People hold signs during a protest at XV square, downtown Rio de Janeiro, Brazil, on September 20, 2019, in the framework of the "Friday for the planet" global demo against climate change. - A Youth Climate Summit will take place at the United Nations on Saturday. UN Secretary-General Antonio Guterres will then host an emergency summit on Monday in which he will urge world leaders to raise their commitments made in the 2015 Paris climate accord. (Photo by MAURO PIMENTEL / AFP)