The Battle Against Climate Change: Has the 1.5 Degree Limit Already Been Lost?

The Debate Over 1.5 Degrees

Countries agreed in 2015 to try and keep global warming to 1.5 degrees. But what if the battle to stay under this limit has already been lost? For years, the fight against climate change has been symbolized by one number: 1.5.

Homes surrounded by flood waters in Hampton, New Hampshire, on January 10, 2024. Climate change is fueling storms in both the summer and winter.

Ever since countries agreed in 2015 to an ambition of restricting global warming to 1.5 degrees Celsius above pre-industrial levels, the number has become synonymous with staving off catastrophic climate change. But what if the battle to keep global warming from overshooting this limit has already been lost?

Makatla Ritchter wades through flood waters in Tarpon Springs, Florida, after after Hurricane Idalia on August 30, 2023.

Some prominent scientists argue it has and it’s irresponsible not to sugarcoat the truth. For others, that view is not only wrong, but even 'dangerous.' It was the renowned climate scientist James Hansen whose comments fueled the debate. In November, he declared the 1.5 degree-limit 'deader than a doornail,' saying it was a shortcoming of the scientific community 'to not make clear to the political leaders what the situation is.'

Destruction in the aftermath of flash flooding caused by Storm Daniel in Libya's eastern port city of Derna on September 17, 2023.

Extraordinary Heat and Unprecedented Global Temperatures

As many parts of the US and Europe deal with an Arctic blast of brutally cold air, it can be hard to recall just how hot 2023 was. Last year saw unprecedented global temperatures, with heat records around the world tumbling. El Niño — a natural climate phenomenon that tends to boost the planet’s average temperature — collided with the long-term trend of global warming, making 2023 the hottest year on record. The year came within a whisker of breaching 1.5 degrees, according to data from the Copernicus Climate Change Service.

While scientists are most concerned about long-term warming over many years, not just one, 2023’s record heat was a stark warning sign. If the world breaches 1.5 degrees over the long term, scientists say the impacts of climate change will start to exceed the ability of humans and ecosystems to adapt. But every fraction of a degree matters, and climate chaos is already emerging.

Is Climate Change Accelerating?

At the center of Hansen’s argument is his much-debated assertion that the planet is warming much faster than predicted. He points to the imbalance between the energy coming in from the sun and what leaves through heat radiating into space. This imbalance has doubled, meaning global warming is escalating, he argued in a November paper he co-authored with more than a dozen other scientists. The paper’s scientists attribute this mainly to successful global efforts to tackle shipping pollution.

Hansen’s research predicts the world will breach the long-term 1.5-degree benchmark this decade, and 2 degrees before 2050. That would mean the world has failed to deliver on the central goal in the Paris Agreement on climate change, under which countries pledged to limit warming to well below 2 degrees.