Weather causes temperature flux even as planet heats up | Fact check

A Sept. 3 Instagram post (direct link, archive link) shows temperature maps originally posted on X, formerly Twitter, by Steve Milloy, a skeptic of human-driven climate change. Text in the screenshotted X post states the average temperature and the maximum temperature average in August 2024 were cooler than in August 1983.
“I thought they told us that CO2 emissions cause global warming? #Hoax,” reads the Instagram post’s caption.
The post garnered more than 300 likes in a week.
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Scientists have documented a sustained long-term global warming trend caused by greenhouse gas emissions from human activity. Fluctuations in average temperature in August from year to year do not negate the overall warming trend. Weather still causes temperature variation even on a warming planet.
The U.S. average temperature and maximum temperature in August 2024 were both cooler than in 1983, according to National Oceanic and Atmospheric Administration data. However, the average temperature in August warmed overall during that same time frame.
This is possible because a statistically significant warming trend doesn’t mean that each month or year will be warmer than all previous months or years, Gavin Schmidt, a NASA climate scientist, previously told USA TODAY.
Weather and natural climate variability, such as the El Niño-Southern Oscillation, can cause temperatures to be warmer or cooler than average over a given timeframe or in a certain place, even as the climate warms overall.
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In addition to a warming August, NOAA data also shows a warming trend both globally and in the U.S. when all months are considered.
“This comparison (in the post) really is not sufficient to draw conclusions about climate trends in the United States nor globally,” Christopher Dickson, a WeatherBell meteorologist, told USA TODAY, adding that it seemed like “cherry-picking data.”
There are a variety of ways scientists know that greenhouse gases released by human activity, including deforestation and the burning of fossil fuels, are causing modern climate change.
Researchers have demonstrated that greenhouse gases such as CO2 warm the planet by slowing the release of radiation into space. They have also shown that greenhouse gas levels in the atmosphere have been increasing for decades.
The amount of excess CO2 in the atmosphere also matches the amount humans have emitted once natural processes are accounted for. And a disproportionate amount of the CO2 contains the kind of carbon found in fossil fuels.
As greenhouse gas levels have increased, researchers have documented a simultaneous rise in global temperatures, Josh Willis, a NASA climate scientist, previously told USA TODAY.
“The amount of warming we see matches what we expect based on the increased CO2 we’ve added,” Willis said. Additionally, “the timing of the warming matches the timing of the CO2 increase caused by people.”
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Scientists have also documented the consequences of this long-term warming trend, which include sea level rise, melting from polar ice sheets and a reduction in Arctic sea ice cover.
The U.S. has warmed more quickly than the global average. Impacts of the long-term warming trend in the U.S. include:
The maps featured in the post are from WeatherBell Analytics and are based on data from the PRISM Climate Group, according to Dickson.
PRISM data is not intended to be used for analyzing climate trends because it does not account for “temporal changes in station data availability, observation time, equipment and sighting, etc., all of which can bias the results,” Chris Daly, an Oregon State University professor who founded the PRISM Climate Group, previously told USA TODAY. He said NOAA data accounts for these issues.
When reached for comment, the Instagram user who posted the claim suggested USA TODAY contact Milloy. Milloy did not respond to a request for comment.
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