Globally, May was 0.63 degrees Celsius warmer than the May average between 1981 and 2010, making it the hottest May in this data file, the Copernican Climate Change Service said.
The May increase follows a clear trend that Copernicus has seen in recent years. During the last twelve months to May, global temperatures were 0.7 degrees Celsius warmer than average – corresponding to the previous high of the year between October 2015 and September 2016.
Europe was generally slightly colder than average, but with strong geographical differences, the report said.
The most impressive spike was in Siberia, the typically icy region extending over much of Russia, which was 10 degrees Celsius on average.
An environmental group has described the damage as “catastrophic” and the concentration of pollutants in nearby waters has already exceeded the permitted levels tens of thousands of times, according to Russia’s environmental service Rosprirodnadzor.
Two-thirds of Russia sits on the permafrost, which declines rapidly, piercing parts with giant sinkholes.
This is followed by an extremely hot winter in Russia, which is usually covered with snow at the beginning of a year.