The rate of Earth’s warming has reached a record level in 2023, with 92% of last year’s surprising, record-breaking 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 heat blast. They said that even with a faster rate of warming, they do not see evidence of a significant acceleration of human-caused climate change beyond increased burning of fossil fuels.
Last year’s record temperatures were so unusual that scientists are wondering what’s behind the big jump and whether climate change is accelerating or other factors are at play.
“If you look at this world accelerating or going through a big tipping point, things don’t happen that way,” said the study’s lead author, Piers Forster, a climate scientist at the University of Leeds. “The temperature is getting worse and worse, just as we predicted.”
This is largely due to the buildup of carbon dioxide from the growing use of fossil fuels, he and a co-author said.
Last year, the rate of warming reached 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, even though this year’s rate is the highest on record, Forster said.
Yet outside scientists say the report highlights an even more alarming situation.
“Choosing to act on climate has become a political talking point, but this report should remind people that it is fundamentally a choice to save human lives,” said Andrea Dutton, climate scientist at the University of Wisconsin, which was not part of the study. the international study team. “To me, that’s something worth fighting for.”
The team of authors – formed to provide annual scientific updates between major UN scientific assessments every seven to eight years – determined that last year the temperature was 1.43 degrees Celsius plus higher than the average from 1850 to 1900, including 1.31 degrees coming from human activity. The remaining 8 percent of warming is primarily due to El Nino, the natural, temporary warming of the central Pacific that changes global weather, as well as abnormal warming along the Atlantic and other climatic hazards.
Over a longer 10-year period, which scientists prefer over single years, the world has warmed about 1.19 degrees Celsius (2.14 degrees Fahrenheit) since pre-industrial times, according to the journal report Earth System Science Data.
The report also states that as the world continues to use coal, oil and natural gas, Earth will likely reach the point in 4.5 years where it can no longer avoid crossing the internationally accepted warming threshold: 1.5 degrees Celsius (2.7 degrees Fahrenheit).
This is consistent with previous studies predicting that Earth would be engaged or stuck at least 1.5 degrees by early 2029 if emission trajectories do not change. The actual reaching of 1.5 degrees could happen years later, but it would be inevitable if all that carbon was used, Forster said.
It’s not the end of the world or humanity if temperatures rise above the 1.5 limit, but it will be very serious, scientists say. Previous UN studies show that massive changes in the Earth’s ecosystem are more likely to result in warming of between 1.5 and 2 degrees Celsius, including the possible loss of the planet’s coral reefs, ice Arctic seas, plant and animal species, as well as more severe extreme weather events that kill people.
Last year’s rise in temperatures was more than just a jump. It was particularly 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 expected range, although it was at the upper end of the range, Seneviratne said.
“If this were to happen, the acceleration would be even worse, like reaching a global tipping point, that would probably be the worst-case scenario,” Seneviratne said. “But what is happening is already extremely serious and already has major consequences. We are in the middle of a crisis.”
University of Michigan Environment Dean Jonathan Overpeck and Berkeley Earth climatologist Zeke Hausfather, who were not part of the study, said they still see an acceleration. Hausfather pointed out that the rate of warming is considerably higher than 0.18 degrees Celsius (0.32 Fahrenheit) per decade of warming between 1970 and 2010.
Scientists had some hypotheses to explain September’s massive jump, which Hausfather called “staggering.” Wednesday’s report did not find enough warming due to other potential causes. The report said reductions in sulfur pollution from shipping – which had brought some cooling to the atmosphere – were outweighed last year by carbon particles released into the air from wildfires in Canada.
The report also states that as the world continues to use coal, oil and natural gas, Earth will likely reach the point in 4.5 years where it can no longer avoid crossing the internationally accepted warming threshold: 1.5 degrees Celsius (2.7 degrees Fahrenheit).
This is consistent with previous studies predicting that Earth would be engaged or stuck at least 1.5 degrees by early 2029 if emission trajectories do not change. The actual reaching of 1.5 degrees could happen years later, but it would be inevitable if all that carbon was used, Forster said.
It’s not the end of the world or humanity if temperatures rise above the 1.5 limit, but it will be very serious, scientists say. Previous UN studies show that massive changes in the Earth’s ecosystem are more likely to result in warming of between 1.5 and 2 degrees Celsius, including the possible loss of the planet’s coral reefs, ice Arctic seas, plant and animal species, as well as more severe extreme weather events that kill people.
Last year’s rise in temperatures was more than just a jump. It was particularly 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 expected range, although it was at the upper end of the range, Seneviratne said.
“If this were to happen, the acceleration would be even worse, like reaching a global tipping point, that would probably be the worst-case scenario,” Seneviratne said. “But what is happening is already extremely serious and already has major consequences. We are in the middle of a crisis.”
University of Michigan Environment Dean Jonathan Overpeck and Berkeley Earth climatologist Zeke Hausfather, who were not part of the study, said they still see an acceleration. Hausfather pointed out that the rate of warming is considerably higher than 0.18 degrees Celsius (0.32 Fahrenheit) per decade of warming between 1970 and 2010.
Scientists had some hypotheses to explain September’s massive jump, which Hausfather called “staggering.” Wednesday’s report did not find enough warming due to other potential causes. The report said reductions in sulfur pollution from shipping – which had brought some cooling to the atmosphere – were outweighed last year by carbon particles released into the air from wildfires in Canada.
The report also says that an undersea volcano that injected massive amounts of heat-trapping water vapor into the atmosphere also spewed cooling particles, with the two forces virtually canceling each other out.
Katharine Hayhoe, a climate scientist at Texas Tech and chief scientist at the Nature Conservancy, said that “the future is in our hands. It is us – not physics, but humans – who will determine how quickly and to what extent the world is warming up.
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By SETH BORENSTEIN AP Science Editor
