Today NASA and NOAA dropped their annual analysis of global temperatures: Last year was tied with 2018 as the sixth-hottest ever, but cooler than 2020. A good sign, right? Yeah, no. Not in the least.“It's easy to want to focus on that year-to-year variability,” says Bridget Seegers, an oceanographer at NASA. “But it's important to look at the trend: The last eight years were the eight hottest on record.”
To calculate global temperatures, the two agencies pull data from weather stations all over the world, plus measurements taken from ships and buoys in the ocean. Other groups like Berkeley Earth, a nonprofit research organization, do the same with their own somewhat different methodology. But the analyses are nearly identical in their findings. As you can see in the graph below, which compares results from Berkeley Earth, NOAA, NASA, and two other groups in Europe, the global average temperature might have been lower in 2021 than 2020, but it’s still soaring.
One reason for cooler temperatures in 2021 was likely La Niña, a band of cold water in the Pacific. It’s the product of strong trade winds that scour the ocean, pushing the top layer of water toward Asia, causing deeper, colder waters to rush to the surface to fill the void. This in turn influences the atmosphere, for instance changing the jet stream above the United States and leading to more hurricanes in the Atlantic. The sea itself cools things off 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 locked down in 2020, fewer emissions went into the sky, including aerosols that typically reflect some of the sun’s energy back into space. “If you take them away, you make the air cleaner, then that's a slight warming impact on the climate,” said Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, during a Thursday press conference announcing the findings. But as economic activity ramped back up in 2021, so did aerosol pollution, contributing again to that cooling effect. The 2021 temperature drop “may be possibly due to a resumption of activity that produces aerosols in the atmosphere,” Schmidt said.
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(The pandemic-based drop in carbon dioxide production didn’t have a cooling effect. Human civilization produces so much of the planet-warming gas every year, and it persists so long in the atmosphere, that the pandemic didn’t even register as a blip.)
Today’s findings are all the more alarming precisely because 2021 managed to overcome these cooling effects and still tally the sixth-highest temperature. And while global temperatures were cooler in 2021 than the year before, last year 1.8 billion people lived in places that experienced their hottest temperatures ever recorded, according to a report released today by Berkeley Earth. This includes Asian countries like China and North and South Korea, African nations like Nigeria and Liberia, and in the Middle East places like Saudi Arabia and Qatar. “We talk a lot about global average temperatures, but no one lives in the global average,” says Zeke Hausfather, a research scientist at Berkeley Earth. “In fact most of the globe, two-thirds of it, is ocean, and no one lives in the ocean—or very few people at least. And land areas, on average, are warming much faster than the rest of the world.”
Because land is heating so quickly, increasingly frequent and intense heat waves are brutalizing people living in different parts of the world. Last summer in western Canada and the US Pacific Northwest, absurd temperatures of over 120 degrees Fahrenheit killed hundreds of people. According to Hausfather, the heat wave in Portland, Oregon, would have been effectively impossible without climate change, something like a once-every-150,000-year event. “By the end of the century, at the rate things are warming right now, it's going to be a 1-in-10, 1-in-5-year event,” says Hausfather. “They're what we call the ‘return periods’ for these extreme heat events that become much shorter the warmer the world becomes.”
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This Berkeley Earth map above gives a better idea of what we’re dealing with. La Niña affected the areas in that patch of cool blue off the coast of South America. But the bright red areas show that North Africa, the Middle East, and China were roasting. And check out the splotches of red over the Arctic, which is warming four times as fast as the rest of the planet. That’s caused by a variety of factors, including the fact that as ice melts it exposes darker ground beneath, which absorbs more of the sun’s energy, raising local temperatures and accelerating melting. Frozen ground known as permafrost is now thawing so rapidly that it’s gouging holes in the Arctic landscape, causing it to spew yet more greenhouse gases.
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Land worldwide is heating faster than the ocean, as you can see in the graph above. But a warmer ocean also raises sea levels, both because water expands as it heats up and because the warmer water melts sea ice. (The graph below from NASA shows the decline of sea ice in the Arctic.) In Antarctica, the Thwaites “Doomsday Glacier” is rapidly degrading, in part because abnormally warm waters are chewing at its belly. If it melts, and triggers a collapse among nearby glaciers, together they could add 10 feet to sea levels.
Extreme heat also leads to crop failures and water shortages, and it supercharges wildfires: In California alone last year, blazes chewed through 4,000 square miles of land. Wildfires have gotten so intense in the western US and Canada that they’re spawning their own thunderclouds, which go on to spark new blazes. Burning all that vegetation only loads the atmosphere with more planet-warming carbon.
Skyrocketing temperatures also exacerbate disasters in more unexpected ways. A warmer atmosphere holds more water, for instance, which makes for stronger downpours and more flooding, as we saw in Europe this summer. Warmer waters in the Gulf of Mexico strengthen hurricanes like last summer’s Ida, which tore through the South and flooded New York City.
“We also saw the worst locust plagues in decades in East Africa. In March there were major floods in eastern Australia, and the worst sandstorm in Beijing in a decade,” said Russ Vose, chief of the analysis and synthesis branch of NOAA’s National Centers for Environmental Information, speaking at the press conference. “In the US in particular, there were 20 weather and climate disasters that had losses exceeding a billion dollars each, and the total damages for 2021 were something like $145 billion, the third-highest on record.”
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The graph above shows the ultimate reason why 2021 not setting an all-time record is nothing to cheer about. Humanity is on course to reach 1.5 degrees Celsius of warming above pre-industrial levels—the optimistic limit set by the Paris Climate Accord—in a decade. By 2059, we’ll hit 2 degrees Celsius, the agreement’s upper limit.
The United Nations Intergovernmental Panel on Climate Change already made that point in August, when it released its alarming 2021 report. But, says Seegers, today’s report adds to scientists’ understanding of climate trends and charts a way forward for change. “Extremes are getting worse. People are losing their homes and their lives and air quality, because the wildfires are bad,” says Seegers. “There's just a lot going on, and I want people to also feel empowered that we understand the problem. It's just this other issue of deciding to take collective action.”
“There's a lot of reasons for optimism,” Seegers continues. “We're in charge. This would be a lot worse if we're like, ‘Oh, it's warming because we're heading toward the sun, and we can't stop it.’”
So it’s bad. But it’s not impossible.
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