Joyce Penner, professor of atmospheric, oceanic and space sciences, talks about climate change with Donald Kennedy, editor in chief of Science magazine, June 15 at an event in Washington, D.C. The American Association for the Advancement of Science (AAAS), the world's largest general science society, and its journal, Science, convened the public conference. Penner says greenhouse gases are warming the Earth faster than aerosols like dust can mask them, according to an AAAS press release. Various types of aerosols—from soot and dust to sulfur—either can cool or warm the climate, she says. Warming is associated with absorbing black carbon emissions such as soot, while non-absorbing aerosols are tied to cooling, which scientists call "negative forcing." "In the long term, greenhouse gas effects are not going to be masked by aerosols," Penner says, debunking a popular myth related to climate change. "But in the short term, we have a problem predicting what aerosols do to the climate. The best current aerosol models give a cooling force, which is larger than we can explain. This must be balanced by other effects that are not properly accounted for in climate models. But eventually, warming caused by greenhouse gases will overwhelm any aerosol-related cooling." (Photo by Mike Waring, U-M Washington Office)