A new study published in Proceedings of the National Academy of Sciences argues that the record warmth was entirely consistent with expectations on a warming planet. When accounting for human-caused warming alongside natural climate variability like El Niño and La Niña climate patterns, the 2024 temperatures actually showed that climate models today are capturing the ongoing warming of the planet well.
Research from climate scientist Michael Mann, Presidential Distinguished Professor of Earth & Environmental Science, and colleagues vindicates climate models and reframes the record heat of 2024.
To counter the sensationalisation of climate science reporting, which can sometimes lead to ‘doomist’ narratives’ which in turn ‘freeze’ public and political action, Mann wants to rebuild trust in the complexities and nuances of science.
‘The truth is bad enough’
Mann commented, ‘Overstating the mystery of events like 2024 feeds the narrative that scientists are either hiding something or don’t know what they’re doing, neither of which is true. The truth is bad enough. We don’t have to invent or exaggerate the gravity of the climate threat to establish the case for urgent action.’
With global temperatures reaching a new high in 2023 and 2024, and with 2024 being declared the hottest year on record, Mann felt that some scientists appeared to be suggesting that this warming was inexplicable, or that the warming was outside what climate models had suggested. He argued, ‘That framing is unfortunate,’ he says. ‘It makes it sound like we don’t understand what’s driving climate change.’
Mann and his team used a modeling technique that combined real-world temperature observations with climate model results to generate 40,000 synthetic climate simulations, essentially creating tens of thousands of alternative versions of climate history. Mann calls this a sort of “climate multiverse,” where human-caused warming remains constant across all simulations, but unpredictable events like El Niño and La Niña get randomized.
The simulations showed that 2024’s record-setting heat was far from an anomaly. When accounting for human-caused warming, the researchers estimated it had roughly a 12 percent probability of occurring—in other words, it could be expected to occur on average once in eight years.
‘There has been a lot of discussion recently about whether the extraordinary warmth of that year means something unexpected is happening in the climate system, including suggestions that models can’t explain what we’re seeing,’ says co-author Xueke Li, an assistant professor at City University of Hong Kong who was formerly a research associate at Penn. ‘Our results show that recent record temperatures would have been extremely unlikely without human influence—but they are entirely consistent with expectations from global warming.’
‘A strong vote of confidence in climate science’
The findings offer a strong vote of confidence for current climate models, which have long incorporated the warming response to human-generated carbon pollution as a core input. Mann says the results are a clear signal that human-caused warming is now the most dominant force shaping our climate—without it, he notes, those temperature highs from two years prior would have been essentially impossible.
‘One of the most important conclusions of the paper is that climate models are doing their job, at least when it comes to the overall warming of the planet,’ Li adds. ‘Rather than contradicting climate models, the 2024 temperature spike—and the ability of the models to explain it—actually reinforces their credibility.’
The paper published today reinforced that climate models were a sound basis for climate policymaking and found no evidence for any departure from expectations of typical natural climate- that there has been no ‘unexpected surge’. ‘Our results show that recent record temperatures would have been extremely unlikely without human influence—but they are entirely consistent with expectations from global warming.’
The paper concluded, ‘Recent record warmth, in conclusion, does not contradict state-of-the-art climate model historical simulations and future projections of GMST. Such models continue to provide accurate assessments of planetary warming and a sound basis for climate policymaking.’
Urgency and Agency
Mann also argued that the same climate models that flag risks of rapid ice sheet disintegration or prolonged heatwaves, flooding and droughts, also point toward a reason for hope: ‘One thing the models tell us with greater confidence now is that the warming of Earth’s surface will cease shortly after we reduce our carbon emissions to zero. There’s urgency, but there’s agency, too.’
Will the 2024 record be broken soon?
Those models also point to what’s coming. Forecasters currently estimate a 60 to 70 percent chance of a new El Niño emerging in mid-2026. ‘When—not if—another big El Niño happens, we shouldn’t be surprised when the 2024 record is broken,’ says co-author Byron Steinman, a professor at the University of Minnesota Duluth.
Climate Thoughts with Brian 