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Archive for June, 2012

New research from last week 25/2012

Posted by Ari Jokimäki on June 25, 2012

Oh, those poor women living in semi-arid regions of Alps in Austria. Tree rings, peatland mosses, sunshine in Iran. Tornadoes, glaciers, boreholes, acidified oceans. New. Research. On. Climate.

Tornadoes in Czech Lands

The tornado history of the Czech Lands, AD 1119–2010 – Brázdil et al. (2012)

Abstract: “Documentary evidence is employed to present the history of tornadoes in the Czech Lands (recently Czech Republic) in AD 1119–2010. Based on contemporaneous descriptions of events, tornadoes are categorised as proven or probable. They are analysed collectively in terms of their spatio-temporal changes, annual variation, specific features, and impacts according to the Enhanced Fujita (EF) scale. The first documented tornado, on 30 July 1119, did great damage to Vyšehrad Castle in Prague (EF3). Only three other tornadoes were recorded before AD 1500. In the following three centuries, the number fluctuated between 11 and 16 events per century. Documented tornado frequency increased significantly from the 19th century onwards, reaching peaks in 1931–1940 (44 tornadoes) and particularly in 2001–2010 (56 tornadoes); this rise, however, reflects the availability of relevant sources as well as increased social awareness and advances in communication technology. A total of 264 tornado days and 307 tornadoes were documented for the Czech Lands in 1119–2010. Although they are relatively homogeneously extended over the territory of the Czech Republic, tornadoes tend to occur more frequently at lower and medium altitudes. The highest frequency of tornadoes is recorded for the summer half-year (mainly from June to August), although they may develop between March and October. Probable tornadoes have also been recorded in the winter months. The strongest tornadoes in the Czech Lands may be classified as EF3, largely with significant damage to buildings and trees, but 13 related deaths have also been recorded. The paper presents not only a new chronology and climatology for Czech tornadoes but is also an important contribution to the study of tornadoes in Europe.”

Citation: Rudolf Brázdil, Kateřina Chromá, Petr Dobrovolný, Zbyněk Černoch, Atmospheric Research,

Global warming trend has been particularly enhanced in semi-arid regions during cold season

Enhanced cold-season warming in semi-arid regions – Huang et al. (2012) [FULL TEXT]

Abstract: “This study examined surface air temperature trends over global land from 1901–2009. It is found that the warming trend was particularly enhanced, in the boreal cold season (November to March) over semi-arid regions (with precipitation of 200–600 mm yr−1) showing a temperature increase of 1.53 °C as compared to the global annual mean temperature increase of 1.13 °C over land. In mid-latitude semi-arid areas of Europe, Asia, and North America, temperatures in the cold season increased by 1.41, 2.42, and 1.5 °C, respectively. The semi-arid regions contribute 44.46% to global annual-mean land-surface temperature trend. The mid-latitude semi-arid regions in the Northern Hemisphere contribute by 27.0% of the total, with the mid-latitude semi-arid areas in Europe, Asia, and North America accounting for 6.29%, 13.81%, and 6.85%, respectively. Such enhanced semi-arid warming (ESAW) imply drier and warmer trend of these regions.”

Citation: Huang, J., Guan, X., and Ji, F.: Enhanced cold-season warming in semi-arid regions, Atmos. Chem. Phys., 12, 5391-5398, doi:10.5194/acp-12-5391-2012, 2012.

Climate change affects women worse than men

Gender and climate change-induced migration: proposing a framework for analysis – Chindarkar (2012) [FULL TEXT]

Abstract: “This paper proposes frameworks to analyze the gender dimensions of climate change-induced migration. The experiences, needs and priorities of climate migrants will vary by gender and these differences need to be accounted for if policies are to be inclusive. Among the vulnerable groups, women are likely to be disproportionately affected due to climate change because on average women tend to be poorer, less educated, have a lower health status and have limited direct access to or ownership of natural resources. Both the process (actual movement) and the outcomes (rural–rural or rural–urban migration, out-migration mainly of men) of climate change-induced migration are also likely to be highly gendered.”

Citation: Namrata Chindarkar, 2012 Environ. Res. Lett. 7 025601 doi:10.1088/1748-9326/7/2/025601.

In European Alps there won’t be much snow at low and medium elevations by 2100

Is snow in the Alps receding or disappearing? – Beniston (2012)

Abstract: “Snow in a populated and economically diverse region such as the Alps plays an important role in both natural environmental systems, (e.g., hydrology and vegetation), and a range of socio-economic sectors (e.g., tourism or hydropower). Changes in snow amount and duration may impact upon these systems in various ways. The objective of this text is to assess whether the public perception that snow has been receding in recent decades in the European Alps is indeed upheld by observations of the behavior of the mountain snow-pack in the last few decades. This article will show that, depending on location—and in particular according to altitude—the quantity of snow and the length of the snow season have indeed changed over the past century. While a major driving factor for this is clearly to be found in recent warming trends, other processes also contribute to the reduction in snow, such as the influence of the North Atlantic Oscillation on the variability of the mountain snow-pack. This article ends with a short glimpse to the future, based on recent model studies that suggest that snow at low to medium elevations will indeed have all but disappeared by 2100.”

Citation: Martin Beniston, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.179.

High frequency climate signals from tree rings and low frequency climate signals from peatland mosses

Comparison of stable carbon and oxygen isotopes in Picea glauca tree rings and Sphagnum fuscum moss remains from subarctic Canada – Holzkämper et al. (2012)

Abstract: “Stable isotope ratios from tree rings and peatland mosses have become important proxies of past climate variations. We here compare recent stable carbon and oxygen isotope ratios in cellulose of tree rings from white spruce (Picea glauca), growing near the arctic tree line; and cellulose of Sphagnum fuscum stems, growing in a hummock of a subarctic peatland, in west-central Canada. Results show that carbon isotopes in S. fuscum correlate significantly with July temperatures over the past ~20 yr. The oxygen isotopes correlate with both summer temperature and precipitation. Analyses of the tree-ring isotopes revealed summer temperatures to be the main controlling factor for carbon isotope variations, whereas tree-ring oxygen isotope ratios are controlled by a combination of spring temperatures and precipitation totals. We also explore the potential of combining high-frequency (annual) climate signals derived from long tree-ring series with low-frequency (decadal to centennial) climate signals derived from the moss remains in peat deposits. This cross-archive comparison revealed no association between the oxygen isotopes, which likely results from the varying sensitivity of the archives to different seasons. For the carbon isotopes, common variance could be achieved through adjustments of the Sphagnum age model within dating error.”

Citation: Steffen Holzkämper, Päivi Kaislahti Tillman, Peter Kuhry, Jan Esper, Quaternary Research,

Sunshine hours have increased over Iran

An examination of the trends in sunshine hours over Iran – Rahimzadeh et al. (2012)

Abstract: “For the purpose of assessing solar energy resources in different parts of Iran, this article provides a synopsis of the spatial and temporal variability of sunshine hours at 37 first-order synoptic stations during the period 1981–2007. Annual and seasonal variations of sunshine duration were determined for four distinct regions within the country. By averaging the time series of sunshine hours in each subregion and standardizing them, four regional representative time series were developed. The results indicate, over all regions, the annual pattern of sunshine duration exhibited large sinusoidal increases and decreases, with minima occurring in 1990 and 2003. The trends of sunshine duration indicated that the sign of the seasonal and annual trends for the vast majority stations has been positive. The maximum positive trend was found across the western parts of the country for all seasons. The spring was found to have a negative trend in sunshine hours at only 2 of the 37 stations. On the annual scale, the change rates in sunshine hours from western to eastern part of Iran have gradually declined over time. The highest positive annual trend was found at Sanandaj station on the west side of Zagross Mountain, with of rate 253 h per decade. Given the increasing trends observed at many stations in Iran over the last 25 years, and recognizing the natural high sunshine duration experienced across the region, a strong case can be made for the introduction of solar energy across the country.”

Citation: Fatemeh Rahimzadeh, Mojdeh Pedram, Michael C. Kruk, Meteorological Applications, DOI: 10.1002/met.1334.

Measuring fossil fuel emissions from tree rings in Los Angeles

The radiocarbon composition of tree rings as a tracer of local fossil fuel emissions in the Los Angeles basin: 1980–2008 – Djuricin et al. (2012)

Abstract: “Quantifying local fossil fuel CO2 emissions in urban areas is challenging due to the heterogeneity in emissions and in atmospheric mixing ratios of CO2. Measurements of the radiocarbon content of urban tree rings are an alternative to large networks of CO2 monitoring stations. In this study, we calculated 3-year averages of CO2 mixing ratios from fossil fuel combustion from 1980 to 2008 using tree rings sampled at six sites within the Los Angeles basin and adjacent mountains. We observed CO2 mixing ratios from fossil fuel combustion of up to 23 μmol·mol−1 in the inland basin and ∼5–10 μmol·mol−1 at coastal sites. Although we expected to see increasing trends of fossil fuel-derived CO2 over time, not all sites showed a significant increase. Analysis of correlations between fossil fuel-derived CO2 and socioeconomic variables revealed that fossil fuel-derived CO2 followed trends in census tract and/or city population or in vehicle statistics at most sites. We also calculated CO/CO2 combustion ratios from tree ring radiocarbon and nearby measurements of atmospheric CO mixing ratios. We observed widespread declines in the combustion ratio that support increases in the efficiency of the automobile fleet over the past few decades. This study demonstrates the utility of tree ring radiocarbon measurements for quantifying temporal and spatial patterns in fossil fuel-derived CO2 emissions in urban areas.”

Citation: Djuricin, S., X. Xu, and D. E. Pataki (2012), The radiocarbon composition of tree rings as a tracer of local fossil fuel emissions in the Los Angeles basin: 1980–2008, J. Geophys. Res., 117, D12302, doi:10.1029/2011JD017284.

Postglacial warming causes errors to borehole reconstructions of last millennium temperatures

Impact of postglacial warming on borehole reconstructions of last millennium temperatures – Rath et al. (2012) [FULL TEXT]

Abstract: “The investigation of observed borehole temperatures has proved to be a valuable tool for the reconstruction of ground surface temperature histories. However, there are still many open questions concerning the significance and accuracy of the reconstructions from these data. In particular, the temperature signal of the warming after the Last Glacial Maximum is still present in borehole temperature profiles. It is shown here that this signal also influences the relatively shallow boreholes used in current paleoclimate inversions to estimate temperature changes in the last centuries by producing errors in the determination of the steady state geothermal gradient. However, the impact on estimates of past temperature changes is weaker. For deeper boreholes, the curvature of the long-term signal is significant. A correction based on simple assumptions about glacial–interglacial temperature changes shows promising results, improving the extraction of millennial scale signals. The same procedure may help when comparing observed borehole temperature profiles with the results from numerical climate models.”

Citation: Rath, V., González Rouco, J. F., and Goosse, H.: Impact of postglacial warming on borehole reconstructions of last millennium temperatures, Clim. Past, 8, 1059-1066, doi:10.5194/cp-8-1059-2012, 2012.

Glaciers of the conterminous United States have been receding for the past century

Glacier variability in the conterminous United States during the twentieth century – McCabe & Fountain (2012)

Abstract: “Glaciers of the conterminous United States have been receding for the past century. Since 1900 the recession has varied from a 24 % loss in area (Mt. Rainier, Washington) to a 66 % loss in the Lewis Range of Montana. The rates of retreat are generally similar with a rapid loss in the early decades of the 20th century, slowing in the 1950s–1970s, and a resumption of rapid retreat starting in the 1990s. Decadal estimates of changes in glacier area for a subset of 31 glaciers from 1900 to 2000 are used to test a snow water equivalent model that is subsequently employed to examine the effects of temperature and precipitation variability on annual glacier area changes for these glaciers. Model results indicate that both winter precipitation and winter temperature have been important climatic factors affecting the variability of glacier variability during the 20th Century. Most of the glaciers analyzed appear to be more sensitive to temperature variability than to precipitation variability. However, precipitation variability is important, especially for high elevation glaciers. Additionally, glaciers with areas greater than 1 km2 are highly sensitive to variability in temperature.”

Citation: Gregory J. McCabe and Andrew G. Fountain, Climatic Change, 2012, DOI: 10.1007/s10584-012-0502-9.

Daily maximum and minimum temperatures have been increasing in Austria

Trends in extreme temperature indices in Austria based on a new homogenised dataset – Nemec et al. (2012)

Abstract: “Instrumental time series are often affected by inhomogeneities which can mask or amplify climate change signals. Various procedures for the detection and adjustment of breaks exist for monthly and annual time series. Homogenization methods on a daily basis are scarce and often disregard uncertainties accompanying the break adjustment. We present a complete homogenization procedure for daily extreme temperature series based on the break detection method PRODIGE and SPLIDHOM for break correction. Both parts of the homogenization rely on the existence of highly correlated reference stations. After the statistical comparison with neighbouring stations, detected breaks are verified and further localized by metadata. Uncertainties of the break adjustments are estimated by altering reference stations and by applying a bootstrapping technique providing an objective indication about the reliability of the homogenization. The method was tested and applied to 71 time series of daily minimum (TN) and maximum temperatures (TX) in Austria covering the period 1948–2009. For some series homogenization was not possible due to large uncertainties in the adjustments or a lack of suitable reference series. In the remaining 57 TN and 54 TX series a total number of 139 breaks were detected. Seventy-five percent of those breaks are documented in the metadata archive, with most of them being caused by station relocations and instrumentation changes. In general, the mean over the temperature dependent adjustments of all stations show a temperature reduction. However, the majority of breaks have mean amplitudes of less than 0.5 °C. A comprehensive analysis was performed on the new homogenized daily dataset, showing a widespread warming trend in both TN and TX series. The warming trend is in general amplified due to the homogenization. However, significant changes in the trend are only observed at very few stations. In autumn, however, the trend is reversed in many temperature based ‘climate change detection indices’.”

Citation: Johanna Nemec, Christine Gruber, Barbara Chimani, Ingeborg Auer, International Journal of Climatology, DOI: 10.1002/joc.3532.

There are always winners and such seems to be case also for ocean acidification

Sea anemones may thrive in a high CO2 world – Suggett et al. (2012)

Abstract: “Increased seawater pCO2, and in turn ‘ocean acidification’ (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA-like conditions can simultaneously enhance the ecological success of non-calcifying anthozoans, which play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft-bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO2 gradient at Vulcano, Italy. Both gross photosynthesis (PG) and respiration (R) increased with pCO2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO2 stimulation) of metabolism. The increase of PG outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO2 limitation of the anemones’ symbiotic microalgal population. Our observations of enhanced productivity with pCO2, which are consistent with previous reports for some calcifying corals, convey an increase in fitness that may enable non-calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO2. Understanding how CO2-enhanced productivity of non- (and less-) calcifying anthozoans applies more widely to tropical ecosystems is a priority where such organisms can dominate benthic ecosystems, in particular following localised anthropogenic stress.”

Citation: David J. Suggett, Jason M. Hall-Spencer, Riccardo Rodolfo-Metalpa, Toby G. Boatman, Ross Payton, D. Tye Pettay, Vivienne R. Johnson, Mark E. Warner, Tracy Lawson, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02767.x.

CLASSIC OF THE WEEK: Zdunkowski & Stowe (1968)

On the influence of CO2 on the radiative flux divergence – Zdunkowski & Stowe (1968) [FULL TEXT]

Abstract: “The influence of carbon dioxide upon the radiative heat budget of the lower few meters of the atmosphere is investigated. For this purpose, Elsasser’s (1960) radiative flux tables for the 15 micron carbon dioxide absorption band have been modified as described by Zdunkowski et al. (1966) and extended to very low optical pathlengths. In order to deal with the water vapor overlap effect in the carbon dioxide band, a series of so-called overlap tables have been constructed for different temperatures. These tables have been applied to obtain radiative flux divergence values for selected air masses which represent arctic, temperate, and tropical conditions. Moreover, for comparison purposes, the water vapor flux divergence, representing the total water vapor spectrum, has been determined for some cases, also. The latter task was accomplished by application of the emissivity method, which was also applied, as an independent check, to obtain carbon dioxide flux divergence. It was found in general that the influence of carbon dioxide upon the air layer near the ground should not be neglected.”

Citation: Wilford G. Zdunkowski, Larry L. Stowe Jr., Tellus, Volume 20, Issue 2, pages 293–299, May 1968, DOI: 10.1111/j.2153-3490.1968.tb00370.x.

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


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Papers on last interglacial climate

Posted by Ari Jokimäki on June 21, 2012

This is a list of papers on last interglacial (so called Eemian interglacial, between about 130000 and 110000 years ago) climate conditions with emphasis on papers that discuss last interglacial as an indicator of future climate conditions and consequences. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

European climate optimum and enhanced Greenland melt during the Last Interglacial – Goñi et al. (2012) “The Last Interglacial climatic optimum, ca. 128 ka, is the most recent climate interval significantly warmer than present, providing an analogue (albeit imperfect) for ongoing global warming and the effects of Greenland Ice Sheet (GIS) melting on climate over the coming millennium. While some climate models predict an Atlantic meridional overturning circulation (AMOC) strengthening in response to GIS melting, others simulate weakening, leading to cooling in Europe. Here, we present evidence from new proxy-based paleoclimate and ocean circulation reconstructions that show that the strongest warming in western Europe coincided with maximum GIS meltwater runoff and a weaker AMOC early in the Last Interglacial. By performing a series of climate model sensitivity experiments, including enhanced GIS melting, we were able to simulate this configuration of the Last Interglacial climate system and infer information on AMOC slowdown and related climate effects. These experiments suggest that GIS melt inhibited deep convection off the southern coast of Greenland, cooling local climate and reducing AMOC by ∼24% of its present strength. However, GIS melt did not perturb overturning in the Nordic Seas, leaving heat transport to, and thereby temperatures in, Europe unaffected.” Maria Fernanda Sánchez Goñi, Pepijn Bakker, Stéphanie Desprat, Anders E. Carlson, Cédric J. Van Meerbeeck, Odile Peyron, Filipa Naughton, William J. Fletcher, Frédérique Eynaud, Linda Rossignol and Hans Renssen, Geology, v. 40 no. 7 p. 627-630, doi: 10.1130/G32908.1. [FULL TEXT]

Sr-Nd-Pb Isotope Evidence for Ice-Sheet Presence on Southern Greenland During the Last Interglacial – Colville et al. (2012) “To ascertain the response of the southern Greenland Ice Sheet (GIS) to a boreal summer climate warmer than at present, we explored whether southern Greenland was deglaciated during the Last Interglacial (LIG), using the Sr-Nd-Pb isotope ratios of silt-sized sediment discharged from southern Greenland. Our isotope data indicate that no single southern Greenland geologic terrane was completely deglaciated during the LIG, similar to the Holocene. Differences in sediment sources during the LIG relative to the early Holocene denote, however, greater southern GIS retreat during the LIG. These results allow the evaluation of a suite of GIS models and are consistent with a GIS contribution of 1.6 to 2.2 meters to the ≥4-meter LIG sea-level highstand, requiring a significant sea-level contribution from the Antarctic Ice Sheet.” Elizabeth J. Colville, Anders E. Carlson, Brian L. Beard, Robert G. Hatfield, Joseph S. Stoner, Alberto V. Reyes, David J. Ullman, Science 29 July 2011: Vol. 333 no. 6042 pp. 620-623, DOI: 10.1126/science.1204673. [FULL TEXT]

Probabilistic assessment of sea level during the last interglacial stage – Kopp et al. (2009) “With polar temperatures ~3–5 °C warmer than today, the last interglacial stage (~125 kyr ago) serves as a partial analogue for 1–2 °C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (≥-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr-1 but is unlikely to have exceeded 9.2 m kyr-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.” Robert E. Kopp, Frederik J. Simons, Jerry X. Mitrovica, Adam C. Maloof & Michael Oppenheimer, Nature 462, 863-867 (17 December 2009) | doi:10.1038/nature08686. [Full text]

Response of the southern Greenland Ice Sheet during the last two deglaciations – Carlson et al. (2012) “The retreat of the southern Greenland Ice Sheet (GIS) during the last deglaciation (Termination I: TI) is poorly dated by conventional means; there is even greater uncertainty about the penultimate deglaciation (Termination II: TII), leading to the assumption that the southern GIS has a significant lag in its response to deglacial warming. Here we use geochemical terrestrial sediment proxies ([Fe] and [Ti]) from a well-studied southern Greenland marine sediment sequence to examine the behavior of the southern GIS during TI and TII. Our records show that during TI and TII the southern GIS response was essentially synchronous with deglacial North Atlantic warming, implying greater climate sensitivity than previously assumed. During TI, elevated ablation lasted ~5 k.y., whereas ablation remained elevated for ~12 k.y. during TII, suggesting a reduced southern GIS during TII that contributed a significant fraction of the higher sea level during the subsequent interglacial.” Anders E. Carlson, Joseph S. Stoner, Jeffrey P. Donnelly and Claude Hillaire-Marcel, Geology May 2008 v. 36, no. 5, p. 359-362, doi: 10.1130/​G24519A.1. [FULL TEXT]

The climate in Europe during the Eemian: a multi-method approach using pollen data – Brewer et al. (2008) “The Last Interglacial period, the Eemian, offers a testbed for comparing climate evolution throughout an interglacial with the current warm period. We present here results from climatic reconstructions from 17 sites distributed across the European continent, allowing an assessment of trends and regional averages of climate changes during this period. We use a multi-method approach to allow for an improved assessment of the uncertainties involved in the reconstruction. In addition, the method takes into account the errors associated with the age model. The resulting uncertainties are large, but allow a more robust assessment of the reconstructed climatic variations than in previous studies. The results show a traditional three-part Eemian, with an early optimum, followed by slight cooling and eventually a sharp drop in both temperatures and precipitation. This sequence is however, restricted to the north, as this latter change is not observed in the south where temperatures remain stable for longer. These variations led to marked variation in the latitudinal temperature gradient during the Eemian. The difference between the two regions is also noticeable in the magnitude of changes, with greater variations in the north than the south. Some evidence is found for changes in lapse rates, however, a greater number of sites is needed to confirm this.” S. Brewer, J. Guiot, M.F. Sánchez-Goñi, S. Klotz, Quaternary Science Reviews, Volume 27, Issues 25–26, December 2008, Pages 2303–2315,

The Deep Ocean During the Last Interglacial Period – Duplessy et al. (2007) “Oxygen isotope analysis of benthic foraminifera in deep sea cores from the Atlantic and Southern Oceans shows that during the last interglacial period, North Atlantic Deep Water (NADW) was 0.4° ± 0.2°C warmer than today, whereas Antarctic Bottom Water temperatures were unchanged. Model simulations show that this distribution of deep water temperatures can be explained as a response of the ocean to forcing by high-latitude insolation. The warming of NADW was transferred to the Circumpolar Deep Water, providing additional heat around Antarctica, which may have been responsible for partial melting of the West Antarctic Ice Sheet.” J. C. Duplessy, D. M. Roche and M. Kageyama, Science 6 April 2007: Vol. 316 no. 5821 pp. 89-91, DOI: 10.1126/science.1138582. [Full text]

Evidence for last interglacial chronology and environmental change from Southern Europe – Brauer et al. (2007) “Establishing phase relationships between earth-system components during periods of rapid global change is vital to understanding the underlying processes. It requires records of each component with independent and accurate chronologies. Until now, no continental record extending from the present to the penultimate glacial had such a chronology to our knowledge. Here, we present such a record from the annually laminated sediments of Lago Grande di Monticchio, southern Italy. Using this record we determine the duration (17.70 ± 0.20 ka) and age of onset (127.20 ± 1.60 ka B.P.) of the last interglacial, as reflected by terrestrial ecosystems. This record also reveals that the transitions at the beginning and end of the interglacial spanned only ≈100 and 150 years, respectively. Comparison with records of other earth-system components reveals complex leads and lags. During the penultimate deglaciation phase relationships are similar to those during the most recent deglaciation, peaks in Antarctic warming and atmospheric methane both leading Northern Hemisphere terrestrial warming. It is notable, however, that there is no evidence at Monticchio of a Younger Dryas-like oscillation during the penultimate deglaciation. Warming into the first major interstadial event after the last interglacial is characterized by markedly different phase relationships to those of the deglaciations, warming at Monticchio coinciding with Antarctic warming and leading the atmospheric methane increase. Diachroneity is seen at the end of the interglacial; several global proxies indicate progressive cooling after ≈115 ka B.P., whereas the main terrestrial response in the Mediterranean region is abrupt and occurs at 109.50 ± 1.40 ka B.P.” Achim Brauer, Judy R. M. Allen, Jens Mingram, Peter Dulski, Sabine Wulf, and Brian Huntley, PNAS January 9, 2007 vol. 104 no. 2 450-455, doi: 10.1073/pnas.0603321104. [Full text]

Paleoclimatic Evidence for Future Ice-Sheet Instability and Rapid Sea-Level Rise – Overpeck et al. (2006) “Sea-level rise from melting of polar ice sheets is one of the largest potential threats of future climate change. Polar warming by the year 2100 may reach levels similar to those of 130,000 to 127,000 years ago that were associated with sea levels several meters above modern levels; both the Greenland Ice Sheet and portions of the Antarctic Ice Sheet may be vulnerable. The record of past ice-sheet melting indicates that the rate of future melting and related sea-level rise could be faster than widely thought.” Jonathan T. Overpeck, Bette L. Otto-Bliesner, Gifford H. Miller, Daniel R. Muhs, Richard B. Alley and Jeffrey T. Kiehl, Science 24 March 2006: Vol. 311 no. 5768 pp. 1747-1750, DOI: 10.1126/science.1115159. [FULL TEXT]

Simulating Arctic Climate Warmth and Icefield Retreat in the Last Interglaciation – Otto-Bliesner et al. (2006) “In the future, Arctic warming and the melting of polar glaciers will be considerable, but the magnitude of both is uncertain. We used a global climate model, a dynamic ice sheet model, and paleoclimatic data to evaluate Northern Hemisphere high-latitude warming and its impact on Arctic icefields during the Last Interglaciation. Our simulated climate matches paleoclimatic observations of past warming, and the combination of physically based climate and ice-sheet modeling with ice-core constraints indicate that the Greenland Ice Sheet and other circum-Arctic ice fields likely contributed 2.2 to 3.4 meters of sea-level rise during the Last Interglaciation.” Bette L. Otto-Bliesner, Shawn J. Marshall, Jonathan T. Overpeck, Gifford H. Miller, Aixue Hu and CAPE Last Interglacial Project members, Science 24 March 2006: Vol. 311 no. 5768 pp. 1751-1753, DOI: 10.1126/science.1120808. [FULL TEXT]

A model-data comparison of European temperatures in the Eemian interglacial – Kaspar et al. (2005) “We present a comparison of reconstructed and simulated January and July temperatures in Europe for a time slice (∼125 kyr BP) within the last interglacial (Eemian, ∼127–116 kyr BP). The reconstructions, based on pollen and plant macrofossils, were performed on 48 European sites using a method based on probability density functions (pdf-method). The reconstructed most probable climate values were compared with a global climate simulation which was realized with a coupled ocean-atmosphere general circulation model. Orbital parameters and greenhouse gas concentrations have been adapted to conditions at 125 kyr BP. Reconstructions and simulation are concordant in showing higher temperatures than today over most parts of Europe in summer and in revealing a west-east-gradient in winter temperature differences with increasing anomalies toward eastern Europe. The results indicate that differences in the orbital parameters are sufficient to explain the reconstructed Eemian temperature patterns.” Kaspar, F., N. Kühl, U. Cubasch, and T. Litt (2005), A model-data comparison of European temperatures in the Eemian interglacial, Geophys. Res. Lett., 32, L11703, doi:10.1029/2005GL022456. [Full text]

Increased seasonality in Middle East temperatures during the last interglacial period – Felis et al. (2004) “The last interglacial period (about 125,000 years ago) is thought to have been at least as warm as the present climate. Owing to changes in the Earth’s orbit around the Sun, it is thought that insolation in the Northern Hemisphere varied more strongly than today on seasonal timescales, which would have led to corresponding changes in the seasonal temperature cycle. Here we present seasonally resolved proxy records using corals from the northernmost Red Sea, which record climate during the last interglacial period, the late Holocene epoch and the present. We find an increased seasonality in the temperature recorded in the last interglacial coral. Today, climate in the northern Red Sea is sensitive to the North Atlantic Oscillation, a climate oscillation that strongly influences winter temperatures and precipitation in the North Atlantic region. From our coral records and simulations with a coupled atmosphere–ocean circulation model, we conclude that a tendency towards the high-index state of the North Atlantic Oscillation during the last interglacial period, which is consistent with European proxy records, contributed to the larger amplitude of the seasonal cycle in the Middle East.” Thomas Felis, Gerrit Lohmann, Henning Kuhnert, Stephan J. Lorenz, Denis Scholz, Jürgen Pätzold, Saber A. Al-Rousan & Salim M. Al-Moghrabi, Nature 429, 164-168 (13 May 2004) | doi:10.1038/nature02546. [Full text]

Timing, Duration, and Transitions of the Last Interglacial Asian Monsoon – Yuan et al. (2004) “Thorium-230 ages and oxygen isotope ratios of stalagmites from Dongge Cave, China, characterize the Asian Monsoon and low-latitude precipitation over the past 160,000 years. Numerous abrupt changes in 18O/16O values result from changes in tropical and subtropical precipitation driven by insolation and millennial-scale circulation shifts. The Last Interglacial Monsoon lasted 9.7 ± 1.1 thousand years, beginning with an abrupt (less than 200 years) drop in 18O/16O values 129.3 ± 0.9 thousand years ago and ending with an abrupt (less than 300 years) rise in 18O/16O values 119.6 ± 0.6 thousand years ago. The start coincides with insolation rise and measures of full interglacial conditions, indicating that insolation triggered the final rise to full interglacial conditions.” Daoxian Yuan, Hai Cheng, R. Lawrence Edwards, Carolyn A. Dykoski, Megan J. Kelly, Meiliang Zhang, Jiaming Qing, Yushi Lin, Yongjin Wang, Jiangyin Wu, Jeffery A. Dorale, Zhisheng An and Yanjun Cai, Science 23 April 2004: Vol. 304 no. 5670 pp. 575-578, DOI: 10.1126/science.1091220. [Full text]

Continental European Eemian and early Würmian climate evolution: comparing signals using different quantitative reconstruction approaches based on pollen – Klotz et al. (2003) “Analyses of Eemian climate dynamics based on different reconstruction methods were conducted for several pollen sequences in the northern alpine foreland. The modern analogue and mutual climate sphere techniques used, which are briefly presented, complement one another with respect to comparable results. The reconstructions reveal the occurrence of at least two similar thermal periods, representing temperate oceanic conditions warmer and with a higher humidity than today. Intense changes of climate processes become obvious with a shift of winter temperatures of about 15 °C from the late Rissian to the first thermal optimum of the Eemian. The transition shows a pattern of summer temperatures and precipitation increasing more rapidly than winter temperatures. With the first optimum during the Pinus–Quercetum mixtum–Corylus phase (PQC) at an early stage of the Eemian and a second optimum period at a later stage, which is characterised by widespread Carpinus, climate gradients across the study area were less intense than today. Average winter temperatures vary between −1.9 and 0.4 °C (present-day −3.6 to 1.4 °C), summer temperatures between 17.8 and 19.6 °C (present-day 14 to 18.9 °C). The timberline expanded about 350 m when compared to the present-day limit represented by Pinus mugo. Whereas the maximum of temperature parameters is related to the first optimum, precipitation above 1100 mm is higher during the second warm period concomitant to somewhat reduced temperatures. Intermediate, smaller climate oscillations and a cooling becomes obvious, which admittedly represent moderate deterioration but not extreme chills. During the boreal semicontinental Eemian Pinus–Picea–Abies phase, another less distinct fluctuation occurs, initiating the oscillating shift from temperate to cold conditions.” Stefan Klotz, Joel Guiot, Volker Mosbrugger, Global and Planetary Change, Volume 36, Issue 4, May 2003, Pages 277–294,

Last Interglacial Climates – Kukla et al. (2002) “The last interglacial, commonly understood as an interval with climate as warm or warmer than today, is represented by marine isotope stage (MIS) 5e, which is a proxy record of low global ice volume and high sea level. It is arbitrarily dated to begin at approximately 130,000 yr B.P. and end at 116,000 yr B.P. with the onset of the early glacial unit MIS 5d. The age of the stage is determined by correlation to uranium–thorium dates of raised coral reefs. The most detailed proxy record of interglacial climate is found in the Vostok ice core where the temperature reached current levels 132,000 yr ago and continued rising for another two millennia. Approximately 127,000 yr ago the Eemian mixed forests were established in Europe. They developed through a characteristic succession of tree species, probably surviving well into the early glacial stage in southern parts of Europe. After ca. 115,000 yr ago, open vegetation replaced forests in northwestern Europe and the proportion of conifers increased significantly farther south. Air temperature at Vostok dropped sharply. Pulses of cold water affected the northern North Atlantic already in late MIS 5e, but the central North Atlantic remained warm throughout most of MIS 5d. Model results show that the sea surface in the eastern tropical Pacific warmed when the ice grew and sea level dropped. The essentially interglacial conditions in southwestern Europe remained unaffected by ice buildup until late MIS 5d when the forests disappeared abruptly and cold water invaded the central North Atlantic ca. 107,000 yr ago.” George J. Kukla, Michael L. Bender, Jacques-Louis de Beaulieu, Gerard Bond, Wallace S. Broecker, Piet Cleveringa, Joyce E. Gavin, Timothy D. Herbert, John Imbrie, Jean Jouzel, Lloyd D. Keigwin, Karen-Luise Knudsen, Jerry F. McManus, Josef Merkt, Daniel R. Muhs, Helmut Müller, Richard Z. Poore, Stephen C. Porter, Guy Seret, Nicholas J. Shackleton, Charles Turner, Polychronis C. Tzedakis, Isaac J. Winograd, Quaternary Research, Volume 58, Issue 1, July 2002, Pages 2–13, [Full text]

High-resolution record of climate stability in France during the last interglacial period – Rioual et al. (2001) “The last interglacial period (127–110 kyr ago) has been considered to be an analogue to the present interglacial period, the Holocene, which may help us to understand present climate evolution. But whereas Holocene climate has been essentially stable in Europe, variability in climate during the last interglacial period has remained unresolved, because climate reconstructions from ice cores, continental records and marine sediment cores give conflicting results for this period. Here we present a high-resolution multi-proxy lacustrine record of climate change during the last interglacial period, based on oxygen isotopes in diatom silica, diatom assemblages and pollen–climate transfer functions from the Ribains maar in France. Contrary to a previous study, our data do not show a cold event interrupting the warm interglacial climate. Instead, we find an early temperature maximum with a transition to a colder climate about halfway through the sequence. The end of the interglacial period is clearly marked by an abrupt change in all proxy records. Our study confirms that in southwestern Europe the last interglacial period was a time of climatic stability and is therefore still likely to represent a useful analogue for the present climate.” Patrick Rioual, Valérie Andrieu-Ponel, Miri Rietti-Shati, Richard W. Battarbee, Jacques-Louis de Beaulieu, Rachid Cheddadi, Maurice Reille, Helena Svobodova & Aldo Shemesh, Nature 413, 293-296 (20 September 2001) | doi:10.1038/35095037.

Comparison of the last interglacial climate simulated by a coupled global model of intermediate complexity and an AOGCM – Kubatzki et al. (2000) “The climate at the Last Interglacial Maximum (125 000 years before present) is investigated with the atmosphere-ocean general circulation model ECHAM-1/LSG and with the climate system model of intermediate complexity CLIMBER-2. Comparison of the results of the two models reveals broad agreement in most large-scale features, but also some discrepancies. The fast turnaround time of CLIMBER-2 permits one to perform a number of sensitivity experiments to (1) investigate the possible reasons for these differences, in particular the impact of different freshwater fluxes to the ocean, (2) analyze the sensitivity of the results to changes in the definition of the modern reference run concerning CO2 levels (preindustrial versus “present”), and (3) estimate the role of vegetation in the changed climate. Interactive vegetation turns out to be capable of modifying the initial climate signals significantly, leading especially to warmer winters in large parts of the Northern Hemisphere, as indicated by various paleodata. Differences due to changes in the atmospheric CO2 content and due to interactive vegetation are shown to be at least of the same order of magnitude as differences between the two completely different models, demonstrating the importance of careful experimental design.” C. Kubatzki, M. Montoya, S. Rahmstorf, A. Ganopolski and M. Claussen, Climate Dynamics, Volume 16, Numbers 10-11 (2000), 799-814, DOI: 10.1007/s003820000078. [Full text]

Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet – Cuffey & Marshall (2000) “During the last interglacial period (the Eemian), global sea level was at least three metres, and probably more than five metres, higher than at present. Complete melting of either the West Antarctic ice sheet or the Greenland ice sheet would today raise sea levels by 6–7 metres. But the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the West Antarctic ice sheet, with model studies attributing only 1–2 m of sea-level rise to meltwater from Greenland. This result was considered consistent with ice core evidence4, although earlier work had suggested a much reduced Greenland ice sheet during the last interglacial period6. Here we reconsider the Eemian evolution of the Greenland ice sheet by combining numerical modelling with insights obtained from recent central Greenland ice-core analyses. Our results suggest that the Greenland ice sheet was considerably smaller and steeper during the Eemian, and plausibly contributed 4–5.5 m to the sea-level highstand during that period. We conclude that the high sea level during the last interglacial period most probably included a large contribution from Greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the West Antarctic ice sheet.” Kurt M. Cuffey & Shawn J. Marshall, Nature 404, 591-594 (6 April 2000) | doi:10.1038/35007053. [Full text]

Multiproxy climate reconstructions for the Eemian and Early Weichselian – Aalbersberg & Litt (1998) “Palaeobotanical, coleopteran and periglacial data from 106 sites across northwestern Europe have been analysed in order to reconstruct palaeoclimatic conditions during the Eemian and Early Weichselian. Three time slices in the Eemian and four in the Early Weichselian have been considered. In the Pinus–Quercetum mixtum–Corylus phase of the Eemian, summer temperatures were probably at their highest and the botanic evidence suggests a southeast to northwest gradient for both the warmest and coldest month. Coleoptera indicate that the summers in southern England were several degrees warmer than those of present day. The climate during theCarpinus–Picea phase was uniform and oceanic without obvious gradients. In the final time slice of the Eemian, the Pinus–Picea–Abies phase, temperatures of the warmest month seem to drop slightly with some indication of a shift towards a more boreal and suboceanic climate. The reconstruction of the palaeoclimate in the Herning Stadial and Rederstall Stadial is hampered by the limited number of sites, but botanical evidence suggests a gradient in temperature of the coldest month from east to west. Coleoptera from the Herning Stadial in central England and eastern Germany suggest similarly cold and continental climates. During the Brørup Interstadial and the Odderade Interstadial the botanical evidence suggests that the minimum mean July temperatures rose to 15–16°C but during the coldest month these temperatures show a gradient between −13°C in the east and −5°C in the west.” Gerard Aalbersberg, Thomas Litt, Journal of Quaternary Science, Special Issue: Palaeoclimate of the last Interglacial- Glacial Cycle in Western and Central Europe, Volume 13, Issue 5, pages 367–390, September/October 1998, DOI: 10.1002/(SICI)1099-1417(1998090)13:53.0.CO;2-I..

An analysis of Eemian climate in Western and Central Europe – Zagwijn (1996) “On the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the Last Interglacial (Eemian) climatic history in Western and Central Europe. The main tool for this analysis is the climatic indicator species method. Only selected woody species are used for the quantification of data. Partial climatic range diagrams are presented for: Abies alba, Acer monspessulanum, Acer tataricum, Buxus sempervirens, Tilia tomentosa. The problem of time correlation and pollen zonation of the Eemian is discussed. The climatic analysis itself is based on an improved version of the indicator species method. In this version not every site is analysed for its climatic values. Instead maps and tables on the migrational history of Hedera, Ilex, Buxus, Abies and species of Acer, Tilia and Abies are the basis for climatic maps showing respectively January and July isotherms for the periods of the Corylus zone (E4a) and the Carpinus zone (E5). It is concluded that mean January temperatures were as much as 3°C higher at Amsterdam (The Netherlands), than at present, and mean temperatures in July were 2°C higher. However, the thermal maximum in winter was later (zone E5) than the summer thermal maximum (zone E4a). Winter temperatures changed parallel to rise and fall of global sea-level. Precipitation changes are more difficult to estimate. In the first part of the Eemian precipitation must have been relatively low, but from zone E4b onward it increased to higher values, reaching 800 mm and probably substantially more in zones E5 and E6. Hence the Eemian climate was in its beginning relatively more contintental, and later (from E4b onward) more oceanic. However, as compared with the Holocene, the Eemian climate was, generally speaking, more oceanic.” W.H. Zagwijn, Quaternary Science Reviews, Volume 15, Issues 5–6, 1996, Pages 451–469,

Rapid changes in ocean circulation and heat flux in the Nordic seas during the last interglacial period – Fronval & Jansen (1996) “THE apparent similarity of climate variability in the North Atlantic region in the last interglacial period and the present interglacial (Holocene) has recently been challenged by the rapid oscillations in climate conditions indicated by some marine and terrestrial climate records8–10 for the last interglacial. Ocean circulation in the northern North Atlantic seems to be intimately coupled to the processes of climate change on various time-scales, so that climate variability—and the associated mechanisms of change—should be well recorded by sediments from these high latitudes. Previous studies in this region have indeed indicated an apparently less stable last-interglacial climate than at middle latitudes of the North Atlantic Ocean4. Here we present detailed records from marine sediments in the Nordic seas of oceanographic conditions during the last interglacial. The records show three large sea surface temperature fluctuations, a weakening of the east–west sea surface temperature gradient with time, and changes in deep-water properties. In contrast, similar analyses of a core from the same region indicate that sea surface temperature during the Holocene has been relatively stable. Our data—along with those from the Labrador Sea7—indicate rapid changes in ocean circulation and oceanic heat fluxes at high northern latitudes during the last interglacial, which may have been associated with marked temperature changes on adjacent continents.” Torben Fronval & Eystein Jansen, Nature 383, 806 – 810 (31 October 1996); doi:10.1038/383806a0.

The Last Interglaciation in Arctic and Subarctic Regions: Time Frame, Structure, and Duration: Selected Papers from a LIGA Symposium Held in Saint-Michel des Saints, Quebec, Canada, May 4-7, 1993 – Lauritzen & Anderson (1995) Selected papers in question are included to this issue of journal Quaternary Research (including Brigham-Grette & Hopkins paper presented below). Stein-Erik Lauritzen, Patricia M. Anderson, Quaternary Research, Volume 43, Issue 2, March 1995, Pages 115–116.

Emergent Marine Record and Paleoclimate of the Last Interglaciation along the Northwest Alaskan Coast – Brigham-Grette & Hopkins (1995) “The last interglacial high sea-level stand, the Pelukian transgression of isotope substage 5e, is recorded along the western and northern coasts of Alaska by discontinuous but clearly traceable marine terraces and coastal landforms up to about 10 m altitude. The stratigraphy indicates that sea level reached this altitude only once during the last interglacial cycle. From the type area at Nome, to St. Lawrence Island in the Bering Sea, to the eastern limit of the Beaufort Sea, Pelukian deposits contain extralimital faunas indicating that coastal waters were warmer than present. Amino acid ratios in molluscs from these deposits decrease to the north toward Barrow, consistent with the modern regional temperature gradient. Fossil assemblages at Nome and St. Lawrence Island suggest that the winter sea-ice limit was north of Bering Strait, at least 800 km north of its present position, and the Bering Sea was perennially ice-free. Microfauna in Pelukian sediments recovered from boreholes indicate that Atlantic water may have been present on the shallow Beaufort Shelf, suggesting that the Arctic Ocean was not stratified and the Arctic sea-ice cover was not perennial for some period. In coastal regions of western Alaska, spruce woodlands extended westward beyond their modern range and in northern Alaska, on the Arctic Coastal Plain, spruce groves may have entered the upper Colville River basin. The Flaxman Member of the Gubik Formation on the Alaskan Arctic Coastal Plain was deposited during marine isotope substage 5a and records the breakup of an intra-stage 5 ice sheet over northwestern Keewatin.” Julie Brigham-Grette, David M. Hopkins, Quaternary Research, Volume 43, Issue 2, March 1995, Pages 159–173, [FULL TEXT]

High-resolution climate records from the North Atlantic during the last interglacial – McManus et al. (1994) “THE two deep ice cores recovered by the GRIP and GISP2 projects at Summit, Greenland, agree in detail over the past 100,000 years and demonstrate dramatic climate variability in the North Atlantic region during the last glacial, before the current period of Holocene stability. This glacial climate instability has subsequently been documented in the marine sedimentary record of surface-ocean conditions in the North Atlantic. Before 100 kyr ago the two ice core records are discrepant, however, casting doubt on whether the oxygen isotope fluctuations during the last interglacial (Eemian) seen in the GRIP core represent a true climate signal. Here we present high-resolution records of foraminiferal assemblages and ice-rafted detritus from two North Atlantic cores for the interval 65 kyr to 135 kyr ago, extending the surface-ocean record back to the Eemian. The correlation between our records and the Greenland ice-core records is good throughout the period in which the two ice cores agree, suggesting a regionally coherent climate response. During the Eemian, our marine records show a more stable climate than that implied by the GRIP ice core, suggesting that localized phenomena may be responsible for the variability in the latter record during the Eemian.” J. F. McManus, G. C. Bond, W. S. Broecker, S. Johnsen, L. Labeyrie & S. Higgins, Nature 371, 326 – 329 (22 September 1994); doi:10.1038/371326a0. [Full text]

Constraints on the age and duration of the last interglacial period and on sea-level variations – Lambeck & Nakada (1992) “The relation between height and age of shorelines formed during the last interglacial period, as revealed by coral reefs, cannot be related directly to changes in ocean volume because of the effect of isostatic uplift in response to changes in ice-sheet loading. Sea-level changes at sites near the melting ice sheet, such as Bermuda and the Caribbean islands, differ from those along the Australian margin. Modelling of these differences constrains the times of onset and termination of the last interglacial, which are at variance with those deduced from oxygen-isotope studies of deep-sea cores.” Kurt Lambeck & Masao Nakada, Nature 357, 125 – 128 (14 May 1992); doi:10.1038/357125a0.

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New research from last week 24/2012

Posted by Ari Jokimäki on June 18, 2012

This week we have temperature studies from Saudi-Arabia, European Alps, and the whole globe. Clouds disturb satellite measurements. Tree rings measure wind too. Some future related issues are methane under glaciers, snow albedo feedback, and AMOC slowdown. Lightning flashes take weekends off. What are the causes for El Niño intensification and for UV radiation increase?

Evidence from Last Interglacial suggests that Greenland melt induced AMOC slowdown might not cool Europe

European climate optimum and enhanced Greenland melt during the Last Interglacial – Goñi et al. (2012) [FULL TEXT]

Abstract: “The Last Interglacial climatic optimum, ca. 128 ka, is the most recent climate interval significantly warmer than present, providing an analogue (albeit imperfect) for ongoing global warming and the effects of Greenland Ice Sheet (GIS) melting on climate over the coming millennium. While some climate models predict an Atlantic meridional overturning circulation (AMOC) strengthening in response to GIS melting, others simulate weakening, leading to cooling in Europe. Here, we present evidence from new proxy-based paleoclimate and ocean circulation reconstructions that show that the strongest warming in western Europe coincided with maximum GIS meltwater runoff and a weaker AMOC early in the Last Interglacial. By performing a series of climate model sensitivity experiments, including enhanced GIS melting, we were able to simulate this configuration of the Last Interglacial climate system and infer information on AMOC slowdown and related climate effects. These experiments suggest that GIS melt inhibited deep convection off the southern coast of Greenland, cooling local climate and reducing AMOC by ∼24% of its present strength. However, GIS melt did not perturb overturning in the Nordic Seas, leaving heat transport to, and thereby temperatures in, Europe unaffected.”

Citation: Maria Fernanda Sánchez Goñi, Pepijn Bakker, Stéphanie Desprat, Anders E. Carlson, Cédric J. Van Meerbeeck, Odile Peyron, Filipa Naughton, William J. Fletcher, Frédérique Eynaud, Linda Rossignol and Hans Renssen, Geology, v. 40 no. 7 p. 627-630, doi: 10.1130/G32908.1.

Less lightning activity during weekends in Atlanta region

Weekend–weekday aerosols and geographic variability in cloud-to-ground lightning for the urban region of Atlanta, Georgia, USA – Stallins et al. (2012)

Abstract: “We characterized the differences in warm-season weekday and weekend aerosol conditions and cloud-to-ground (CG) flashes (1995–2008) for an 80,000 square kilometer region around Atlanta, Georgia, a city of 5.5 million in the humid subtropics of the southeastern United States. An integration of distance-based multivariate techniques (hierarchical agglomerative clustering, multiresponse permutation procedures, fuzzy kappa statistics, and Mantel tests) indicated a greater concentration of CG flash activity within a 100 km radius around Atlanta under weekday aerosol concentrations. On weekends, these effects contracted toward the city. This minimized any weekly anthropogenic cycle over the more densely populated urban center even though this location had a higher flash density, a higher percentage of days with flashes, and stronger peak currents over the course of a week compared to the surrounding region. The sharper contrasts in weekday and weekend lightning regime developed outside the perimeter of the city over nonurban land uses. Here, lightning on weekend and weekdays differed more in its density, frequency, polarity, and peak current. Across the full extent of the study region, weekday peak currents were stronger and flash days more frequent, suggesting that weekly CG lightning signals have a regional component not tied to a single city source. We integrate these findings in a conceptual model that illustrates the dependency of weekly anthropogenic weather signals on spatial and temporal extent.”

Citation: J. Anthony Stallins, James Carpenter, Mace L. Bentley, Walker S. Ashley and James A. Mulholland, Regional Environmental Change, 2012, DOI: 10.1007/s10113-012-0327-0.

Ozone changes cannot explain increase of UV radiation in Austria

Trends in spectral UV radiation from long-term measurements at Hoher Sonnblick, Austria – Fitzka et al. (2012)

Abstract: “High-quality long-term records of spectral UV irradiance from the Network for the Detection of Atmospheric Composition Change-affiliated Bentham spectroradiometer at the high-mountain site Hoher Sonnblick (47.05° N, 12.95° E, 3,106 m above sea level) from the period 1997–2011 have been investigated for the existence of trends. Throughout the year, significant upward trends are found at wavelengths of 315 nm and longer. The magnitudes at 315 nm range from +9.3 ± 4.5 %/dec at 45° solar zenith angle (SZA) to +14.2 ± 3.7 %/dec at SZA 65° for all-sky conditions. The trend estimates at 305 nm are considerably smaller and less significant, yielding between +5.1 ± 6.5 and +7.9 ± 7.3 %/dec, depending on SZA. Seasonally, the largest trends are found during winter and spring. Total ozone has significantly increased by year-round +1.9 ± 1.3 %/dec since 1997 and therefore cannot explain these significant increases. They are rather attributed to decreases in total cloud cover and aerosol optical depth.”

Citation: M. Fitzka, S. Simic and J. Hadzimustafic, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0684-0.

Evaluation of the strength of snow albedo feedback

Using models and satellite observations to evaluate the strength of snow albedo feedback – Fletcher et al. (2012) [FULL TEXT]

Abstract: “Snow albedo feedback (SAF) is important for global climate change, with strong regional impacts over northern continental areas. SAF calculated from the seasonal cycle is a good predictor of SAF in climate change among a suite of coupled climate models. A previous linear decomposition of the simulated total SAF (NET) found 80% was related to the albedo contrast of snow covered and snow-free land (SNC), and 20% was related to the temperature dependence of snow albedo (TEM). By contrast, recent work using snow cover and surface albedo derived from APP-x satellite observations found that TEM and SNC contributed almost equally to NET. In the present study, revised estimates of TEM and SNC for northern land areas are calculated for the period 1982–99 using a simplified and reproducible method for comparing SAF in models and observations. The observed NET is −1.11% K−1, of which 69% comes from SNC and 31% from TEM; the approximate additivity of SNC and TEM indicates that these two terms fully explain the total SAF. Regionally, the SNC term dominates equatorward of 65°N, while TEM dominates over the Arctic. The mean of 17 CMIP3 climate models shows NET is 7% larger than observed, caused primarily by a bias in TEM equatorward of 65°N. A newer model (NCAR CCSM4) with improved land surface and snow schemes reproduces observed values of NET and SNC closely. However, TEM in all models examined is 50–100% weaker than observed over the Arctic. There is a strong correlation between SAF in the seasonal cycle and SAF in climate change for all components, but the correlation is weakest for TEM. The TEM term also exhibits a much larger spread in the seasonal cycle than in climate change, which partially explains a discrepancy between previous published studies examining TEM.”

Citation: Fletcher, C. G., H. Zhao, P. J. Kushner, and R. Fernandes (2012), Using models and satellite observations to evaluate the strength of snow albedo feedback, J. Geophys. Res., 117, D11117, doi:10.1029/2012JD017724.

Recent intensification of central Pacific El Niño could be due to natural variability

Statistical evidence for the natural variation of the central Pacific El Niño – Kim et al. (2012)

Abstract: “Extensive studies claimed that the central equatorial Pacific (CP) El Niño has occurred more frequently and strongly than the eastern equatorial Pacific El Niño in recent years. To explain this phenomenon, spatial patterns and principal component time series from several sea surface temperature (SST) data sets in the tropical Pacific are analyzed for the period of 1951–2010. Cyclostationary empirical orthogonal function analysis separates two modes of SST variability, which explain about 50% and 10% of the total SST variability, respectively. Their spatial and temporal patterns are similar among the different SST data sets. The first mode captures the typical El Niño pattern, while the second mode is a dipole pattern in the tropical Pacific. The two modes are, by definition, uncorrelated over the analysis period but are in phase since the late 1990s; superposition of the two modes results in a significant warming in the CP region, which is a potential explanation for a more frequent occurrence of the CP El Niño in the recent decades. Similar analysis is conducted based on the 500 year data from the Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 under the preindustrial condition. The result is generally consistent with the observations yielding occasional in-phase relationship between the two modes. Thus, it cannot be ruled out that a more frequent occurrence of the CP El Niño in recent years is a natural feature of the equatorial climate system.”

Citation: Kim, J.-S., K.-Y. Kim, and S.-W. Yeh (2012), Statistical evidence for the natural variation of the central Pacific El Niño, J. Geophys. Res., 117, C06014, doi:10.1029/2012JC008003.

Methane under glaciers and ice sheets – what happens when glaciers retreat?

Methanogenic potential of Arctic and Antarctic subglacial environments with contrasting organic carbon sources – Stibal et al. (2012)

Abstract: “Subglacial environments are largely anoxic, contain organic carbon (OC) overridden by glacier ice during periods of advance, and harbour active microbial communities. This creates favourable conditions for OC degradation via methanogenesis. It has been hypothesised that OC beneath ice sheets is converted to methane (CH4) and may be released to the atmosphere during retreat. However, there are limited data available to support this contention. Here, we present new data on the abundance, diversity and activity of methanogenic archaea and the amount and character of OC in subglacial sediments from Arctic and Antarctic glacial systems based on different substrate types. We employed long-term laboratory incubations to quantify the CH4 production potential in different subglacial settings. Significant numbers of methanogens (up to 7×104 cells g−1) were detected in the samples and clones of Methanomicrobiales and Methanosarcinales were identified in clone libraries. Long lag periods (up to >200 days) were observed before significant CH4 concentrations were measured. We report order of magnitude differences in rates of CH4 production (101-105 fmol g−1 d−1) in different subglacial sediments, reflecting contrasts in the origin of the sediment and the OC character. Hence, we predict that contrasting rates of CH4 production are likely to occur beneath glaciers and ice sheets that overran different types of substrate. We subsequently estimated the potential for CH4 production beneath the Laurentide/Inuitian/Cordilleran and Fennoscandian Ice Sheets during a typical 85 ka Quaternary glacial/interglacial cycle. CH4 production from lacustrine-derived OC is likely to be an order of magnitude higher (~6.3-27 Pg C) than that from overridden soils (~0.55-0.68 Pg C), possibly due to a difference in lability between lacustrine and soil OC. While representing a fraction of the entire OC pool (~418-610 Pg C), this finding highlights the importance of considering the character of different OC pools when calculating subglacial CH4 production.”

Citation: Marek Stibal, Jemma L. Wadham, Grzegorz P. Lis, Jon Telling, Richard D. Pancost, Ashley Dubnick, Martin J. Sharp, Emily C. Lawson, Catriona E. H. Butler, Fariha Hasan, Martyn Tranter, Alexandre M. Anesio, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02763.x.

Tree rings as windstorm indicators

A 300-Year History of Pacific Northwest Windstorms Inferred from Tree Rings – Knapp & Hadley (2012)

Abstract: “Hurricane-force winds are frequently allied with mid-latitude cyclones yet little is known about their historical timing and geographic extent over multiple centuries. This research addresses these issues by extending the historical record of major mid-latitude windstorms along North America’s Pacific Northwest (PNW) coast using tree-ring data collected from old-growth (> 350 yrs.), wind-snapped trees sampled at seven coastal sites in Oregon, USA. Our objectives were to: 1) characterize historical windstorm regimes; 2) determine the relationship between high-wind events (HWEs) and phases of the PDO, ENSO and NPI; and 3) test the hypothesis that PNW HWEs have migrated northward. We based our study on the identification of tree-growth anomalies resulting from windstorm-induced canopy changes corresponding to documented (1880–2003) and projected HWEs (1701–1880). Our methods identified all major windstorm events recorded since the late 1800 s and confirmed that variations in coastal tree-growth are weakly related to temperature, precipitation, and drought, but are significantly related to peak wind speeds. These results suggest wind-induced changes in canopy conditions control tree growth at all sites. Comparisons between the tree-ring record and the PDO, NPI, and ENSO revealed a significant positive correlation between HWEs and neutral to warm PDO conditions and a slightly weaker correlation with the NPI. ENSO events were not significantly related to the occurrence of HWEs. Latitudinal groupings of our sites revealed a gradual and non-significant northerly shift of HWEs until the late 19th century followed by a significant northward shift during the past 120 years. These results mark the application of dendroanemology as a method for characterizing windstorm regimes for multiple centuries.”

Citation: Paul A. Knapp, Keith S. Hadley, Global and Planetary Change,

20th century surface temperature evolution as a test for climate models

Reproduction of twentieth century intradecadal to multidecadal surface temperature variability in radiatively forced coupled climate models – Brown et al. (2012)

Abstract: “Coupled Model Intercomparison Project 3 simulations that included time-varying radiative forcings were ranked according to their ability to consistently reproduce twentieth century intradecadal to multidecadal (IMD) surface temperature variability at the 5° by 5° spatial scale. IMD variability was identified using the running Mann-Whitney Z method. Model rankings were given context by comparing the IMD variability in preindustrial control runs to observations and by contrasting the IMD variability among the ensemble members within each model. These experiments confirmed that the inclusion of time-varying external forcings brought simulations into closer agreement with observations. Additionally, they illustrated that the magnitude of unforced variability differed between models. This led to a supplementary metric that assessed model ability to reproduce observations while accounting for each model’s own degree of unforced variability. These two metrics revealed that discernable differences in skill exist between models and that none of the models reproduced observations at their theoretical optimum level. Overall, these results demonstrate a methodology for assessing coupled models relative to each other within a multimodel framework.”

Citation: Brown, P. T., E. C. Cordero, and S. A. Mauget (2012), Reproduction of twentieth century intradecadal to multidecadal surface temperature variability in radiatively forced coupled climate models, J. Geophys. Res., 117, D11116, doi:10.1029/2011JD016864.

Reasons for different amount of warming at low and high elevations in European Alps region

Greenhouse warming and solar brightening in and around the Alps – Philipona (2012)

Abstract: “At low elevations (500 m a.s.l.) Central Europe’s surface temperature increased about 1.3 °C since 1981. Interestingly, at high elevations (2200 m a.s.l.) in the Alps, temperature rose less than 1 °C over the same period. Detailed investigations of temperature, humidity and the radiation budget at lowland and alpine climate stations now show that the difference in temperature rise is likely related to unequal solar- and greenhouse warming. The analysis shows that the important decline of anthropogenic aerosols in Europe since the mid-1980s led to solar brightening at low elevations, whereas inherent low aerosol concentrations at high elevations led to only minor changes of solar radiation in the Alps. In the Lowland, absolute humidity and also total net radiation show an about 6% K−1 Clausius–Clapeyron conform increase with temperature since the 1980s. In the Alps, however, the percentage increase rate of humidity and total net radiation is more than twice as large. This large water vapour increase in the Alps is likely related to strong warming and thermal advection in the Lowlands, and may also have increased due to atmospheric circulation changes. Hence, while in the Alps temperature increased primarily due to strong water vapour enhanced greenhouse warming, solar brightening combined with anthropogenic greenhouse gas and water vapour feedback greenhouse warming led to a higher temperature increase at low elevations in Central Europe.”

Citation: Rolf Philipona, International Journal of Climatology, DOI: 10.1002/joc.3531.

Clouds make trace gas measurements from satellites more difficult

Decadal Biases in long-term NO2 averages inferred from satellite observations due to cloud selection criteria – Geddes et al. (2012)

Abstract: “Retrievals of atmospheric trace gas column densities from space are compromised by the presence of clouds, requiring most studies to exclude observations with significant cloud fractions in the instrument’s field of view. Using NO2 observations at three ground stations representing urban, suburban, and rural environments, and tropospheric vertical column densities measured by the Ozone Monitoring Instrument (OMI) over each site, we show that the observations from space represent monthly averaged ground-level pollutant conditions well (R = 0.86) under relatively cloud-free conditions. However, by analyzing the ground-level data and applying the OMI cloud fraction as a filter, we show there is a significant bias in long-term averaged NO2 as a result of removing the data during cloudy conditions. For the ground-based sites considered in this study, excluding observations on days when OMI-derived cloud fractions were greater than 0.2 causes 12:00–14:00 mean summer mixing ratios to be underestimated by 12% ± 6%, 20% ± 7%, and 40% ± 10% on average (± 1 standard deviation) at the urban, suburban, and rural sites respectively. This bias was investigated in particular at the rural site, a region where pollutant transport is the main source of NO2, and where long-term observations of NOy were also available. Evidence of changing photochemical conditions and a correlation between clear skies and the transport of cleaner air masses play key roles in explaining the bias. The magnitude of a bias is expected to vary from site to site depending on meteorology and proximity to NOx sources, and decreases when longer averaging times of ground station data (e.g. 24-h) are used for the comparison.”

Citation: Jeffrey A. Geddes, Jennifer G. Murphy, Jason M. O’Brien, Edward A. Celarier, Remote Sensing of Environment, Volume 124, September 2012, Pages 210–216,

Saudi Arabia has gotten even warmer

Decadal variability of the observed daily temperature in Saudi Arabia during 1979–2008 – Athar (2012)

Abstract: “Variability in the observed daily temperature for the 30-year period (1979–2008) is studied from a total of 19 stations in Saudi Arabia (SA) by calculating the empirical anomaly probability distribution functions (PDFs) on annual basis. The 30-year period is divided into three decades. As compared with the first decade, the PDFs for the remaining decades display a relative frequency rise in warmer temperatures. The mean values of the PDFs depict an average decadal positive shift of 0.83, 0.66, and 0.49 °C, for the maximum, the mean, and the minimum temperature, respectively, relative to the 30-year base value.”

Citation: H. Athar, Atmospheric Science Letters, DOI: 10.1002/asl.390.

CLASSIC OF THE WEEK: Ohring & Mariano (1963)

The effect of cloudiness on a greenhouse model of the venus atmosphere – Ohring & Mariano (1963) [FULL TEXT]

Abstract: “In previous models of the greenhouse effect in the Venus atmosphere, it has been assumed that infrared-absorbing atmospheric gases provide the sole contribution to the infrared opacity of the Venus atmosphere. In the present study, the influence of an extensive cloud-cover, opaque to infrared radiation, is also included in the greenhouse model. The magnitude of the greenhouse effect, which is defined here as the ratio of the surface temperature produced by the greenhouse to the surface temperature of an atmosphere-less Venus, is computed as a function of infrared opacity of the atmosphere, and amount and height (actually ratio of cloud-top pressure to surface pressure) of clouds. It is assumed that the Venus atmosphere is grey, the absorbing gas has a constant mixing ratio, and the temperature variation with altitude is linear. Calculations are made for two temperature lapse rates: the adiabatic lapse rate, and nine-tenths of the adiabatic lapse rate. The adiabatic lapse rate maximizes the greenhouse effect; for this case estimates of the minimum infrared opacity required to maintain the observed surface temperature can be determined. For a surface temperature of 700K, 99% cloudiness, and cloud-top temperature of 240K, the minimum required infrared opacity is six. Uncertainties and questionable side effects of the model are discussed.”

Citation: Ohring, G., Mariano, J. F., NASA report NASA-CR-51176.

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

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New research from last week 23/2012

Posted by Ari Jokimäki on June 11, 2012

One important thing in science is method development. Science works at the edge between known and unknown, and in order to reveal little bit more of unknown, it is quite often needed to improve our research methods and even come up with some new ones. That is because the studied issues, or at least some aspects of them, have not been known for long, and research methods developed originally to study something else might not be suitable for studying the new issue.

We have some studies this week that are at least partially method development papers. There is a paper about a meeting of statisticians, mathematicians, and climate scientists, where they discussed how uncertainties should be quantified in climate observations. One paper makes an effort to determine surface air temperatures using satellite measurements. Ice core syncronisation is the subject of one paper. Speaking of ice cores, there’s another paper on ice cores which is borderline method development. Ice cores are used to study past climates but they have limited reach back in time. Currently longest ice core reaches back 800,000 years. Now researchers have studied ice flows in Allan Hills icefield and found out that there old ice has moved upwards, so old ice is there at the surface presenting possibility to extend ice core records beyond 800,000 years.

Other studies this week are touching the unknowns of carbon cycle, temperatures in European Alps, atmospheric carbon dioxide effects, Greenland glaciers, Southern Ocean wind, climate change scepticism, tropical and African rainfall, and atmospheric methane.

Carbon cycle uncertainty is larger than thought and could strongly amplify climate warming

Carbon cycle uncertainty increases climate change risks and mitigation challenges – Higgins & Harte (2012)

Abstract: “Projections of greenhouse gas concentrations over the 21st century generally rely on two optimistic, but questionable, assumptions about the carbon cycle: 1) that elevated atmospheric CO2 concentrations will enhance terrestrial carbon storage, and 2) that plant migration will be fast relative to climate changes. This paper demonstrates that carbon cycle uncertainty is considerably larger than currently recognized and that plausible carbon cycle responses could strongly amplify climate warming. This has important implications for societal decisions that relate to climate change risk management because it implies that a given level of human emissions could result in much larger climate changes than we now realize or that stabilizing atmospheric greenhouse gas concentrations at a “safe” level could require lower human emissions than currently understood. These results also suggest that terrestrial carbon cycle responses could be sufficiently strong to account for the changes in atmospheric carbon dioxide that occurred during transitions between ice age and interglacial periods.”

Citation: Paul A. T. Higgins and John Harte, Journal of Climate 2012, doi:

Let’s synchronise our ice cores

Volcanic synchronisation between the EPICA Dome C and Vostok ice cores (Antarctica) 0–145 kyr BP – Parrenin et al. (2012) [FULL TEXT]

Abstract: “This study aims at refining the synchronisation between the EPICA Dome C (EDC) and Vostok ice cores in the time interval 0–145 kyr BP by using the volcanic signatures. 102 common volcanic events were identified by using continuous electrical conductivity (ECM), di-electrical profiling (DEP) and sulfate measurements while trying to minimize the distortion of the glaciological chronologies. This is an update and a continuation of previous works performed over the 0–45 kyr interval that provided 56 tie points to the ice core chronologies (Udisti et al., 2004). This synchronisation will serve to establish Antarctic Ice Core Chronology 2012, the next synchronised Antarctic dating. A change of slope in the EDC-depth/Vostok-depth diagram is probably related to a change of accumulation regime as well as to a change of ice thickness upstream of the Lake Vostok, but we did not invoke any significant temporal change of surface accumulation at EDC relative to Vostok. No significant phase difference is detected between the EDC and Vostok isotopic records, but depth shifts between the Vostok 3G and 5G ice cores prevent from looking at this problem accurately. Three possible candidates for the Toba volcanic super-eruption ~73 kyr ago are suggested in the Vostok and EDC volcanic records. Neither the ECM, DEP nor the sulfate fingerprints for these 3 events are significantly larger than many others in the records.”

Citation: Parrenin, F., Petit, J.-R., Masson-Delmotte, V., Wolff, E., Basile-Doelsch, I., Jouzel, J., Lipenkov, V., Rasmussen, S. O., Schwander, J., Severi, M., Udisti, R., Veres, D., and Vinther, B. M.: Volcanic synchronisation between the EPICA Dome C and Vostok ice cores (Antarctica) 0–145 kyr BP, Clim. Past, 8, 1031-1045, doi:10.5194/cp-8-1031-2012, 2012.

Using satellites to measure surface air temperature

Estimating air surface temperature in Portugal using MODIS LST data – Benali et al. (2012)

Abstract: “Air surface temperature (Tair) is an important parameter for a wide range of applications such as vector-borne disease bionomics, hydrology and climate change studies. Air temperature data is usually obtained from measurements made in meteorological stations, providing only limited information about spatial patterns over wide areas. The use of remote sensing data can help overcome this problem, particularly in areas with low station density, having the potential to improve the estimation of Tair at both regional and global scales. Some studies have tried to derive maximum (Tmax), minimum (Tmin) and average air temperature (Tavg) using different methods, with variable estimation accuracy; errors generally fall in the 2–3 °C range while the level of precision generally considered as accurate is 1–2 °C. The main objective of this study was to accurately estimate Tmax, Tmin and Tavg for a 10 year period based on remote sensing—Land Surface Temperature (LST) data obtained from MODIS—and auxiliary data using a statistical approach. An optimization procedure with a mixed bootstrap and jackknife resampling was employed. The statistical models estimated Tavg with a MEF (Model Efficiency Index) of 0.941 and a RMSE of 1.33 °C. Regarding Tmax and Tmin, the best MEF achieved was 0.919 and 0.871, respectively, with a 1.83 and 1.74 °C RMSE. The developed datasets provided weekly 1 km estimations and accurately described both the intra and inter annual temporal and spatial patterns of Tair. Potential sources of uncertainty and error were also analyzed and identified. The most promising developments were proposed with the aim of developing accurate Tair estimations at a larger scale in the future.”

Citation: A. Benali, A.C. Carvalho, J.P. Nunes, N. Carvalhais, c, A. Santos, Remote Sensing of Environment, Volume 124, September 2012, Pages 108–121,

Highest summer temperatures in European Alps during 1053-1996 happened in the end of 20th century

Multi-archive summer temperature reconstruction for the European Alps, AD 1053–1996 – Trachsel et al. (2012)

Abstract: “We present a multi-archive, multi-proxy summer temperature reconstruction for the European Alps covering the period AD 1053–1996 using tree-ring and lake sediment data. The new reconstruction is based on nine different calibration approaches and errors were estimated conservatively. Summer temperatures of the last millennium are characterised by two warm (AD 1053–1171 and 1823–1996) and two cold phases (AD 1172–1379 and 1573–1822). Highest pre-industrial summer temperatures of the 12th century were 0.3 °C warmer than the 20th century mean but 0.35 °C colder than proxy derived temperatures at the end of the 20th century. The lowest temperatures at the end of the 16th century were ∼1 °C lower than the 20th century mean.”

Citation: Mathias Trachsel, Christian Kamenik, Martin Grosjean, Danny McCarroll, Anders Moberg, Rudolf Brázdil, Ulf Büntgen, Petr Dobrovolný, Jan Esper, David C. Frank, Michael Friedrich, Rüdiger Glaser, Isabelle Larocque-Tobler, Kurt Nicolussi, Dirk Riemann, Quaternary Science Reviews, Volume 46, 16 July 2012, Pages 66–79,

Atmospheric carbon dioxide concentration affects land water balance

Effects of increased CO2 on land water balance from 1850 to 1989 – Pern et al. (2012)

Abstract: “Numerous studies have shown that increased atmospheric CO2 concentration is one of the most important factors altering land water balance. In this study, we investigated the effects of increased CO2 on global land water balance using the dataset released by the Coupled Model Intercomparison Project Phase 5 derived from the Canadian Centre for Climate Modelling and Analysis second-generation Earth System Model. The results suggested that the radiative effect of CO2 was much greater than the physiological effect on the water balance. At the model experiment only integrating CO2 radiative effect, the precipitation, evapotranspiration (ET) and runoff had significantly increased by 0.37, 0.12 and 0.31 mm year−2, respectively. Increases of ET and runoff caused a significant decrease of soil water storage by 0.05 mm year−2. However, the results showed increases of runoff and decreases of precipitation and ET in response to the CO2 fertilisation effect, which resulted into a small, non-significant decrease in the land water budget. In the Northern Hemisphere, especially on the coasts of Greenland, Northern Asia and Alaska, there were obvious decreases of soil water responding to the CO2 radiative effect. This trend could result from increased ice–snow melting as a consequence of warmer surface temperature. Although the evidence suggested that variations in soil moisture and snow cover and vegetation feedback made an important contribution to the variations in the land water budget, the effect of other factors, such as aerosols, should not be ignored, implying that more efforts are needed to investigate the effects of these factors on the hydrological cycle and land water balance.”

Citation: Jing Peng, Wenjie Dong, Wenping Yuan, Jieming Chou and Yong Zhang, et al., Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0673-3.

Glaciers are melting away in Ammassalik region, southeast Greenland

Multi-decadal marine- and land-terminating glacier recession in the Ammassalik region, southeast Greenland – Mernild et al. (2012) [FULL TEXT]

Abstract: “Landsat imagery was applied to elucidate glacier fluctuations of land- and marine-terminating outlet glaciers from the Greenland Ice Sheet (GrIS) and local land-terminating glaciers and ice caps (GIC) peripheral to the GrIS in the Ammassalik region, Southeast Greenland, during the period 1972–2011. Data from 21 marine-terminating glaciers (including the glaciers Helheim, Midgaard, and Fenris), the GrIS land-terminating margin, and 35 GIC were examined and compared to observed atmospheric air temperatures, precipitation, and reconstructed ocean water temperatures (at 400 m depth in the Irminger Sea). Here, we document that net glacier recession has occurred since 1972 in the Ammassalik region for all glacier types and sizes, except for three GIC. The land-terminating GrIS and GIC reflect lower marginal and areal changes than the marine-terminating outlet glaciers. The mean annual land-terminating GrIS and GIC margin recessions were about three to five times lower than the GrIS marine-terminating recession. The marine-terminating outlet glaciers had an average net frontal retreat for 1999–2011 of 0.098 km yr−1, which was significantly higher than in previous sub-periods 1972–1986 and 1986–1999. For the marine-terminating GrIS, the annual areal recession rate has been decreasing since 1972, while increasing for the land-terminating GrIS since 1986. On average for all the observed GIC, a mean net frontal retreat for 1986–2011 of 0.010 ± 0.006 km yr−1 and a mean areal recession of around 1% per year occurred; overall for all observed GIC, a mean recession rate of 27 ± 24% occurred based on the 1986 GIC area. Since 1986, five GIC melted away in the Ammassalik area.”

Citation: Mernild, S. H., Malmros, J. K., Yde, J. C., and Knudsen, N. T.: Multi-decadal marine- and land-terminating glacier recession in the Ammassalik region, southeast Greenland, The Cryosphere, 6, 625-639, doi:10.5194/tc-6-625-2012, 2012.

Wind speed has been increasing in recent decades over Macquarie Island

Observed Trends in Wind Speed over the Southern Ocean – Hande et al. (2012)

Abstract: “Most studies of trends in regional climate focus on temperature, however for maritime environments in particular, changes in the wind are equally important. An analysis of trends in the wind over Macquarie Island is performed with a radio-sonde database spanning nearly four decades. The results indicate that the surface wind speed is increasing, with the trend for the upper levels being less well defined. The surface wind is highly correlated with the upper level winds, and the wind at all levels are moderately correlated with the Southern Annular Mode. ECMWF ERA-Interim reanalysis data shows significant trends in wind speed over several levels, however slightly smaller than trends in the soundings over a similar time period. The correlations in ERA-Interim are similar to those in the soundings. A clustering analysis of the wind reveals four distinct regimes, with a trend towards a regime characterised by strong north westerly winds.”

Citation: Hande, L. B., S. T. Siems, and M. J. Manton (2012), Observed Trends in Wind Speed over the Southern Ocean, Geophys. Res. Lett., 39, L11802, doi:10.1029/2012GL051734.

Analysis of Australian climate change scepticism

Climate change scepticism and public support for mitigation: Evidence from an Australian choice experiment – Akter et al. (2012)

Abstract: “Public scepticism surrounding climate change is an obstacle for implementing climate change mitigation measures in many countries. However, very little is known about: (1) the nature and sources of climate change scepticism; and (2) its influence on preferences for climate change mitigation policies. In this paper, we investigate these two issues using evidence and analysis from an Australian public survey and choice experiment. The study has three key findings. First, the intensity of scepticism varies depending on its type; we observed little scepticism over the cause, trend and impact of climate change and widespread scepticism over the effectiveness of mitigation measures and global co-operation. Second, cause and mitigation scepticism play significant roles in determining public support for climate change abatement. Respondents who believed in human-induced climate change were significantly more supportive of mitigation. Likewise, respondents who believed that mitigation would be successful in slowing down climate change were significantly more likely to be supportive. Third, the general public tend to give the benefit of the doubt to supporting mitigation. Those who expressed higher uncertainty about climate outcomes were more supportive of mitigation than others with similar expectations but lower uncertainty.”

Citation: Sonia Akter, Jeff Bennett, Michael B. Ward, Global Environmental Change,

Statisticians, mathematicians, and climate scientists discussed uncertainty quantifications in climate observations

Uncertainty Quantification for Climate Observations – Matthews et al. (2012) [FULL TEXT]

Abstract: “Approximately 60 statisticians, mathematicians, and climate scientists from academia and governmental institutions met in Asheville, NC, USA in January 2012 to discuss the issues surrounding uncertainty quantification in the context of climate observations. This workshop was an opportunity to engage with and understand the different concerns and perspectives from the largely academic mathematical and statistical communities and climate data product scientists and providers. Major outcomes of the workshop include the realization of interest in collaboration as well as identification of possible steps to work towards the mutual goal of robustly characterizing uncertainty in climate observation.”

Citation: Jessica L. Matthews, Elizabeth Mannshardt, Pierre Gremaud, Bulletin of the American Meteorological Society 2012, doi:

Allan Hills icefield in Antarctica has potential to extend ice core record beyond 800 000 years

Ice motion and mass balance at the Allan Hills blue-ice area, Antarctica, with implications for paleoclimate reconstructions – Spaulding et al. (2012)

Abstract: “We present a new surface-balance and ice-motion dataset derived from high-precision GPS measurements from a network of steel poles within three icefields of the Allan Hills blue-ice area, Antarctica. The surveys were conducted over a 14 year time period. Ice-flow velocities and mass-balance estimates for the main icefield (MIF) are consistent with those from pre-GPS era measurements but have much smaller uncertainties. The current study also extends these measurements through the near-western icefield (NWIF) to the eastern edge of the mid-western icefield (MWIF). The new dataset includes, for the first time, well-constrained evidence of upward motion within the Allan Hills MIF, indicating that old ice should be present at the surface. These data and terrestrial meteorite ages suggest that paleoclimate reconstructions using the surface record within the Allan Hills MIF could potentially extend the ice-core-based record beyond the 800 000 years currently available in the EPICA Dome C core.”

Citation: Spaulding, Nicole E.; Spikes, Vandy B.; Hamilton, Gordon S.; Mayewski, Paul A.; Dunbar, Nelia W.; Harvey, Ralph P.; Schutt, John; Kurbatov, Andrei V., Journal of Glaciology, Volume 58, Number 208, April 2012 , pp. 399-406(8), DOI:

Tropical land regions are projected to have more wet and dry months with global warming

Amplification of wet and dry month occurrence over tropical land regions in response to global warming – Lintner et al. (2012)

Abstract: “Quantifying how global warming impacts the spatiotemporal distribution of precipitation represents a key scientific challenge with profound implications for human systems. Utilizing monthly precipitation data from Coupled Model Intercomparison Project (CMIP3) climate change simulations, the results here show that the occurrence of very dry (10 mm/day) months comprises a straightforward, robust metric of anthropogenic warming on tropical land region rainfall. In particular, differencing tropicswide precipitation frequency histograms for 25-year periods over the late 21st and 20th centuries shows increased late-21st-century occurrence of both histogram extremes in the model ensemble and across individual models. Mechanistically, such differences are consistent with the view of enhanced tropical precipitation spatial gradients. Similar diagnostics are calculated for two 15-year subperiods over 1979-2008 for the CMIP3 models and three observational precipitation products to assess whether the signature of late-21st-century warming has already emerged in response to recent warming. While both the observations and CMIP3 ensemble-mean hint at similar amplification in the warmer (1994-2008) subinterval, the changes are not robust, as substantial differences are evident among the observational products and the intraensemble spread is large. Comparing histograms computed from the warmest and coolest years of the observational period further demonstrates effects of internal variability, notably the El Niño/Southern Oscillation, which appear to oppose the impact quasi-uniform anthropogenic warming on the wet tail of the monthly precipitation distribution. These results identify the increase of very dry and wet occurrences in monthly precipitation as a potential signature of anthropogenic global warming but also highlight the continuing dominance of internal climate variability on even bulk measures of tropical rainfall.”

Citation: Lintner, B., M. Biasutti, N. S. Diffenbaugh, J.-E. Lee, M. J. Niznik, and K. L. Findell (2012), Amplification of wet and dry month occurrence over tropical land regions in response to global warming, J. Geophys. Res., doi:10.1029/2012JD017499.

Atmospheric methane concentration is increasing again

Renewed methane increase for five years (2007–2011) observed by solar FTIR spectrometry – Sussmann et al. (2012) [FULL TEXT]

Abstract: “Trends of column-averaged methane for the time period (1996, Sep 2011) are derived from the mid-infrared (mid-IR) solar FTIR time series at the Zugspitze (47.42° N, 10.98° E, 2964 m a.s.l.) and Garmisch (47.48° N, 11.06° E, 743 m a.s.l.). Trend analysis comprises a fit to the de-seasonalized time series along with bootstrap resampling for quantifying trend uncertainties. We find a positive trend during [1996, 1998] of 9.0 [3.2, 14.7] ppb yr−1 for Zugspitze (95% confidence interval), an insignificant growth during [1999, mid 2006] of 0.8 [−0.1, 1.7] ppb yr−1 (Zugspitze), and a significant renewed increase during [mid 2006, Sep 2011] of 5.1 [4.2, 6.0] ppb yr−1 for Garmisch, which is in agreement with 4.8 [3.8, 5.9] ppb yr−1 for Zugspitze. The agreement of methane trends at the two closely neighboring FTIR sites Zugspitze and Garmisch within the uncertainties indicates a good station-to-station consistency as a basis for future trend analyses by the ground-based mid-IR FTIR network on the global scale. Furthermore, the Zugspitze FTIR trend for the time interval [Jul 2006, Jun 2009] is found to agree with the trend derived from SCIAMACHY (WFM-DOAS v2.0.2) data within the 95% confidence intervals. In case a 1000-km pixel selection radius around the Zugspitze is used, the confidence interval is narrower for the FTIR trend (6.9 [4.2, 9.5] ppb yr−1) compared to SCIAMACHY (7.1 [5.1, 8.6] ppb yr−1). If, however, a loosened pixel selection is used (≈1000-km half-width latitudinal band), the SCIAMACHY trend significance interval is narrower (6.8 [5.1, 8.6] ppb yr−1) compared to Zugspitze FTIR (5.7 [3.0, 8.3] ppb yr−1). While earlier studies using surface network data revealed changes of 8.0 ± 0.6 ppb in 2007, 6.4 ± 0.6 ppb in 2008, and 4.7 ± 0.6 ppb in 2009 (Dlugokencky et al., 2011), our updated result proves that the renewed methane increase meanwhile has been persisting for >5 years [mid 2006, Sep 2011]. This is either the longest and largest positive trend anomaly since the beginning of systematic observations more than 25 years ago or the onset of a new period of strongly increasing CH4 levels in the atmosphere. Several scenarios have been developed to explain the persistent increase observed, mainly invoking an increase in emissions from natural wetlands, an increase in fossil fuel-related emissions or a decrease in OH concentrations. However, more work is needed to fully attribute this increase to a particular source or sink.”

Citation: Mark Sussmann, R., Forster, F., Rettinger, M., and Bousquet, P.: Renewed methane increase for five years (2007–2011) observed by solar FTIR spectrometry, Atmos. Chem. Phys., 12, 4885-4891, doi:10.5194/acp-12-4885-2012, 2012.

River flows and rainfall have increased in sub-Saharan Africa

A return to wet conditions over Africa: 1995–2010 – Jury (2012)

Abstract: “Climatic trends over sub-Saharan Africa are described using major river flows, European Community Medium-Range Weather Forecasts, Coupled Forecast System, global land surface data assimilation and National Center for Environmental Prediction reanalysis, Global Precipitation Climate Center gauge data, and satellite observations in the period 1995–2010. The Niger and Zambezi rivers reached flow levels last seen in the 1950s (2,000 and 5,000 m3 s−1, respectively), and rainfall across the Congo Basin increased steadily ~+0.16 mm day−1 year−1. Weather events that contributed to flooding are studied and include the Zambezi tropical trough of 4 January 2008 and the Sahelian easterly wave of 19 July 2010. Diurnal summer rainfall increased threefold over the 1995–2010 period in conjunction with a strengthened land–sea temperature contrast, onshore flow, and afternoon uplift. 700 mb zonal winds over East Africa became easterly after 2001, so clean Indian Ocean air was entrained to the Congo, improving convective efficiency. Relationships between the African monsoon circulation and global teleconnections are explored. Zonal wind convergence around the Congo appears related with the tropical multi-decadal oscillation and signals in the Atlantic during the study period.”

Citation: Mark R. Jury, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0677-z.

CLASSIC OF THE WEEK: Huntington (1913)

Changes of Climate and History – Huntington (1913) [FULL TEXT]

Abstract: No abstract.

Citation: Ellsworth Huntington, The American Historical Review , Vol. 18, No. 2 (Jan., 1913), pp. 213-232.

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

Posted in Climate science | Leave a Comment »

New research from last week 22/2012

Posted by Ari Jokimäki on June 4, 2012

This week we have really cool collection of new papers. We have special section for papers on Greenland ice sheet – past, present, and future. Another special section deals with Arctic affairs – cryosphere, atmosphere, and biosphere. We also have other papers on diverse subjects, such as biomass burning, ENSO, Italian newspapers, Great Cormorants, black carbon, and diurnal temperature range.

GREENLAND ICE SHEET, THE PAST: What Greenland ice sheet melting did to North Atlantic climate during Last Interglacial?

Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial – Bakker et al. (2012) [FULL TEXT]

Abstract: “During the Last Interglacial (LIG; ~130 000 yr BP), part of the Greenland Ice Sheet (GIS) melted due to a warmer than present-day climate. However, the impact of this melting on the LIG climate in the North Atlantic region is relatively unknown. Using the LOVECLIM Earth system model of intermediate complexity, we have systematically tested the sensitivity of the LIG climate to increased freshwater runoff from the GIS. In addition, experiments have been performed to investigate the impact of an idealized reduction of both surface elevation and extent of the GIS on the LIG climate. Based on changes in the maximum sea-ice cover and the strength of the overturning circulation, three regimes have been identified, which are characterized by a specific pattern of surface temperature change in the North Atlantic region. By comparing the simulated deep ocean circulation with proxy-based reconstructions, the most realistic simulated climate could be discerned. The resulting climate is characterized by a shutdown of deep convection and a subsequent ~4 °C cooling in the Labrador Sea. Furthermore, a cooling of ~1 °C over the North Atlantic Ocean between 40° N and 70° N is seen. The prescribed reduction in surface elevation and extent of the GIS results in a local warming of up to 4 °C and amplifies the freshwater-forced reduction in deep convection and the resultant cooling in the Nordic Seas. A further comparison of simulated summer temperatures with both continental and oceanic proxy records reveals that the partial melting of the GIS during the LIG could have delayed maximum summer temperatures in the western part of the North Atlantic region relative to the insolation maximum.”

Citation: Bakker, P., Van Meerbeeck, C. J., and Renssen, H.: Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial, Clim. Past, 8, 995-1009, doi:10.5194/cp-8-995-2012, 2012.

GREENLAND ICE SHEET, THE PRESENT: Watching that Greenland ice flow

Ice flow in Greenland for the International Polar Year 2008–2009 – Rignot & Mouginot (2012)

Abstract: “A digital representation of ice surface velocity is essential for a variety of glaciological, geologic and geophysical analyses and modeling. Here, we present a new, reference, comprehensive, high-resolution, digital mosaic of ice motion in Greenland assembled from satellite radar interferometry data acquired during the International Polar Year 2008 to 2009 by the Envisat Advanced Synthetic-Aperture Radar (ASAR), the Advanced Land Observation System (ALOS)’s Phase-Array L-band SAR (PALSAR) and the RADARSAT-1 SAR that covers 99% of the ice sheet in area. The best mapping performance is obtained using ALOS PALSAR data due to higher levels of temporal coherence at the L-band frequency; but C-band frequency SAR data are less affected by the ionosphere. The ice motion map reveals various flow regimes, ranging from patterned enhanced flow into a few large glaciers in the cold, low precipitation areas of north Greenland; to diffuse, enhanced flow into numerous, narrow, fast-moving glaciers in the warmer, high precipitation sectors of northwest and southeast Greenland. We find that the 100 fastest glaciers (v > 800 m/yr) drain 66% of the ice sheet in area, marine-terminating glaciers drain 88% of Greenland, and basal-sliding motion dominates internal deformation over more than 50% of the ice sheet. This view of ice sheet motion provides significant new constraints on ice flow modeling.”

Citation: Rignot, E. and J. Mouginot (2012), Ice flow in Greenland for the International Polar Year 2008–2009, Geophys. Res. Lett., 39, L11501, doi:10.1029/2012GL051634.

GREENLAND ICE SHEET, THE FUTURE: Uncertainties in projecting Greenland ice sheet future melting

An assessment of key model parametric uncertainties in projections of Greenland Ice Sheet behavior – Applegate et al. (2012) [FULL TEXT]

Abstract: “Lack of knowledge about the values of ice sheet model input parameters introduces substantial uncertainty into projections of Greenland Ice Sheet contributions to future sea level rise. Computer models of ice sheet behavior provide one of several means of estimating future sea level rise due to mass loss from ice sheets. Such models have many input parameters whose values are not well known. Recent studies have investigated the effects of these parameters on model output, but the range of potential future sea level increases due to model parametric uncertainty has not been characterized. Here, we demonstrate that this range is large, using a 100-member perturbed-physics ensemble with the SICOPOLIS ice sheet model. Each model run is spun up over 125 000 yr using geological forcings and subsequently driven into the future using an asymptotically increasing air temperature anomaly curve. All modeled ice sheets lose mass after 2005 AD. Parameters controlling surface melt dominate the model response to temperature change. After culling the ensemble to include only members that give reasonable ice volumes in 2005 AD, the range of projected sea level rise values in 2100 AD is ~40 % or more of the median. Data on past ice sheet behavior can help reduce this uncertainty, but none of our ensemble members produces a reasonable ice volume change during the mid-Holocene, relative to the present. This problem suggests that the model’s exponential relation between temperature and precipitation does not hold during the Holocene, or that the central-Greenland temperature forcing curve used to drive the model is not representative of conditions around the ice margin at this time (among other possibilities). Our simulations also lack certain observed physical processes that may tend to enhance the real ice sheet’s response. Regardless, this work has implications for other studies that use ice sheet models to project or hindcast the behavior of the Greenland Ice Sheet.”

Citation: Applegate, P. J., Kirchner, N., Stone, E. J., Keller, K., and Greve, R.: An assessment of key model parametric uncertainties in projections of Greenland Ice Sheet behavior, The Cryosphere, 6, 589-606, doi:10.5194/tc-6-589-2012, 2012.

Changes in diurnal temperature range in United States since 1901

U.S. Diurnal Temperature Range Variability and Regional Causal Mechanisms, 1901-2002 – Lauritsen & Rogers (2012)

Abstract: “Long-term (1901-2002) diurnal air temperature range data (DTR) are evaluated to examine its spatial and temporal variability across the United States, the early-century origin of the DTR declines, and the relative regional contributions to DTR variability among cloud cover, precipitation, soil moisture and atmosphere/ocean teleconnections. Rotated principal component analysis (RPCA) of the Climate Research Unit (CRU) TS 2.1 dataset identifies 5 regions of unique spatial U.S. DTR variability. RPCA creates regional orthogonal indices of cloud cover, soil moisture, precipitation and the teleconnections used subsequently in stepwise multiple linear regression to examine their regional impact on DTR, maximum (Tmax), and minimum (Tmin) temperatures. The southwestern U.S. has the smallest DTR and cloud cover trends as both Tmax and Tmin increase over the century. Tmin increases are the primary influence on DTR trend in other regions except in the south central U.S. where downward Tmax trend largely affects its DTR decline. Tmax and DTR tend to both exhibit simultaneous decadal variations during unusually wet and dry periods in response to cloud cover, soil moisture, and precipitation variability. The widely-reported post-1950 DTR decline began regionally at various times ranging from around 1910 to the 1950s. Cloud cover alone accounts for up to 63.2% of regional annual DTR variability, with cloud cover trends driving DTR in northern states. Cloud cover, soil moisture, precipitation, and atmospheric/oceanic teleconnection indices account for up to 80.0% of regional variance over 1901-2002 (75.4% in detrended data) although the latter only account for small portions of this variability.”

Citation: Ryan G. Lauritsen and Jeffrey C. Rogers, Journal of Climate 2012, doi:

The increase of anthropogenic black carbon emissions in China since 1980

Spatial and temporal variation of anthropogenic black carbon emissions in China for the period 1980–2009 – Qin & Xie (2012) [FULL TEXT]

Abstract: “Multi-year inventories of anthropogenic black carbon emissions, including both fuel consumption and biomass open burning, at a high spatial resolution of 0.25°×0.25° have been constructed in China using GIS methodology for the period 1980–2009, based on official statistical data and time-varying emission factors. Results show that black carbon emissions increased from 0.87 Tg in 1980 to 1.88 Tg in 2009 with a peak in about 1995, and had been continually increasing in the first decade of the 21 century. Residential contribution to the total BC emissions declined from 82.03% in 1980 to 42.33% in 2009 at a continuous diminishing trend, but had always been the dominant contributor in China. While contributions from industry and transportation sectors had increased notably. BC emissions were mainly concentrated in the central eastern districts, the three northeastern provinces and the Sichuan Basin, covering 22.30% of China’s territory, but were responsible for 43.02%, 50.47%, 50.69% and 54.30% of the national black carbon emissions in 1985, 1995, 2005 and 2009, respectively. Besides, China made up 70%–85% of BC emissions in East Asia, half of the emissions in Asia, and accounted for averagely 18.97% of the global BC emissions during the estimation period.”

Citation: Qin, Y. and Xie, S. D.: Spatial and temporal variation of anthropogenic black carbon emissions in China for the period 1980–2009, Atmos. Chem. Phys., 12, 4825-4841, doi:10.5194/acp-12-4825-2012, 2012.

Colony of Great Cormorants emits nitrous oxide

The Great Cormorant (Phalacrocorax carbo) colony as a “hot spot” of nitrous oxide (N2O) emission in central Japan – Mizota et al. (2012)

Abstract: “Unusual high soil fluxes up to ca. 500 mg N2O m−2 h−1 emission were associated with a continued breeding/roosting colony of Great Cormorant in central Japan. This flux is nearly two-orders of magnitude higher than those hitherto documented. The flux was markedly dependent upon the soil surface temperature, i.e., higher in April–October during the prevailing high air temperatures, as compared with November to March. Integrated input of fecal N at rearing and fledging stages of chicks followed by coupled mineralization, nitrification and subsequently denitrification processes under humid and temperate regimes is responsible for such an unusual flux. The Great Cormorant colony serves as a “hot spot” of N2O emission of natural origin.”

Citation: Chitoshi Mizota, Kosuke Noborio, Yoshiaki Mori, Atmospheric Environment, Volume 57, September 2012, Pages 29–34,

Study reveals the climate change agendas of Italian newspapers

How do the media affect public perception of climate change and geohazards? An Italian case study – Pasquaré & Oppizzi (2012)

Abstract: “This paper uses a combination of a qualitative approach and a quantitative, software-based approach to explore the Italian print media construction of climate change and geohazards between 2007 and 2010. We have broken down our analysis in two sections: the first one deals with the coverage of climate change; the second one focuses on the media representation of hydrogeological hazards and extreme events in Italy. Our software-based, qualitative and quantitative analysis of 1253 storylines from two major Italian broadsheets (the La Repubblica and the Corriere della Sera) has enabled us to assess the presence of typical journalistic frames such as conflict and dramatization, as well as newly-introduced ones such as “prevention vs damages”, and “weather vs climate”. Our results show that the two newspapers appear to have different “agendas” that might have different impacts on their own readerships: the La Repubblica has been on the forefront of forging a broad public consensus on the need for actions aimed at tackling climate change, whereas the Corriere della Sera has gradually built a journalistic agenda aimed at minimizing the urgency of the climate change problem. As regards the media’s representation of hydrogeological hazards, we have confirmed what assessed by previous research, i.e. that Italian journalists still prefer to focus on damages rather than prevention; on a better note, the tendency of the Italian press to confuse weather with climate, blaming climate change for extreme rainfalls causing landslides and floods, has decreased in the last four years.”

Citation: Federico A. Pasquaré, Paolo Oppizzi, Global and Planetary Change, Volumes 90–91, June 2012, Pages 152–157,

ENSO makes it difficult to detect anthropogenic trend in eastern Tropical Pacific

The Effect of ENSO Events on the Tropical Pacific Mean Climate: Insights from an Analytical Model – Liang et al. (2012)

Abstract: “To better understand the causes of climate change in the tropical Pacific on the decadal and longer time scales, we delineate the rectification effect of ENSO events into the mean state by contrasting the time-mean state of a low-order model for the Pacific with its equilibrium state. The model encapsulates the essential physics of the ENSO system, but remains simple enough to allow us to obtain its equilibrium state. The model has an oscillatory regime that resembles the observations. In this oscillatory regime, the time-mean SST in the eastern equatorial Pacific is found to be significantly different from the corresponding equilibrium SST, with the former being warmer than the latter. The difference is found to be proportional to the amplitude of ENSO. In addition, the zonal SST contrast of the time-mean state is found to be less sensitive to increases in external forcing than that of the equilibrium state, due to warming effect of ENSO events on the eastern Pacific. It is further shown this rectification effect of ENSO events owns to the nonlinear advection term in the heat budget equation. The study elucidates the role of ENSO events in shaping the tropical mean climate state and suggests that decadal warming in the recent decades in the eastern tropical Pacific may be more a consequence than a cause of the elevated ENSO activity during the same period. The results also provide a simple explanation for why it is difficult to detect an anthropogenically forced trend in the zonal SST contrast in the observations.”

Citation: Jin Liang, Xiu-Qun Yang, and De-Zheng Sun, Journal of Climate 2012, doi:

Anthropogenic activities have altered natural trends in biomass burning from about 5500 years ago

Trends in biomass burning in the Carpathian region over the last 15,000 years – Feurdean et al. (2012)

Abstract: “Fire is recognized as a critical process with significant impacts on biota and the atmosphere. In this study, 11 micro- and macrocharcoal sedimentary records extracted from peat bogs and lakes at different elevations in the Carpathian region (in Hungary and Romania) were used to explore the patterns and the potential underlying mechanisms in biomass burning in this region during the last 15,000 years. Results from micro-charcoal and macro-charcoal data show similar trends in biomass burning and suggest that the major signal of both charcoal size-fragments relates mainly to local fires. Fire activity was low during the lateglacial, attained maximum values in the early Holocene (11,700–8000 cal. yr BP), become lower than present during the mid-late Holocene (8000–1000 cal yr BP), and increased again over the last 1000 years. The reconstructed spatial trends in biomass burning display different degrees of heterogeneity through time. Generally, there was more spatial similarity in fire activity across the study region during the lateglacial and early Holocene (15,000–8000 cal yr BP), followed by increased spatial heterogeneity from ca 8000 cal yr BP onwards. Biomass burning appears to have been primarily modulated by climate during both the lateglacial and Holocene, through its effect on vegetation productivity and therefore fuel availability (lateglacial), and fuel structure, moisture and flammability (the Holocene). Onsite human activities are likely to have provided an extra ignition source already in the early Holocene. However, evidence suggest that anthropogenic activities have markedly altered the natural trends in biomass burning from about 5500 yr BP (lowlands) and over the last 2000-1000 years (in the mountain environments), by either removing the biomass (in the lowlands) or igniting fire where it seldom occurs naturally (i.e., in the mountain environments). On the other hand, burning activity also appears coincident with significant changes in tree species compositions, indicating that fire has likely acted as a driving factor in forest dynamics. Results also suggest that peat deposits provide a more localized fire record than lakes, and that trends and patterns of change can be different even for sites situated close to each other.”

Citation: Angelica Feurdeana, Allan Spessa, Enikö K. Magyari, Katherine J. Willis, Daniel Veres, Thomas Hickler, Quaternary Science Reviews, Volume 45, 29 June 2012, Pages 111–125.

ARCTIC AFFAIRS, CRYOSPHERE: How long has mountain permafrost existed continuously in Norway?

The relative age of mountain permafrost – estimation of Holocene permafrost limits in Norway – Lilleøren et al. (2012)

Abstract: “For Scandinavia in general and Norway in particular the regional distribution of mountain permafrost is reasonably well known, both through ground temperature measurements in boreholes, geophysical soundings and spatial modeling. However, the evolution of permafrost over longer time periods, such as the Holocene, is unknown, but is considered to have significance for landscape development and geomorphological processes in high mountain areas of Scandinavia. In this study two mean annual air temperature series covering the Holocene have been compiled to drive a 1D heat flow model over a 10 kyr period for several sites in Norway. At each site temperature-monitored boreholes exist, which were used to calibrate the model. In addition the spatial distribution of permafrost during selected time periods of the Holocene was addressed using a newly implemented version of an equilibrium permafrost model. The result of this study indicates an altitudinal zonation of relative permafrost age in Norway. We find that permafrost has existed continuously since the deglaciation at the highest altitudes, whereas in large areas where permafrost currently is present, it degraded during the Holocene thermal maximum (HTM). In all boreholes the coldest simulated permafrost occurred during the ‘Little Ice Age’ (LIA), and also the largest areal distribution of Holocene permafrost in Norway seems to be connected to the LIA.”

Citation: Karianne S. Lilleøren, Bernd Etzelmüller, Kjersti Gisnås, Thomas V. Schuler, Ole Humlum, Global and Planetary Change,

ARCTIC AFFAIRS, CRYOSPHERE & ATMOSPHERE: Arctic sea ice retreats, clouds go higher

The Impact of Arctic sea-ice retreat on the recent change in cloud-base height during autumn – Sato et al. (2012)

Abstract: “Cloud-base observations over the ice-free Chukchi and Beaufort Seas in autumn were conducted using a shipboard ceilometer and radiosondes during the 1999–2010 cruises of the Japanese R/V Mirai. In comparison with cloud-base heights in an ice-covered case (the Surface Heat Budget of the Arctic Ocean project in 1998), our ice-free results showed a 30% decrease (increase) in the frequency of low clouds with a ceiling below (above) 500 m. Temperature profiles revealed that the boundary layer was well developed over the ice-free ocean in the 2000s, whereas a stable layer dominated during the ice-covered period in 1998. The change in surface boundary conditions likely resulted in the difference in cloud-base height, although it had little impact on air temperatures in the mid- and upper troposphere. Data from the 2010 R/V Mirai cruise were investigated in detail in terms of air-sea temperature difference. Stratus clouds near the sea surface were predominant under a warm advection situation, whereas stratocumulus clouds with a cloud-free layer were significant under a cold advection situation. The threshold temperature difference between sea surface and air temperatures for distinguishing the dominant cloud types was 3 K. Anomalous upward turbulent heat fluxes associated with the sea-ice retreat have likely contributed to warming of the lower troposphere.”

Citation: Sato, K., J. Inoue, Y.-M. Kodama, and J. E. Overland (2012), Impact of Arctic sea-ice retreat on the recent change in cloud-base height during autumn, Geophys. Res. Lett., 39, L10503, doi:10.1029/2012GL051850.

ARCTIC AFFAIRS, ATMOSPHERE: Factors contributing to Arctic warming

Local and remote controls on observed Arctic warming – Screen et al. (2012)

Abstract: “The Arctic is warming two to four times faster than the global average. Debate continues on the relative roles of local factors, such as sea ice reductions, versus remote factors in driving, or amplifying, Arctic warming. This study examines the vertical profile and seasonality of observed tropospheric warming, and addresses its causes using atmospheric general circulation model simulations. The simulations enable the isolation and quantification of the role of three controlling factors of Arctic warming: 1) observed Arctic sea ice concentration (SIC) and sea surface temperature (SST) changes; 2) observed remote SST changes; and 3) direct radiative forcing (DRF) due to observed changes in greenhouse gases, ozone, aerosols, and solar output. Local SIC and SST changes explain a large portion of the observed Arctic near-surface warming, whereas remote SST changes explain the majority of observed warming aloft. DRF has primarily contributed to Arctic tropospheric warming in summer.”

Citation: Screen, J. A., C. Deser, and I. Simmonds (2012), Local and remote controls on observed Arctic warming, Geophys. Res. Lett., 39, L10709, doi:10.1029/2012GL051598.

ARCTIC AFFAIRS, BIOSPHERE: Review of evidence on climate and sea ice effects to polar bears

Effects of Climate Warming on Polar Bears: A Review of the Evidence – Stirling & Derocher (2012)

Abstract: “Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival. To maintain viable subpopulations, polar bears depend upon sea ice as a platform from which to hunt seals for long enough each year to accumulate sufficient energy (fat) to survive periods when seals are unavailable. Less time to access to prey, because of progressively earlier breakup in spring, when newly-weaned ringed seal (Pusa hispida) young are available, results in longer periods of fasting, lower body condition, decreased access to denning areas, fewer and smaller cubs, lower survival of cubs as well as bears of other age classes and, finally, subpopulation decline toward eventual extirpation. The chronology of climate-driven changes will vary between subpopulations, with quantifiable negative effects being documented first in the more southerly subpopulations, such as those in Hudson Bay or the southern Beaufort Sea. As the bears’ body condition declines, more seek alternate food resources so the frequency of conflicts between bears and humans increases. In the most northerly areas, thick multiyear ice, through which little light penetrates to stimulate biological growth on the underside, will be replaced by annual ice which facilitates greater productivity and may create habitat more favorable to polar bears over continental shelf areas in the short term. If the climate continues to warm and eliminate sea ice as predicted, polar bears will largely disappear from the southern portions of their range by mid-century. They may persist in the northern Canadian Arctic Islands and northern Greenland for the foreseeable future, but their long-term viability, with a much reduced global population size in a remnant of their former range, is uncertain.”

Citation: Ian Stirling, Andrew E. Derocher, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02753.x.

CLASSIC OF THE WEEK: Barrell (1908)

Relations between Climate and Terrestrial Deposits – Barrell (1908) [FULL TEXT]

Abstract: No abstract.

Citation: Joseph Barrell, The Journal of Geology, Vol. 16, No. 2 (Feb. – Mar., 1908) (pp. 159-190).

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