Fact check: 2001 climate change statement misrepresented to disparage climate models

·5 min read

The claim: IPCC said 'long-term prediction of future climate states is not possible'

The Intergovernmental Panel on Climate Change is a group assembled by the United Nations to produce regular scientific assessments of climate change implications and risks as well as potential mitigation options.

In a 2001 IPCC report, the authors said "long-term prediction of future climate states is not possible" because "the climate system is a coupled non-linear chaotic system."

Some social media users are using this statement to challenge the idea that reliable climate projections can be made at all.

"It is hard to believe that any rational person could still believe that climate models can work, given the IPCC’s statement that 'long-term prediction of future climate states is not possible,'“ reads a March 29 Facebook post.

The post garnered hundreds of interactions and USA TODAY found versions of the claim dating back to 2019. Similar claims spread on Twitter.

However, the post misrepresents the IPCC statement by treating the phrase "climate states" as though it is interchangeable with the word "climate." That's not the case.

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The word "climate" refers to the range of expected weather conditions, including temperature and precipitation levels. Conversely, "climate states" refers to the presence or absence of relatively discrete weather events like a rainstorm.

The phrase also refers to natural climate fluctuations such as the El Niño–Southern Oscillation, which can cause temporary warming and cooling trends.

"What this quotation is about is the limits on weather forecasts and forecasts of other variability, like El Niño," Baylor Fox-Kemper, an associate professor at Brown University and an author on a 2021-22 IPCC report, told USA TODAY. It is not an attack on the veracity of climate models, which project broad climate trends over time, he said.

USA TODAY reached out to the social media users who shared the claim for comment.

Social media claim misinterprets IPCC statement

The social media post fundamentally misinterprets the 2001 IPCC statement, Zeke Hausfather, a research scientist at Berkeley Earth and IPCC author, told USA TODAY.

The statement correctly indicates that climate models cannot predict exact "climate states," such as a particular weather event, on a given day in the distant future, he said in an email.

Fact check: Warming varies across oceans and atmosphere, doesn't contradict climate change

But they can successfully predict important broader trends.

"We can never predict if it will rain on March 2, 2055, in San Francisco, or even know for sure that 2055 will be warmer or cooler than 2054 given internal variability in the climate due – primarily – to El Niño and La Niña events," Hausfather said. "However, we can be absolutely sure that – barring a massive volcanic eruption – 2055 will be much warmer than 2022."

Climate models reliable

One of the ways that climate scientists confirm the validity of climate models is by examining models that were created in the past to see if they accurately predicted subsequent global temperatures, Fox-Kemper said.

For instance, NOAA, NASA, Massachusetts Institute of Technology and Berkeley Earth researchers recently analyzed the projections made by climate models published between 1970 and 2007.

The researchers compared the temperature projections from each model to the actual observed temperatures that occurred after the model results were published.

They found that most of the models made warming predictions consistent with subsequent temperature rise. For some of the models, the authors either overestimated or underestimated model inputs, such as the amount of CO2 humans would produce in the future.

For these models, the results matched actual observed warming when the models were re-run with the corrected inputs – actual CO2 emissions, for instance.

"We find that climate models published over the past five decades were generally quite accurate in predicting global warming in the years after publication, particularly when accounting for differences between modeled and actual changes in atmospheric CO2 and other climate drivers," the study authors wrote.

While many of these older climate models reliably predicted warming, more recent models are advantaged by the powerful computing technology that has come online in recent years, Elizabeth Maroon, a climate scientist and assistant professor at the University of Wisconsin, Madison, told USA TODAY.

Fact check: Short term global temperature fluctuations do not negate climate science, overall warming

"Because we have more computational power, you can have higher resolution. You can have more details in your climate model," Maroon said. "If anything, we've become more certain, not less, in more recent times, with what the range of our projections are."

Our rating: Missing context

Based on our research, we rate MISSING CONTEXT the claim that the IPCC said "long-term prediction of future climate states is not possible," because without additional information the claim is misleading. The IPCC statement accurately asserts that "climate states" such as weather events or the occurrence of an El Niño cannot be predicted very far in advance. However, this does not mean that climate models are unreliable, according to IPCC researchers.

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This article originally appeared on USA TODAY: Fact check: Climate models reliable, IPCC statement misrepresented