Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
The United Nation’s Intergovernmental Panel on Climate Change (IPCC) seems more intent on maintaining the crumbling “consensus” on anthropogenic global warming than on following climate science to its logical conclusion—a conclusion that increasingly suggests that human greenhouse gas emissions are less important in driving climate change than commonly held.
This fact is obvious from the embarrassing lack of internal inconsistency contained in the leaked versions of the IPCC’s Fifth Assessment Report. The Summary for Policymakers, a succinct and brief document supposedly encapsulating what is in the entire 3,000-page report is supposed to be approved by closing time on Friday, at a meeting currently taking place in Stockholm.
In no place will this internal inconsistency be more obvious than in how the IPCC deals with the discrepancy between the observed effectiveness of greenhouse gases in warming the earth and this effectiveness calculated by the climate models that the IPCC uses to project future climate change.
The warming effectiveness is known as the “climate sensitivity” and is the key parameter in how much the earth’s surface temperature rise as a result of the increasing atmospheric concentration of carbon dioxide and other greenhouse gases. Most all climate impacts are related to the climate sensitivity—the lower the climate sensitivity, the fewer the impacts.
One problem. Climate scientists don’t know what the value of the climate sensitivity really is.
Not because the calculation is complicated—just take how much the global average temperature has changed over some longish time period (a couple of decades or longer) and divide by much energy was used to force that change.