The World’s Troubling New Tempo of Temperature Records

January 14, 2022, 12:01 AM EST

Source: NASA Goddard Institute for Space Studies

New data from the U.S. government’s temperature takers just ranked 2021 as the sixth-hottest year, near the very top of a list that stretches back into the 19th century. The hottest eight entries in the federal heat records have all occurred in the last eight years.

Last year’s global average temperature was at least 1.04°C above the average from 1880 to 1900, according to reports released Thursday by NASA’s Goddard Institute for Space Studies, NOAA and Berkley Earth, a research nonprofit. A dataset updated on Monday by the EU Copernicus Climate Change Service put 2021 in fifth place for heat.

In a stable climate, without annual re-orderings at the top of the hottest-years list, the world should set hot and cold records about evenly. But as greenhouse gas pollution continues to rise, hot extremes are intensifying and becoming more frequent. Cold spells are becoming weaker and more rare, a major UN-backed assessment concluded in August. Of 458 new regional temperature records counted in one analysis, just 54 were cold extremes.

The June-to-August average land temperature reached unprecedented highs, and the ocean broke the subsurface annual heat record set in 2020. But even these topline temperature readings can actually conceal how difficult it is for people to cope with consistently higher extreme heat.

Record high average temperatures were set in 25 countries last year, even in a year that didn’t end up as the hottest on record. China, South Korea and Nigeria were among them, according to Berkeley Earth.

Ten countries, mostly in the Mediterranean, Middle East and North America, set new national heat records. More than 100 nations registered a highest monthly mark, a rate 21 times higher than cold records, according to Maximiliano Herrera, a climatologist who tracks global temperature records. The Arctic was slightly cooler last year but is still warming two to three times the global average.

“We've had almost a full decade of these elevated temperatures, and it can't help but to have an impact on the weather and on the extremes,” said Gavin Schmidt, director of NASA GISS. “It's not the case that you have to have a record set at the global mean to have lots and lots of records being set locally.”

The areas marked on this globe set new records for local high temperatures in 2021, according to a Bloomberg analysis of Copernicus data.

Not all of these superlatives made global headlines like the heat dome that stretched across the U.S.-Canada border, which scientists in July determined was made at least 150 times more likely by climate change.

Temperatures soared well above 40°C (100°F) in parts of this region, breaking records by unprecedented margins in what had previously been a temperate zone with little need for air conditioners.

A Mediterranean heat wave in August brought Europe a record high as Italy reached 48.8°C (120°F). Snails cooked in their shells. Spain hit 47.4°C, and Tunisia saw 49°C.

One of Pakistan’s typically hottest cities, Jacobabad, reached 52°C in June.

After a deadly cold spell in February, Texas ended 2021 with its hottest-ever December. The states of Montana, Wyoming, Washington and North Dakota also broke records that month.

July 2021 technically became the hottest month ever recorded, according to NOAA, edging out by 0.02°C the prior record set by the Julys of 2016, 2019 and 2020.

Source: Copernicus ECWMF

NASA’s top climate scientist once met skepticism when predicting that 1988 would end as the world’s hottest year. He was right—but now that year seems mild by today’s standards, ranking 28th for heat.

Now predictions of increasing heat are beyond doubt. In fact, greenhouse gas has propelled every decadal temperature average higher than the one before it since the 1960s. Twenty-one of the hottest 22 years since 1880 have occurred in this century, reflected in these maps of heat records from previous years. The pattern is too clear to miss.

“What matters is the long-term trend, and this is pretty much directly on trend,” Schmidt said. “That’s not going to change. Next year, I predict—just me predicting—that 2022 will be warmer than 2021. That makes it another close-to top-five year.”

NASA, NOAA, Berkeley Earth and the U.K. Met Office, which has yet to report its 2021 results, all base their analyses on global weather station and ocean data. Copernicus’s ERA5 model conducts what’s called a reanalysis of many variables and estimates its results in near-real time.

Consequences of record-breaking heat

Heat can kill in several ways, all of them preventable with cooling infrastructure. Hotter nighttime temperatures, which prevent bodies from cooling down, are sometimes linked to more deaths than daytime extremes. In June’s western North American heat wave, nighttime temperatures didn't drop in some places below 25°C (77°F). This contributed to a spike in excess deaths in British Columbia that dwarfed the mortality impact of Covid-19 that week.

Erich Fischer is a climate scientist at ETH Zurich. In 2019, he and two colleagues had begun to study something they thought researchers had given too little attention: The margin by which new heat records surpass the old ones. It would be a way to complement the many analyses that compare extreme heat waves with the local normal.

They simulated heat waves in the U.S. Midwest, the site of the historic Dust Bowl. It’s a region that hasn’t notched many new heat records in decades. What they saw floored them—a leap in maximum temperature far beyond a 1-in-1,000-year event. “You basically think, OK, something went wrong,” Fischer said of the results. His colleagues agreed. Maybe an axis was mislabeled or something went haywire deep inside the model. But it all checked out.

Fischer and his partners took their results to outside researchers, some of whom accused them of potentially fear-mongering. After more work, the paper was accepted by the journal Nature Climate Change in May. Exactly four weeks later, the heat wave of unprecedented scale hit western North America, smashing records by multiple degrees. “It is exactly the type of event we had been thinking about,” he said.

Source: E. M. Fischer, S. Sippel and R. Knutti, “Increasing probability of record-shattering climate extremes”, *Nature Climate Change*

Seemingly minor, gradual increases in global average temperatures are already bringing about disruptive weather swings. Fischer said he hopes future research will give regions a preview of what’s possible.

“It's much harder to convince people who then have to spend a lot of money on getting prepared that this is actually real and that it's plausible,” he said.

Editors: Aaron Rutkoff and Alex Tribou

With assistance from: Paul Murray, Jin Wu, Hayley Warren, Jane Pong, Allison McCartney and Andre Tartar

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Methodology:

Global temperature records for mapping were calculated from Copernicus ECWMF's ERA5 Reanalysis 2m temperature data, obtained through the the Copernicus Climate Data Store and Google Earth Engine. Annual maximum temperatures were compared against the maximum temperatures for all previous years going back to 1979 to find the margin by which heat records were broken.

Results were corroborated against maximum temperature records calculated from NOAA’s GHCN (Global Historical Climatology Network). The GHCN data was downloaded and analyzed with the R package 'rnoaa'.

The World’s Troubling New Tempo of Temperature Records

Where temperature records were broken in 2021

Record heat from past years

Consequences of record-breaking heat

Estimated excess mortality in British Columbia

Projected occurrence of record-shattering extremes in northern midlatitudes

Methodology: