Record-breaking heat in 2024 has brought the world to a dangerous threshold. Now what?

Source: Copernicus/ECMWF

Note: Temperature anomalies compared to 1850-1900 averages.

By midnight on December 31, Earth had ended the hottest year in recorded history, scientists said on Friday. The previous hottest year was 2023. The next will come before long: by continuing to burn huge amounts of coal, oil and gas, humanity has ensured that.

The planet’s high average temperature last year reflects weeks-long spring heat waves of 104 degrees Fahrenheit, which closed schools in Bangladesh and India. They reflected the effects of warm ocean waters that led to an increase in hurricanes in the Gulf of Mexico and typhoons in the Philippines. This reflects the hot summer and fall conditions that prepared Los Angeles this week for the most destructive wildfires in its history.

“We are facing a very new climate and new challenges, challenges for which our society was not prepared,” said Carlo Bontempo, director of the Copernicus Climate Change Service, an EU monitoring agency.

But even with this progress of warmer years and increasingly severe risks to homes, communities and the environment, 2024 has emerged in another, unwelcome way. According to Copernicus, this was the first year in which average global temperatures were more than 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, higher than those the planet experienced at the beginning of the industrial age.

Over the past decade, the world has sought to avoid crossing this dangerous threshold. Nations enshrined this goal in the 2015 Paris Agreement to combat climate change. “Keep 1.5 alive” was the slogan repeated at UN summits.

And yet here we are. Global temperatures will fluctuate somewhat, as they always do, which is why scientists often look at average warming over longer periods, not just one year.

But even by that standard, staying below 1.5 degrees seems increasingly out of reach, researchers say. The researchers who ran the numbers. Globally, despite hundreds of billions of dollars invested in clean energy technologies, carbon dioxide emissions hit a record high in 2024 and show no signs of declining.

One of the recent studies A study published in the journal Nature concluded that the best humanity can hope for now is about 1.6 degrees of warming. And to achieve it, O nations You will need to start cutting emissions At a pace that would put pressure on political, social and economic viability.

But what if we started earlier?

By releasing greenhouse gases into the atmosphere, humanity has raised global temperatures to record levels.

If countries had started cutting emissions in 2005, they could have made gradual cuts to limit temperature rise to 1.5 degrees.

Starting in 2015, when the Paris Agreement was adopted, more severe cuts were required.

Starting today, it will require cuts so radical that they may seem impossible in the first place.

“It was certain that we were going to get to this point where the gap between reality and the path we needed to get to 1.5 degrees was so large that it was ridiculous,” said David Victor, a professor of public policy at the University of California, San Diego.

The question now is what should replace 1.5 as a guiding star for countries’ climate aspirations.

“These high-level goals are at best a compass,” Dr. Victor said. “It’s a reminder that if we don’t do more, we will face significant climate impacts.”

The threshold of one and a half degrees has never been the difference between safety and ruin, or between hope and despair. It was a number negotiated by governments in an attempt to answer a big question: what is the highest increase in global temperature – and the level of associated risks, whether heatwaves, wildfires or melting glaciers – that our societies should strive to avoid. ?

The result, as codified in the Paris Agreement, was that countries would aspire to keep temperature rise to “well below” 2 degrees Celsius while “continuing efforts” to limit it to 1.5 degrees.

Even then, some experts called the latter target unrealistic, because it would require such deep and rapid emissions cuts. However, the United States, the European Union, and other governments have adopted it as a guideline for climate policy.

The urgency of Target 1.5 has spurred companies of all types — automakers, cement makers, electric utilities — to start thinking seriously about what a complete shutdown would mean, said Christophe Bertram, an associate research professor at the Center for Global Sustainability at the University of Maryland. emissions by mid-century. “I think this has led to some serious action,” Dr. Bertram said.

But the high ambition of the 1.5 target also exposed deep fault lines between countries.

China and India have never supported this goal, because it would require them to limit their use of coal, gas and oil at a pace they said would hinder their development. Rich countries that were struggling to reduce their emissions began Stifling finance In the developing world for fossil fuel projects that were economically beneficial. Some low-income countries felt it was extremely unfair to do so Ask them to sacrifice As for climate, since it is the rich countries – not them – that have produced most of the greenhouse gases that are now causing the world to warm.

The 1.5 degree target has created a lot of tension between rich and poor countries, said Vijaya Ramachandran, director of energy and development at the Breakthrough Institute, an environmental research organization.

Costa Samaras, a professor of environmental engineering at Carnegie Mellon University, compared the warming goals to guidelines set by health officials on cholesterol, for example. “We don’t set health goals based on what is realistic or possible,” Dr. Samaras said. “And we say, ‘This is good for you. This is how you won’t get sick.’

“If we were to say, ‘Well, 1.5 is probably out of the question, let’s say 1.75,’ that gives people a false sense of reassurance that 1.5 wasn’t that important,” said Dr. Samaras, who helped shape the idea. U.S. Climate Policy from 2021 to 2024 at the White House Office of Science and Technology Policy. “It’s very important.”

Scientists invited by the United Nations The researchers concluded that limiting temperature rise to 1.5 degrees instead of 2 degrees would save tens of millions of people from exposure to life-threatening heat waves, water shortages, and coastal flooding. It could mean the difference between a world that has coral reefs and Arctic sea ice in summer, and a world that doesn’t.

Every small increase in additional warming, whether it is 1.6 degrees versus 1.5, or 1.7 versus 1.6, increases the risk. “Even if the world exceeds 1.5 degrees, and the chances of this happening are increasing every day, we must continue to strive” to reduce emissions to zero as soon as possible, said Inger Anderson, Executive Director of the United Nations Environment Programme.

Officially, the sun has not yet set on Target 1.5. The Paris Agreement remains in effect, even as President-elect Donald J. Trump has pledged to withdraw the United States from it for a second time. In the UN climate negotiations, talk about 1.5 has become more muted compared to previous years. But it barely disappeared.

“With appropriate measures, 1.5 degrees Celsius is still achievable,” Cedric Schuster, Minister of Natural Resources and Environment on the Pacific island of Samoa, said at last year’s summit in Azerbaijan. He said countries must “rise to the occasion with new and very ambitious policies.”

For Dr. Victor of the University of California, San Diego, it is strange, but highly to be expected, that governments continue to talk this way about what appears to be an unattainable goal. “No major political leader who wants to be taken seriously on climate wants to stick his neck out and say: ‘1.5 degrees is not possible.’ “Let’s talk about more realistic goals,” he said.

However, the world will eventually do so Need to have that discussionDr. Victor said. It is unclear how things will go.

“It could be constructive, where we start asking the question: ‘How much warming are we actually seeing? And how do we deal with that?’” he said. “Or it could seem very toxic, with a bunch of political accusations.”

methodology

The second chart shows carbon emissions reduction pathways that have a 66 percent chance of limiting global warming this century to no more than 1.5 degrees Celsius above the pre-industrial average.