La Niña cools Earth, but 2021 goes down as 6th-warmest year

Earth simmered to the sixth-hottest year on record in 2021, according to several newly released temperature measurements.

And scientists say the exceptionally hot year is part of a longterm warming trend that shows hints of accelerating.

Two U.S. science agencies — NASA and the National Oceanic and Atmospheric Administration — and a private measuring group released their calculations for last year’s global temperature on Thursday, and all said it wasn’t far behind ultra-hot 2016 and 2020.

Six different calculations found 2021 was between the fifth and seventh hottest year since the late 1800s. NASA said 2021 tied with 2018 for sixth warmest, while NOAA puts last year in sixth place by itself.

Scientists say a La Niña — natural cooling of parts of the central Pacific that changes weather patterns globally and brings chilly deep ocean water to the surface — dampened global temperatures just as its flip side, El Niño, boosted them in 2016.

Still, they said 2021 was the hottest La Niña year on record and that the year did not represent a cooling off of human-caused climate change but provided more of the same heat.

“So it’s not quite as headline-dominating as being the warmest on record, but give it another few years and we’ll see another one of those” records, said climate scientist Zeke Hausfather of the Berkeley Earth monitoring group that also ranked 2021 as the sixth hottest. “It’s the longterm trend, and it’s an indomitable march upward.”

Gavin Schmidt, the climate scientist who heads NASA’s temperature team, said “the long-term trend is very, very clear. And it’s because of us. And it’s not going to go away until we stop increasing the amount of carbon dioxide in the atmosphere.”

The last eight years have been the eight hottest on record, NASA and NOAA data agree. Global temperatures, averaged over a 10-year period to take out natural variability, are nearly 2 degrees warmer than 140 years ago, their data shows.

The other 2021 measurements came from the Japanese Meteorological Agency and satellite measurements by Copernicus Climate Change Service in Europe and the University of Alabama in Huntsville.

There was such a distinctive jump in temperatures about eight to 10 years ago that scientists have started looking at whether the rise in temperatures is speeding up. Both Schmidt and Hausfather said early signs point to that but it’s hard to know for sure.

“If you just look at the last the last 10 years, how many of them are way above the trend line from the previous 10 years? Almost all of them,” Schmidt said.

There’s a 99 percent chance that 2022 will be among the 10 warmest years on record and a 10 percent chance it will be the hottest on record, NOAA climate analysis chief Russell Vose said in a Thursday news conference.