James Hansen

James Edward Hansen (born March 29, 1941) is an American climatologist. He is an adjunct professor directing the Program on Climate Science, Awareness and Solutions of the Earth Institute at Columbia University. He is best known for his research in climatology, his 1988 Congressional testimony on climate change that helped raise broad awareness of global warming, and his advocacy of action to avoid dangerous climate change. In recent years, he has become a climate activist to mitigate the effects of global warming, on a few occasions leading to his arrest.

Hansen also proposed an alternative approach of global warming, where the 0.7°C global mean temperature increase of the last 100 years can essentially be explained by the effect of greenhouse gases other than carbon dioxide (such as methane). Provided by Wikipedia