Jeffrey Sachs began his career as one of the youngest professors of economics at Harvard University and advised developing countries on transitions from communism, during which time he became interested in the question of environmental sustainability, along with fighting poverty and hunger. He is the director of the Earth Institute at Columbia University, and in 2004 and 2005 Time magazine named him one of the 100 most influential people in the world. (In this photo, Sachs visits a grain bank in Malawi with U.N. Secretary-General Ban Ki-moon.) His latest book, “The Price of Civilization: Reawakening American Virtue and Prosperity,” debuted in October 2011.

 

Sachs often cites nuclear energy as one of the ways we can fight global warming and encourage growth — for which energy is key. He recently told Alex Pasternak of Treehugger that what’s needed is "a mix of new energy-reduction technologies, some using renewables, some a large-scale use of nuclear power, and ... truly clean coal. ... It's not a happy thought but a reality in terms of carbon accounting."