Greta Thunberg is a Swedish activist seeking to stop global warming and climate change. The teenager first staged a school strike for the climate in front of the Swedish parliament in August 2018. Since then, she's become a global phenomenon, speaking at the UN and Davos.
Her climate strike has inspired thousands of other young people across the world to carry out similar protests.
Now she has been nominated as a candidate to receive this year's Nobel Peace Prize.
Sir David Attenborough's haunting message on plastic pollution in the oceans.
Capt. Charles Moore of the Algalita Marine Research Foundation first discovered the Great Pacific Garbage Patch -- an endless floating waste of plastic trash. Now he's drawing attention to the growing, choking problem of plastic debris in our seas.
In her most provocative book yet, Naomi Klein, author of the global bestsellers The Shock Doctrine and No Logo, tackles the most profound threat humanity has ever faced: the war our economic model is waging against life on earth.
With his 2006 documentary, An Inconvenient Truth, former U.S. vice president Al Gore drew public attention to the threat of climate change. This July, An Inconvenient Sequel opens in theaters. Gore, 69, says the stakes are higher now but the solutions are clearer.