A new era in the global heat

It has been confirmed: 2023 was the hottest year on Earth ever recorded and perhaps in the past 100,000 years. By far.

According to an announcement this morning by Copernicus, the European Union’s climate monitor, average temperatures were 1.48 degrees Celsius, or 2.66 Fahrenheit, above pre-industrial levels. The previous record was from 2016.

In June, temperature records began to be broken. From then on, every month was the warmest on record.

Climate scientists are not surprised that unabated greenhouse gas emissions have caused global warming to reach new highs, my colleagues Raymond Zhong and Keith Collins reported. If you have read this newsletter, you should not be surprised.

But they’re still trying to understand whether 2023 portends many more years in which heat records will not only be broken, but broken. In other words, they wonder whether the numbers are a sign that planetary warming is accelerating.

Many factors

The consequences of all this extra heat were felt all over the world. Canada experienced its most destructive wildfire season on record, Antarctica had the smallest amount of sea ice on record, and relentless heat ravaged several countries including Iran, China, Greece, the United States, Malawi and Chile.

Climate scientists are examining several factors that may have contributed to 2023 being so remarkably hot, aside from increases in greenhouse gas emissions.

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

And El Niño, the cyclical climate pattern often associated with record warmth worldwide, began last year. (The second warmest year on record, 2016, was also an El Niño year.)

A culmination of 100,000 years

Carlo Buontempo, the director of Copernicus, said the average temperatures his team had documented were the highest in the climate agency’s data going back to 1850. But there is evidence that Earth has not been this warm in at least 100,000 years.

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

Buontempo’s comment reminded me why countries agreed in the 2015 Paris Agreement to work to keep warming below 1.5 degrees Celsius and well below 2 degrees Celsius. As mine 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 evolved.

Last year’s figures came incredibly close to reaching the 1.5 degree threshold that has guided global efforts to curb climate change since 2015. Nearly half of the year has been above that level, and researchers fear we may blow over that mark 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 that the planet must remain 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 turning point. “There is no physical threshold that is crossed if we are at 1.51 degrees Celsius instead of 1.49,” Gavin Schmidt, a climate scientist at NASA, told me.

But every fraction of a degree matters. With a warming of 1.5 to 2 degrees Celsius, coral reefs could disappear and the number of people suffering from extreme heat would more than double. The consequences will be worse as the planet warms.

The biggest danger for the public debate is “that people may get the feeling that exceeding the 1.5 degree Celsius limit means that nothing can be done about climate change,” says Schmidt. “And that is absolutely wrong.”

Global climate change is reflected in the dramatically rising temperatures of 2023. But it is also unfolding as a story of extremes.

A series of powerful storms will wreak havoc across the United States today, bringing significant weather events of almost every kind to much of the Pacific Northwest, the Plains, Midwest, South and East Coast.

It may seem counterintuitive that on a warming planet, winter storms can produce so much snow. Last week we told you about below-normal snowfall at the end of 2023. But these extreme fluctuations are actually a fairly logical consequence of the consequences of climate change.

More extreme precipitation events, both snow and 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 is eventually released as precipitation.

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

“On its own, this storm would pose a flood risk, but the combination of melting snow and rain will worsen flood risks,” he added.

There’s more to come. A new storm will strengthen again on Friday and Saturday and will hit the east. After that, temperatures are expected to drop and a more wintry storm is likely to hit the East early next week.

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

• The eastern third of the US will experience widespread hazardous weather, mainly in the form of heavy rain that could cause flooding, from the Florida Panhandle to southern Maine.

• Heavy rain will hit the New York region late Tuesday through Wednesday, increasing the risk of significant river flooding around New Jersey, the Lower Hudson Valley and parts of Connecticut.

• In southern New England, up to two inches of rain could blanket ground that is already saturated and covered in snow in some places. Strong winds of up to 50 kilometers per hour are also a problem.

• Blizzard conditions will continue across the Upper Midwest’s High Plains, with more snow possible toward the end of the week. Parts of the region will experience snowstorms with up to six inches of snow, coupled with winds of up to 40 miles per hour, or nearly 40 miles per hour, and gusts of up to 60 miles per hour.

• A powerful cold front will continue to impact the Pacific Northwest, bringing several feet of heavy snow and blizzards across the Cascades. Heavy snow will also continue to blanket the northern Rockies.

The Times monitors extreme weather risks across the country and can alert you to the places that matter to you with customized alerts. — Derrick Bryson Taylor and Elena Shao