“Passing this measure for the first time should set off serious alarm bells,” said Julie Brigham-Grette, a geoscientist at the University of Massachusetts Amherst.
And yet, there is far from consensus among climatologists on the loudness of these alarms or on the real importance of this measure.
There is something undeniable about this moment, even though Harvard climatologist Daniel Schrag said: This does not mean that the planet has passed “a point of no return where it is too late”.
The reality: “1.5°C is bad, 2°C is worse, 2.5°C is much worse,” and so on, he said. “It can always get worse. And therefore, there’s no point in throwing up our hands and saying, “Oh, we failed, we’re done.” »
Certainly, a year after passing 1.5°C This threshold does not indicate that global temperatures are stuck at such a high level. This is certainly a worrying sign, but 2024 could be a failure. Climate is what happens over decades, not what happens in any given year.
Many climatologists have also long been clear-headed that 1.5 degrees of warming was inevitable. “I could tell 20 years ago that we were going to pass this threshold,” said Schrag, co-director of Harvard’s Science, Technology and Public Policy program.
What this goal signaled, more than anything else, was an aspiration, a goal that, while probably unachievable, provided a benchmark for global ambition. A 2016 report of the United Nations declared that it was “not a scientific question of feasibility, but rather a moral imperative of necessity.”
This objective was agreed in 2015, when world leaders gathered in Paris for the United Nations Annual Assembly. global climate negotiations. They agreed to keep the Earth’s temperature well below 2 degrees above pre-industrial times and to aim for the goal of 1.5 degrees.
This more ambitious goal was particularly important for low-lying island nations – those most at risk from rising sea levels and least responsible for burning large quantities of fossil fuels that cause climate change .
Meanwhile, climate change continues to outpace even the best models.
“Frankly, it has been quite surprising how quickly the warming has occurred over the last couple of years,” said Peter Huybers, a professor in the department of Earth and planetary sciences at Harvard University. In 2023 and 2024, in particular, temperatures warmed faster than expected, likely due to decreasing cloud cover over the oceans, leading to increased absorption of solar heat by Earth.
The cause of the decrease in cloud cover is currently debated, Huybers said: perhaps it is natural variability, or perhaps an unintended consequence of banning one type of fuel from particularly dirty transport, which caused emissions likely to increase cloudiness.
Since Paris, the objective has changed. A 2023 Report found that exceeding the 1.5 degree target was becoming “rapidly inevitable” as countries failed to reduce their carbon emissions fast enough.
NOW, the goal is to minimize the time the planet spends above this threshold, by rapidly eliminating greenhouse gas emissions and scaling up technologies to remove carbon from the atmosphere. Only by taking this second step can we reverse climate change, because heat-trapping gases, such as carbon dioxide, remain in the atmosphere for an extended period of time. hundreds of years.
Currently, these carbon removal technologies are expensive and only exist on a small scale, meaning there is no clear mechanism to remove emissions already in the atmosphere. The best path forward, scientists say, is to reduce carbon pollution as quickly as possible and let temperatures remain stable at a high level since pre-industrial times.
There are positive signs on this, said Max Holmes, CEO of the Woodwell Climate Research Center in Falmouth. Globally, emissions are expected to soon peak as clean energy is rapidly adopted and polluting power plants are retired. Yet progress is measured in decades.
“It will be a long time before the temperature stabilizes and then changes direction – probably not in our lifetimes – but the emissions will and that is something to celebrate,” he said.
In the meantime, “science is not going to disappear,” said Adam Schlosser, deputy director and senior fellow at MIT’s Center for Sustainability Science and Strategy. Continuing to emit greenhouse gases only leads to one thing: rising temperatures. And while the annual average could fluctuate above and below 1.5 degrees in coming years, it will eventually stay above the threshold, likely by the mid-2030s, Schlosser said.
Always, At stake in the 1.5 degree goal is whether the ambitious nature of the goal will ultimately be recognized as something that has motivated nations around the world to accelerate their response to the climate crisis, or whether Failure to achieve it will result in the public perception of failure — and, worse, an excuse to give up, Holmes said.
“If people think it’s game over, then you lose all motivation to do what needs to be done.”
Sabrina Shankman can be contacted at sabrina.shankman@globe.com. Follow her @shankman.