James Hansen

A fierce climate change activist that has even been arrested on more than one occasion for his protest activities. To some, the American adjunct professor at Columbia University is too strong in his views on climate change, but to most he is an indispensable asset who has contributed greatly to our understanding of global warming over a number of decades. His testimony in front of the US Senate committee in 1988 is regarded as a turning point that brought awareness of climate change to the public domain, and he is still battling on behalf of better policies to mitigate the effects of global warming.

Location: New York

Age: 76

Twitter: @DrJamesHansen