Department of Climate and Space Sciences and Engineering in the College of Engineering at the University of Michigan

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Professors Penner and Flanner contributed expertise to IPCC report

Posted: September 27, 2013

Professors Penner and Flanner contributed expertise to IPCC report

Professor Joyce Penner and Assistant Professor Mark Flanner contributed to the latest Intergovernmental Panel on Climate Change (IPCC) report, which will be released on Monday, September 30. The report’s Summary for Policymakers was released today, Friday, September 27.

Penner was the review editor for the entire report’s technical summary and a review editor for the chapter on clouds and aerosols. Aerosols are suspended particles such as soot from coal burning. She says one of the issues presented in the report is the absence of a temperature increase in the last decade. The temperature has not been increasing as quickly as it previously was, and it is not increasing as quickly as climate models predicted it would.

One way to explain this is if aerosol forcing is more negative in the last ten years than has been estimated,” Penner says. “But the smaller total estimated aerosol forcing in this assessment is difficult to accept if aerosol forcing is important to explaining the temperature hiatus.”

Aerosol forcing refers to the cooling effect of sulfate aerosols.

Penner was also among the IPCC recipients of the Nobel Peace Prize with Al Gore in 2007.

Flanner was also involved with the chapter on clouds and aerosols as a contributing author. He summarized the current knowledge of how aerosol particles that rest on snow and sea-ice change how those surfaces reflect sunlight and contribute to climate change.

The impact of aerosols on the climate via snow and sea-ice (called albedo) is relatively small in the global picture. However, it is a unique contribution because it is a warming effect despite the net cooling effect of aerosols on the climate.

“It is also a substantially more effective forcing than other components of the aerosol forcing, because of the way in which it triggers albedo feedback (by melting snow and exposing much darker surfaces that absorb more sunlight),” Flanner says. “Because of this feedback, this component of the aerosol forcing has a larger effect on climate in northern high latitudes during spring and summer.”

To view the summary of the report, please click here.

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