Christiana Figueres

If Mother Nature held auditions for a guardian, Figueres, 59, would be first in line. The daughter of a Costa Rican President who led a landmark revolution in 1948, Figueres became the United Nations climate-change chief in 2010, tasked with nothing less than halting the potentially catastrophic effects of global warming. For six years she worked to convince governments that a binding agreement on limiting carbon emissions and slowing fossil fuel-led growth was in the world’s best interest.   Figueres’s efforts culminated in December at the Paris climate conference, where 195 countries signed a deal committing them to limit worldwide temperature increases to no more than 2° C above pre-industrial levels, a critical if hard-to-attain benchmark. “To bring all countries together on something everyone has been fighting on for decades, and to get them to agree, was brilliant,” says Jean Krasno, a political science lecturer at City College of New York and the author of The United Nations: Confronting the Challenges of a Global Society. Figueres is stepping down in July, and many believe she could become the first woman to be named UN Secretary-General.