Study on warming trends misrepresented to promote climate denial

"A sensational paper in top science journal Nature has found 'no change in the warming rate beyond the 1970s,' blowing holes in alarmist claims that global temperatures are surging, says Chris Morrison," an October 18, 2024 X post by Toby Young, who has spread myths debunked by AFP in the past.

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A screenshot of an X post taken on October 18, 2024

Other posts and climate-skeptic publications drew similar conclusions across platforms and in languages, including French, Dutch, Greek, Italian  and German, following the publication of a study (archived here) in the scientific journal, Nature, on October 14.

But using the article's conclusions to claim that there has been no additional warming since the 1970s is highly misguided, scientists say, noting that the models used in the study instead detect a consistent increase over time.

'Steadily increasing temperatures'

"Our study affirms steadily increasing surface temperatures since the 1970s," Claudie Beaulieu, associate professor in the Ocean Sciences Department at the University of California Santa Cruz and lead author of the paper (archived here), told AFP on October 17.

"It is very worrying to hear that our paper is used by climate deniers to make false claims," she said.

The study uses global mean surface temperature, a measure regularly examined to monitor climate change, to focus on analyzing warming trends in the past 50 years. The series of models it uses attempt to answer if there has been an acceleration or deceleration in the warming pace and it found that a change is not statistically detectable after the 1970s.

"Our results suggest that if a recent acceleration in global warming is occurring, the size of that acceleration is either too small or too recent to robustly detect it in globally averaged surface temperature records," Beaulieu said.

Study co-author Colin Gallagher, an associate professor at the Department of Mathematical Sciences at Clemson University (archived here), also said the study shows continued warming. 

"We found no statistical evidence of a slowdown in global warming but rather statistically confirm global warming occurring at a consistent rate since the 1970s," he said on October 18.

Climatologist Zeke Hausfather, of the independent climate science non-profit Berkeley Earth (archived here), said that this paper "should really give no comfort to those skeptical of man-made climate change."

Four datasets on global temperatures included in the study clearly demonstrate a rapid rise in human-induced emissions of CO2 and other greenhouse gases over the years, he said.

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A screenshot taken on October 17, 2024 of charts showing global mean surface temperature anomalies across four datasets, as published in Beaulieu et al.'s study

He also pointed out the methods applied in the study would not effectively detect anything short of an approximately 55 percent increase (or decrease) in the rate of warming -- which the study's authors confirmed.

"The debate about whether warming has accelerated is an important one, but does not really impact our broader understanding of the human role in the rapid warming the Earth has experienced over the past 50 years," Hausfather concluded.

'Unequivocal' influence

Concentrations of CO2 -- the main driver of anthropogenic warming -- have risen to levels not recorded on Earth in the last 14-16 million years.

Six datasets from educational and governmental agencies (archived here) have tracked the resulting rise in global average temperature (archived here).

"Today we are increasing CO2 at a rate that may be faster than ever before in the geological record," Bärbel Hönisch, a professor at Columbia University's Lamont-Doherty Earth Observatory (archived here), previously told AFP. "This CO2 contributes to the greenhouse effect and warms our planet."

The United Nations Intergovernmental Panel on Climate Change (IPCC) says it is "unequivocal that human influence has warmed the atmosphere, ocean and land" -- and that CO2 is the main culprit (archived here and here).

Hundreds of independent scientists who contribute to IPCC reports on climate science agree that current global greenhouse gas emission projections for 2030 indicate that warming will likely exceed the 1.5 degrees Celsius threshold set during the Paris Agreement in this century, and that it would in turn make it harder to limit warming to below 2 degrees (archived here).

Current climate models project significant impacts from such an increase that would affect land and ocean temperatures and lead to heat extremes in most inhabited regions (archived here).

Find more of AFP's fact-checks on climate questions, here.