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Soot climate forcing via snow and ice albedos
James Hansen1, Larissa Nazarenko
1National Aeronautics and Space Administration Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA. jhansen@giss.nasa.gov
Summary
Reducing soot emissions can mitigate global warming and delay dangerous climate change impacts. This soot forcing is twice as effective as carbon dioxide (CO2) in altering global temperatures.
Area of Science:
- Climate Science
- Atmospheric Chemistry
- Glaciology
Background:
- Soot deposition darkens snow and ice, reducing their reflectivity (albedo).
- This darkening effect has been estimated to cause significant climate forcing, particularly in the Northern Hemisphere.
Purpose of the Study:
- To quantify the climate forcing from soot on snow and ice albedos.
- To assess the efficacy of soot forcing compared to carbon dioxide (CO2).
- To evaluate the role of soot in past and future global warming.
Main Methods:
- Estimating the effect of soot on snow and ice albedos in the Arctic and Northern Hemisphere land areas.
- Calculating the resulting climate forcing in the Northern Hemisphere.
- Comparing the efficacy of soot forcing to CO2 forcing in altering global surface air temperature.
Main Results:
- Soot reduces albedos by 1.5% in the Arctic and 3% in Northern Hemisphere land areas.
- This results in a Northern Hemisphere climate forcing of +0.3 W/m(2).
- Soot forcing is approximately twice as effective as CO2 in altering global surface air temperature.
Conclusions:
- Soot emissions have likely contributed to past global warming, including early springs, thinning Arctic sea ice, and melting land ice.
- Reducing soot emissions offers a dual benefit: mitigating global warming and raising the threshold for dangerous anthropogenic climate interference.
- Anthropogenic greenhouse gases remain the primary driver of current global warming and the predominant future climate forcing.