December 7, 2003: Government’s Top Atmospheric Scientists Say Global Warming Is Caused by Greenhouse Gases

The journal Science publishes a paper written by two of the nation’s leading atmospheric scientists concluding that “modern climate change is dominated by human influences” and cannot be explained by natural causes. The article, titled “Modern Climate Change,” warns that climate change “may prove to be humanity’s greatest challenge” and that “it is very unlikely to be adequately addressed without greatly improved international cooperation and action.” The authors, Kevin Trenberth, head of National Center for Atmospheric Research (NCAR)‘s Climate Analysis Section, and Thomas Karl, director of NOAA’s National Climatic Data Center, insist that “there is no doubt that the composition of the atmosphere is changing because of human activities, and today greenhouse gases are the largest human influence on global climate.” [San Francisco Chronicle, 12/4/2003; Karl and Trenberth, 12/7/2003; Union of Concern Scientists and Government Accountability Project, 1/30/2007, pp. 31 ]