AGW Observer

Observations of anthropogenic global warming

New research from last week 45/2012

Posted by Ari Jokimäki on November 12, 2012

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

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

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

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

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

Citation: Pekka Vanhala, Anna Repo, Jari Liski, Current Opinion in Environmental Sustainability,

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

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

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

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

Atlantic Multidecadal Oscillation might show in Romania summer temperatures

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

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

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

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

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

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

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

Arctic climate simulations of past 1150 years

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

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

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

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

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

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

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

How continental ice retreat affects future global climate

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

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

Citation: Aixue Hu, Gerald A. Meehl, Weiqing Han, Jianjun Yin, Bingyi Wu, and Masahide Kimoto, Journal of Climate 2012, doi:

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

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

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

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

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

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

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

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

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

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

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

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

Boreal plants seem to be methane sinks

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

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

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

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

Other studies from last week

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

CLASSIC OF THE WEEK: Tyndall (1863)

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

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

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

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

One Response to “New research from last week 45/2012”

  1. [...] 2012/11/12: AGWObserver: New research from last week 45/2012 [...]

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