A Harvard-led analysis published in Science found that between 1977 and 2003, Exxon scientists' global warming projections were 'shocking' in their accuracy: 63-83% of projections matched actual temperatures, with the best scoring 99%. For comparison, James Hansen's famous 1988 NASA testimony scored 38-66%. Exxon correctly predicted warming of ~0.2C per decade, that human-caused warming would be detectable by 2000 (plus or minus 5 years), and dismissed the possibility of a coming ice age. Despite this, Exxon publicly took out ads claiming climate science was 'poorly understood.'