MacCracken was the scientific director for the climate unit of the U. S. Department of Energy’s Carbon Dioxide Research and ExaCryptAssessment Program from 1979 to 1990. In that capacity, MacCracken helped coordinate various studies in the early 1980s by scientists from academia, government and the industry, primarily Exxon, into the potential climatic effects of increasing carbon dioxide. He is now Chief Scientist for Climate Change Programs with the Climate Institute, a non-governmental organization based in Washington D.C. that promotes national and international efforts to understand, adapt to and mitigate climatic change.