The fight against climate change has been symbolized by a single number for years: 1.5.
Since countries agreed in 2015 to limit global warming to 1.5 degrees Celsius above pre-industrial levels, the figure has become synonymous with preventing catastrophic climate change.
But what if the fight to prevent global warming from exceeding this limit is already lost?
Some leading scientists argue that this is so and that it is irresponsible not to cover up the truth. For some, this view is not only wrong but also “dangerous”.
The person whose comments sparked the debate was renowned climate scientist James Hansen. In November, he declared that the 1.5-degree limit was “more lethal than a doornail” and said it was a failure of the scientific community to “not explain to political leaders what the situation is.”
At a press conference in November, he said that the rate of global warming is increasing and the world’s warming is certain to exceed 1.5 degrees. “Anyone who understands physics knows this.”
Hansen’s words carry great importance; He is considered the first scientist to publicly sound the alarm about climate change in the 1980s. But other scientists pushed back harshly.
“I have three degrees in physics, and I can tell you Jim is wrong,” said Michael Mann, a leading climate scientist at the University of Pennsylvania, referring to Hansen. He told CNN that the problem is politics, not physics. “Political obstacles can also be overcome”
Incoming reply Friederike OttoDr D., a climate scientist at Imperial College London’s Grantham Institute. “I think that’s a very stupid thing to say,” he told reporters in November. “Right now (1.5 degrees) is achievable and pretending it’s not will just lead to doing nothing for a longer period of time.”
Disagreements over climate science are not uncommon; Our planet is a highly complex system, and the nature of reaching consensus often begins with scientists disagreeing.
But as global warming fuels extreme weather such as heat waves, hurricanes and even severe winter storms that have devastated parts of the United States, debates about the future of 1.5 are becoming unusually heated.
extraordinary heat
With many parts of the U.S. and Europe facing a blast of severe cold air in the Arctic, it can be hard to remember just how warm 2023 is. The past year has seen unprecedented global temperatures, with temperature records falling across the world.
El Niño, a natural climate phenomenon that tends to increase the planet’s average temperature, has collided with the long-term global warming trend, making 2023 the hottest year in history. According to the data of the Copernicus Climate Change Service, the year was close to exceeding 1.5 degrees.
While scientists are most concerned about long-term warming that will last for many years, not just one year, the record heat in 2023 was a stark warning sign. Scientists say that if the world exceeds 1.5 degrees in the long term, the effects of climate change will begin to exceed the ability of people and ecosystems to adapt.
But every part of the degree matters, and climate chaos is already emerging.
“It’s not like before 1.5 everything will be fine and after 1.5 an asteroid will hit us,” Otto told CNN. He said keeping warming below 1.5 degrees is a political goal, not a physical threshold.
In just a few years, the world has warmed from 1 degree Celsius above pre-industrial levels to about 1.2 degrees today; that’s fractions of a degree that translates into record-breaking extreme weather.
According to Hansen, recent global temperatures provide compelling evidence that 1.5 is dead. “I haven’t spent much time arguing about this point because I know nature is in the process of proving us right,” he told CNN.
It predicts that by May the planet will have a 12-month period in which average temperatures are 1.6 to 1.7 degrees higher than pre-industrial levels.
“For all practical purposes, we will only be looking at 1.5 degrees in the rearview mirror,” he said.
Is climate change accelerating?
At the heart of Hansen’s argument is his much-discussed claim that the planet is warming much faster than predicted.
It draws attention to the imbalance between the energy coming from the sun and the energy radiated into space through heat. In a November article he wrote with more than a dozen scientists, he argued that this imbalance had doubled, meaning global warming was increasing.
The paper’s scientists attribute this mainly to successful global efforts to combat ship pollution.
Ships burn fossil fuels, which produce carbon emissions that have a significant impact on global warming. However, ship exhaust fumes also contain sulfur dioxide. Strangely enough, the pollutant, which is extremely dangerous to human health, has a global cooling effect as the particles reflect sunlight away from Earth.
Hansen’s research predicts that the world will exceed the long-term 1.5 degree limit this decade and 2 degrees before 2050. This means that countries around the world are failing to meet the key goal of the Paris Agreement on climate change. Limit warming to well below 2 degrees.
Bill McGuire, emeritus professor of earth sciences at University College London, shares Hansen’s concerns about the pace of change.
“The energy balance of our world is now greatly disrupted,” McGuire told CNN, adding that it was “frankly appalling.”
However, according to many other scientists, there is no evidence to show that global warming is accelerating. At least not yet.
Chris Smith, a climate modeler at the University of Leeds in the United Kingdom, said it was too early to make that claim. “We really need three or four years of data that are all pointing in the same direction,” he told CNN.
Last year’s unprecedented warmth was enhanced by El Niño and “does not constitute a change in the trend line,” Mann said.
The rate of global warming accelerated after the 1970s as clean air laws reduced air pollution, but since then “the planet has warmed at a roughly constant rate,” he said. “Reality is bad enough,” he added. “There’s no need to exaggerate.”
Samantha Burgess, deputy director of Copernicus, said there have been recent climate events that scientists have difficulty understanding, including the record-breaking ocean temperatures of 2023.
But in terms of Hansen’s warning about the significant effects of cleaning up shipping pollution on global warming, “we’re not seeing the signal,” he said.
Why is 1.5 important?
Few scientists would disagree that the world faces the difficult task of limiting warming to 1.5 degrees. Despite current climate policies, the planet is heading for almost 3 degrees of warming.
In some ways, their divide is essentially an argument about the value of having a 1.5 degree limit.
If we say 1.5 degrees is dead, “that probably means for a lot of people the outcome is ‘OK, then it’s not even worth trying,'” Otto said.
Smith said this risks “devolving into a fatalistic narrative, which is actually quite dangerous” and potentially persuading leaders to think “we failed, everything’s fine now.”
He told CNN it would be “very difficult” for the temperature to stay below 1.5 degrees, but it was too early to say it was impossible.
Mann said it was “irresponsible” to claim 1.5 degrees was dead when the world could avoid crossing the threshold by making significant and immediate reductions in carbon pollution.
McGuire has the opposite view. He said it was impossible for the world to meet this limit, which would require emissions to be cut by almost half by 2030. “To suggest otherwise is hypocritical and gives an inaccurate picture of where we are.” Framing 1.5 as a “target” to be met, rather than a limit to stay below, gave the illusion that we had more time to overcome it than we actually did. He said the crisis allowed countries and companies to continue burning fossil fuels.
But one of the key concerns is that if politicians abandon 1.5 degrees, they will not try to limit global warming to 1.6 or 1.7 degrees, but will instead focus on 2 degrees, the upper limit promised in the 2015 Paris Agreement.
“This is a huge danger and would be truly disastrous,” Otto said.
Between 1.5 and 2 degrees lies disaster: the melting of the ice sheet and the risk of triggering multiple climate turning points, including the mass die-off of coral reefs and the loss of lives and livelihoods of millions of people.
Otto said we will probably reach 1.5 degrees as the global average temperature next year. “Whether we stay there or how much we go above that is still a political question, and it’s up to us to change that.”
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