He worked on global climate problems, particularly those involving interactions between the biosphere and the atmosphere, and was involved in constructing computer models of the global climate system, satellite data interpretation and conducting large-scale field experiments in the U.S., Canada, Africa, and Brazil. He is the recipient of the NASA Exceptional Scientific Achievement Award, the Arthur Fleming Award, the AMS Houghton Award, and, most recently, in 2011, Officer of the British Empire (OBE) for services to science, and is a Fellow both AGU and AMS.