STORY UPDATED: check for updates below.
Was the Earth's average temperature 2 degrees Celsius warmer 55,000 years ago? No, that's not true: Climate experts contacted by Lead Stories all agreed that the Earth's temperature 55,000 years ago was colder than today's average temperature, not warmer. Ice core samples and other geological data show that global temperatures were lower due to extensive ice sheets and lower greenhouse gas concentrations.
The claim about Earth's temperature 55,000 years ago appeared in a reel (archived here) posted on Facebook on June 14, 2024, under the on-screen title "Global Warming is a joke?" The post's caption said:
#DanPena #exploremore #ElonMusk #4upage #explorepage #ai #fyp #foryou #business #success #money #Superintelligence #QuantumLeapAdvantage
This is what the post looked like on Facebook at the time of writing:
(Source: Facebook screenshot taken on Fri Jun 21 15:51:01 2024 UTC)
The post provided no attribution or other evidence to substantiate its claim.
The video
The video, featuring American businessman Dan Peña, is a heavily edited 33-second clip from "The Joe Rogan Experience" podcast, Episode #929, which aired on March 10, 2017. About an hour and five minutes into the show, Peña started talking about a trip he said he took with his wife to the South Pole in 2011. This is the edited version of what he said:
Peña: So, we're down there. We're talking with all the goofball scientists and he said ... 55,000 years ago, it was 2 degrees warmer Celsius than it is today. What? Stop. Fifty-five thousand years ago, it was 2 degrees warmer than it is today? And I said, 'What about global warming?' Simultaneously, all 10, scientists started laughing. All 10 Ph.D.s from MIT [Massachusetts Institute of Technology], Caltech [California Institute of Technology], Stanford started laughing.
Rogan: Why'd they laugh?
Peña: Because global warming is a joke.
Climate experts
MIT
In a June 21, 2024, email to Lead Stories, Timothy Cronin, an associate professor of atmospheric science at MIT, called the social media post's claim "bogus." He continued:
There is no good evidence of globally warmer conditions 55 thousand years ago -- the world was colder, likely by around 2 degrees C or more. We were in the middle of a glacial period of the ice age with much larger than present ice extent, and sea level was lower by around 60 meters or 200 feet because there was so much water locked up in the ice sheets over North America and Eurasia.
Cronin cited an article published in the scientific journal Nature Communications in February 2021 to support his stance.
Edward Boyle, a professor of ocean geochemistry, also at MIT, told Lead Stories in a June 21, 2024, email that the claim is "Made up nonsense."
I am aware of no data that shows the earth being 2°C warmer 55,000 years ago. Data from ice cores, speleothems [mineral deposits], and deep sea sediments show very cool temperatures at that time, although not as cool as during the glacial maximum. There were warmings and coolings on millennial time scales, but the peaks were still cooler than the present day.
Ice core samples make it possible to measure directly the past concentration of atmospheric gases trapped in the ice, including the major greenhouse gases, allowing scientists to estimate temperatures up to 800,000 years ago.
University of Georgia
In a June 21, 2024, email to Lead Stories, Patricia Yager, professor of marine science at the University of Georgia and director of the Georgia Climate Project, said ice core data from Greenland and the Antarctic tell a clear story -- our planet's thermal record shows (emphasis hers):
55 thousand years ago, the earth was definitely cooler than today.
Northwestern University
Brad Sageman, a professor of earth and planetary sciences at Northwestern University, called the claim "TOTAL BUNK" and "Complete nonsense" in a June 21, 2024, email to Lead Stories. He added:
It was NOT warmer than today at 55 ka [55,000 years ago] - I believe the speaker is confusing this with 55 Ma [million years ago], which was the PETM [Paleocene-Eocene Thermal Maximum] ... and that is estimated to have been MUCH MORE THAN 2°C warmer.
The PETM was a brief period of extreme warmth that lasted around 100,000 years during the late Paleocene and early Eocene epochs, approximately 55 million years ago. This period experienced the highest global temperatures of the Cenozoic Era, which spans from 65 million years ago to the present.
National Centers for Environmental Information
In a June 22, 2024, email to Lead Stories, Carrie Morrill, a paleoclimatologist and physical scientist with the National Centers for Environmental Information, echoed the other climate experts. She said:
It is not true that the Earth's temperature was 2 degrees Celsius warmer 55,000 years ago. At that time, Earth was experiencing the last ice age, which lasted from between 115,000 to 11,800 years ago. Best estimates for Earth's temperature 55,000 years ago are between about 3 and 5 degrees Celsius colder than modern.
Global warming
Even if the claim in the social media post that the Earth's average temperature was warmer 55,000 years ago than in 2024 were true, that still wouldn't prove that global warming, also known as climate change, is a hoax. Sageman explained:
None of these observations change our interpretations about what is happening today as a consequence of human activities. The temp we reach in 2024 does not matter - the specific temps we see in any given year will be influenced by many factors.
... I stress that long-term averages are the measurements that reveal the status of the Earth's climate system (yearly averages, peak record high temps, higher peak low temps in winter, etc. ALL of which have been rising, especially since the 1970s) AND the fact that these changes are occurring over ~150 years (i.e., since we started burning fossil fuels at industrial scale and converting forests to farms).
Previously, these oscillations took hundreds of thousands, if not, millions of years to manifest, instead of just a century or so. Sageman shared this graph showing the global temperature curve for Earth that was published in the journal Science in May 2019. It appears below:
(Source: Science screenshot taken on Fri Jun 21 22:24:51 2024 UTC)
According to Morrill, the temperature data tells a clear story. She said it shouldn't be ignored:
Regardless of what the temperature was 55,000 years ago, it is a common argument that global warming is either not occurring or is not important because certain past time periods were warmer than today. This argument is not correct, though, because it does not take into consideration what is causing warming today and also how fast the Earth is warming.
Both of these factors are different now than they were in the past. Earth is warming now due to human activities, including the burning of carbon-based fuels. Warming is also happening much faster now than it did in the past, making it more difficult for human societies and natural systems to adapt.
And Yager concluded:
The earth has certainly been warmer in the past. There is no question of that.
The point is that we have good evidence telling us why the earth was warm during those times: 'natural changes' in the distribution of solar heating and the concentration of greenhouse gases in the atmosphere. No mystery.
We also know why we are warming now: extra greenhouse gases from burning fossil fuels.
National Oceanic and Atmospheric Administration
A National Oceanic and Atmospheric Administration article (archived here) published on October 12, 2022, titled "If the globe is still warming, then why are some locations not warming while others have experienced cooling?" explains some of the nuances of climate change. The article begins:
Global warming means Earth's annual average air temperature is rising over long time spans (many decades to centuries), but not necessarily in every location and not necessarily in all seasons. It's like your grades--if you get Bs and Cs in your first semester and in the next semester you get all As and Cs, your overall grade point average rises even though you didn't improve in every class. Differences in exposure to sunlight, cloud cover, atmospheric circulation patterns, aerosol concentrations, atmospheric humidity, land surface cover, etc., all vary from place to place which, in turn, influence whether and how much a location is warming or cooling.
Additional details from NOAA on climate change are available here, here, here and here.
Read more
At the time this fact check was written, multiple fact checking organizations, including PolitiFact and Sky 106.1 FM had reviewed the claim in 2022 about Earth's temperature 55,000 years ago.
Other Lead Stories fact checks of claims about Earth's temperature and climate change are here.
Updates:
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2024-06-24T22:35:24Z 2024-06-24T22:35:24Z Adds context from Carrie Morrill at the National Centers for Environmental Information.
