The rate Earth is warming hit an all-time high in 2023, with 92 percent of last year’s surprising record-shattering heat caused by humans, top scientists have calculated.
The group of 57 scientists from around the world used United Nations-approved methods to examine what’s behind last year’s deadly burst of heat. They said that even with a faster warming rate, they don’t see evidence of significant acceleration in human-caused climate change beyond increased fossil fuel burning.
Last year’s record temperatures were so unusual that scientists have been debating what’s behind the big jump and whether climate change is accelerating or if other factors are in play.
“If you look at this world accelerating or going through a big tipping point, things aren’t doing that,” said Leeds University climate scientist Piers Forster, lead author of the study. “Things are increasing in temperature and getting worse in sort of exactly the way we predicted.”
It’s pretty much explained by the buildup of carbon dioxide from rising fossil fuel use, he and a co-author said.
Last year, the rate of warming hit 0.26 degrees Celsius (0.47 degrees Fahrenheit) per decade — up from 0.25 degrees Celsius (0.45 degrees Fahrenheit) the year before. That’s not a significant difference, though it does make this year’s rate the highest ever, Forster said.
Still, outside scientists said this report highlights an ever more alarming situation.
“Choosing to act on climate has become a political talking point, but this report should be a reminder to people that in fact it is fundamentally a choice to save human lives,” said University of Wisconsin climate scientist Andrea Dutton, who wasn’t part of the international study team. “To me, that is something worth fighting for.”
The team of authors determined last year was 1.43 degrees Celsius warmer than the 1850-to-1900 average, with 1.31 degrees of that coming from human activity. The other 8 percent of the warming is due mostly to El Nino, the natural and temporary warming of the central Pacific that changes weather worldwide, and also a freak warming along the Atlantic and other weather events.
On a larger 10-year time frame, which scientists prefer to single years, the world has warmed about 1.19 degrees Celsius (2.14 degrees Fahrenheit) since pre-industrial times, the report in the journal Earth System Science Data found.
The report also said that as the world keeps using coal, oil and natural gas, Earth is likely to reach the point in 4.5 years that it can no longer avoid crossing the internationally accepted threshold for warming: 1.5 degrees Celsius (2.7 degrees Fahrenheit).
That fits with earlier studies projecting Earth being committed or stuck to at least 1.5 degrees by early 2029 if emission trajectories don’t change. The actual hitting of 1.5 degrees could be years later, but it would be inevitable if all that carbon is used, Forster said.
It’s not the end of the world or humanity if temperatures blow past the 1.5 limit, but it will be quite bad, scientists said. Past U.N. studies show massive changes to Earth’s ecosystem are more likely to kick in between 1.5 and 2 degrees Celsius of warming, including eventual loss of the planet’s coral reefs, Arctic sea ice, species of plants and animals — along with nastier extreme weather events that kill people.
Last year’s temperature rise was more than just a little jump. It was especially unusual in September, said study co-author Sonia Seneviratne, head of land-climate dynamics at ETH Zurich, a Swiss university.
The year was within the range of what was predicted, albeit it was at the upper edge of the range, Seneviratne said.
“Acceleration if it were to happen would be even worse, like hitting a global tipping point. It would be probably the worst scenario,” Seneviratne said. “But what is happening is already extremely bad, and it is having major impacts already now. We are in the middle of a crisis.”
