The world was cooler in 2021 than in 2020. That’s not good news

Today NASA i NOAA dropped its annual analysis of global temperatures – last year tied 2018 as the sixth warmest in history, but colder than 2020. A good sign, right? If not. No more and no less.

“It’s easy to want to focus on this variability year after year,” says Bridget Seegers, a NASA oceanographer. “But it’s important to look at the trend: the last eight years were the hottest eight on record.”

To calculate global temperatures, the two agencies extract data from weather stations around the world, as well as measurements taken from ships and buoys in the ocean. Other groups like Berkeley Earth, a non-profit research organization, do the same with their own slightly different methodology. But the analyzes are almost identical in their findings. As you can see in the chart below, which compares the results of Berkeley Earth, NOAA, NASA, and two other groups in Europe, the average global temperature may have been lower in 2021 than in 2020, but it is still skyrocketing. .

Illustration: Berkeley Earth

One of the reasons for the cooler temperatures in 2021 was probably La Niña, a cold water band in the Pacific. It is the product of strong trade winds that blow across the ocean, pushing the top layer of water toward Asia, causing deeper, colder water to come to the surface to fill the void. This in turn influences the atmosphere, for example, by changing the lightning current over the United States and causing more hurricanes in the Atlantic. The sea itself cools things down by absorbing heat from the atmosphere.

The Covid-19 pandemic may have had an additional influence, but not in the way you might think. As the world froze in 2020, fewer emissions reached the sky, including aerosols that normally reflect some of the sun’s energy into space. “If you take them out, make the air cleaner, then that’s a slight warming impact on the climate,” Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, told a conference. press release on Thursday announced the findings. But as economic activity increased again in 2021, so did aerosol contamination, again contributing to this cooling effect. The 2021 drop in temperature “may be due to a resumption of aerosol-producing activity in the atmosphere,” Schmidt said.

NASA data on rising temperatures over the decades

Illustration: NASA / NOAA

(The pandemic-based fall in carbon dioxide production did not have a cooling effect. Human civilization produces so much of the gas that heats the planet each year, and persists so much in the atmosphere, that the pandemic does not even recorded as a tap.)

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