Last month was the hottest May ever recorded and the 12th straight month of record heat, UN Secretary-General Antonio Guterres warned Wednesday in a major speech on climate change.

Guterres also said the world faces an 80 percent chance of surpassing the 1.5 degree Celsius target for limiting average temperature increases in at least one of the next five years, he said, quoting reports from Europe's Copernicus program and the World Meteorological Organization.