The rate of global warming and sea level rise may be slightly higher than predicted in the next century based on new information gathered by the Intergovernmental Panel on Climate Change, says a climate scientist who analyzed preliminary data.
Tom M.L. Wigley of the National Center for Atmospheric Research said yesterday that his new estimates are based on new emission scenarios developed by the IPCC, a group of scientists organized by the United Nations to study climate change.
In 1995, the group estimated that human releases of heat-trapping "greenhouse gases" would increase the mean global surface temperatures 1.4 to 6.3 degrees Fahrenheit by the end of the next century. But Wigley, in a report released by the Pew Center on Global Climate Change, said the IPCC's latest estimates suggest that the mean warming of the globe's surface will be slightly higher, 2.3 to 7.3 degrees Fahrenheit.
Estimated sea level rise also would be higher, from a mean global range of 5 to 37 inches to a range of 7 to 39 inches, Wigley wrote.
The new estimates are based primarily on a finding of significantly lower levels of sulfur dioxide emissions than previously assumed, Wigley said. Sulfate particles cool the atmosphere, mitigating the impact of the greenhouse gases, mainly carbon dioxide from burning fossil fuels. Sulfur emissions are dropping because of the push to reduce surface air pollution.
Skeptic John Christy, an atmospheric science professor at the University of Alabama, said sulfates' impact is not known well enough and is only one part of a complex system.