Michael Mann knows more about Earth's climate over the last 1,000 years than most. He's studied the history of changes in Earth's climate over the past 1,000 years to better understand how human-driven climate change of the 21st century compares. Mann has also pioneered techniques the climate scientists use today to discover patterns in past climate change to better understand how our situation may develop in the next 10, 100, and 1,000 years.
Mann is outspoken against skeptics of climate change: One of his notable achievements was helping to found Real Climate, a website run by a group of climate scientists who strive to provide the scientific facts on mainstream discussions of climate change. If you're looking for the statistics, facts, and other real science of the latest news or hype regarding what a celebrity, politician, or even the Pope said about climate change, you're likely to find it on Real Climate.
For his work, Mann has received numerous awards including the first Friend of the Planet Award from the National Center for Science Education.
Mann is a distinguished professor of Meteorology and Director of Earth System Science Center at Penn State University.
Source : http://www.businessinsider.com/50-scientists-changing-the-world-2015-7229