The Claim: The IPCC has stated that “long-term prediction of future climate states is not possible”
the Intergovernmental Panel on Climate Change is a group convened by the United Nations to produce regular scientific assessments of the implications and risks of climate change as well as potential mitigation options.
In a IPCC Report 2001the authors stated that “long-term prediction of future climatic states is not possible” because “the climate system is a coupled nonlinear chaotic system”.
Some social media users are using this statement to challenge the idea that reliable climate projections can be made.
“It is hard to believe that any rational person can still believe that climate models can work, given the IPCC statement that ‘long-term prediction of future climate states is not possible’,” it read. in a March 29 Facebook post.
However, the message misrepresents the IPCC statement by treating the term “climate states” as if it were interchangeable with the word “climate”. This is not the case.
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The word “climate” refers to the range of expected weather conditions, including temperature and precipitation levels. Conversely, “weather states” refer to the presence or absence of relatively discrete weather events such as a rainstorm.
The term also refers to natural climate fluctuations such as El Niño–Southern Oscillationwhich can lead to temporary warming and cooling trends.
“This quote is about the limitations of weather forecasts and forecasts of other variability, such as El Niño,” Baylor Fox-Kemper, an associate professor at Brown University who has authored other IPCC reports, told USA TODAY. This is not an attack on the veracity of climate models, which project broad climate trends over time, he said.
USA TODAY has reached out to social media users who shared the claim for comment.
Social media claim misinterprets IPCC statement
The statement correctly states 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.
But they can successfully predict important larger trends.
“We can never predict whether 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 the internal climate variability due – primarily – to the El Niño and La Niña.” Hausfather said. “However, we can be absolutely sure that – barring a massive volcanic eruption – 2055 will be much hotter than 2022.”
Reliable climate models
One of the ways climatologists confirm the validity of climate models is to examine models that have been created in the past to see if they accurately predicted future global temperatures, Fox-Kemper said.
For example, researchers from NOAA, NASA, Massachusetts Institute of Technology, and Berkeley Earth recently analyzed projections made by climate models published between 1970 and 2007.
The researchers compared each model’s temperature projections to actual temperatures observed after the model’s results were released.
They found that most models made warming predictions consistent with the subsequent temperature increase. For some of the models, the authors overestimated or underestimated model inputs, such as how much CO2 humans would produce in the future.
For these models, the results corresponded to the actual warming observed when the models were rerun with the corrected inputs – the actual CO2 emissions, for example.
“We find that climate models published over the past five decades were generally fairly accurate in predicting global warming in the years following publication, particularly when it comes to accounting for differences between modeled and actual changes in climate. Atmospheric CO2 and other climatic factors”, the study authors wrote.
While many of these older climate models reliably predicted warming, newer models are advantaged by the powerful computer technology that has come online in recent years, Elizabeth Brownclimatologist and assistant professor at the University of Wisconsin, Madison, told USA TODAY.
“Because we have more computing power, you can have higher resolution. You can have more detail in your climate model,” Maroon said. “If anything, we’ve become more certain, not less certain, of late about the scope of our projections.”
Our opinion: Missing context
Based on our research, we note MISSING CONTEXT the claim that the IPCC has stated that “long-term prediction of future climate states is not possible” because without additional information the claim is misleading. The IPCC statement correctly states 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.
Our fact-checking sources:
- Elizabeth BrownMay 5, Phone interview with USA TODAY
- Robert KoppApril 26, email exchange with USA TODAY
- Baylor Fox-KemperMay 6-10, Telephone interview and email exchange with USA TODAY
- Zeke HausfatherMay 6-11, email exchange with USA TODAY
- IPCC, accessed May 5, TAR Climate Change 2001: the scientific basis
- Geophysical Research Letters, December 4, 2019, Assessing the performance of past climate model projections
- Berkeley Earth, accessed May 9 On
- NOAA, May 5, 2014, What is El Niño-Southern Oscillation (ENSO) in a nutshell?
- High Meadows Environmental Institute, October 5, 2021, Princeton’s Syukuro Manabe receives Nobel Prize in Physics for modeling climate change
- Max-Planck-Gesellschaft, October 5, 2021, 2021 Nobel Prize in Physics for Klaus Hasselmann
- IPCC, accessed May 12, Home page
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