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A participant holds a sign reading "There is no Planet B" during the "Global Climate March" organised by environmental NGOs on November 29, 2015 in Berlin on the eve of the official opening of a 195-nation UN climate summit in Paris. AFP PHOTO / JOHN MACDOUGALL / AFP / JOHN MACDOUGALL (Photo credit should read JOHN MACDOUGALL/AFP/Getty Images)

A participant holds a sign reading "There is no Planet B" during the "Global Climate March" organised by environmental NGOs on November 29, 2015 in Berlin on the eve of the official opening of a 195-nation UN climate summit in Paris. AFP PHOTO / JOHN MACDOUGALL / AFP / JOHN MACDOUGALL        (Photo credit should read JOHN MACDOUGALL/AFP/Getty Images)