High ancient temperatures don't prove modern warming a 'hoax' | Fact check

The claim: Study shows global warming is a 'hoax'

A Sept. 21 Facebook post (direct link, archive link) shows a Washington Post headline that reads, "Scientists have captured Earth’s climate over the last 485 million years. Here’s the surprising place we stand now." The post includes a graph that shows Earth is currently cooler than it has been for most of the last 485 million years.

"Global warming is a hoax," reads the post's caption.

The post was shared more than 70 times in a month.

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Our rating: False

The study in question states Earth has been warmer than it is now for most of the last 485 million years. But rather than showing global warming is a "hoax," the paper reports modern global warming is proceeding at an unprecedented rate.

A warm past doesn't disprove modern global warming

The scientific paper covered by The Washington Post was published in the journal Science in September examining Earth's temperature trends across the last 485 million years. Its authors – including lead author Emily Judd, a paleoclimate researcher at the Smithsonian Natural History Museum – combined fossilized evidence and climate models to determine global temperatures have been much warmer in the past.

However, rather than demonstrating that modern global warming is a "hoax," the study states that modern temperatures are warming more rapidly than at any other point in the study period. It also states that warmer temperatures are correlated with higher atmospheric CO2 levels throughout the study period − an observation that is consistent with the enormous body of research that shows modern global warming is driven by CO2.

"I’ve seen quite a bit of misinformation crop up surrounding our paper, particularly the claim that we − humans − have nothing to worry about, with respect to climate change, since the Earth has been warmer for much of the last half-billion years," Judd told USA TODAY. "I cannot stress enough how reductive and problematic this viewpoint is."

The geologic record shows that when global temperatures change slowly, organisms can keep up by evolving, adapting or migrating, she said. But "when CO2 and temperatures change rapidly, as is happening today due to (emissions generated by humans), evolution can’t keep pace with the environmental change."

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This leads to mass extinction events such as the end-Permian extinction around 250 million years ago, when roughly 90% of Earth's species disappeared. Modern climate change is proceeding more rapidly than the change that drove this event, according to Judd's findings.

Abundant evidence shows that humans are changing Earth's climate

Earth's average temperature has warmed 2.45 degrees since the late 1800s due to the burning of fossil fuels, deforestation and other human activities, according to NASA. This modern warming trend has been documented by multiple independent climate agencies.

The fact that humans are causing modern global warming has been substantiated by a large body of research, including the 2021 Intergovernmental Panel on Climate Change report, which incorporated nearly 13,000 peer-reviewed papers and other resources − reflecting the work of around 39,000 researchers.

The consequences of this warming include:

• Arctic sea ice loss
• An increase in the frequency of heat waves
• Melting ice sheets in Antarctica and Greenland
• Melting glaciers
• Sea level rise
• Changes in the ranges of animal species
• Changing precipitation patterns
• Shrinking snowpack in the western U.S.
• Changing plant bloom times
• An increase in flooding events due to sea level rise

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These changes are already impacting human populations around the world, Judd said.

"To minimize the consequences of (modern) climate change by misrepresenting our findings is to dismiss the very real suffering of our fellow humans," she added.

When reached by USA TODAY, the social media user who shared the post said Earth's climate has changed in the past and that their statement was "about opening discussions and being thought-provoking."

Our fact-check sources:

• Emily Judd, Oct. 15, Email exchange with USA TODAY
• Daniel Stolte, Oct. Oct. 14, Email exchange with USA TODAY
• The Washington Post, Sept. 19, Scientists have captured Earth’s climate over the last 485 million years. Here’s the surprising place we stand now
• USA TODAY, Oct. 31, 2023, False claim 'climate crisis hoax' statement signed by thousands of scientists | Fact check
• Science, Sept. 20, A 485-million-year history of Earth’s surface temperature
• Intergovernmental Panel on Climate Change Sixth Assessment Report, 2021, Climate Change 2021: The Physical Science Basis 
• Carbon Brief, March 16, Guest post: What 13,500 citations reveal about the IPCC’s climate science report 
• NASA Vital Signs of the Planet, accessed Sept. 11, Ice sheets 
• NASA Vital Signs of the Planet, accessed Sept. 11, Sea level 
• NASA Vital Signs of the Planet, accessed Sept. 11, Methane 
• NASA Vital Signs of the Planet, accessed Sept. 11, Carbon dioxide 
• NASA Vital Signs of the Planet, accessed Sept. 11, Arctic Sea Ice Minimum Extent 
• Environmental Protection Agency, July 2022, Climate Change Indicators: Heat Waves 
• Environmental Protection Agency, February 2023, Climate Change Indicators: Marine Species Distribution 
• Environmental Protection Agency, July 2022, Climate Change Indicators: Snowpack 
• Environmental Protection Agency, September 2023, Climate Change Indicators: Coastal Flooding 
• Environmental Protection Agency, April 2021, Climate Change Indicators: Leaf and Bloom Dates 
• Environmental Protection Agency, July 2022, Community Connection: Ice Breakup in Three Alaskan Rivers 
• Environmental Protection Agency, August 2016, Climate Change Indicators: Glaciers 
• Environmental Protection Agency, May 2014, Climate Change Indicators: Bird Wintering Ranges 
• Grist, Oct. 2, Climate change is destroying American homes. Who should have to move? 
• United Nations, accessed Oct. 28, Five ways the climate crisis impacts human security 
• The U.N. Refugee Agency, accessed Oct. 28, Climate change and displacement 
• AP News, Oct. 11, Climate change gave significant boost to Milton’s destructive rain, winds, scientists say 
• CDC, March 21, Climate and Infectious Diseases 
• BBC, March 18, Climate change is fuelling the US insurance problem

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