temperatures), both global and regional papers are included. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Associations of diurnal temperature range change with the leading climate variability modes during the Northern Hemisphere wintertime and their implication on the detection of regional climate trends – Wu (2010) “This study examines associations of diurnal temperature range (DTR) changes in observations at the global, hemispheric, subcontinental, and grid box scales with five leading climate variability modes, including the Arctic Oscillation (AO), hemispheric Pacific–North America (PNA)–like mode, Pacific Decadal Oscillation, El Niño Southern Oscillation (ENSO), and Antarctic Oscillation (AAO) during the Northern Hemisphere winter season (Jan–Mar). Winter DTR variability in most subcontinental regions is significantly related to variations in either the AO, or hemispheric PNA-like mode, or ENSO index in the Northern Hemisphere. In the Southern Hemisphere, the DTR variability appears closely coupled with variations in the ENSO and AAO. From 1951 to 2000, variations in the circulation patterns account for a significant fraction of the DTR increase at all scales although the strength of these associations varies geographically. After removing the linearly congruent component of leading climate variability modes from the total wintertime DTR trends in the observations, statistically significant residual trends in DTR are still found at the global, hemispheric, and most subcontinental regions. Ensemble mean multimodel averaged DTR trends to major anthropogenic and natural forcing are significantly smaller than not only observed total DTR trends but also residual trends at these large scales. The implication of changes in the leading climate variability modes on the detection of regional DTR trends is discussed. We find that the detection of the regional response to combined anthropogenic and natural forcing is robust to the exclusion of trends related to changes of the five modes considered here.” Wu, Q. (2010), J. Geophys. Res., 115, D19101, doi:10.1029/2010JD014026.

Detection and attribution of anthropogenic forcing to diurnal temperature range changes from 1950 to 1999: comparing multi-model simulations with observations – Zhou et al. (2009) “Observations show that the surface diurnal temperature range (DTR) has decreased since 1950s over most global land areas due to a smaller warming in maximum temperatures (T max) than in minimum temperatures (T min). This paper analyzes the trends and variability in T max, T min, and DTR over land in observations and 48 simulations from 12 global coupled atmosphere-ocean general circulation models for the later half of the 20th century. It uses the modeled changes in surface downward solar and longwave radiation to interpret the modeled temperature changes. When anthropogenic and natural forcings are included, the models generally reproduce observed major features of the warming of T max and T min and the reduction of DTR. As expected the greenhouse gases enhanced surface downward longwave radiation (DLW) explains most of the warming of T max and T min while decreased surface downward shortwave radiation (DSW) due to increasing aerosols and water vapor contributes most to the decreases in DTR in the models. When only natural forcings are used, none of the observed trends are simulated. The simulated DTR decreases are much smaller than the observed (mainly due to the small simulated T min trend) but still outside the range of natural internal variability estimated from the models. The much larger observed decrease in DTR suggests the possibility of additional regional effects of anthropogenic forcing that the models can not realistically simulate, likely connected to changes in cloud cover, precipitation, and soil moisture. The small magnitude of the simulated DTR trends may be attributed to the lack of an increasing trend in cloud cover and deficiencies in charactering aerosols and important surface and boundary-layer processes in the models.” Liming Zhou, Robert E. Dickinson, Aiguo Dai and Paul Dirmeyer, Climate Dynamics, Volume 35, Numbers 7-8, 1289-1307, DOI: 10.1007/s00382-009-0644-2. [Full text]

Diurnal temperature range over Europe between 1950 and 2005 – Makowski et al. (2008) “It has been widely accepted that diurnal temperature range (DTR) decreased on a global scale during the second half of the twentieth century. Here we show however, that the long-term trend of annual DTR has reversed from a decrease to an increase during the 1970s in Western Europe and during the 1980s in Eastern Europe. The analysis is based on the high-quality dataset of the European Climate Assessment and Dataset Project, from which we selected approximately 200 stations covering the area bordered by Iceland, Algeria, Turkey and Russia for the period 1950 to 2005. We investigate national and regional annual means as well as the pan-European mean with respect to trends and reversal periods. 17 of the 24 investigated regions including the pan-European mean show a statistical significant increase of DTR since 1990 at the latest. Of the remaining 7 regions, two show a non-significant increase, three a significant decrease and two no significant trend. Changes in DTR are affected by both surface shortwave and longwave radiation, the former of which has undergone a change from dimming to brightening in the period considered. Consequently, we discuss the connections between DTR, shortwave radiation and sulfur emissions which are thought to be amongst the most important factors influencing the incoming solar radiation through the primary and secondary aerosol effect. We find reasonable agreement between trends in SO2 emissions, radiation and DTR in areas affected by high pollution. Consequently, we conclude that the trends in DTR could be mostly determined by changes in emissions and the associated changes in incoming solar radiation.” Makowski, K., Wild, M., and Ohmura, A., Atmos. Chem. Phys., 8, 6483-6498, doi:10.5194/acp-8-6483-2008, 2008. [Full text]

Impact of global dimming and brightening on global warming – Wild et al. (2007) “Speculations on the impact of variations in surface solar radiation on global warming range from concerns that solar dimming has largely masked the full magnitude of greenhouse warming, to claims that the recent reversal from solar dimming to brightening rather than the greenhouse effect was responsible for the observed warming. To disentangle surface solar and greenhouse influences on global warming, trends in diurnal temperature range are analyzed. They suggest that solar dimming was effective in masking greenhouse warming, but only up to the 1980s, when dimming gradually transformed into brightening. Since then, the uncovered greenhouse effect has revealed its full dimension, as manifested in a rapid temperature rise (+0.38°C/decade over land since mid-1980s). Recent solar brightening cannot supersede the greenhouse effect as main cause of global warming, since land temperatures increased by 0.8°C from 1960 to 2000, even though solar brightening did not fully outweigh solar dimming within this period.” Wild, M., A. Ohmura, and K. Makowski (2007), Geophys. Res. Lett., 34, L04702, doi:10.1029/2006GL028031. [Full text]

Maximum and minimum temperature trends for the globe: An update through 2004 – Vose et al. (2005) “New data acquisitions are used to examine recent global trends in maximum temperature, minimum temperature, and the diurnal temperature range (DTR). On average, the analysis covers the equivalent of 71% of the total global land area, 17% more than in previous studies. Consistent with the IPCC Third Assessment Report, minimum temperature increased more rapidly than maximum temperature (0.204 vs. 0.141°C dec−1) from 1950–2004, resulting in a significant DTR decrease (−0.066°C dec−1). In contrast, there were comparable increases in minimum and maximum temperature (0.295 vs. 0.287°C dec−1) from 1979–2004, muting recent DTR trends (−0.001°C dec−1). Minimum and maximum temperature increased in almost all parts of the globe during both periods, whereas a widespread decrease in the DTR was only evident from 1950–1980.” Vose, R. S., D. R. Easterling, and B. Gleason (2005), Maximum and minimum temperature trends for the globe: An update through 2004, Geophys. Res. Lett., 32, L23822, doi:10.1029/2005GL024379. [Short version of the article]

Diurnal temperature range as an index of global climate change during the twentieth century – Braganza et al. (2004) “The usefulness of global-average diurnal temperature range (DTR) as an index of climate change and variability is evaluated using observations and climate model simulations representing unforced climate variability and anthropogenic climate change. On decadal timescales, modelled and observed intrinsic variability of DTR compare well and are independent of variations in global mean temperature. Observed reductions in DTR over the last century are large and unlikely to be due to natural variability alone. Comparison of observed and anthropogenic-forced model changes in DTR over the last 50 years show much less reduction in DTR in the model simulations due to greater warming of maximum temperatures in the models than observed. This difference is likely attributed to increases in cloud cover that are observed over the same period and are absent in model simulations.” Braganza, K., D. J. Karoly, and J. M. Arblaster (2004), Geophys. Res. Lett., 31, L13217, doi:10.1029/2004GL019998. [Full text]

Daily maximum and minimum temperature trends in a climate model – Stone & Weaver (2003) “The recent observed global warming trend over land has been characterised by a faster warming at night, leading to a considerable decrease in the diurnal temperature range (DTR). Analysis of simulations of a climate model including observed increases in greenhouse gases and sulphate aerosols reveals a similar trend in the DTR of −0.2°C per century, albeit of smaller magnitude than the observed −0.8°C per century. This trend in the model simulations is related to changes in cloud cover and soil moisture. These results indicate that the observed decrease in the DTR could be a signal of anthropogenic forcing of recent climate change.” Stone, D. A., and A. J. Weaver (2002), Geophys. Res. Lett., 29(9), 1356, doi:10.1029/2001GL014556. [Full text]

Effects of Clouds, Soil Moisture, Precipitation, and Water Vapor on Diurnal Temperature Range – Dai et al. (1999) “The diurnal range of surface air temperature (DTR) has decreased worldwide during the last 4–5 decades and changes in cloud cover are often cited as one of the likely causes. To determine how clouds and moisture affect DTR physically on daily bases, the authors analyze the 30-min averaged data of surface meteorological variables and energy fluxes from the the First International Satellite Land Surface Climatology Project Field Experiment and the synoptic weather reports of 1980–1991 from about 6500 stations worldwide. The statistical relationships are also examined more thoroughly in the historical monthly records of DTR, cloud cover, precipitation, and streamflow of this century. It is found that clouds, combined with secondary damping effects from soil moisture and precipitation, can reduce DTR by 25%–50% compared with clear-sky days over most land areas; while atmospheric water vapor increases both nighttime and daytime temperatures and has small effects on DTR. Clouds, which largely determine the geographic patterns of DTR, greatly reduce DTR by sharply decreasing surface solar radiation while soil moisture decreases DTR by increasing daytime surface evaporative cooling. Clouds with low bases are most efficient in reducing the daytime maximum temperature and DTR mainly because they are very effective in reflecting the sunlight, while middle and high clouds have only moderate damping effects on DTR. The DTR reduction by clouds is largest in warm and dry seasons such as autumn over northern midlatitudes when latent heat release is limited by the soil moisture content. The net effects of clouds on the nighttime minimum temperature is small except in the winter high latitudes where the greenhouse warming effect of clouds exceeds their solar cooling effect. The historical records of DTR of the twentieth century covary inversely with cloud cover and precipitation on interannual to multidecadal timescales over the United States, Australia, midlatitude Canada, and former U.S.S.R., and up to 80% of the DTR variance can be explained by the cloud and precipitation records. Given the strong damping effect of clouds on the daytime maximum temperature and DTR, the well-established worldwide asymmetric trends of the daytime and nighttime temperatures and the DTR decreases during the last 4–5 decades are consistent with the reported increasing trends in cloud cover and precipitation over many land areas and support the notion that the hydrologic cycle has intensified.” Dai, Aiguo, Kevin E. Trenberth, Thomas R. Karl, 1999: Effects of Clouds, Soil Moisture, Precipitation, and Water Vapor on Diurnal Temperature Range. J. Climate, 12, 2451–2473, doi: 10.1175/1520-0442(1999)0122.0.CO;2. [Full text]

Maximum and Minimum Temperature Trends for the Globe – Easterling et al. (1997) “Analysis of the global mean surface air temperature has shown that its increase is due, at least in part, to differential changes in daily maximum and minimum temperatures, resulting in a narrowing of the diurnal temperature range (DTR). The analysis, using station metadata and improved areal coverage for much of the Southern Hemisphere landmass, indicates that the DTR is continuing to decrease in most parts of the world, that urban effects on globally and hemispherically averaged time series are negligible, and that circulation variations in parts of the Northern Hemisphere appear to be related to the DTR. Atmospheric aerosol loading in the Southern Hemisphere is much less than that in the Northern Hemisphere, suggesting that there are likely a number of factors, such as increases in cloudiness, contributing to the decreases in DTR.” David R. Easterling, Briony Horton, Philip D. Jones, Thomas C. Peterson, Thomas R. Karl, David E. Parker, M. James Salinger, Vyacheslav Razuvayev, Neil Plummer, Paul Jamason and Christopher K. Folland, Science 18 July 1997, Vol. 277 no. 5324 pp. 364-367, DOI: 10.1126/science.277.5324.364. [Full text]

The Influence of Land Use/Land Cover on Climatological Values of the Diurnal Temperature Range – Gallo et al. (1996) “The diurnal temperature range (DTR) at weather observation stations that make up the U.S. Historical Climatology Network was evaluated with respect to the predominant land use/land cover associated with the stations within three radii intervals (100, 1000, and 10 000 m) of the stations. Those stations that were associated with predominantly rural land use/land cover (LULC) usually displayed the greatest observed DTR, whereas those associated with urban related land use or land cover displayed the least observed DTR. The results of this study suggest that significant differences in the climatological DTR were observed and could be attributed to the predominant LULC associated with the observation stations. The results also suggest that changes in the predominant LULC conditions, within as great as a 10 000 m radius of an observation station, could significantly influence the climatological DTR. Future changes in the predominant LULC associated with observation sites should be monitored similar to the current practice of monitoring changes in instruments or time of observation at the observations sites.” Gallo, Kevin P., David R. Easterling, Thomas C. Peterson, 1996, J. Climate, 9, 2941–2944. [Full text]

Southwest Pacific temperatures: trends in maximum and minimum temperatures – Salinger (1995) “Diurnal temperature trends are described for newly homogenised climate data sets for a large area of the South Pacific. The diurnal trends differ from those documented for Northern Hemisphere land areas, where decreases are observed in the diurnal temperature range as a result of increases principally in minimum temperature. The Southwest Pacific divides into four regions that share coherent diurnal temperature trends over the past five decades. Two regions southwest of the South Pacific Convergence Zone (SPCZ) display steady warming in mean temperature. The other two regions, located northeast of the SPCZ, cooled in the 1970’s and warmed in the 1980’s. The warming in three of the four regions can be attributed to increases in both mean daily maximum (mostly daytime) and mean daily minimum (mostly night time) temperature, with little change in the diurnal temperature range. In New Zealand, modification of the regional temperature trend occurs as atmospheric circulation interacts with the high orography, producing different local behaviour in trends of maximum and minimum temperature and diurnal temperature range. The present results come from sites where there can be no question of any urban influence. Most of the Southwest Pacific sites provide a very good climate monitoring platform for the surrounding oceans because of their island location.” M. J. Salinger, Atmospheric Research, Volume 37, Issues 1-3, July 1995, Pages 87-99, doi:10.1016/0169-8095(94)00071-K. [Full text]

Recent variations in mean temperature and the diurnal temperature range in the Antarctic – Jones (1995) “Monthly mean surface temperature data are available from nearly twenty stations for the period since the International Geophysical Year 1957. All but three stations show an increase in mean temperatures over this time, amounting in the average to 0.57°C over 1957 to 1994. All of this warming occurred before the early 1970s. Since then, there has been no change. The warming has been greatest in the Antarctic Peninsula. Analyses of the less‐widely available diurnal temperature range (DTR) (maximum‐minimum) data show regions of increase and decrease over Antarctica. An average continental DTR series shows no trend over 1957 to 1992. Analyses for six mid‐to‐high latitude Southern Ocean islands show increases in mean temperature over 1961–90. Given the low year‐to‐year variability in these data, these trends are more significant than for any of the stations on the Antarctic continent. The marked decrease in mean temperatures over Antarctica during 1993 and 1994 seems unrelated to sea‐ice variations which show little change since the early 1980s.” Jones, P. D. (1995), Geophys. Res. Lett., 22(11), 1345–1348, doi:10.1029/95GL01198.

Asymmetric diurnal temperature change in the Alpine Region – Weber et al. (1994) “By now there is general agreement that the annual mean temperature of earth’s surface has increased during the last century. Recently, it has become obvious that this warming is quite inhomogeneous in various respects. Besides the spatial and seasonal variability of the temperature trend a diurnal asymmetry of increase has been observed. In large continental regions the annual mean of the daily minimum temperature has increased noticeably faster than the annual mean of the daily maximum. The same behaviour is found in the present study for low‐lying stations in Central Europe. However, data from mountain top stations show a similar increase for both minimum and maximum of daily temperatures. No diurnal asymmetry was observed for these stations. The good agreement of the time series from different mountain stations leads us to believe that the observed trends of minimum and maximum temperature are not caused by particular local influences or observation errors. An analysis of monthly and seasonal means shows that most of the warming took place in fall.” Weber, R. O., P. Talkner, and G. Stefanicki (1994), Geophys. Res. Lett., 21(8), 673–676, doi:10.1029/94GL00774. [Full text]

Nighttime warming and the greenhouse effect – Kukla & Karl (1993) No abstract.

A New Perspective on Recent Global Warming: Asymmetric Trends of Daily Maximum and Minimum Temperature – Karl et al. (1993) “Monthly mean maximum and minimum temperatures for over 50% (10%) of the Northern (Southern) Hemisphere landmass, accounting for 37% of the global landmass, indicate that the rise of the minimum temperature has occurred at a rate three times that of the maximum temperature during the period 1951–90 (0.84°C versus 0.28°C). The decrease of the diurnal temperature range is approximately equal to the increase of mean temperature. The asymmetry is detectable in all seasons and in most of the regions studied. The decrease in the daily temperature range is partially related to increases in cloud cover. Furthermore, a large number of atmospheric and surface boundary conditions are shown to differentially affect the maximum and minimum temperature. Linkages of the observed changes in the diurnal temperature range to large-scale climate forcings, such as anthropogenic increases in sulfate aerosols, greenhouse gases, or biomass burning (smoke), remain tentative. Nonetheless, the observed decrease of the diurnal temperature range is clearly important, both scientifically and practically.” Karl, Thomas R., and Coauthors, 1993, Bull. Amer. Meteor. Soc., 74, 1007–1023. [Full text]

Southwest Pacific temperatures: Diurnal and seasonal trends – Salinger et al. (1993) “Temperature trends are presented for a large part of the southwest Pacific. The trends differ from those documented for Northern Hemisphere land areas, where warming has occurred mainly through increases in minimum temperature. The New Zealand patterns are derived from recently completed analyses of monthly and annual mean maximum and minimum surface temperature records for a newly homogenised historical climate data series for New Zealand and outlying islands. They indicate that the warming in the New Zealand region over the past five decades can be attributed to increases in both mean maximum (mostly daytime) and mean minimum (mostly night time) temperature. All seasons show a temperature increase, with the largest occurring in summer (DJF). Northern Hemisphere evidence suggests that changes in cloud cover and the presence of sulfate aerosols plays a direct role. The present results imply that, while the observed warming in a large portion of the Northern Hemisphere landmass may be significantly affected by both these factors, sulfate aerosol effects may be less important in the Southern Hemisphere.” Salinger, M. J., J. Hay, R. McGann, and B. Fitzharris (1993), Geophys. Res. Lett., 20(10), 935–938, doi:10.1029/93GL01113.

Global warming: Evidence for asymmetric diurnal temperature change – Karl et al. (1990) “Analyses of the year‐month mean maximum and minimum surface thermometric record have now been updated and expanded to cover three large countries in the Northern Hemisphere (the contiguous United States, the Soviet Union, and the People’s Republic of China). They indicate that most of the warming which has occurred in these regions over the past four decades can be attributed to an increase of mean minimum (mostly nighttime) temperatures. Mean maximum (mostly daytime) temperatures display little or no warming. In the USA and the USSR (no access to data in China) similar characteristics are also reflected in the changes of extreme seasonal temperatures, e.g., increase of extreme minimum temperatures and little or no change in extreme maximum temperatures. The continuation of increasing minimum temperatures and little overall change of the maximum leads to a decrease of the mean (and extreme) temperature range, an important measure of climate variability. The cause(s) of the asymmetric diurnal changes are uncertain, but there is some evidence to suggest that changes in cloud cover plays a direct role (where increases in cloudiness result in reduced maximum and higher minimum temperatures). Regardless of the exact cause(s), these results imply that either: (1) climate model projections considering the expected change in the diurnal temperature range with increased levels of the greenhouse gases are underestimating (overestimating) the rise of the daily minimum (maximum) relative to the maximum (minimum), or (2) the observed warming in a considerable portion of the Northern Hemisphere landmass is significantly affected by factors unrelated to an enhanced anthropogenically‐induced greenhouse effect.” Karl, T. R., G. Kukla, V. N. Razuvayev, M. J. Changery, R. G. Quayle, R. R. Heim Jr., D. R. Easterling, and C. B. Fu (1991), Geophys. Res. Lett., 18(12), 2253–2256, doi:10.1029/91GL02900.

Is Recent Climate Change Across the United States Related to Rising Levels of Anthropogenic Greenhouse Gases? – Plantico et al. (1990) “Global warming as a result of rising concentrations of anthropogenic greenhouse gases is predicted by current climate models. During the period 1948–1987, the concentration of anthropogenic greenhouse gases increased by more than 30%, and the mean annual temperature of the northern hemisphere increased by about 0.15°C. The mean annual temperature of the contiguous United States, however, does not show any significant trend. To gain a better understanding of why the United States’ temperature record does not reflect the anticipated greenhouse warming, we studied the inter-relationships between trends of temperature, cloudiness, sunshine and precipitation. Both the seasonal and annual trends for 23 geographic regions covering the United States were analyzed using Monte Carlo field significance tests. Several seasonal and regional differences were noted. While winters and autumns cooled, springs and summers warmed. Annually, cooling has occurred across the eastern half of the country, while warming dominates in the West. The largest changes in maximum temperature, daily temperature range, cloud amount, percent of possible sunshine and precipitation occur during autumn. Autumn also has the most significant correlations between trends. We found that the recent decrease of the maximum temperature and daily temperature range in autumn is statistically associated with increasing cloud amount and precipitation, and with decreasing sunshine. The widespread reduction in the temperature range is a result of decreased maximum and increased minimum temperatures. Cloud amount increased over most of the country during all seasons except spring. During spring the cloud amount remained fairly constant even though precipitation increased. Interestingly, no significant correlation was found between trends of mean temperature and cloud amount. Although several features of the recent climate change across the United States agree qualitatively with the model-predicted impact of increasing anthropogenic greenhouse gases, the regional and seasonal distribution of the observed trends do not appear in line with the model results. We conclude that either the recent changes of temperature, cloud amount, sunshine and precipitation over the United States are as yet unrelated to the increasing anthropogenic greenhouse gases, or that the transient response of regional climates to the greenhouse effect is not proportional to the modeled difference between the 1 × CO2 and 2 × CO2 equilibrium climates.” Plantico, M. S., T. R. Karl, G. Kukla, and J. Gavin (1990), J. Geophys. Res., 95(D10), 16,617–16,637, doi:10.1029/JD095iD10p16617.

Relationship between Decreased Temperature Range and Precipitation Trends in the United States and Canada, 1941–80 – Karl et al. (1986) “Previous work has shown significant decreases of the diurnal temperature range (1941–80) across a network of 130 stations in the United States and Canada. In the present study, changes in monthly total precipitation at these same stations were related to the decrease in temperature range using various Monte Carlo. These tests indicate that factors other than those related to precipitation contributed to the decrease of daily temperature range. Further study of the mechanisms responsible for the decreased temperature range is warranted, based on these results. The decreased range may be one of the few pieces of evidence available in North America that is consistent with potential impacts of increased greenhouse gases and/or anthropogenic aerosols.” Karl, Thomas R., George Kukla, Joyce Gavin, 1986, J. Climate Appl. Meteor., 25, 1878–1886. [Full text]

Decreasing Diurnal Temperature Range in the United States and Canada from 1941 through 1980 – Karl et al. (1984) “An appreciable number of nonurban stations in the United States and Canada have been identified with statistically significant (at the 90% level) decreasing trends in the monthly mean diurnal temperature range between 1941–80. The percentage of stations in the network showing the decrease is higher than expected due to chance throughout the year, with a maximum reached during late summer and early autumn and a minimum in December. Monte Carlo tests indicate that during five months the field significance of the decreasing range is above the 99% level, and in 12 months above the 95% level. There is a negligible probability that such a result is due to chance. In contrast, trends of increasing or decreasing monthly mean maximum or minimum temperatures have at most only two months with field significance at or above the 90% level. This is related to the tendency toward increasing temperature in the western portions of North America and decreasing temperature in the east. The physical mechanism responsible for the observed decrease in the diurnal range is not known. Possible explanations include greenhouse effects such as changes in cloudiness, aerosol loading, atmospheric water vapor content, or carbon dioxide. Change in circulation is also a possibility, but it will be difficult to isolate since the patterns of the decreased diurnal temperature range have high field significance throughout much of the year, relatively low spatial coherence, and occur at many stations where individual trends in the maximum and minimum temperature are not statistically significant. Our data show that the trends in the maximum and minimum temperatures may differ considerably from trends in the mean.” Karl, T. R., G. Kukla, J. Gavin, 1984, J. Climate Appl. Meteor., 23, 1489–1504. [Full text]

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New research from last week 46/2010

Posted by Ari Jokimäki on November 22, 2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

NOTE! From now on, I’ll start posting these as whole abstracts and in the same format as the papers are in my paperlists. That way the new papers will be easier to transfer to the lists. It also saves me the time and effort to try to say the same things in my own words. The abstracts are usually quite understandably written anyway.

Published last week:

20th century dust cooled climate

A new study has looked into the climatic effects of desert dust during the 20th century. Th net radiative effect of desert dust was found to be -0.14 ± 0.11 W/m2 (this is the difference between 1990–1999 and 1905–1914). Effect can be very strong at times:

“The estimated radiative change due to dust is especially strong between the heavily loaded 1980–1989 and the less heavily loaded 1955–1964 time periods (−0.57 ± 0.46 W/m2), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 °C.”

Dust also had an effect to the ocean productivity:

“Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans.”

Citation: Mahowald, N. M., Kloster, S., Engelstaedter, S., Moore, J. K., Mukhopadhyay, S., McConnell, J. R., Albani, S., Doney, S. C., Bhattacharya, A., Curran, M. A. J., Flanner, M. G., Hoffman, F. M., Lawrence, D. M., Lindsay, K., Mayewski, P. A., Neff, J., Rothenberg, D., Thomas, E., Thornton, P. E., and Zender, C. S.: Observed 20th century desert dust variability: impact on climate and biogeochemistry, Atmos. Chem. Phys., 10, 10875-10893, doi:10.5194/acp-10-10875-2010, 2010. [abstract, full text]

Anthropogenic aerosols might cool Arctic after all

Current thinking is that anthropogenic aerosols indirect cloud effect might have increased surface temperatures in the Arctic. Previous studies have concentrated on the longwave processes regionally. New study is making an effort to estimate the full situation including the shortwave effects for the whole Arctic area. They use climate model simulations in their study. The result:

“Results show that the longwave indirect effect at the surface lies between 0.10 and 0.85 W/m2 averaged annually north of 71°N, while the shortwave indirect effect lies between −1.29 W/m2 and −0.52 W/m2. Due to longwave dominance in winter, 6 of 11 simulations give a positive change in net cloud forcing between October and May (−0.16 to 0.29 W/m2), while the change in forcing averaged over the summer months is negative for all model simulations (from −2.63 to −0.23 W/m2). The annually averaged change in net cloud forcing at the surface is negative in 10 of 11 simulations, lying between −0.98 and 0.12 W/m2. In conclusion, our results point to a small decrease in the surface radiative flux due to the aerosol indirect effect in the Arctic, but these estimates are subject to uncertainties in the frequency of thin clouds and biases in the estimated cloud cover.”

Citation: Alterskjær, K., J. E. Kristjánsson, and C. Hoose (2010), Do anthropogenic aerosols enhance or suppress the surface cloud forcing in the Arctic?, J. Geophys. Res., 115, D22204, doi:10.1029/2010JD014015. [abstract]

New global upper air dataset reaches back to 1918

REC2 is the name for the new product that offers upper-air observation-based estimates of some weather parameters, including temperature, between 1918 and 1957. So far similar data sets have reached back to 1948 at best so this seems to be considerable improvement to that situation. there is some problems with the sparsity of the data, especially in early years, but still:

“We show the results of several validation experiments, compare our new data set with a number of existing data sets, and demonstrate that it is suitable for analysing large-scale climate variability on interannual time-scales.”

Citation: Stefan Brönnimann, Thomas Griesser and Alexander Stickler, A gridded monthly upper-air data set from 1918 to 1957, 2010, Climate Dynamics, DOI: 10.1007/s00382-010-0940-x. [abstract]

Troposphere temperature trends – review

A new review article has looked at 195 research articles on tropospheric temperatures. They find that observations show troposphere warming as expected both theoretically and in climate models.

Citation: Peter W. Thorne, John R. Lanzante, Thomas C. Peterson, Dian J. Seidel, Keith P. Shine, Tropospheric temperature trends: history of an ongoing controversy, 2010, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.80. [abstract, full text, NOAA press release]

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Papers on CO2 fertilization effect

Posted by Ari Jokimäki on November 18, 2010

This is a list of papers on the CO2 fertilization effect to the plant growth. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Tree ring evidence for limited direct CO2 fertilization of forests over the 20th century – Gedalof & Berg (2010) “The effect that rising atmospheric CO2 levels will have on forest productivity and water use efficiency remains uncertain, yet it has critical implications for future rates of carbon sequestration and forest distributions. Efforts to understand the effect that rising CO2 will have on forests are largely based on growth chamber studies of seedlings, and the relatively small number of FACE sites. Inferences from these studies are limited by their generally short durations, artificial growing conditions, unnatural step-increases in CO2 concentrations, and poor replication. Here we analyze the global record of annual radial tree growth, derived from the International Tree ring Data Bank (ITRDB), for evidence of increasing growth rates that cannot be explained by climatic change alone, and for evidence of decreasing sensitivity to drought. We find that approximately 20 percent of sites globally exhibit increasing trends in growth that cannot be attributed to climatic causes, nitrogen deposition, elevation, or latitude, which we attribute to a direct CO2 fertilization effect. No differences were found between species in their likelihood to exhibit growth increases attributable to CO2 fertilization, although Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa), the two most commonly sampled species in the ITRDB, exhibit a CO2 fertilization signal at frequencies very near their upper and lower confidence limits respectively. Overall these results suggest that CO2 fertilization of forests will not counteract emissions or slow warming in any substantial fashion, but do suggest that future forest dynamics may differ from those seen today depending on site conditions and individual species’ responses to elevated CO2.” Gedalof, Z., and A. A. Berg (2010), Global Biogeochem. Cycles, 24, GB3027, doi:10.1029/2009GB003699.

CO2 Enhancement of Forest Productivity Constrained by Limited Nitrogen Availability – Norby et al. (2009) “Here, we provide new evidence from a FACE experiment in a deciduous Liquidambar styraciflua (sweetgum) forest stand in Tennessee, USA, that N limitation has significantly reduced the stimulation of NPP by elevated atmospheric CO2 concentration (eCO2). Isotopic evidence and N budget analysis support the premise that N availability in this forest ecosystem has been declining over time, and declining faster in eCO2. Model analyses and evidence from leaf- and stand-level observations provide mechanistic evidence that declining N availability constrained the tree response to eCO2. These results provide a strong rationale and process understanding for incorporating N limitation and N feedback effects in ecosystem and global models used in climate change assessments.” Norby, Richard, Warren, Jeffrey, Iversen, Colleen, Garten, Charles, Medlyn, Belinda, and McMurtrie, Nature Precedings, hdl:10101/npre.2009.3747.1, 2009. [Full text]

Why is plant-growth response to elevated CO2 amplified when water is limiting, but reduced when nitrogen is limiting? A growth-optimisation hypothesis – McMurtrie et al. (2008) “Experimental evidence indicates that the stomatal conductance and nitrogen concentration ([N]) of foliage decline under CO2 enrichment, and that the percentage growth response to elevated CO2 is amplified under water limitation, but reduced under nitrogen limitation. We advance simple explanations for these responses based on an optimisation hypothesis applied to a simple model of the annual carbon–nitrogen–water economy of trees growing at a CO2-enrichment experiment at Oak Ridge, Tennessee, USA. The model is shown to have an optimum for leaf [N], stomatal conductance and leaf area index (LAI), where annual plant productivity is maximised. The optimisation is represented in terms of a trade-off between LAI and stomatal conductance, constrained by water supply, and between LAI and leaf [N], constrained by N supply. At elevated CO2 the optimum shifts to reduced stomatal conductance and leaf [N] and enhanced LAI. The model is applied to years with contrasting rainfall and N uptake. The predicted growth response to elevated CO2 is greatest in a dry, high-N year and is reduced in a wet, low-N year. The underlying physiological explanation for this contrast in the effects of water versus nitrogen limitation is that leaf photosynthesis is more sensitive to CO2 concentration ([CO2]) at lower stomatal conductance and is less sensitive to [CO2] at lower leaf [N].” Ross E. McMurtrie, Richard J. Norby, Belinda E. Medlyn, Roderick C. Dewar, David A. Pepper, Peter B. Reich, Craig V. M. Barton, Functional Plant Biology, 2008, 35(6) 521–534, doi:10.1071/FP08128. [Full text]

The Power of Monitoring Stations and a CO2 Fertilization Effect: Evidence from Causal Relationships between NDVI and Carbon Dioxide – Kaufmann et al. (2008) “Two hypotheses are tested: 1) monitoring stations (e.g., Mauna Loa) are not able to measure changes in atmospheric concentrations of CO2 that are generated by changes in terrestrial vegetation at distant locations; 2) changes in the atmospheric concentration of carbon dioxide do not affect terrestrial vegetation at large scales under conditions that now exist in situ, by estimating statistical models of the relationship between satellite measurements of the normalized difference vegetation index (NDVI) and the atmospheric concentration of carbon dioxide measured at Mauna Loa and Point Barrow. To go beyond simple correlations, the notion of Granger causality is used. Results indicate that the authors are able to identify locations where and months when disturbances to the terrestrial biota “Granger cause” atmospheric CO2. The authors are also able to identify locations where and months when disturbances to the atmospheric concentration of carbon dioxide generate changes in NDVI. Together, these results provide large-scale support for a CO2 fertilization effect and an independent empirical basis on which observations at monitoring stations can be used to test hypotheses and validate models regarding effect of the terrestrial biota on atmospheric concentrations of carbon dioxide.” Kaufmann, R. K., L. F. Paletta, H. Q. Tian, R. B. Myneni, R. D. D’Arrigo, 2008, Earth Interact., 12, 1–23, doi: 10.1175/2007EI240.1. [Full text]

Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2 – Finzi et al. (2007) “Forest ecosystems are important sinks for rising concentrations of atmospheric CO2. In previous research, we showed that net primary production (NPP) increased by 23 ± 2% when four experimental forests were grown under atmospheric concentrations of CO2 predicted for the latter half of this century. Because nitrogen (N) availability commonly limits forest productivity, some combination of increased N uptake from the soil and more efficient use of the N already assimilated by trees is necessary to sustain the high rates of forest NPP under free-air CO2 enrichment (FACE). In this study, experimental evidence demonstrates that the uptake of N increased under elevated CO2 at the Rhinelander, Duke, and Oak Ridge National Laboratory FACE sites, yet fertilization studies at the Duke and Oak Ridge National Laboratory FACE sites showed that tree growth and forest NPP were strongly limited by N availability. By contrast, nitrogen-use efficiency increased under elevated CO2 at the POP-EUROFACE site, where fertilization studies showed that N was not limiting to tree growth. Some combination of increasing fine root production, increased rates of soil organic matter decomposition, and increased allocation of carbon (C) to mycorrhizal fungi is likely to account for greater N uptake under elevated CO2. Regardless of the specific mechanism, this analysis shows that the larger quantities of C entering the below-ground system under elevated CO2 result in greater N uptake, even in N-limited ecosystems. Biogeochemical models must be reformulated to allow C transfers below ground that result in additional N uptake under elevated CO2.” Adrien C. Finzi, Richard J. Norby, Carlo Calfapietra, Anne Gallet-Budynek, Birgit Gielen, William E. Holmes, Marcel R. Hoosbeek, Colleen M. Iversen, Robert B. Jackson, Mark E. Kubiske, Joanne Ledford, Marion Liberloo, Ram Oren, Andrea Polle, Seth Pritchard, Donald R. Zak, William H. Schlesinger, and Reinhart Ceulemans, PNAS August 28, 2007 vol. 104 no. 35 14014-14019, doi: 10.1073/pnas.0706518104. [Full text]

Nitrogen limitation constrains sustainability of ecosystem response to CO2 – Reich et al. (2006) “Enhanced plant biomass accumulation in response to elevated atmospheric CO2 concentration could dampen the future rate of increase in CO2 levels and associated climate warming. However, it is unknown whether CO2-induced stimulation of plant growth and biomass accumulation will be sustained or whether limited nitrogen (N) availability constrains greater plant growth in a CO2-enriched world. Here we show, after a six-year field study of perennial grassland species grown under ambient and elevated levels of CO2 and N, that low availability of N progressively suppresses the positive response of plant biomass to elevated CO2. Initially, the stimulation of total plant biomass by elevated CO2 was no greater at enriched than at ambient N supply. After four to six years, however, elevated CO2 stimulated plant biomass much less under ambient than enriched N supply. This response was consistent with the temporally divergent effects of elevated CO2 on soil and plant N dynamics at differing levels of N supply. Our results indicate that variability in availability of soil N and deposition of atmospheric N are both likely to influence the response of plant biomass accumulation to elevated atmospheric CO2. Given that limitations to productivity resulting from the insufficient availability of N are widespread in both unmanaged and managed vegetation, soil N supply is probably an important constraint on global terrestrial responses to elevated CO2.” Peter B. Reich, Sarah E. Hobbie, Tali Lee, David S. Ellsworth, Jason B. West, David Tilman, Johannes M. H. Knops, Shahid Naeem and Jared Trost, Nature 440, 922-925 (13 April 2006) | doi:10.1038/nature04486.

Food for Thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO2 Concentrations – Long et al. (2006) “Model projections suggest that although increased temperature and decreased soil moisture will act to reduce global crop yields by 2050, the direct fertilization effect of rising carbon dioxide concentration ([CO2]) will offset these losses. The CO2 fertilization factors used in models to project future yields were derived from enclosure studies conducted approximately 20 years ago. Free-air concentration enrichment (FACE) technology has now facilitated large-scale trials of the major grain crops at elevated [CO2] under fully open-air field conditions. In those trials, elevated [CO2] enhanced yield by ∼50% less than in enclosure studies. This casts serious doubt on projections that rising [CO2] will fully offset losses due to climate change.” Stephen P. Long, Elizabeth A. Ainsworth, Andrew D. B. Leakey, Josef Nösberger and Donald R. Ort, Science 30 June 2006, Vol. 312 no. 5782 pp. 1918-1921, DOI: 10.1126/science.1114722.

Effect of natural atmospheric CO2 fertilization suggested by open-grown white spruce in a dry environment – Wang et al. (2006) “Evidence of an atmospheric CO2-fertilization effect on radial growth rates was uncovered for open-grown white spruce in a mixed-grass prairie of southwestern Manitoba, Canada. Consistent upward trends of the residuals from dendroclimatic models indicated a decreased ability for climatic parameters to predict radial growth. Despite that a similar amount (61%) of the total variation in radial growth index was explained by climate for both young and old trees, residuals from young trees for the period of 1955–1999 demonstrated a stronger upward trend (R2=0.551, P<0.0001) than old trees for the period of 1900–1996 (R2=0.020, P=0.167). Similar to young trees, the residuals from the early growth period (1900–1929) of old trees also demonstrated a stronger upward trend (R2=0.480, P<0.0001) than the period of 1900–1996. Likewise, a comparable period (1970–1999) of young trees also demonstrated a stronger upward trend (R2=0.619, P<0.0001) than the early growth period (1900–1929) of old trees. In addition, postdrought growth response was much stronger for young trees (1970–1999) compared with old trees at the same development stage (1900–1929) (P=0.011) or within the same time period (1970–1999) (P=0.014). There was no difference (P=0.221) in drought recovery between the early (1900–1929) period and the late (1970–1999) period within old trees. Together, our results suggest that (1) open-grown white spruce trees improved their growth with time at the early developmental stage, and (2) at the same developmental stage, a greater growth response occurred in the late period when atmospheric CO2 concentration, and the rate of atmospheric CO2 increase were both relatively high. While it is impossible to rule out other factors, these results are consistent with expectations for CO2-fertilization effects.” G. Geoff Wang, Sophan Chhin, William L. Bauerle, Global Change Biology, Volume 12, Issue 3, pages 601–610, March 2006, DOI: 10.1111/j.1365-2486.2006.01098.x.

Forest response to elevated CO2 is conserved across a broad range of productivity – Norby et al. (2005) “Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric [CO2] (“CO2 fertilization”), thereby slowing the rate of increase in atmospheric [CO2]. Carbon exchanges between the terrestrial biosphere and atmosphere are often first represented in models as net primary productivity (NPP). However, the contribution of CO2 fertilization to the future global C cycle has been uncertain, especially in forest ecosystems that dominate global NPP, and models that include a feedback between terrestrial biosphere metabolism and atmospheric [CO2] are poorly constrained by experimental evidence. We analyzed the response of NPP to elevated CO2 (≈550 ppm) in four free-air CO2 enrichment experiments in forest stands. We show that the response of forest NPP to elevated [CO2] is highly conserved across a broad range of productivity, with a stimulation at the median of 23 ± 2%. At low leaf area indices, a large portion of the response was attributable to increased light absorption, but as leaf area indices increased, the response to elevated [CO2] was wholly caused by increased light-use efficiency. The surprising consistency of response across diverse sites provides a benchmark to evaluate predictions of ecosystem and global models and allows us now to focus on unresolved questions about carbon partitioning and retention, and spatial variation in NPP response caused by availability of other growth limiting resources.” Richard J. Norby, Evan H. DeLucia, Birgit Gielen, Carlo Calfapietra, Christian P. Giardina, John S. King, Joanne Ledford, Heather R. McCarthy, David J. P. Moore, Reinhart Ceulemans, Paolo De Angelis, Adrien C. Finzi, David F. Karnosky, Mark E. Kubiske, Martin Lukac, Kurt S. Pregitzer, Giuseppe E. Scarascia-Mugnozza, William H. Schlesinger, and Ram Oren, PNAS December 13, 2005 vol. 102 no. 50 18052-18056, doi: 10.1073/pnas.0509478102. [Full text]

Climate change impacts on crop yield and quality with CO2 fertilization in China – Erda et al. (2005) “A regional climate change model (PRECIS) for China, developed by the UK’s Hadley Centre, was used to simulate China’s climate and to develop climate change scenarios for the country. Results from this project suggest that, depending on the level of future emissions, the average annual temperature increase in China by the end of the twenty-first century may be between 3 and 4 °C. Regional crop models were driven by PRECIS output to predict changes in yields of key Chinese food crops: rice, maize and wheat. Modelling suggests that climate change without carbon dioxide (CO2) fertilization could reduce the rice, maize and wheat yields by up to 37% in the next 20–80 years. Interactions of CO2 with limiting factors, especially water and nitrogen, are increasingly well understood and capable of strongly modulating observed growth responses in crops. More complete reporting of free-air carbon enrichment experiments than was possible in the Intergovernmental Panel on Climate Change’s Third Assessment Report confirms that CO2 enrichment under field conditions consistently increases biomass and yields in the range of 5–15%, with CO2 concentration elevated to 550 ppm Levels of CO2 that are elevated to more than 450 ppm will probably cause some deleterious effects in grain quality. It seems likely that the extent of the CO2 fertilization effect will depend upon other factors such as optimum breeding, irrigation and nutrient applications.” Lin Erda, Xiong Wei, Ju Hui, Xu Yinlong, Li Yue, Bai Liping and Xie Liyong, Phil. Trans. R. Soc. B 29 November 2005 vol. 360 no. 1463 2149-2154, doi: 10.1098/rstb.2005.1743. [Full text]

Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment – Norby et al. (2004) “Fine-root production and turnover are important regulators of the biogeochemical cycles of ecosystems and key components of their response to global change. We present a nearly continuous 6-year record of fine-root production and mortality from minirhizotron analysis of a closed-canopy, deciduous sweetgum forest in a free-air CO2 enrichment experiment. Annual production of fine roots was more than doubled in plots with 550 ppm CO2 compared with plots in ambient air. This response was the primary component of the sustained 22% increase in net primary productivity. Annual fine-root mortality matched annual production, and the mean residence time of roots was not altered by elevated CO2, but peak fine-root standing crop in midsummer was significantly higher in CO2-enriched plots, especially deeper in the soil profile. The preferential allocation of additional carbon to fine roots, which have a fast turnover rate in this species, rather than to stemwood reduces the possibility of long-term enhancement by elevated CO2 of carbon sequestration in biomass. However, sequestration of some of the fine-root carbon in soil pools is not precluded, and there may be other benefits to the tree from a seasonally larger and deeper fine-root system. Root-system dynamics can explain differences among ecosystems in their response to elevated atmospheric CO2; hence, accurate assessments of carbon flux and storage in forests in a globally changing atmosphere must account for this unseen and difficult-to-measure component.” Richard J. Norby, Joanne Ledford, Carolyn D. Reilly, Nicole E. Miller, and Elizabeth G. O’Neill, PNAS June 29, 2004 vol. 101 no. 26 9689-9693, doi: 10.1073/pnas.0403491101. [Full text]

Net primary productivity of a CO2-enriched deciduous forest and the implications for carbon storage – Norby et al. (2002) “A central question concerning the response of terrestrial ecosystems to a changing atmosphere is whether increased uptake of carbon in response to increasing atmospheric carbon dioxide concentration results in greater plant biomass and carbon storage or, alternatively, faster cycling of C through the ecosystem. Net primary productivity (NPP) of a closed-canopy Liquidambar styraciflua (sweetgum) forest stand was assessed for three years in a free-air CO2-enrichment (FACE) experiment. NPP increased 21% in stands exposed to elevated CO2, and there was no loss of response over time. Wood increment increased significantly during the first year of exposure, but subsequently most of the extra C was allocated to production of leaves and fine roots. These pools turn over more rapidly than wood, thereby reducing the potential of the forest stand to sequester additional C in response to atmospheric CO2 enrichment. Hence, while this experiment provides the first evidence that CO2 enrichment can increase productivity in a closed-canopy deciduous forest, the implications of this result must be tempered because the increase in productivity resulted in faster cycling of C through the system rather than increased C storage in wood. The fate of the additional C entering the soil system and the environmental interactions that influence allocation need further investigation.” Richard J. Norby, Paul J. Hanson, Elizabeth G. O’Neill, Tim J. Tschaplinski, Jake F. Weltzin, Randi A. Hansen, Weixin Cheng, Stan D. Wullschleger, Carla A. Gunderson, Nelson T. Edwards, and Dale W. Johnson, 2002, Ecological Applications 12:1261–1266, doi:10.1890/1051-0761(2002)012[1261:NPPOAC]2.0.CO;2. [Full text]

Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere – Oren et al. (2001) “Northern mid-latitude forests are a large terrestrial carbon sink. Ignoring nutrient limitations, large increases in carbon sequestration from carbon dioxide (CO2) fertilization are expected in these forests. Yet, forests are usually relegated to sites of moderate to poor fertility, where tree growth is often limited by nutrient supply, in particular nitrogen. Here we present evidence that estimates of increases in carbon sequestration of forests, which is expected to partially compensate for increasing CO2 in the atmosphere, are unduly optimistic. In two forest experiments on maturing pines exposed to elevated atmospheric CO2, the CO2-induced biomass carbon increment without added nutrients was undetectable at a nutritionally poor site, and the stimulation at a nutritionally moderate site was transient, stabilizing at a marginal gain after three years. However, a large synergistic gain from higher CO2 and nutrients was detected with nutrients added. This gain was even larger at the poor site (threefold higher than the expected additive effect) than at the moderate site (twofold higher). Thus, fertility can restrain the response of wood carbon sequestration to increased atmospheric CO2. Assessment of future carbon sequestration should consider the limitations imposed by soil fertility, as well as interactions with nitrogen deposition.” Ram Oren, David S. Ellsworth, Kurt H. Johnsen, Nathan Phillips, Brent E. Ewers, Chris Maier, Karina V.R. Schäfer, Heather McCarthy, George Hendrey, Steven G. McNulty & Gabriel G. Katul, Nature 411, 469-472 (24 May 2001) | doi:10.1038/35078064. [Full text]

Transient nature of CO2 fertilization in Arctic tundra – Oechel et al. (1994) “THERE has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary production and on net ecosystem CO2 flux. Apparently conflicting experimental findings could be the result of differences in genetic potential and resource availability, different experimental conditions and the fact that many studies have focused on individual components of the system rather than the whole ecosystem. Here we present results of an in situ experiment on the response of an intact native ecosystem to elevated CO2. An undisturbed patch of tussock tundra at Toolik Lake, Alaska, was enclosed in greenhouses in which the CO2 level, moisture and temperature could be controlled, and was subjected to ambient (340 p.p.m.) and elevated (680 p.p.m.) levels of CO2 and temperature (+4 °C). Air humidity, precipitation and soil water table were maintained at ambient control levels. For a doubled CO2 level alone, complete homeostasis of the CO2 flux was re-established within three years, whereas the regions exposed to a combination of higher temperatures and doubled CO2 showed persistent fertilization effect on net ecosystem carbon sequestration over this time. This difference may be due to enhanced sink activity from the direct effects of higher temperatures on growth and to indirect effects from enhanced nutrient supply caused by increased mineralization. These results indicate that the responses of native ecosystems to elevated CO2 may not always be positive, and are unlikely to be straightforward. Clearly, CO2 fertilization effects must always be considered in the context of genetic limitation, resource availability and other such factors.” Walter C. Oechel, Sid Cowles, Nancy Grulke, Steven J. Hastings, Bill Lawrence, Tom Prudhomme, George Riechers, Boyd Strain, David Tissue & George Vourlitis, Nature 371, 500 – 503 (06 October 1994); doi:10.1038/371500a0.

Tree growth in carbon dioxide enriched air and its implications for global carbon cycling and maximum levels of atmospheric CO2 – Idso & Kimball (1993) “In the longest carbon dioxide enrichment experiment ever conducted, well-watered and adequately fertilized sour orange tree seedlings were planted directly into the ground at Phoenix, Arizona, in July 1987 and continuously exposed, from mid-November of that year, to either ambient air or air enriched with an extra 300 ppmv of CO2 in clear-plastic-wall open-top enclosures. Only 18 months later, the CO2-enriched trees had grown 2.8 times larger than the ambient-treated trees; and they have maintained that productivity differential to the present day. This tremendous growth advantage is due to two major factors: a CO2-induced increase in daytime net photosynthesis and a CO2-induced reduction in nighttime dark respiration. Measurements of these physiological processes in another experiment have shown three Australlian tree species to respond similarly; while an independent study of the atmosphere’s seasonal CO2 cycle suggests that all earth’s trees, in the mean, probably share this same response. A brief review of the plant science literature outlines how such a large growth response to atmospheric CO2 enrichment might possibly be maintained in light of resource limitations existing in nature. Finally, it is noted that a CO2 “fertilization effect” of this magnitude should substantially slow the rate at which anthropogenic carbon dioxide would otherwise accumulate in the atmosphere, possibly putting an acceptable upper limit on the level to which the CO2 content of the air may ultimately rise.” Idso, S. B., and B. A. Kimball (1993), Global Biogeochem. Cycles, 7(3), 537–555, doi:10.1029/93GB01164.

Posted in Global warming effects | 3 Comments »

New research from last week 45/2010

Posted by Ari Jokimäki on November 15, 2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as I write them. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Atmospheric CO2 leads glacial terminations

A proxy for atmospheric carbon dioxide concentration is described in a new study. The proxy is based on carbon-13 in ocean floor. The carbon-13 based proxy is found to correlate well with atmospheric carbon dioxide concentration. The proxy also gives information about the timing of the events during the glacial periods:

“[The proxy] reproduces characteristic differences between pCO2 and ice volume during Late Pleistocene glaciations and indicates that pCO2 usually leads terminations by 0.2–3.7 kyr but lags by 3–10 kyr during two “failed” terminations at 535 and 745 ka.”

Lowest concentration of carbon dioxide in the atmosphere during the last 1.5 million years is found to be about 155 ppm at about 920,000 years ago.

Citation: Lisiecki, L. E. (2010), A benthic δ13C-based proxy for atmospheric pCO2 over the last 1.5 Myr, Geophys. Res. Lett., 37, L21708, doi:10.1029/2010GL045109. [abstract]

Removing confusion from solar-climate relationships

Legras et al. have looked into the work presented in two recent papers about solar-climate relationships:

“A recent work by Le Mouël et al. (2010) and its companion paper by Kossobokov et al. (2010) show spectacular correlations between solar activity and temperature series from three European weather stations over the last two centuries.”

The result:

“We stress (1) that correlation with solar forcing alone is meaningless unless other forcings are properly accounted for and that sunspot counting is a poor indicator of solar irradiance, (2) that long temperature series require homogenization to remove historical artefacts that affect long term variability, (3) that incorrect application of statistical tests leads to interpret as significant a signal which arises from pure random fluctuations. As a consequence, we reject the results and the conclusions of Le Mouël et al. (2010) and Kossobokov et al. (2010).”

Citation: Legras, B., Mestre, O., Bard, E., and Yiou, P.: A critical look at solar-climate relationships from long temperature series, Clim. Past, 6, 745-758, doi:10.5194/cp-6-745-2010, 2010. [abstract, full text]

Arctic sea ice decrease adds clouds which cause more warming

Satellite measurements spanning 5 “last” years were used to evaluate the effect of Arctic sea ice extent to the polar cloud fraction and vertical distribution:

“We find an anticorrelation between sea ice extent and cloud fraction with maximum cloudiness occurring over areas with little or no sea ice. We also find that over ice-free regions, there is greater low cloud frequency and average optical depth.”

Polar cloud fraction during the five years increased by about 7 % in October and about 10 % in March. Average sea ice decrease was about 5 to 7 %. Here is the surprising conclusion:

“Increasing cloud amount and changes in vertical distribution and optical properties have the potential to affect the radiative balance of the Arctic region by decreasing both the upwelling terrestrial longwave radiation and the downward shortwave solar radiation. Because longwave radiation dominates in the long polar winter, the overall effect of increasing low cloud cover is likely a warming of the Arctic and thus a positive climate feedback, possibly accelerating the melting of Arctic sea ice.”

Citation: Palm, S. P., S. T. Strey, J. Spinhirne, and T. Markus (2010), Influence of Arctic sea ice extent on polar cloud fraction and vertical structure and implications for regional climate, J. Geophys. Res., 115, D21209, doi:10.1029/2010JD013900. [abstract]

Arctic ocean was net carbon dioxide sink between 1998 and 2003

Reduction of sea ice in the Arctic is expected to cause changes in the air-sea carbon dioxide flux because there’s new areas of sea exposed to exchange gases with atmosphere. A new study has evaluated the air-sea exchange of carbon dioxide indirectly:

“The present study utilizes remotely sensed data on distributions of both sea ice and chlorophyll a, together with modeled temperature and salinity fields, to obtain high-resolution basin-scale estimates of the air-sea flux of CO2 (FCO2) in the Arctic Ocean for the years 1998–2003.”

From those it is possible to calculate the FCO2. Some results from that:

“Annual FCO2 was highest in the Atlantic-dominated Greenland and Barents sectors due to their lower sea ice cover, although area-normalized FCO2 in these sectors was low. Only the Siberian sector exhibited a significant increase in annual FCO2 during the time of our study, due to a corresponding increase in ice-free water.”

The end result:

“Overall, the Arctic Ocean was a net atmospheric sink for CO2, with annual FCO2 averaging 118 ± 7 Tg C yr−1 during 1998–2003.”

Citation: Arrigo, K. R., S. Pabi, G. L. van Dijken, and W. Maslowski (2010), Air-sea flux of CO2 in the Arctic Ocean, 1998–2003, J. Geophys. Res., 115, G04024, doi:10.1029/2009JG001224. [abstract]

Maximum estimates of global potential of bio-energy reduced?

A new study has estimated the global potential for bio-energy which has been though to be able to substitute fossil energy. Currently about 10 % of energy humans use comes from bio-energy (about 50 EJ/year). Previous (recent) estimates of the future potential of bio-energy have spanned from 30 to 1000 EJ/year. However, the maximum estimates might be too large:

“In our opinion, the high end of the range is implausible because of (1) overestimation of the area available for bio-energy crops due to insufficient consideration of constraints (e.g., area for food, feed or nature conservation) and (2) too high yield expectations resulting from extrapolation of plot-based studies to large, less productive areas.”

The new improved estimate is:

“According to this review, the global technical primary bio-energy potential in 2050 is in the range of 160–270 EJ/yr if sustainability criteria are considered.”

If that is true, then the potential of bio-energy is only a little over 50 % of current energy demand, and the energy demand is also expected to grow.

Citation: Helmut Haberl, Tim Beringer, Sribas C Bhattacharya, Karl-Heinz Erb and Monique Hoogwijk, 2010, The global technical potential of bio-energy in 2050 considering sustainability constraints, Current Opinion in Environmental Sustainability, doi:10.1016/j.cosust.2010.10.007. [abstract]

Future hot spots of vegetation-climate feedbacks in Europe

Future vegetation-climate feedbacks in Europe were simulated in a new study:

“Simulated variations in leaf area index and in the relative coverage of evergreen forest, deciduous forest, and open land vegetation in response to simulated climate influence atmospheric state via variations in albedo, surface roughness, and the partitioning of the land-atmosphere heat flux into latent and sensible components.”

Three hot spots of vegetation-climate feedbacks were identified:

“In the Scandinavian Mountains, reduced albedo resulting from the snow-masking effect of forest expansion enhanced the winter warming trend. In central Europe, the stimulation of photosynthesis and plant growth by “CO2 fertilization” mitigated warming, through a negative evapotranspiration feedback associated with increased vegetation cover and leaf area index. In southern Europe, increased summer dryness restricted plant growth and survival, causing a positive warming feedback through reduced evapotranspiration.”

Overall conclusion from this is that while Europe as a whole exhibits quite modest vegetation-climate feedbacks, they can be strong regionally.

Citation: Wramneby, A., B. Smith, and P. Samuelsson (2010), Hot spots of vegetation-climate feedbacks under future greenhouse forcing in Europe, J. Geophys. Res., 115, D21119, doi:10.1029/2010JD014307. [abstract]

Methane escape features in ocean floor off New Zealand

A new study has found gas release features from the ocean floor near New Zealand. Features cover a region of at least 20,000 square kilometers and they are thought to be signs of methane hydrate dissociation. Of the features found, 10 were 8-11 km in diameter and about 1000 were 1-5 km in diameter. Also about 10,000 features of about 150 m diameter were observed. The released methane amounts are impressive:

“The amount of methane potentially released from hydrates at each of the largest features is ~7*1012 g. If the methane from a single event at one 8–11 km scale pockmark reached the atmosphere, it would be equivalent to ~3% of the current annual global methane released from natural sources into the atmosphere.”

Citation: Davy, B., I. Pecher, R. Wood, L. Carter, and K. Gohl (2010), Gas escape features off New Zealand: Evidence of massive release of methane from hydrates, Geophys. Res. Lett., 37, L21309, doi:10.1029/2010GL045184. [abstract]

Climate warms, Alaska gets dry -> more wildfires observed

Climate has warmed in Alaska which has resulted in more dry conditions in the summer. 55-year wildfire observation dataset from Alaska has been analysed in a new study. It was found that annual area burned has increased. Furthermore:

“Due to climate change, the last three decades have shown to be warmer than the previous decades. Hence, in the first 28 years of the data, two fires were observed with an area burned greater than 10,000 km2, while there were four in the last 27 years.”

The study also provides a full analysis of the year 2004 which was especially bad wildfire year in Alaska.

Citation: G. Wendler, J. Conner, B. Moore, M. Shulski and M. Stuefer, Climatology of Alaskan wildfires with special emphasis on the extreme year of 2004, Theoretical and Applied Climatology, 2010, DOI: 10.1007/s00704-010-0357-9. [abstract]

Extra water coming to Mediterranean sea from somewhere

Water runoff to Mediterranean sea has been estimated in a new study. The study period was 1980-2000. Their result for long term trends:

“Finally, it was shown through a trend analysis, that the fresh water discharge into the Mediterranean Sea did not exhibit any significant change during the study period in spite of a significant increase in temperature and partial decrease of precipitation. Consequently, awareness should be raised on possible depletion of other water stocks in the Mediterranean river basins, such as mountain glaciers and aquifers.”

Citation: Bouraoui, F., B. Grizzetti, and A. Aloe (2010), Estimation of water fluxes into the Mediterranean Sea, J. Geophys. Res., 115, D21116, doi:10.1029/2009JD013451. [abstract]

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Papers on Arctic Oscillation and global warming

Posted by Ari Jokimäki on November 10, 2010

This is a list of papers on the global warming effects to the Arctic Oscillation – both observed changes and future projections are included. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Arctic Oscillation responses to greenhouse warming and role of synoptic eddy feedback – Choi et al. (2010) “This study investigates possible changes in the leading mode over the Northern Hemisphere, representing the Arctic Oscillation (AO), in response to the projected increases in greenhouse gas concentrations. This is performed by comparing present-day and future patterns simulated by a relatively high-resolution atmospheric general circulation model. It is demonstrated that the dipole pattern associated with the AO distinctively shifts poleward in the future climate. The poleward shift is more pronounced over the Pacific region than over the Atlantic region. This change in the AO pattern is consistent with the change in the synoptic eddy feedback, estimated from the divergence of the eddy-vorticity flux, indicating a close linkage between the AO change and the change in the synoptic eddy feedback. Further analysis of changes in eddy feedback strength suggests a possible hypothesis that the poleward shift of the jet stream and storm tracks can make synoptic eddy feedback more effective over the higher latitudes, which in turn enhances the poleward shift of the AO mode.” Choi, D.-H., J.-S. Kug, W.-T. Kwon, F.-F. Jin, H.-J. Baek, and S.-K. Min (2010), Arctic Oscillation responses to greenhouse warming and role of synoptic eddy feedback, J. Geophys. Res., 115, D17103, doi:10.1029/2010JD014160.

Changes in the Arctic Oscillation under increased atmospheric greenhouse gases – Wu et al. (2007) “The Arctic Oscillation (AO) under increased atmospheric concentration of greenhouse gases (GHG) was studied by comparing an ensemble of simulations from 13 coupled general circulation models with GHG at the pre-industrial level and at the late 20th century level, for November to March. The change in the linear AO pattern as GHG increased reveals positive sea level pressure (SLP) anomalies centered over the Gulf of Alaska, and weaker negative SLP anomalies over eastern Canada and North Atlantic – a pattern resembling the nonlinear AO pattern arising from a quadratic relation to the AO index. This quadratic AO pattern itself has positive SLP anomalies receding from Europe but strengthening over the Gulf of Alaska and surrounding areas as GHG increased. This study points to the importance of the nonlinear structure in determining how the linear oscillatory pattern changes when there is a change in the mean climate.” Wu, A., W. W. Hsieh, G. J. Boer, and F. W. Zwiers (2007), Geophys. Res. Lett., 34, L12701, doi:10.1029/2007GL029344. [Full text]

Influence of Arctic Oscillation towards the Northern Hemisphere Surface Temperature Variability under the Global Warming Scenario – Hori et al. (2007) “Future projection of the Arctic Oscillation (AO) signature and its significance towards the northern hemispheric surface temperature trend have been examined using 20 state-of-the-art Atmosphere-Ocean General Circulation Model (AOGCM) outputs forced under the IPCC SRES-A1B and 20C3M emission scenario. Models are mostly successful in simulating the observed AO structure and the corresponding surface temperature variability. It is found that while AO exhibits a large positive trend, especially during the autumn season with a relatively smaller trend during the winter and spring seasons. In all seasons the interannual variance in AO remains the same for both scenarios. These features in the timeseries leads to two distinct patterns of temperature variability. One is the “polar amplification” pattern due to the long-term anthropogenic forcing, which is much larger in its amplitude. Another is related to the natural variability of the AO, which is confined over the land surface and is marked by a dipole pattern of temperature between the Eurasian continent and Greenland. It is argued that the gradual trend in the AO is not a result of enhanced natural variability of the AO dynamics itself, but rather a result of the large anthropogenic forced linear trend projected onto the mean climatological state of the Arctic region. Distinguishing these two patterns of warming is crucial for detecting the signal of future global warming trend over the Eurasian continent and other regions.” Masatake E. Hori, Daisuke Nohara and Hiroshi L. Tanaka, Journal of the Meteorological Society of Japan, Vol. 85 (2007) , No. 6 pp.847-859. [Full text]

The NAO, the AO, and Global Warming: How Closely Related? – Cohen & Barlow (2005) “The North Atlantic Oscillation (NAO) and the closely related Arctic Oscillation (AO) strongly affect Northern Hemisphere (NH) surface temperatures with patterns reported similar to the global warming trend. The NAO and AO were in a positive trend for much of the 1970s and 1980s with historic highs in the early 1990s, and it has been suggested that they contributed significantly to the global warming signal. The trends in standard indices of the AO, NAO, and NH average surface temperature for December–February, 1950–2004, and the associated patterns in surface temperature anomalies are examined. Also analyzed are factors previously identified as relating to the NAO, AO, and their positive trend: North Atlantic sea surface temperatures (SSTs), Indo–Pacific warm pool SSTs, stratospheric circulation, and Eurasian snow cover. Recently, the NAO and AO indices have been decreasing; when these data are included, the overall trends for the past 30 years are weak to nonexistent and are strongly dependent on the choice of start and end date. In clear distinction, the wintertime hemispheric warming trend has been vigorous and consistent throughout the entire period. When considered for the whole hemisphere, the NAO/AO patterns can also be distinguished from the trend pattern. Thus the December–February warming trend may be distinguished from the AO and NAO in terms of the strength, consistency, and pattern of the trend. These results are insensitive to choice of index or dataset. While the NAO and AO may contribute to hemispheric and regional warming for multiyear periods, these differences suggest that the large-scale features of the global warming trend over the last 30 years are unrelated to the AO and NAO. The related factors may also be clearly distinguished, with warm pool SSTs linked to the warming trend, while the others are linked to the NAO and AO.” Cohen, Judah, Mathew Barlow, 2005, J. Climate, 18, 4498–4513. [Full text]

The Arctic climate paradox: The recent decrease of the Arctic Oscillation – Overland & Wang (2005) “A current paradox is that many physical and biological indicators of Arctic change—summer sea-ice extent, spring surface air temperature and cloud cover, and shifts in vegetation and other ecosystems—show nearly linear trends over the previous two and a half decades, while the Arctic Oscillation, a representative atmospheric circulation index often associated with Arctic change, has had a different, more episodic behavior, with a near-neutral or negative phase for 6 of the last 9 years (1996–2004) following a positive phase (1989–1995). Stratospheric temperature anomalies over the Arctic, which serve as an index of the strength of the polar vortex, also show this episodic character. Model projections of Arctic temperature for 2010–2029 show model-to-model and region-to-region differences suggesting large variability in the future response of atmospheric circulation to external forcing. Thus internal processes in the western Arctic may have a larger role in shaping the present persistence of Arctic change than has been previously recognized.” Overland, J. E., and M. Wang (2005), Geophys. Res. Lett., 32, L06701, doi:10.1029/2004GL021752. [Full text]

Interdecadal Arctic Oscillation in twentieth century climate simulations viewed as internal variability and response to external forcing – Yukimoto & Kodera (2005) “Interdecadal variations similar to the Arctic Oscillation (AO) are investigated for internal variability (INTV) and response to external forcing (REXT) in an ensemble simulation of twentieth century climate. The significant trend in REXT implies that a sizeable part of the observed AO trend in recent decades can also be attributed to anthropogenic forcing. INTV is characterized by a barotropic dipole of zonal wind anomalies and associated wave propagation, suggesting a mechanism similar to the month-to-month AO. Its thermal structure can be attributed to dynamic processes. REXT exhibits a thermal structure that can be explained by responses to the forcing due to increased greenhouse gases. A westerly wind anomaly in the stratosphere as a thermal response corresponds to anomalies in wave propagation and meridional circulation that are similar to INTV, which may induce the AO-like annular pattern.” Yukimoto, S., and K. Kodera (2005), Geophys. Res. Lett., 32, L03707, doi:10.1029/2004GL021870.

The Recent Trend and Variance Increase of the Annular Mode – Feldstein (2002) “This study examines whether both the trend and the increase in variance of the Northern Hemisphere winter annular mode during the past 30 years arise from atmospheric internal variability. To address this question, a synthetic time series is generated that has the same intraseasonal stochastic properties as the annular mode. By generating a distribution of linear trend values for the synthetic time series, and through a chi-square statistical analysis, it is shown that this trend and variance increase are well in excess of the level expected from internal variability of the atmosphere. This implies that both the trend and the variance increase of the annular mode are due either to coupling with the hydrosphere and/or cryosphere or to driving external to the climate system. This behavior contrasts that of the first 60 years of the twentieth century, for which it is shown that all of the interannual variability of the annular mode can be explained by atmospheric internal variability.” Feldstein, Steven B., 2002, J. Climate, 15, 88–94. [Full text]

How linear is the Arctic Oscillation response to greenhouse gases? – Gillett et al. (2002) “We examine the sensitivity of the Arctic Oscillation (AO) index to increases in greenhouse gas concentrations in integrations of five climate models (the Hadley Centre coupled models (HadCM2 and HadCM3), the European Centre/Hamburg models (ECHAM3 and ECHAM4), and the Goddard Institute for Space Studies stratosphere-resolving (GISS-S) model) and in the National Centers for Environmental Prediction reanalysis. With the exception of HadCM2 all the models show a significant positive AO response to greenhouse gas forcing, but in the models lacking a well-resolved stratosphere that response is smaller than observed. In these models the AO index is linearly dependent on the radiative forcing, even up to ~20 times current CO2 levels. By contrast, the GISS-S stratosphere-resolving model shows an AO response comparable to that observed, but the sensitivity of the model to further increases in forcing is reduced when CO2 levels exceed ~1.5 times preindustrial values. It has been suggested that greenhouse gas forcing results in the equatorward deflection of planetary waves, which leads to a cooling and strengthening of the polar vortex and hence an increase in the surface Arctic Oscillation. In the observations the number of sudden warmings has reduced dramatically, consistent with this planetary wave effect, leading to a large mean cooling of the vortex. However, neither the GISS-S nor the HadCM3 models are able to reproduce the observed temperature changes, suggesting that this explanation for the impact of the inclusion of a stratosphere in the model may be incomplete.” Gillett, N. P., M. R. Allen, R. E. McDonald, C. A. Senior, D. T. Shindell, and G. A. Schmidt (2002), J. Geophys. Res., 107(D3), 4022, doi:10.1029/2001JD000589. [Full text]

Annular Modes in the Extratropical Circulation. Part II: Trends – Thompson et al. (2000) “The authors exploit the remarkable similarity between recent climate trends and the structure of the “annular modes” in the month-to-month variability (as described in a companion paper) to partition the trends into components linearly congruent with and linearly independent of the annular modes. The index of the Northern Hemisphere (NH) annular mode, referred to as the Arctic Oscillation (AO), has exhibited a trend toward the high index polarity over the past few decades. The largest and most significant trends are observed during the “active season” for stratospheric planetary wave–mean flow interaction, January–March (JFM), when fluctuations in the AO amplify with height into the lower stratosphere. For the periods of record considered, virtually all of the JFM geopotential height falls over the polar cap region and the strengthening of the subpolar westerlies from the surface to the lower stratosphere, 50% of the JFM warming over the Eurasian continent, 30% of the JFM warming over the NH as a whole, 40% of the JFM stratospheric cooling over the polar cap region, and 40% of the March total column ozone losses poleward of 40°N are linearly congruent with month-to-month variations in the AO index. Summertime sea level pressure falls over the Arctic basin are suggestive of a year-round drift toward the positive polarity of the AO, but the evidence is less conclusive. Owing to the photochemical memory inherent in the ozone distribution, roughly half the ozone depletion during the NH summer months is linearly dependent on AO-related ozone losses incurred during the previous active season.” Thompson, David W. J., John M. Wallace, Gabriele C. Hegerl, 2000, J. Climate, 13, 1018–1036. [Full text, Paper 1 full text]

The Arctic and Antarctic oscillations and their projected changes under global warming – Fyfe et al. (1999) “The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) are the leading modes of high‐latitude variability in each hemisphere as characterized by the first EOF of mean sea‐level pressure. Observations suggest a recent positive trend in the AO and it is speculated that this may be related to global warming. The CCCma coupled general circulation model control simulation exhibits a robust and realistic AO and AAO. Climate change simulations for the period 1900–2100, with forcing due to greenhouse gases and aerosols, exhibit positive trends in both the AO and the AAO. The model simulates essentially unchanged AO/AAO variations superimposed on a forced climate change pattern. The results do not suggest that a simulated trend in the AO/AAO necessarily depends on stratospheric involvement nor that forced climate change will be expressed as a change in the occurence of one phase of the AO/AAO over another. This pattern of climate change projects exclusively on the AAO pattern in the southern hemisphere but not in the northern hemisphere where other EOFs are involved. The extent to which this forced climate change pattern and the unforced modes of variation are determined by the same mechanisms and feedbacks remains an open question.” Fyfe, J. C., G. J. Boer, and G. M. Flato (1999), Geophys. Res. Lett., 26(11), 1601–1604, doi:10.1029/1999GL900317. [Full text]

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New research from last week 44/2010

Posted by Ari Jokimäki on November 8, 2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as I write them. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Man-made increase in GHG’s changes North Atlantic Oscillation (NAO) through stratosphere

Changes have been observed in NAO: NAO action centres have moved eastward, zonal wind anomalies have moved poleward, and NAO climate anomalies have extended “downstream”. A new study has used climate models to investigate these changes and their causes. It is found that the increase in atmospheric carbon dioxide and the increase in sea surface temperature both can cause the observed effects. When SST causes the changes, it is through tropospheric dynamics. However, the increase in carbon dioxide affects in other way – it has to do with changes in stratosphere:

“However, there is a significant response in the stratosphere, characterized by a strengthened climatological polar vortex with strongly enhanced interannual variability. … The similarity of changes in many characteristics of NAO interannual variability between the model response to doubling CO2 and those in observations in the mid-1970s implies that the increase of greenhouse gas concentration in the atmosphere, and the resulting changes in the stratosphere, might have played an important role in the multidecadal change of interannual NAO variability and its associated climate anomalies during the late twentieth century.”

Citation: Buwen Dong, Rowan T. Sutton and Tim Woollings, Changes of interannual NAO variability in response to greenhouse gases forcing, Climate Dynamics, DOI: 10.1007/s00382-010-0936-6. [abstract]

Different snow volume trends in Eurasia and North America

Measurements from satellites were used to evaluate changes in snow volume in northern high latitudes except Greenland in a new study. The study found a differing trends from Eurasia and North America:

“While the snow volume exhibits a statistically significant negative trend (-9.7±3.8 km3.year-1, p-value=0.02) over North America, it presents a positive, but not statistically significant trend (11.3±9.3 km3.year-1, p-value=0.25) over Eurasia.”

The reason for different trends probably is found from differences in regional climates. In Eurasia the snow volume is related to Arctic Oscillation and Atlantic Multidecadal Oscillation (AMO) while in North America it is related to Pacific North American pattern and AMO.

Citation: Sylvain Biancamaria, Anny Cazenave, Nelly M. Mognard, William Llovel and Frédéric Frappart, Satellite-based high latitude snow volume trend, variability and contribution to sea level over 1989/2006, 2010, Global and Planetary Change, doi:10.1016/j.gloplacha.2010.10.011. [abstract]

Fish populations track climate patterns in San Francisco Bay

San Francisco Bay fish and invertebrates have been followed since 1980 which shows that there are large changes in the populations. One particularly dramatic change occurred in 1999 when Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) reversed their signs. The conclusion of the study:

“We infer that synchronous shifts in climate patterns and community variability in San Francisco Bay are related to changes in oceanic wind forcing that modify coastal currents, upwelling intensity, surface temperature, and their influence on recruitment of marine species that utilize estuaries as nursery habitat.”

What I find interesting here is that the species seem to react surprisingly strongly to changes in climate. I would have thought that most of the species are not affected by very brief changes in climate. For example one could imagine that fish communities would be used to oscillations in the ocean currents but here it seems that even short time natural variability causes rather dramatic changes in the populations of species.

Citation: Cloern, J. E., et al. (2010), Biological communities in San Francisco Bay track large-scale climate forcing over the North Pacific, Geophys. Res. Lett., 37, L21602, doi:10.1029/2010GL044774. [abstract]

Global brightening caused by aerosols – not clouds?

A new research article describes studies on the global brightening issue. Abstract is short so it’s quoted here in full:

“Solar radiation at the Earth surface has increased over land and ocean since about 1990 (‘global brightening’). An analysis of various global (ocean only) aerosol and (global) cloud data sets from geostationary and polar orbiting satellites is performed to determine whether changes in these quantities have occurred in accordance with ‘global brightening’, and to analyse the global distribution of these changes. Change-point detection and trend analysis are employed in the analysis. In a period from the mid-1980s to the mid-2000s, aerosol optical depth is found to have started declining in the early 1990s, while cloud data sets do not agree on trends. Ångström exponent data seem to suggest changes in pollution.”

Citation: Cermak, J., M. Wild, R. Knutti, M. I. Mishchenko, and A. K. Heidinger (2010), Consistency of global satellite-derived aerosol and cloud data sets with recent brightening observations, Geophys. Res. Lett., 37, L21704, doi:10.1029/2010GL044632. [abstract]

New review article on climate science and social movement

New review paper traces the history of climate change knowledge and social movement:

“This article reviews relevant studies and theories of social movements with special attention to the role of knowledge-making in social movements, before tracing the relations between social movements and climate change knowledge from the 1970s to the present. Climate change first emerged as an issue of public concern within the context of the environmental movements of the 1970s and 1980s, while skepticism was shaped, in significant ways, by the neo-conservative and neo-nationalist movements that grew to political significance in the 1980s and 1990s.”

Citation: Andrew Jamison, Climate change knowledge and social movement theory, Wiley Interdisciplinary Reviews: Climate Change, Volume 1, Issue 6, pages 811–823, November/December 2010, DOI: 10.1002/wcc.88. [abstract, full text]

Sulfur hexafluoride concentration is increasing

Sulfur hexafluoride is the strongest greenhouse gas with global warming potential of 22,800. It’s current concentration is low so it contributes only 0.1 % of total anthropogenic radiative forcing. Rigby et al. have analysed atmospheric measurements of sulfur hexafluoride and published a record of sulfur hexafluoride concentration between 1973 and 2008. The concentration is on the rise:

“Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was the highest recorded, at 0.29 ± 0.02 pmolmol−1 yr−1.”

They also studied the emissions:

“Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also the highest in the 1973–2008 period, reaching 7.4 ± 0.6 Gg yr−1 (1-σ uncertainties) and surpassing the previous maximum in 1995.”

They note that between 2004 and 2008:

“…we find that it is likely that much of the global emissions rise during this five-year period originated primarily from Asian developing countries that do not report detailed, annual emissions to the United Nations Framework Convention on Climate Change (UNFCCC).”

Citation: Rigby, M., Mühle, J., Miller, B. R., Prinn, R. G., Krummel, P. B., Steele, L. P., Fraser, P. J., Salameh, P. K., Harth, C. M., Weiss, R. F., Greally, B. R., O’Doherty, S., Simmonds, P. G., Vollmer, M. K., Reimann, S., Kim, J., Kim, K.-R., Wang, H. J., Olivier, J. G. J., Dlugokencky, E. J., Dutton, G. S., Hall, B. D., and Elkins, J. W.: History of atmospheric SF6 from 1973 to 2008, Atmos. Chem. Phys., 10, 10305-10320, doi:10.5194/acp-10-10305-2010, 2010. [abstract, full text]

No sign of MWP in East Antarctic coast

Holocene geological records from East Antarctic coast have been reviewed in a new study. Two warm periods are found. The Early Holocene warm period (11.5-9 ka BP) shows in records very clearly and synchronously. Quite well shows also another warm period between 4.7 and 1 ka BP but for this one there’s little more timing differences between the records. On the MWP and LIA:

“There is no evidence along the East Antarctic coastline for an equivalent to the Northern Hemisphere Medieval Warm Period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the Northern Hemisphere’s Little Ice Age.”

Citation: Verleyen, E., et al. (2010), Post-glacial regional climate variability along the East Antarctic coastal margin – evidence from shallow marine and coastal terrestrial records, Earth-Science Reviews, doi:10.1016/j.earscirev.2010.10.006. [abstract]

Tropical ozone doesn’t recover to pre-1980’s values

New study has looked how the ozone situation evolves in the future by using climate model simulations. Result for the tropics is:

“In the tropics, simulated peak ozone amounts occur by about 2050 and thereafter total ozone column declines. Consequently, simulated ozone does not recover to values which existed prior to the early 1980s.”

In the northern and southern hemisphere situation differs from each other:

“The results also show a distinct hemispheric asymmetry, with recovery to 1980 values in the Northern Hemisphere extratropics ahead of the chlorine return by about 20 years. In the Southern Hemisphere midlatitudes, ozone is simulated to return to 1980 levels only 10 years ahead of chlorine. In the Antarctic, annually averaged ozone recovers at about the same rate as chlorine in high latitudes and hence does not return to 1960s values until the last decade of the simulations.”

Citation: Austin, J., et al. (2010), Decline and recovery of total column ozone using a multimodel time series analysis, J. Geophys. Res., 115, D00M10, doi:10.1029/2010JD013857. [abstract]

Cyclones change location with global warming

Li et al. have studied how cyclone frequency evolves in North Pacific while the globe is warming. They used climate models with A1B scenario. They found a change in cyclones:

“A significant shift is found in the location of tropical cyclones from the western to central Pacific. The shift to more tropical cyclones in the central and less in the western Pacific is not attributable to a change in atmospheric static stability, but to a change in the variance of tropical synoptic-scale perturbations associated with a change in the background vertical wind shear and boundary layer divergence.”

Citation: Li, T., M. Kwon, M. Zhao, J.-S. Kug, J.-J. Luo, and W. Yu (2010), Global warming shifts Pacific tropical cyclone location, Geophys. Res. Lett., 37, L21804, doi:10.1029/2010GL045124. [abstract, full text]

Contribution of sea ice loss to Arctic amplification

In a new study the observed sea ice conditions during 2007 were fed to climate models in an effort to gain further information of how sea ice contributes to the Arctic amplification of global warming. It turns out that sea ice loss causes almost all of the amplification. The effect of the sea ice to the amplification only contributes in the high latitudes (north from 60°N) both in surface and in atmosphere. The amplification induced warming occurs vertically within lowest 1000 meters. The temperature response to sea ice loss is strongly seasonal:

“A weak signal of Arctic amplification in surface based warming is found during boreal summer, whereas a dramatically stronger signal is shown to develop during early autumn that persisted through December even as sea ice coverage approached its climatological values in response to the polar night.”

Citation: Kumar, A., J. Perlwitz, J. Eischeid, X. Quan, T. Xu, T. Zhang, M. Hoerling, B. Jha, and W. Wang (2010), Contribution of sea ice loss to Arctic amplification, Geophys. Res. Lett., 37, L21701, doi:10.1029/2010GL045022. [abstract, full text]

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Papers on climate science history

Posted by Ari Jokimäki on November 4, 2010

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

UPDATE (July 12, 2012): Mudge (1997) added. Thanks to Francis Mudge for pointing it out (in another thread).
UPDATE (May 6, 2012): Barry (2012) added.

A brief history of the terms climate and climatology – Barry (2012) “The paper traces the origins of the terms climate and climatology in the English language. The term climate has a 600-year history, but only came into widespread scientific use about 150 years ago. Climatology began to find wide usage in the mid-late 19th century.” Roger G. Barry, International Journal of Climatology, DOI: 10.1002/joc.3504.

Linking energy and climate (before 1974) – Shulman (2010) “Establishing a link between the consumption of fossil fuels and global climate change has depended both on scientific research as well as assumptions about the pace of social change, technological innovation, and economic growth. Late 19th century research into the role of carbon dioxide and climate focused on explaining the historical cooling of the ice ages; consideration of future warming as a result of energy use remained theoretical and focused on benefits centuries away. After declining scientific interest in the carbon dioxide theory in the early 20th century, it was revived again in the late 1930s, gradually stimulating further research that led to a more sophisticated understanding of the global carbon cycle and prospects for future warming. This research began incorporating more realistic expectations of future energy growth. In the early 1970s, scientists, politicians, and the general public began paying more attention to research into anthropogenic climate change, in part due to a renewed attention to the social costs of energy systems alongside a growing focus on global environmental issues. Future historical research into energy and climate change should examine the role of predictions and expectations of social change in shaping the agenda of scientific research.” Peter A. Shulman, Wiley Interdisciplinary Reviews: Climate Change, 2010, DOI: 10.1002/wcc.78. [Full text]

History of climate engineering – Bonnheim (2010) “The modern concept of geoengineering as a response to anthropogenic climate change evolved from much earlier proposals to modify the climate. The well-documented history of weather modification provides a much-needed historical perspective on geoengineering in the face of current climate anxiety and the need for responsive action. Drawing on material from the mid-20th century until today, this paper asserts the importance of looking at geoengineering holistically—of integrating social considerations with technical promise, and scientific study with human and moral dimensions. While the debate is often couched in scientific terms, the consequences of geoengineering the climate stretch far beyond the world of science into the realms of ethics, legality, and society. Studying the history of geoengineering can help produce fresh insights about what has happened and about what may happen, and can help frame important decisions that will soon be made as to whether geoengineering is a feasible alternative to mitigation, a possible partner, or a dangerous experiment with our fragile planet.” Noah Byron Bonnheim, Wiley Interdisciplinary Reviews: Climate Change, 2010, DOI: 10.1002/wcc.82. [Full text]

The evolution of climate ideas and knowledge – Heymann (2010) “Ideas and knowledge about climate have changed considerably in history. Ancient philosophers like Hippocrates and Aristotle shaped the understandings of climate, which remained very influential until well into the eighteenth century. The Scientific Revolution of the seventeenth century gave rise to new ways of systematic instrument-based observation of and increased public interest in weather and climate. These developments led to a mechanistic understanding and a reductionist physical description of climate in the twentieth century, eventually in the form of a complex earth system. Furthermore, different understandings of climate co-existed in many periods of time. Only in the nineteenth and twentieth centuries specific scientific concepts of climate (a geographical understanding of climate in climatology until about the mid-twentieth century and a physical understanding of climate in climate science in the second half of the twentieth century) gained superior social credibility and cultural dominance. The understanding of climate involved more than the accumulation of scientific knowledge. It was rooted in social processes and cultural interests, which shaped different ideas of climate in different communities of actors and different historical times.” [Full text]

Suomi: Pragmatic Visionary – Lewis et al. (2010) “The steps on Verner Suomi’s path to becoming a research scientist are examined. We argue that his research style—his natural interests in science and engineering, and his methodology in pursuing answers to scientific questions—was developed in his youth on the Iron Range of northeastern Minnesota, as an instructor in the cadet program at the University of Chicago (U of C) during World War II and as a fledgling academician at University of Wisconsin—Madison. We examine several of his early experiments that serve to identify his style. The principal results of this study are 1) despite austere living conditions on the Iron Range during the Great Depression, Suomi benefited from excellent industrial arts courses at Eveleth High School; 2) with his gift for designing instruments, his more practical approach to scientific investigation flourished in the company of world-class scientific thinkers at U of C; 3) his dissertation on the heat budget over a cornfield in the mid-1950s served as a springboard for studying the Earth–atmosphere energy balances in the space-age environment of the late 1950s; and 4) his design of radiometers—the so-called ping-pong radiometer and its sequel, the hemispheric bolometer—flew aboard Explorer VI and Explorer VII in the late 1950s, and analysis of the radiances from these instruments led to the first accurate estimate of the Earth’s mean albedo.” Lewis, John M., David W. Martin, Robert M. Rabin, Hans Moosmüller, 2010: Suomi: Pragmatic Visionary. Bull. Amer. Meteor. Soc., 91, 559-577, doi: 10.1175/2009BAMS2897.1. [Full text]

The idea of anthropogenic global climate change in the 20th century – Weart (2010) “People had long speculated that human activities might affect a region’s climate. But a developed conjecture that humanity might change the climate of the entire planet first appeared in 1896: a calculation that carbon dioxide from fossil fuel combustion could gradually warm the globe. Scientists soon rejected the idea. Most people thought it incredible that climate could change globally except on a geological timescale, pushed by forces far stronger than human activity. In midcentury, a few scientists revived the hypothesis of global warming. Meanwhile, the exponential growth of human activity, especially chemical pollution and nuclear armaments, was showing that humanity really could affect the entire atmosphere. Moreover, during the 1960s research suggested that small perturbations might lead to an abrupt change in the climate system. Although nobody expected serious impacts until the distant 21st century, some began to frame global warming not just as a scientific puzzle but as an environmental risk, a security risk, a practical policy question, an international relations issue, and even a moral problem. In the late 1970s a scientific consensus began to take shape, culminating around the end of the century in unanimous agreement among government representatives on essential points, although many uncertainties remained. Meanwhile, increasing media warnings of peril made most of the literate world public aware of the issue, which had deep implications for the human relationship with nature. Skepticism persisted, correlated with aversion to regulation. The majority of the world public were now concerned, but disinclined to take action.” [Full text]

Money for Keeling: Monitoring CO2 levels – Weart (2007) “C.D. Keeling’s measurements of the level of carbon dioxide (CO2) in the atmosphere since 1957, tracking a rise that threatens global warming, form one of the most important scienti.c data sets ever created. Yet the relatively small funding Keeling required was rarely secure. He could begin his measurements only because of a one-time injection of funds into geophysics during the International Geophysical Year. The original aim was to take a “snapshot” which could be repeated a few decades later to .nd whether the level of the gas had risen as predicted. Keeling and his sponsors made personal appeals to divert additional funds so he could re.ne and extend his measurements; in consequence, with just two years of data he showed that the level was rising. In the following decades, maintaining fund-ing was problematic. Agencies saw the work as “routine monitoring” rather than cutting-edge research. In the 1970s, the rise of an environmental movement helped reframe climate change and CO2 emissions as a threat. Funding expanded within a context of monitoring atmospheric pollution and government agency empire building. But in the early 1980s, political reaction against environmentalism again threatened Keeling’s program. The story re.ects larger trends over the past half-century towards the bureaucratization and politicization of science funding.” Spencer R. Weart, Historical Studies in the Physical and Biological Sciences, March 2007, Vol. 37, No. 2, Pages 435–452, DOI 10.1525/hsps.2007.37.2.435. [Full text]

Guy Stewart Callendar: A Pioneer of Anthropogenic Climate Change Theory – Graßl (2007) “Already in 1938, Guy Stewart Callendar had established the carbon dioxide theory of anthropogenic climate change. In The Callendar effect, James R. Fleming tells his story. But why did it take decades until the rest of the scientific community and the public were convinced of his findings?” [Full text]

The pathological history of weather and climate modification: Three cycles of promise and hype – Fleming (2006) “The checkered history of weather and climate modification exhibits a modicum of promise and an excess of hype. This paper examines two completed historical cycles: the first, dating from 1839, involved western proprietary rainmaking or “pluviculture;” the second, from 1946 to 1978 involved “cloud seeding,” commercial rainmaking, and the attempted weaponization of the clouds. Recently, discussion of weather and climate modification has returned to the science-policy agenda, framed as seemingly inevitable responses to killer storms and global warming. The long history of deceptive and delusional attempts to “control” nature, however, raised serious questions about the rationality of these options.” James Rodger Fleming, The pathological history of weather and climate modification: Three cycles of promise and hype, Historical Studies in the Physical and Biological Sciences, September 2006, Vol. 37, No. 1, Pages 3–25 , DOI 10.1525/hsps.2006.37.1.3. [Full text]

The Discovery of Rapid Climate Change – Weart (2003) “How fast can our planet’s climate change? Too slowly for humans to notice, according to the firm belief of most scientists through much of the 20th century. Any shift of weather patterns, even the Dust Bowl droughts that devastated the Great Plains in the 1930s, was seen as a temporary local excursion. To be sure, the entire world climate could change radically: The ice ages proved that. But common sense held that such transformations could only creep in over tens of thousands of years.” Spencer Weart, Physics Today, Volume 56, Issue 8, August 2003. [Full text]

The carbon dioxide theory of climate change: emergence, eclipse, and reemergence, ca. 1850–1950 – Fleming (2002) “This paper examines the discovery of the carbon dioxide theory of climate change, its eclipse during the first five decades of the twentieth century, and its reemergence in the work of G.S. Callendar. It provides historical perspectives on the study of climate dynamics (C/t) from the perspective of science dynamics (S/t). In the nineteenth century, the work of John Tyndall, Svante Arrhenius, T.C. Chamberlin and others drew scientific attention to the role of carbon dioxide as a possible mechanism of climate change. Throughout the first half of the twentieth century, however, most scientists did not think that increased carbon dioxide levels would result in climate warming. Spectroscopic work by Knut Ångström, Clemens Schaefer, and others led meteorologists to believe that water vapor was controlling the infra-red heat budget and that doubling or halving the amount of CO2 in the atmosphere would not appreciably affect the amount of radiation actually absorbed by it. Most meteorologists gave other mechanisms of climatic change more credence. Beginning in 1938 Guy Steward Callendar began a revival of the carbon dioxide theory of climate change and placed it on a more solid scientific basis. Callendar based his theory on new detailed measurements of the infrared spectrum, rising fossil fuel emissions, and the warming trend recorded in the Northern Hemisphere from about 1900 to 1950. Hans Seuss and Roger Revelle later named the rising levels of atmospheric carbon dioxide caused by industrial fuel combustion the “Callendar effect.” The CO2 theory of climate change has changed dramatically on timescales of decades to centuries (eg. 1850 to 2000). Since climate ideas (in relation to changes in technology, and social organization of science) can change faster than the climate itself, they are worthy of serious historical study. Clearly, a student of climate dynamics must also be a student of science dynamics.” Fleming, James R., 2002, “The carbon dioxide theory of climate change: emergence, eclipse, and reemergence, ca. 1850–1950″, 13th Symposium on Global Change and Climate Variations, AMS. [Full text]

T. C. Chamberlin, Climate Change, and Cosmogony – Fleming (2000) “This paper examines the life and work of T. C. Chamberlin, a prominent glacial geologist who developed an interest in interdisciplinary earth science. His work on the geological agency of the atmosphere informed his understanding of climate change and other terrestrial phenomena and led him to propose a new theory of the formation of the Earth and the solar system. Chamberlin’s graduate seminar at the University of Chicago in 1896 contained all the themes that informed his research programme over the next three decades. These included the carbon dioxide theory of climate change in its relationship to diastrophism and oceanic circulation, the role of water vapour feedbacks in the climate system, and the relationship between multiple glaciations, the climate system, and the formation of the planet.” James R. Fleming, Studies In History and Philosophy of Science Part B: Studies In History and Philosophy of Modern Physics, Volume 31, Issue 3, September 2000, Pages 293-308, doi:10.1016/S1355-2198(00)00015-0.

Joseph Fourier, the ‘greenhouse effect’, and the quest for a universal theory of terrestrial temperatures – Fleming (1999) “The central role that the theory of terrestrial temperatures played in Fourier’s mathematical physics has not received the attention it deserves from historians, although his cryptic allusions to the heating of a greenhouse, taken out of context, have been widely cited by subsequent authors.” James R. Fleming, Endeavour, Volume 23, Issue 2, 1999, Pages 72-75, doi:10.1016/S0160-9327(99)01210-7.

Arrhenius and current climate concerns: continuity or a 100-year gap? – Fleming (1998) Fleming, J. R. (1998), Arrhenius and current climate concerns: continuity or a 100-year gap?, Eos Trans. AGU, 79(34), 405.

Charles Lyell and climatic change: speculation and certainty – Fleming (1998) “In the first edition of the Principles of Geology, Charles Lyell announced his theory of the geographical determination of climate and speculated on possible climatic changes during the geological and historical past. In light of the subsequent discovery of ice ages, the proliferation of theories of climatic change, and the great climate debates of his time. Lyell’s theory remained remarkably stable. This paper examines Lyell’s appropriation, modification and rejection of the views of his contemporaries. It provides perspectives on elite and popular ideas of climate and climatic change from the late eighteenth century to 1875, examines Lyell’s position on climatic change in geological and historical times, and explores in some detail the mutual influences of Lyell and James Croll, the proponent of an astronomical theory of ice ages.” James Rodger Fleming, Geological Society, London, Special Publications; 1998; v. 143; p. 161-169, DOI: 10.1144/GSL.SP.1998.143.01.14. [Full text]

The development of the ‘greenhouse’ theory of global climate change from Victorian times – Mudge (1997) No abstract. Quote from the beginning of the article: “The greenhouse effect, perhaps the most popular current vehicle of ‘environmentalism’, was at the centre of active scientific debate in late Victorian times. This article examines the development of the Victorian notion of the greenhouse effect, and why it fell out of favour until just before the Second World War.” F. B. Mudge, Weather, Volume 52, Issue 1, pages 13–17, January 1997, DOI: 10.1002/j.1477-8696.1997.tb06243.x. [Full text]

Early Development in the Study of Greenhouse Warming: The Emergence of Climate Models – Manabe (1997) “Following the pioneering contributions of Arrhenius, Callendar and others, climate models emerged as a very promising tool for the study of greenhouse warming. In the early 1960s, a one-dimensional, radiative-convective equilibrium model was developed as the first step towards the development of a three-dimensional model of climate. Incorporating not only the radiative but also the convective heat exchange between the earth’s surface and the atmosphere, the model overcame the difficulty encountered by the earlier approach of surface radiative heat balance in estimating the magnitude of greenhouse warming. By the 1970s, a three-dimensional, general circulation model (GCM) of the atmosphere, coupled to a very idealized ocean of swamp-like wet surface, had been used for studies of greenhouse warming. Despite many drastic simplifications, the GCM was very effective for elucidating the physical mechanisms that control global warming and served as a stepping stone towards the use of more comprehensive, coupled ocean-atmosphere GCMs for the study of this problem.” Syukuro Manabe, Ambio, Vol. 26, No. 1, Arrhenius and the Greenhouse Gases (Feb., 1997), pp. 47-51. [Full text]

The Discovery of the Risk of Global Warming – Weart (1997) “It is now a century since Syante Arrhenius published the idea: As human activity puts ever more carbon dioxide into the atmosphere, global warming becomes ever more likely. (See figure 1 and the box on page 36.) His paper attracted notice, and one might suppose that knowledge of the so-called “greenhouse effect” has grown steadily ever since. But that is not in fact how the science proceeded. During more than half a century after 1896 almost nothing of value was learned about global warming. Only in the late 1950s did scientists at last begin to regard it as a serious possibility, indeed a potential danger.” Spencer R. Weart, Physics Today, Volume 50, Issue 1, January 1997.

Climate and history in the late 18th and early 19th centuries – Feldman (1992) Feldman, T. S. (1992), Climate and history in the late 18th and early 19th centuries, Eos Trans. AGU, 73(1), 1.

T. C. Chamberlain and H2O climate feedbacks: A voice from the past – Fleming (1992) Fleming, J. R. (1992), T. C. Chamberlain and H2O climate feedbacks: A voice from the past, Eos Trans. AGU, 73(47), 505.

History of the greenhouse effect – Jones (1990) “The greenhouse effect is now commonly accepted by the scientific community, politicians and the general public. However, the misnomer ‘greenhouse effect’ has perpetuated, and there are a number of aspects of the effect which are poorly understood outside the atmospheric sciences. On such misconception is that greenhouse research is a recent phenomenon; another is that glasshouses are warmed by the same mechanism as lies at the heart of the greenhouse effect. This review traces the theory as far back as 1827, highlighting new directions and significant advances over that time. Four main themes can be discerned: 1) certain radiatively active gases are responsible for warming the planet ; 2) that humans can inadvertently influence this warming; 3) climate models are designed to permit prediction of the climatic changes in the atmospheric loadings of these gases but that they have not yet achieved this goal of prediction; and 4) many scenarios of changes, and especially of impact, are premised on relatively weak analysis. This latter point is illustrated by an examination of the relationship between increasing temperature and sea level change (the oceanic response to atmospheric warming). Current research suggests that sea-level rise is not likely to be as high as had previously been anticipated.” M.D.H. Jones, Progress in Physical Geography March 1990 vol. 14 no. 1 1-18, doi: 10.1177/030913339001400101.

Closely related

Challenging Knowledge: How Climate Science Became a Victim of the Cold War – Oreskes & Conway (2010) [Full text]

The Discovery of Global Warming – Weart (2009) [Full text]

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New research from last week 43/2010

Posted by Ari Jokimäki on November 1, 2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as I write them. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Massive methane release from seafloor recently near Japan

Bangs et al. found a V-shaped recently eroded depression from seafloor offshore southwestern Japan. UPDATE (November 1, 2010): Kees van der Leun just informed me (thanks! :) ) – after asking Nathan Banks about this – that “recently” here means about 40,000 to 50,000 years ago.

“The shape of the relic BSR indicates that the seafloor depression was once a large anticline that has recently been eroded and released an estimated 1.51 × 1011 m3 of methane.”

One possible explanation for the release is that bottom-water currents might have caused erosion and eventually revealed methane hydrates.

“Once triggered, gas-driven erosion created a positive feedback mechanism, releasing gas and eroding hydrate-bearing sediment. We suggest that erosive currents in deep-water methane hydrate provinces act as hair triggers, destabilizing kilometer-scale swaths of the seafloor where large concentrations of underlying overpressured methane exist.”

Citation: N.L. Bangs, M.J. Hornbach, G.F. Moore, and J.-O. Park, Massive methane release triggered by seafloor erosion offshore southwestern Japan, Geology, 2010, v. 38 no. 11 p. 1019-1022, doi: 10.1130/G31491.1. [abstract]

New review article on sun’s effect to climate

New review article looks at the current state of research on sun’s effect to climate. General conclusion on the recent climate change is that while sun obviously affects Earth’s climate in many ways, anthropogenic forcing is required to explain the warming in last few decades. On cosmic rays:

“We therefore conclude that the currently available data do not provide substantial support for the hypothesized global cloud cover linkage to cosmic rays.”

Citation: Gray, L. J., et al. (2010), SOLAR INFLUENCES ON CLIMATE, Rev. Geophys., 48, RG4001, doi:10.1029/2009RG000282. [abstract, full text]

Thousand-year drough reconstruction from Unites States

New research article describes a 1000-year drought reconstruction using subfossil oak tree-rings from central United States. Driest year during the instrumental record (after 1895) was 1934 but before instrumental record there were three years that were even drier.

“Thirteen decadal to multidecadal droughts (i.e., ≥10 years) occurred during the last millennium – the longest lasting sixty-one years and centered on the late twelfth century.”

There were also some signs of periodicity:

“Reconstructions exhibited quasi-periodicity at bidecadal and century-scale periods. Significant rhythms in drought were identified near 20-yr and 128-yr periods.”

Citation: Michael C. Stambaugh, Richard P. Guyette, Erin R. McMurry, Edward R. Cook, David M. Meko, and Anthony R. Lupo, Drought duration and frequency in the U.S. Corn Belt during the last millennium (AD 992–2004), Agricultural and Forest Meteorology, doi:10.1016/j.agrformet.2010.09.010. [abstract]

How much should the public know about climate science?

Just published editorial comment in Climatic Change discusses “How much should the public know about climate science?” But discusses at the same time also some basics of climate science.

“The greenhouse effect is well understood. It is as real as gravity. The foundations of the science are more than 150 years old. Carbon dioxide in the atmosphere traps heat. We know carbon dioxide is increasing because we measure it. We know the increase is due to human activities like burning fossil fuels because we can analyze the chemical evidence for that.”

Citation: Richard C. J. Somerville, How much should the public know about climate science?, 2010, Climatic Change, DOI: 10.1007/s10584-010-9938-y. [abstract, full text]

When will the Arctic be free of sea-ice?

Numerical experiments are used in a new study to estimate the timing of ice-free Arctic with different amounts of anthropogenic warming and climate variability. If surface temperature increase is 4°C and climate variability is similar to past two decades, the ice-free state is likely reached by mid-2040’s. If surface temperature increase is 2°C with same variability, the ice-free state is unlikely before 2050. If surface temperature is 4°C and climate variability is similar to past five decades, the ice-free state also is unlikely before 2050. They mention an interesting negative feedback for volume loss:

“The rate of annual mean ice volume decrease relaxes approaching 2050. This is because, while increasing SAT increases summer ice melt, a thinner ice cover increases winter ice growth. A thinner ice cover also results in a reduced ice export, which helps to further slow ice volume loss.”

Citation: Zhang, J., M. Steele, and A. Schweiger (2010), Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability, Geophys. Res. Lett., 37, L20505, doi:10.1029/2010GL044988. [abstract]

In Hong Kong modern times are hotter and wetter

Extreme temperatures and rainfall from 1885 to 2008 in Hong Kong were analysed in a new study.

“Results showed that the extreme daily maximum and minimum temperatures, annual numbers of very hot days (daily maximum temperature ≥ 33.0 °C) and hot nights (daily minimum temperature ≥ 28.0 °C) as well as the warm spell duration index (WSDI) in Hong Kong exhibited statistically significant long-term rising trends, whereas the annual number of cold days (daily minimum temperatures ≤ 12.0 °C) and cold spell duration (CSDI) index had a statistically significant decreasing trend.”

Both extreme rain and annual precipitation also increased significantly. However, the dry spell in summer months also got little longer.

Citation: M. C. Wong, H. Y. Mok, T. C. Lee, Observed changes in extreme weather indices in Hong Kong, International Journal of Climatology, 2010, DOI: 10.1002/joc.2238. [abstract]

Cereal production in Russia might not benefit from climate change after all

Climate change is generally thought to improve the agriculture in North. A new study has found out that this might not be so:

“We analyzed the impact of climate change on production of cereals in Russia and found that this general perception of beneficiary effect of a warmer climate is unlikely to hold, primarily due to increasing risk of droughts in the most important agricultural areas of the country.”

Citation: Nikolai Dronin and Andrei Kirilenko, Climate change, food stress, and security in Russia, Regional Environmental Change, DOI: 10.1007/s10113-010-0165-x. [abstract]

New paper claims there’s not much empirical evidence for AGW

A new study claims:

“At best, the empirical evidence for human impact on climate change, more specifically, the anthropogenic global warming (AGW), is based on correlational research”

Study concentrates on the details of correlational research. There’s some very questionable remarks in the paper, for example this one:

“Unfortunately, when a theoretical phenomenon such as AGW becomes a global political program, it soon becomes vulnerable to methodological fallacies in the realm of social and political science.”

However, above claims are largely left unproven (there’s no empirical evidence review at all in the paper), but it is mentioned that:

“However, since the author of this article is no expert on climate science, the issue of whether or not data used in climate science are of enough quality will be left for others to decide.”

The references in the paper relating to climate science are mostly known denier papers.

Citation: Jarl K. Kampen, A methodological note on the making of causal statements in the debate on anthropogenic global warming, Theoretical and Applied Climatology, DOI: 10.1007/s00704-010-0355-y. [abstract, full text]

Groundwater is diminishing globally and causing sea-level rise

A new study gives an overview of groundwater depletion. Groundwater recharge was estimated with a hydrological model and groundwater abstraction estimates were subtracted from recharge estimates. Mankind uses groundwater especially in places where other water sources are not present. The results:

“Restricting our analysis to sub-humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (±32) km3 a-1 in 1960 to 283 (±40) km3 a-1 in 2000. The latter equals 39 (±10)% of the global yearly groundwater abstraction, 2 (±0.6)% of the global yearly groundwater recharge, 0.8 (±0.1)% of the global yearly continental runoff and 0.4 (±0.06)% of the global yearly evaporation, contributing a considerable amount of 0.8 (±0.1) mm a-1 to current sea-level rise.”

Citation: Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman, S. Vasak, and M. F. P. Bierkens (2010), Global depletion of groundwater resources, Geophys. Res. Lett., 37, L20402, doi:10.1029/2010GL044571. [abstract]

Tropospheric humidity drop reveals surface warming

Radiosonde humidity resords have been analysed in a new study. It is a general expectation that tropospheric humidity increases with surface warming. According to observations, tropopause is going higher. These both are shown also in this new study. However, there was a surprise:

“The most remarkable finding of this trend analysis is a significant drop in upper tropospheric humidity (UTH) around autumn 2001, which marks an end to the upper tropospheric moistening of the precedent decade. This UTH drop in autumn 2001 coexists with a sudden lifting and cooling of the tropopause and with a significant stretch-out of the free troposphere. Therefore, we conclude that these autumn 2001 trends are certainly associated with the dynamical behavior of the troposphere, triggered by the surface warming.”

Citation: Van Malderen, R., and H. De Backer (2010), A drop in upper tropospheric humidity in autumn 2001, as derived from radiosonde measurements at Uccle, Belgium, J. Geophys. Res., 115, D20114, doi:10.1029/2009JD013587. [abstract]

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