A New Era in Global Heat

It’s confirmed: 2023 was the planet’s warmest year on record and perhaps in the last 100,000 years. By far.

Average temperatures were 1.48 degrees Celsius, or 2.66 Fahrenheit, above preindustrial levels, according to an announcement this morning by Copernicus, the European Union’s climate monitor. The previous record was in 2016.

Temperature records started being shattered in June. From then on, every month has been the warmest on record.

Climate scientists aren’t surprised that unabated emissions of greenhouse gases caused global warming to reach new highs, my colleagues Raymond Zhong and Keith Collins reported. If you’ve been reading this newsletter, you shouldn’t be surprised, either.

But they are still trying to understand whether 2023 foretells many more years in which heat records are not merely broken, but smashed. In other words, they are asking whether the numbers are a sign that the planet’s warming is accelerating.

Many factors

The consequences of all this additional heat played out around the world. Canada has its most destructive wildfire season on record, Antarctica had the smallest amount of sea ice ever measured and unrelenting heat battered several countries including Iran, China, Greece, the United States, Malawi and Chile.

Climate scientists are investigating several factors that may have helped make 2023 so remarkably hot, beyond the increase in greenhouse gas emissions.

There was the eruption of an underwater volcano near the island nation of Tonga, which spewed a lot of water vapor that helped trap more heat near the planet’s surface. Recent limits on sulfur pollution from ships may have curbed aerosol emissions that can reflect solar radiation back into space and cool the planet.

And El Niño, the cyclical climate pattern that is often linked with record-setting heat worldwide, began last year. (The second-warmest year on record, 2016, was also an El Niño year.)

A 100,000-year high

Carlo Buontempo, the director of Copernicus, said that average temperatures his team had documented were the highest in the climate organization’s records dating back to 1850. But evidence suggests, he added, that Earth hasn’t been this warm in at least 100,000 years.

“There were simply no cities, no books, agriculture or domesticated animals on this planet the last time the temperature was so high,” he said.

Buontempo’s comment reminded me of why nations agreed to make an effort to keep warming below 1.5 degrees Celsius, and well below 2 degrees Celsius, in the 2015 Paris Agreement. As my colleague Brad Plumer wrote in Vox at the time, researchers argued that it would be safer for humanity to stay within the temperature range in which humans originally developed.

Last year’s numbers came incredibly close to reaching the 1.5 degree threshold that has guided global efforts to curb climate change since 2015. Almost half the year was above that level, and researchers fear we may blow past that limit this year.

But that doesn’t mean the world has failed. At least, not yet.

First, the Paris Agreement set a long-term target, so the planet would need to stay above the 1.5 degree limit for several years in a row to officially exceed the target. So far, the planet has warmed between 1.1 and 1.3 degrees Celsius.

Second, 1.5 degrees is not a planetary tipping point. “There is no physical threshold that is crossed if we are at 1.51 degree Celsius instead of 1.49,” Gavin Schmidt, a climate scientist at NASA, told me.

But every fraction of a degree matters. Between 1.5 and 2 degrees Celsius of warming, coral reefs may disappear and the number of people suffering from extreme heat would more than double. Impacts will be worse the warmer the planet gets.

For the public debate, the biggest danger “is that people might feel that breaching the 1.5 degree Celsius level means that there is nothing to be done about climate change,” Schmidt said. “And that is absolutely wrong.”

Global climate change can be seen in the dramatically rising temperatures of 2023. But it also unfolds as a story of extremes.

A series of powerful storms will wreak havoc across the United States today, bringing significant weather of nearly every variety to large parts of the Pacific Northwest, the Plains, Midwest, South and East Coast.

It can seem counterintuitive that on a warming planet, winter storms can produce so much snow. Just last week, we were telling you about the below-normal snowfall at the end of 2023. But these extreme fluctuations are actually a fairly logical consequence of climate change’s effects.

More extreme precipitation events, snow as well as rain, are “exactly what we expect in a warming world,” said Rick Thoman, a climate specialist at the University of Alaska Fairbanks.

As the planet warms, so do both the oceans and the atmosphere. Warmer oceans increase the amount of water that evaporates into the air, and warmer air can hold more water vapor, which it eventually releases as precipitation.

“The storm is so widespread that it’s impacting everyone in the Eastern U.S.,” said Judson Jones, a reporter and meteorologist at The Times. “And it’s arriving just 36 hours after a coastal storm dropped large amounts of snow in the Northeast.”

“Alone, this storm would bring a flooding risk, but the combination of melting snow and rain will exacerbate the flood risks,” he added.

There’s more to come. Another storm will strengthen and hit the East again on Friday and into Saturday. Then, temperatures are expected to drop and a more wintery storm is likely to hit the East early next week.

Here are some of the extreme weather expected in the United States:

• The eastern third of the U.S. will see widespread hazardous weather, mainly in the form of heavy rain capable of producing flooding, from the Florida Panhandle all the way up to southern Maine.

• Heavy rain will hit the New York area from late Tuesday into Wednesday, raising the risk of significant river flooding around New Jersey, the Lower Hudson Valley and parts of Connecticut.

• In southern New England, up to three inches of rain could cover ground that is already saturated, and in some places covered with snow. Strong winds up to 50 miles per hour are also a concern.

• Blizzard conditions will persist in the High Plains through the Upper Midwest with potentially more snow on the way by the end of the week. Portions of the region will see blizzard conditions with up to six inches of snow coupled with winds up to 40 m.p.h., or nearly 65 k.p.h., and gusts hitting 60 m.p.h.

• A potent cold front will continue to affect the Pacific Northwest, bringing several feet of heavy snow and blizzard conditions across the Cascades. Heavy snow will also continue to blanket the Northern Rockies.

The Times is tracking extreme weather risks across the country, and can notify you with custom alerts for the places that are important to you. — Derrick Bryson Taylor and Elena Shao