AGW Observer

Observations of anthropogenic global warming

New research from last week 33/2012

Posted by Ari Jokimäki on August 20, 2012

What happens when we dump greenhouse gases to atmosphere? Temperature rises, there will be more heat waves, ice and snow melts, sea level rises, there are changes in clouds and other climate feedbacks such as methane bursting out from ocean sediments, forest fire frequency changes, hydrological cycle changes, biosphere reacts, and economy is affected. Below you will find new research on each of these subjects.


Arctic sea ice loss has created negative NAO-like conditions to atmospheric circulation

The atmospheric response to three decades of observed Arctic sea ice loss – Screen et al. (2012)

Abstract: “Arctic sea ice is declining at an increasing rate with potentially important repercussions. In order to understand better the atmospheric changes that may have occurred in response to Arctic sea ice loss, we present results from atmospheric general circulation model (AGCM) experiments in which the only time-varying forcings prescribed were observed variations in Arctic sea ice and accompanying changes in Arctic sea surface temperatures from 1979 to 2009. We utilize two independent AGCMs in order to assess the robustness of the response across different models. The results suggest that the atmospheric impacts of Arctic sea ice loss have been manifest most strongly within the maritime and coastal Arctic, and in the lowermost atmosphere. Sea ice loss has driven increased energy transfer from the ocean to the atmosphere, enhanced warming and moistening of the lower troposphere, has decreased the strength of the surface inversion, and increased lower-tropospheric thickness; all these changes are most pronounced in autumn and early winter (September-December). The early winter (November-December) atmospheric circulation response resembles the negative phase of the North Atlantic Oscillation (NAO); however, the NAO-type response is quite weak and is often masked by intrinsic (unforced) atmospheric variability. We also find some evidence of a late winter (March-April) polar stratospheric cooling response to sea ice loss, which may have important implications for polar stratospheric ozone concentrations. The attribution and quantification of other aspects of the possible atmospheric response are hindered by model sensitivities and large intrinsic variability. The potential remote responses to Arctic sea ice change are currently hard to confirm and remain uncertain.”

Citation: James A. Screen and Ian Simmonds, Clara Deser and Robert Tomas, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00063.1.


Small decline in total cloud cover over land areas since 1971

A 39-Year Survey of Cloud Changes from Land Stations Worldwide 1971-2009: Long-Term Trends, Relation to Aerosols, and Expansion of the Tropical Belt – Eastman & Warren (2012) [FULL TEXT]

Abstract: “An archive of land-based, surface-observed cloud reports has been updated and now spans 39 years from 1971 through 2009. Cloud-type information at weather stations is available in individual reports or in long-term, seasonal, and monthly averages. A shift to a new data source and the automation of cloud reporting in some countries has reduced the number of available stations; however this dataset still represents most of the global land area. Global average trends of cloud cover suggest a small decline in total cloud cover, on the order of 0.4% per decade. Declining clouds in middle latitudes at high and middle levels appear responsible for this trend. An analysis of zonal cloud cover changes suggests poleward shifts of the jet streams in both hemispheres. The observed displacement agrees with other studies. Changes seen in cloud types associated with the Indian monsoon are consistent with previous work suggesting that increased pollution (black carbon) may be affecting monsoonal precipitation, causing drought in North India. A similar analysis over northern China does not show an obvious aerosol connection. Past reports claiming a shift from stratiform to cumuliform cloud types over Russia were apparently partially based on spurious data. When the faulty stations are removed, a tradeoff of stratiform and cumuliform cloud cover is still observed, but muted, over much of northern Eurasia.”

Citation: Ryan Eastman and Stephen G. Warren, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00280.1.


Sea level is predicted to rise at least 80cm by 2100 and continues to rise at least next 200 years

Lower bounds to future sea-level rise – Zecca & Chiari (2012)

Abstract: “Sea-level rise is among the most important changes expected as a consequence of anthropogenic global warming. Climate model-based projections made until the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) yield a 21st century rise spanning nearly 20–60 cm. However, it is known that current climate models are likely to underestimate sea-level change in response to rapid climatic variations. Recent alternative semi-empirical approaches predict a much higher sea-level rise than the IPCC AR4 projections. Nevertheless, the underway depletion of conventional fossil fuels might, at least in principle, constrain future fossil CO2 emissions and, in turn, affect also the extent of sea-level rise. Here we project 2000–2200 sea-level rise with a semi-empirical method coupled to a simple climate model that is run under a range of fossil-fuel exhaustion scenarios. We find that, in spite of fossil-fuel depletion, sea level is predicted to rise by at least ~ 80 cm at the end of this century and is expected to continue rising for at least the next two hundred years. The present results support the need for prompt and substantial emission cuts in order to slow down future sea-level rise and implement adaptation measures.”

Citation: Antonio Zecca, Luca Chiari, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.08.002.


Ocean circulation promotes methane release from gas hydrate outcrops

Ocean circulation promotes methane release from gas hydrate outcrops at the NEPTUNE Canada Barkley Canyon node – Thomsen et al. (2012)

Abstract: “The NEPTUNE Canada cabled observatory network enables non-destructive, controlled experiments and time-series observations with mobile robots on gas hydrates and benthic community structure on a small plateau of about 1 km2 at a water depth of 870 m in Barkley Canyon, about 100 km offshore Vancouver Island, British Columbia. A mobile Internet operated vehicle was used as an instrument platform to monitor and study up to 2000 m2 of sediment surface in real-time. In 2010 the first mission of the robot was to investigate the importance of oscillatory deep ocean currents on methane release at continental margins. Previously, other experimental studies have indicated that methane release from gas hydrate outcrops is diffusion-controlled and should be much higher than seepage from buried hydrate in semipermeable sediments. Our results show that periods of enhanced bottom currents associated with diurnal shelf waves, internal semidiurnal tides, and also wind-generated near-inertial motions can modulate methane seepage. Flow dependent destruction of gas hydrates within the hydrate stability field is possible from enhanced bottom currents when hydrates are not covered by either seafloor biota or sediments. The calculated seepage varied between 40–400 μmol CH4 m−2 s−1. This is 1–3 orders of magnitude higher than dissolution rates of buried hydrates through permeable sediments and well within the experimentally derived range for exposed gas hydrates under different hydrodynamic boundary conditions. We conclude that submarine canyons which display high hydrodynamic activity can become key areas of enhanced seepage as a result of emerging weather patterns due to climate change.”

Citation: Thomsen, L., C. Barnes, M. Best, R. Chapman, B. Pirenne, R. Thomson, and J. Vogt (2012), Ocean circulation promotes methane release from gas hydrate outcrops at the NEPTUNE Canada Barkley Canyon node, Geophys. Res. Lett., 39, L16605, doi:10.1029/2012GL052462.


Climate in Romania has become warmer during the last decades

Changes in daily extreme temperatures in the extra-Carpathians regions of Romania – Croitoru & Piticar (2012)

Abstract: “Changes in daily extreme temperatures have been identified in many studies conducted at local, regional or global scales. For Romanian territory, only little research on this issue was done. In this article, the extra-Carpathians regions of Romania located southward and eastward from the Carpathians Chain were considered. This study is focused on analyzing daily extreme temperature trends at a regional scale (eastern, southern and southeastern regions of Romania) across 50 years (1961–2010). Data sets of daily minimum and maximum temperature recorded in 14 weather stations were analyzed. The main goal was to find changes in extreme daily temperatures using a set of 20 indices adopted from the core indices developed by ETCCDMI with appropriate modifications to suit to the analyzed territory. The main results suggest that regional temperature trends at the scale of extra-Carpathians areas of Romania are similar to those calculated for global and European continental scales; the climate has become warmer during the last decades. It has been identified that both extreme daily maximum and minimum temperatures have increased in the analyzed areas. For all the indices related to hot temperature most trends are significantly positive. The strongest increase was detected for hot related extremes such as summer days and tropical nights as well as for maximum values of maximum and minimum daily temperatures. For indices related to cold there are different sign slopes, but negative slopes prevail, especially for number of days under a defined threshold. This is also an evidence of the important warming in the area. Generally, it was found that the daily maximum temperature is getting more extreme, whereas the minimum is getting less extreme.”

Citation: Adina-Eliza Croitoru, Adrian Piticar, International Journal of Climatology, DOI: 10.1002/joc.3567.


Antarctic sea ice variability and trends, 1979–2010

Antarctic sea ice variability and trends, 1979–2010 – Parkinson & Cavalieri (2012) [FULL TEXT]

Abstract: “In sharp contrast to the decreasing sea ice coverage of the Arctic, in the Antarctic the sea ice cover has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978–December 2010 reveal an overall positive trend in ice extents of 17 100 ± 2300 km2 yr−1. Much of the increase, at 13 700 ± 1500 km2 yr−1, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has (like the Arctic) instead experienced significant sea ice decreases, with an overall ice extent trend of −8200 ± 1200 km2 yr−1. When examined through the annual cycle over the 32-yr period 1979–2010, the Southern Hemisphere sea ice cover as a whole experienced positive ice extent trends in every month, ranging in magnitude from a low of 9100 ± 6300 km2 yr−1 in February to a high of 24 700 ± 10 000 km2 yr−1 in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and western Pacific Ocean had a mixture of positive and negative trends. Comparing ice-area results to ice-extent results, in each case the ice-area trend has the same sign as the ice-extent trend, but the magnitudes of the two trends differ, and in some cases these differences allow inferences about the corresponding changes in sea ice concentrations. The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen Seas region and increasing ice coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.”

Citation: Parkinson, C. L. and Cavalieri, D. J.: Antarctic sea ice variability and trends, 1979–2010, The Cryosphere, 6, 871-880, doi:10.5194/tc-6-871-2012, 2012.


Arctic sea ice variability and trends, 1979–2010

Arctic sea ice variability and trends, 1979–2010 – Cavalieri & Parkinson (2012) [FULL TEXT]

Abstract: “Analyses of 32 yr (1979–2010) of Arctic sea ice extents and areas derived from satellite passive microwave radiometers are presented for the Northern Hemisphere as a whole and for nine Arctic regions. There is an overall negative yearly trend of −51.5 ± 4.1 × 103 km2 yr−1 (−4.1 ± 0.3% decade−1) in sea ice extent for the hemisphere. The yearly sea ice extent trends for the individual Arctic regions are all negative except for the Bering Sea: −3.9 ± 1.1 × 103 km2 yr−1 (−8.7 ± 2.5% decade−1) for the Seas of Okhotsk and Japan, +0.3 ± 0.8 × 103 km2 yr−1 (+1.2 ± 2.7% decade−1) for the Bering Sea, −4.4 ± 0.7 × 103 km2 yr−1 (−5.1 ± 0.9% decade−1) for Hudson Bay, −7.6 ± 1.6 × 103 km2 yr−1 (−8.5 ± 1.8% decade−1) for Baffin Bay/Labrador Sea, −0.5 ± 0.3 × 103 km2 yr−1 (−5.9 ± 3.5% decade−1) for the Gulf of St. Lawrence, −6.5 ± 1.1 × 103 km2 yr−1 (−8.6 ± 1.5% decade−1) for the Greenland Sea, −13.5 ± 2.3 × 103 km2 yr−1 (−9.2 ± 1.6% decade−1) for the Kara and Barents Seas, −14.6 ± 2.3 × 103 km2 yr−1 (−2.1 ± 0.3% decade−1) for the Arctic Ocean, and −0.9 ± 0.4 × 103 km2 yr−1 (−1.3 ± 0.5% decade−1) for the Canadian Archipelago. Similarly, the yearly trends for sea ice areas are all negative except for the Bering Sea. On a seasonal basis for both sea ice extents and areas, the largest negative trend is observed for summer with the next largest negative trend being for autumn. Both the sea ice extent and area trends vary widely by month depending on region and season. For the Northern Hemisphere as a whole, all 12 months show negative sea ice extent trends with a minimum magnitude in May and a maximum magnitude in September, whereas the corresponding sea ice area trends are smaller in magnitude and reach minimum and maximum values in March and September.”

Citation: Cavalieri, D. J. and Parkinson, C. L.: Arctic sea ice variability and trends, 1979–2010, The Cryosphere, 6, 881-889, doi:10.5194/tc-6-881-2012, 2012.


Decrease in biomass burning after year 1500 is similar in duration and timing to Little Ice Age

Climatic control of the biomass-burning decline in the Americas after AD 1500 – Power et al. (2012) [FULL TEXT]

Abstract: “The significance and cause of the decline in biomass burning across the Americas after AD 1500 is a topic of considerable debate. We synthesized charcoal records (a proxy for biomass burning) from the Americas and from the remainder of the globe over the past 2000 years, and compared these with paleoclimatic records and population reconstructions. A distinct post-AD 1500 decrease in biomass burning is evident, not only in the Americas, but also globally, and both are similar in duration and timing to ‘Little Ice Age’ climate change. There is temporal and spatial variability in the expression of the biomass-burning decline across the Americas but, at a regional–continental scale, ‘Little Ice Age’ climate change was likely more important than indigenous population collapse in driving this decline.”

Citation: M J Power, F E Mayle, P J Bartlein, J R Marlon, R S Anderson, H Behling, K J Brown, C Carcaillet, D Colombaroli, D G Gavin, D J Hallett, S P Horn, L M Kennedy, C S Lane, C J Long, P I Moreno, C Paitre, G Robinson, Z Taylor, M K Walsh, The Holocene August 14, 2012 0959683612450196, doi: 10.1177/0959683612450196.


Domestic tourism increases in northern Spain and decreases in southern Spain with climate change

Climate change and summer mass tourism: the case of Spanish domestic tourism – Bujosa & Rosselló (2012)

Abstract: “This paper investigates the impact of climate change on destination choice decisions in a context of domestic coastal tourism in Spain. Destinations are characterized in terms of travel cost and coastal ‘attractors’, such as temperature and beach-related attributes. By means of a discrete choice model based on the random utility theory, these variables are used to explain the observed pattern of interprovincial domestic trips, showing trade-offs between temperature and attractiveness in the probability of a particular destination being chosen. The model is used to investigate the impact of two climate change scenarios on the allocation of domestic tourism within Spain. The findings show that while Spain’s northern colder provinces would benefit from rising temperatures, provinces in the south would experience a decrease in the frequency of trips.”

Citation: Angel Bujosa and Jaume Rosselló, Climatic Change, 2012, DOI: 10.1007/s10584-012-0554-x.


Satellite measurements of soil moisture

A method to improve satellite soil moisture retrievals based on Fourier analysis – Du (2012)

Abstract: “Knowledge of the spatial distribution and temporal changes of the global soil moisture for a long period of time is crucial to the understanding of climate changes and hydrological processes. By applying Fourier analysis to the time-series observations from the space-borne passive microwave sensors, this paper proposes a method to extract the high-frequency part of the satellite observed signals that reflect the soil moisture changes and help to generate the historical soil moisture datasets with an improved accuracy. The method is applied to the observations from Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E). Validations using field sampled soil moisture from two watersheds in the U.S. indicate that the method can effectively improve the sensitivity of current National Aeronautics and Space Administration (NASA) soil moisture products to the temporal changes of the surface soil moisture, with the correlation coefficients of the retrievals and measurements increased from 0.462 to 0.595 and 0.403 to 0.613 for the two watersheds, respectively.”

Citation: Du, J. (2012), A method to improve satellite soil moisture retrievals based on Fourier analysis, Geophys. Res. Lett., 39, L15404, doi:10.1029/2012GL052435.


Heat waves have increased in western Turkey

Summer heat waves over western Turkey between 1965 and 2006 – Unal et al. (2012)

Abstract: “Global warming is one of the greatest environmental, economic, and social threats in the world. There are many assessments to estimate climate variability over many regions. A change in the Earth’s surface temperature leads to increase in extreme temperature events, which are harmful to the ecosystem, and moreover, they create danger on human health. In this study, we have selected the western part of Turkey as the study area, since climate change projections for Turkey point out that the highest temperature change can be expected on this region during summer, and the Turkish population is very dense here to be affected by extreme events. We have used apparent temperatures to define the heat waves which we have determined their frequencies for the summer months (June–August) of 1965–2006. Since the regional comparisons of station results are intended, we selected the 90th percentile value for each station as a threshold value to be used in the delineation of heat waves. Then, the number of heat waves is determined by imposing the constraint that apparent temperatures stay above the threshold value at least for three consecutive days. Then, the changes in the number of hot days and heat waves and also their durations are analyzed by using the linear least square method. We have found that the number of hot days, heat waves, and heat wave durations is increased between 1965 and 2006 on the western part of Turkey. Additionally, their rate of change is larger within the last decade and extremes are frequently observed after 1998. Regional distributions show that the tendency of the number of heat wave events increases towards the southern latitudes of the domain. Moreover, we investigated the relationship between the number of hot days and the sea surface temperatures of the Mediterranean Sea and Black Sea. Correlation analyses are carried out by the number of hot days and averaged sea surface temperatures on the regions of the western, central, and eastern Mediterranean Sea and the Black Sea. It is found that the number of hot days of west Turkey is better correlated with the sea surface temperatures averaged over eastern Mediterranean and Black Seas. The number of heat waves is found significantly correlated with the fire occurrences for most of the stations.”

Citation: Yurdanur Sezginer Unal, Elcin Tan and S. Sibel Mentes, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0704-0.


Snow cover is expected to decrease in China with climate change

Projection of snow cover changes over China under RCP scenarios – Ji & Kang (2012)

Abstract: “Snow cover changes in the middle (2040–2059) and end (2080–2099) of the twenty-first century over China were investigated with a regional climate model, nested within the global model BCC_CSM1.1. The simulations had been conducted for the period of 1950–2099 under the RCP4.5 and RCP8.5 scenarios. Results show that the model perform well in representing contemporary (1986–2005) spatial distributions of snow cover days (SCDs) and snow water equivalent (SWE). However, some differences between observation and simulation were detected. Under the RCP4.5 scenarios, SCDs are shortened by 10–20 and 20–40 days during the middle and end of the twenty-first century, respectively. Whereas simulated SWE is lowered by 0.1–10 mm in most areas over the Tibetan Plateau (TP). On the other hand, the spatial distributions of SWE are reversed between the middle and end terms in the northeast China. Furthermore, compared with the changes of RCP4.5 scenario, SCDs are reduced by 5–20 days in the middle period under RCP8.5 scenario with even larger decreasing amplitude in the end term. SWE was lowered by 0.1–2.5 mm in most areas except the northeast of China in middle term under RCP8.5 scenario. The great center of SCDs and SWE changes are always located over TP. The regional mean of SCDs and SWE for the TP and for China display a declining trend from 2006 to 2099 with more pronounced changes in the TP than in China as a whole. Under the RCP8.5 scenario, the changes are enhanced compared to those under RCP4.5.”

Citation: Zhenming Ji and Shichang Kang, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1473-2.


Using satellite measurements in mosquito population dynamics studies

Satellite microwave remote sensing for environmental modeling of mosquito population dynamics – Chuang et al. (2012)

Abstract: “Environmental variability has important influences on mosquito life cycles and understanding the spatial and temporal patterns of mosquito populations is critical for mosquito control and vector-borne disease prevention. Meteorological data used for model-based predictions of mosquito abundance and life cycle dynamics are typically acquired from ground-based weather stations; however, data availability and completeness are often limited by sparse networks and resource availability. In contrast, environmental measurements from satellite remote sensing are more spatially continuous and can be retrieved automatically. This study compared environmental measurements from the NASA Advanced Microwave Scanning Radiometer on EOS (AMSR-E) and in situ weather station data to examine their ability to predict the abundance of two important mosquito species (Aedes vexans and Culex tarsalis) in Sioux Falls, South Dakota, USA from 2005 to 2010. The AMSR-E land parameters included daily surface water inundation fraction, surface air temperature, soil moisture, and microwave vegetation opacity. The AMSR-E derived models had better fits and higher forecasting accuracy than models based on weather station data despite the relatively coarse (25-km) spatial resolution of the satellite data. In the AMSR-E models, air temperature and surface water fraction were the best predictors of Aedes vexans, whereas air temperature and vegetation opacity were the best predictors of Cx. tarsalis abundance. The models were used to extrapolate spatial, seasonal, and interannual patterns of climatic suitability for mosquitoes across eastern South Dakota. Our findings demonstrate that environmental metrics derived from satellite passive microwave radiometry are suitable for predicting mosquito population dynamics and can potentially improve the effectiveness of mosquito-borne disease early warning systems.”

Citation: Ting-Wu Chuang, Geoffrey M. Henebry, John S. Kimball, Denise L. VanRoekel-Patton, Michael B. Hildreth, Michael C. Wimberly, Remote Sensing of Environment, Volume 125, October 2012, Pages 147–156, http://dx.doi.org/10.1016/j.rse.2012.07.018.


CLASSIC OF THE WEEK: Yokoyama (1911)

Climatic Changes in Japan since the Pliocene Epoch – Yokoyama (1911) [FULL TEXT]

Abstract: No abstract. Discusses the climate of Japan during glacial and interglacial ages. Carbon dioxide is mentioned as a possible cause for climate change.

Citation: Yokoyama, Matajiro, The Journal of the College of Science, Imperial University of Tokyo, Japan, v32 art5, 1911.10.2, pp. 1-16.


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.

One Response to “New research from last week 33/2012”

  1. […] 2012/08/20: AGWObserver: New research from last week 33/2012 […]

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