Earth Has Hottest May on Record

"This is unquestionably an alarming sign."

The Earth just experienced its hottest May on record, scientists said Friday—just a day after it was announced that atmospheric CO2 levels hit a new high.

Scientists at Europe's Copernicus Climate Change Service (C3S) announced the temperature record Friday. The agency said that globally, last month 0.63°C warmer than the 1981-2020 average for May. That tops the previous warmest May, which occurred in 2016, by 0.05°C.

The last 12-month period, C3S added, was nearly 0.7°C warmer than average.

"The last month has been the warmest May on record globally and this is unquestionably an alarming sign," Freja Vamborg, a scientist at C3S, toldCNBC.

The agency added in its new findings:

Outside Europe, temperatures were most above average over parts of Siberia, where they were up to 10°C above average. They were also much above average over western Alaska, along the Andes bordering Chile and Argentina, and over regions in West and East Antarctica. It was also much warmer than average over western North America, the far north and south of South America, north-western, central and south-western Africa, and south-eastern Asia.

The "highly anomalous" temperatures in parts of Siberia follow a warmer than ever April for the Arctic and evidence of the emergence of so-called "zombie fires"—reignited fires from last year's Arctic wildfires that continued to survive by smoldering underground.

The new data from European scientists follows NOAA's Thursday announcement that atmospheric CO2 levels also hit new highs last month.

The levels recorded at the Mauna Loa Observatory show a seasonal peak of 417.1 parts per million in May, the highest monthly reading ever recorded.

Record high daily averages hit last month had already sparked urgent calls for bold climate action.

The trend of the planet-heating gas in the atmosphere is unmistakable.

"Progress in emissions reductions is not visible in the CO2 record," Pieter Tans, senior scientist with NOAA’s Global Monitoring Laboratory, said in a statement. "We continue to commit our planet—for centuries or longer—to more global heating, sea level rise, and extreme weather events every year."

The record atmospheric CO2 levels come as the global coronavirus pandemic has triggered global economic shutdowns, but the resulting emissions drops and pollution declines were not enough to budge CO2 levels.

Geochemist Ralph Keeling, who runs the Scripps Oceanography program at Mauna Loa, explained why, likening global emissions to "trash in a landfill."

"People may be surprised to hear that the response to the coronavirus outbreak hasn't done more to influence CO2 levels," he said. "But the buildup of CO2 is a bit like trash in a landfill. As we keep emitting, it keeps piling up."

"The crisis has slowed emissions, but not enough to show up perceptibly at Mauna Loa," Keeling continued. "What will matter much more is the trajectory we take coming out of this situation."

The new data comes as global policy makers mark World Environment Day, a moment United Nations Secretary-Gneral António Guterres took to say, "To care for humanity, we MUST care for nature."

"Climate disruption is getting worse," Guterres said in his message, urging all parties to "commit to a green and resilient future."