Portland State Magazine Spring 2007

Aslam Khalil, physics professor, conducts some of his research in Nanjing, China (top photo), with researchers who measure methane emissions from rice paddies. 14 PORTLA ND STATE MAGAZINE SPRING 2007 FOR NEARLY 3 0 YE AR S, atmospheric physicist Aslam Khalil has been ruffiing the feathers of scientific colleagues across the globe-and time after time, seeing the establishment come around to his way of thinking. His work, which has often led to controversy, is incorporated into the Kyoto protocol on global warming and the Montreal protocol on ozone depletion. Now, Khalil, professor of physics and director of PSU's Environmental Science and Resources Program, is at it again. In a paper published in a recent issue of Environmental Science and Technology, Khalil reported that his research team has found that global annual emissions of methane-one of the most potent greenhouse gases in the Earth's atmosphere– have not increased for the past 25 years after more than doubling in the past century. Methane is the second most harmful greenhouse gas after carbon dioxide. The sticking point is that Khalil believes the stability will last. Other scientists are incredulous, sure that regulation is required to guarantee any lasting change. WHAT'S AT STAKE? If Khalil is right, climate models predicting global warming will need to be revised. Khalil and his team analyzed methane levels measured in recent years at strategic locations around the globe, then combined that data with their own measurements going back nearly 25 years to create the longest timeline of methane measurements yet. They found that atmospheric concentrations of this greenhouse gas had leveled off during this time period despite a growing human population. Basically, the amount of methane emitted into the atmosphere is being destroyed in the atmosphere at about the same rate.