Fact check: Climate change measured in decades, day to day temperature fluctuation common

The claim: On May 9, 2022, global average temperatures were only slightly higher than 1979-2000 average

Global temperatures have risen markedly over the past century, but some social media posts are zeroing in on select pieces of data to show that temperature changes have been insignificant.

One claim takes the global temperature record on a single day of this year to show that consequential, human-driven global warming doesn't exist.

"Today, 9 May 2022, Earth’s temperature is just ONE-TENTH of one degree above the 1979-2000 average, yet there are still idiots out there who believe in catastrophic, man-made global warming," reads a May 9 Facebook post that received more than 500 interactions in a week.

The post includes a world temperature map that appears to have been created using Climate Reanalyzer, an online tool that allows users to access global weather and climate data.

Daily temperature maps generated by Climate Reanalyzer include a calculation of the average global temperature "anomaly" for a particular day. The anomaly shows the difference between the average global temperature that day and the same day's average temperature between 1979-2000.

The map featured in the post shows a 0.1 degree Celsius temperature anomaly for May 9, 2022.

The claim was also posted on Twitter.

USA TODAY found similar claims that have shown minimal temperature anomalies based on Climate Reanalyzer. For instance, one Facebook post challenged the existence of global warming when Climate Reanalyzer showed a 0.1 degree Celsius temperature anomaly on Feb. 8, 2021.

However, the claims are baseless. Global warming assessments are determined by temperature changes over decades or longer, according to climate researchers. Short term deviations are common due to weather and other variability in Earth's climate systems, but they do not negate the overall warming trend.

Follow us on Facebook! Like our page to get updates throughout the day on our latest debunks

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

Temperatures on one day can't prove or disprove global climate change

The map graphic in the social media post came from the "Today's Weather Maps" section of Climate Reanalyzer, according to Sean Birkel, a climatologist and research assistant professor at the University of Maine who developed and maintains the site.

Despite what the post implies, climate patterns cannot be established using one day's data, he told USA TODAY in an email.

"Anomaly values can vary significantly from day-to-day ... depending on weather patterns," Birkel said. "However, long-term warming trends are clear based on data going back several decades to more than a century."

He also said this caveat is included in the "Data Sources & Additional Information" section located directly under the Climate Reanalyzer mapping feature used in the social media post.

"The daily temperature anomaly values shown on these maps reflect current weather patterns, and therefore global and regional means can vary significantly from day-to-day and week-to-week. Climate trends should only be inferred from long-term datasets," reads the web page.

The page then refers the user to the NOAA Climate at a Glance online climate data visualization tool, which shows a temperature increase of about 0.08 degrees Celsius per decade since 1880.

This change has resulted in an overall increase of more than one degree, which is consistent with the warming reported by other major climate agencies.

This degree of warming has already resulted in polar ice loss, sea-level rise and other consequential ecological changes. More change is projected, but "experts believe there is still time to avoid the most negative of outcomes by limiting warming and reducing emissions to zero as quickly as possible," according to the NOAA website.

Fact check: Ireland and Sweden have warmed since 1988, data show

USA TODAY has previously debunked other misleading claims based on cherry-picked data from public climate datasets.

Our rating: Missing context

Based on our research, we rate MISSING CONTEXT the claim that global average temperatures were only slightly higher than the 1979-2000 average on May 9, 2022. Weather behavior on one day does not negate the overall global warming trend reported by multiple climate agencies.

Our fact-check sources:

• Sean Birkel, May 17, Email exchange with USA TODAY

• NASA Earth Observatory, accessed May 16, World of Change: Global Temperatures

• Met Office Climate Dashboard, accessed May 16, Annual global mean temperature difference from pre-industrial conditions

• Climate Reanalyzer, accessed May 16, Home page

• Climate Reanalyzer, accessed May 16, Monthly Reanalysis Timeseries

• Climate Reanalyzer, accessed May 17, Today's weather maps

• NASA Vital Signs of the Planet, accessed May 17, Global Temperature

• NASA Vital Signs of the Planet, accessed May 17, Effects

• USA TODAY, March 9, Fact check: Misleading data used in claim alleging a global cooling trend

• NASA Vital Signs of the Planet, accessed May 17, Climate change: How do we know?

• NOAA, accessed May 24, Climate at a Glance 1880-2021 Trend

• NOAA, March 15, 2021, Climate Change: Global Temperature

• NOAA, August 13, 2021, Climate change impacts

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper replica here.

Our fact-check work is supported in part by a grant from Facebook.

This article originally appeared on USA TODAY: Fact check: Climate change measured in decades, not days