22 September 201922.15 The 2015-2019 five-year period starts to be the hottest ever. It is certified by a United Nations report, according to which the average temperature in this period was 1.1 degrees higher than in the pre-industrial era (1850-1900) and greater than 0.2 degrees compared to the five-year period 2011-2015. tomorrow opens in New York the "Climate Action Summit", world summit convened by the UN secretary, Guterres, to combat climate change, where the young Swedish activist Greta Thunberg will also speak.