New Paper “Climate Response To Regional Radiative Forcing During The Twentieth Century” By Shindell And Faluvegi 2009

Climate Science has reported on the role of aerosols in the Arctic as a radiative warming effect; e.g. see

New Study On The Role Of Soot Within the Climate In The Higher Latitudes And On “Global Warming”/

New Paper Elevates The Role Of Black Carbon In Global Warming

Arctic Tundra Shrub Invasion And Soot Deposition: Consequences For Spring Snowmelt And Near-surface Air Temperatures.

This includes the study we published

Strack, J., R.A. Pielke Sr., and G. Liston, 2007: Arctic tundra shrub invasion and soot deposition: Consequences for spring snowmelt and near-surface air temperatures. J. Geophys. Res., 112, G04S44, doi:10.1029/2006JG000297

There is a very important new paper that adds significantly to this subject. it is

Drew Shindell & Greg Faluvegi, 2009: Climate response to regional radiative forcing during the twentieth century. Nature Geoscience 2, 294 – 300 (2009) Published online: 22 March 2009 | doi:10.1038/ngeo473.

The abstract reads

“Regional climate change can arise from three different effects: regional changes to the amount of radiative heating that reaches the Earth’s surface, an inhomogeneous response to globally uniform changes in radiative heating and variability without a specific forcing. The relative importance of these effects is not clear, particularly because neither the response to regional forcings nor the regional forcings themselves are well known for the twentieth century. Here we investigate the sensitivity of regional climate to changes in carbon dioxide, black carbon aerosols, sulphate aerosols and ozone in the tropics, mid-latitudes and polar regions, using a coupled ocean–atmosphere model. We find that mid- and high-latitude climate is quite sensitive to the location of the forcing. Using these relationships between forcing and response along with observations of twentieth century climate change, we reconstruct radiative forcing from aerosols in space and time. Our reconstructions broadly agree with historical emissions estimates, and can explain the differences between observed changes in Arctic temperatures and expectations from non-aerosol forcings plus unforced variability. We conclude that decreasing concentrations of sulphate aerosols and increasing concentrations of black carbon have substantially contributed to rapid Arctic warming during the past three decades.”

The conclusion of the paper includes the text

“Our results suggest that aerosols have had a large role in both global and regional climate change during the twentieth century. Both these results and forward modelling indicate that Arctic climate is especially sensitive to Northern Hemisphere short- lived pollutants. Arctic trends may also be related to internal atmosphere-ocean dynamics. Our analysis is consistent with a large role for internal variability, but suggests an even greater impact from aerosol forcing on trends since 1930. A large aerosol contribution to mid-twentieth century Arctic cooling perhaps accounts for the lack of polar amplification in some studies. During 1976-2007, we estimate that aerosols contributed 1.09 +/- 0.81 C to the observed Arctic surface temperature increase of 1.48 +/- 0.28 C. Hence, much of this warming may stem from the unintended consequences of clean-air policies that have greatly decreased sulphate precursor emissions from North America and Europe (reducing the sulphate masking of greenhouse warming) and from large increases in Asian black carbon emissions.”

“Our calculations suggest that black carbon and tropospheric ozone have contributed ~0.5-1.4 C and ~0.2-0.4 C, respectively, to Arctic warming since 1890, making them attractive targets for Arctic warming mitigation. In addition, they respond quickly to emissions controls, and reductions have ancillary benefits including improved human and ecosystem health”.

This new paper further bolsters the conclusion that, as reported on Climate Science (see), that

“Research has shown that the focus on just carbon dioxide as the dominate human climate forcing is too narrow. We have found that natural variations are still quite important, and moreover, the human influence is significant, but it involves a diverse range of first-order climate forcings, including, but not limited to the human input of CO2 (e.g. see NRC, 2005 and Kabat et al, 2004). These other forcings, such as land use change and from atmospheric pollution aerosols, may have a greater effect on our climate than the effects that have been claimed for CO2.”

My perspective on the diversity of human climate forcings beyond the radiative effect of added CO2 is sumarized in

Pielke Sr., Roger A., 2008: A Broader View of the Role of Humans in the Climate System is Required In the Assessment of Costs and Benefits of Effective Climate Policy. Written Testimony for the Subcommittee on Energy and Air Quality of the Committee on Energy and Commerce Hearing “Climate Change: Costs of Inaction” – Honorable Rick Boucher, Chairman. June 26, 2008, Washington, DC., 52 pp. [View PDF of Oral Summary].


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