Fact check: Graph shows dated data from one area in Greenland, not global temperature change

Eleanor McCrary and Kate S. Petersen, USA TODAY
·5 min read

The claim: 'Climate history' graph shows recent temperatures at 'lower end of the historical range'

A Jan. 14 Twitter post (direct link, archive link) features a graph labeled "Climate History Over 9,500 years." It purportedly shows temperature change from year to year, with the most recent data depicting relatively cool temperatures compared to the rest of the graph.

"Most recent global temperatures are at the lower end of the historical range," reads text on the graph.

"How can anyone see this chart and seriously still be brainwashed into believing that we are at the end of days? It's very basic stuff," reads the post's caption.

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The post was viewed more than 11 million times on Twitter and garnered more than 100 Facebook shares in three weeks , according to Crowdtangle, a social media analytics tool. A similar graph, captioned in German, garnered hundreds of additional interactions on Facebook.

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Our rating: False

The graph cannot show modern global temperature change because no data is displayed after 1885. Modern global warming began around that time and escalated significantly in the 1980s, according to data from the National Oceanic and Atmospheric Administration. The graph is also built on data from a single location in Greenland and isn't representative of global temperatures, experts say.

Graph data from one location, does not represent global temperatures

The graph cites a 2004 publication based on limited 1997 data from a group of scientists including Gary Clow, now a senior research associate at the Institute of Arctic and Alpine Research at the University of Colorado.

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"This graph is mostly based on data from a single location in Greenland," Clow told USA TODAY in an email. "I must emphasize that this site does not represent the entire planet."

Temperatures at a single site are much more variable than average temperatures over broader areas, such as "all of Greenland or the Northern Hemisphere," he said.

"To infer that this data reflects global temperature changes ... is really misleading," Clow said.

The data referenced in the graph is not based on direct temperature measurements either, he said. Instead, temperatures are inferred based on the types of oxygen locked in the ice core samples.

Fact check: Global temperatures and atmospheric CO2 levels are correlated, contrary to claim

Though the ice cores were collected in the 1990s, the nature of the analysis means the resulting temperature record only goes into the late 1800s, Clow said.

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In other words, even if the listed ice core data – which runs through 1885 – did represent the entire planet, it excludes data from the last roughly 140 years.

This is the timeframe when most of the recent warming trends have occurred, Carrie Morrill, the director of the World Data Service for Paleoclimatology at NOAA's National Centers for Environmental Information, told USA TODAY in an email.

Despite these inaccuracies, versions of the graph have circulated online for years, according to Richard Alley, a professor of geosciences at the Pennsylvania State University and lead author of the 2004 publication cited in the graph.

"I receive a few inquiries about this per year, and have done so for more than a decade now," he said.

Studies find Earth warmer now than last 10,000 years

Despite the claims made in the social media post, recent studies have concluded that global warming, driven by human behavior, has contributed to increasing global temperatures that are now warmer than those of the past thousands or tens of thousands of years. This research is contrary to previous work suggesting the Earth had warmer temperatures within the last 10,000 years, according to a Rutgers press release.

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Fact check: Contemporary, human-driven warming has different ramifications than past warming

"(Earth's) climate has changed for many reasons, but especially because of changing CO2, which focuses special attention on our release of CO2 to the atmosphere from fossil-fuel burning and other activities," said Alley.

USA TODAY has debunked a variety of claims about climate change, including that it's more likely oceans are causing global warming than CO2 and that the greenhouse gas effect is a hoax.

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

The graph was also debunked by AFP.

Our fact-check sources:

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This article originally appeared on USA TODAY: Fact check: False claim graph shows Earth colder than 1,000 years ago

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