2021 Was Earth’s Fifth-Hottest Year, Scientists Say


Last year was Earth’s fifth hottest on record, European scientists announced on Monday. But the fact that the worldwide average temperature didn’t beat the record is hardly reason to stop worrying about global warming’s grip on the planet, they said.

Not when both the United States and Europe had their warmest summers on the books. Not when higher temperatures around the Arctic caused it to rain for the first time at the Greenland ice sheet’s normally frigid summit.

And certainly not when the seven hottest years ever recorded were, by a clear margin, the past seven.

The events of 2021 “are a stark reminder of the need to change our ways, take decisive and effective steps toward a sustainable society and work toward reducing net carbon emissions,” said Carlo Buontempo, director of the Copernicus Climate Change Service, the European Union program that conducted the analysis made public on Monday.

The mean temperature globally last year was 1.1 to 1.2 degrees Celsius (2 to 2.2 degrees Fahrenheit) higher than it was before industrialization led humans to begin pumping large quantities of carbon dioxide into the air.

The year was fifth warmest by a slight margin over 2015 and 2018, by Copernicus’s ranking. The hottest years on record are 2016 and 2020, in a virtual tie.

“If you look at all the last seven years, they’re not super close, but they’re quite close together,” said Freja Vamborg, a senior climate scientist at Copernicus. “And they stand well off from the ones that came before that.”

Copernicus’s temperature records start in 1950, but in its analyses, the group combines these with other records that go back about another century.

The steady warming corresponds with the scientific consensus that increasing levels of greenhouse gases in the atmosphere are causing long-lasting changes in the global climate. Copernicus said its preliminary analysis of satellite measurements had found that concentrations of heat-trapping gases continued to rise last year, helped by 1,850 megatons of carbon emissions from wildfires worldwide.

The rate of increase in carbon dioxide levels appears to have been down somewhat from a few years earlier, the Copernicus analysis found. However, concentrations of methane, the second-most prevalent greenhouse gas, grew at their fastest pace in two decades, and Copernicus scientists said they were still trying to understand why.

One big reason for 2021’s lower mean temperature was the presence during the early part of the year of La Niña conditions, a recurring climate pattern characterized by lower surface temperatures in the Pacific Ocean. (La Niña has returned in recent months, which could presage a drier winter in the Southern United States but wetter conditions in the Pacific Northwest.)

Those effects were offset in the 2021 average, however, by higher temperatures in many parts of the world between June and October, Copernicus said.

“When we think about climate change, it’s not just a single progression, year after year after year being the warmest,” said Robert Rohde, the lead scientist at Berkeley Earth, an independent environmental research group.

“The preponderance of evidence —…



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