Weather happens. Hot August in 1983 doesn't show climate change is a 'hoax' | Fact check
The claim: August temperature comparison shows CO2-driven global warming is a 'hoax'
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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Our rating: False
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.
Post ignores August warming trend, weather
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 Ni?o-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."
Modern global warming clearly caused by emissions from human activity
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:
Earlier ice breakup dates in Alaskan river systems
Changes in the ranges of various marine species
An increase in the frequency of heat waves
Changing time frames for the emergence of leaves and flowers in the spring
Melting glaciers in Alaska and Washington
Shrinking snowpack in the western U.S.
Increase in flooding events due to sea level rise
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 sent USA TODAY a video that reiterated the claims in his original post.
Our fact-check sources:
Chris Daly, Sept. 10, Email exchange with USA TODAY
Christopher Dickson, Sept. 10, Email exchange with USA TODAY
NASA Vital Signs of the Planet, accessed Sept. 11, Causes
NASA Vital Signs of the Planet, accessed Sept. 11, Ocean warming
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
Environmental Protection Agency, July 2022, Climate Change Indicators: U.S. and Global Temperature
The Guardian, Nov. 14, 2023, ‘The science is irrefutable’: US warming faster than global average, says report
USA TODAY, Nov. 28, 2022, Fact check: Earth's warming well documented, other planets' climate data limited
USA TODAY, Jan. 20, 2023, Fact check: Global warming caused by greenhouse gas emissions, not mysterious ocean warming
USA TODAY, Dec. 20, 2023, How we know humans are causing warming: A brief history of climate science | Fact check
USA TODAY, March 31, 2022, Fact check: Short-term global temperature fluctuations do not negate climate science, overall warming
USA TODAY, March 1, 2022, Fact check: Japan Meteorological Agency data shows warming on Japanese island
NOAA, Oct. 12, 2022, How do we know the build-up of carbon dioxide in the atmosphere is caused by humans?
NOAA, July 17, El Ni?o & La Ni?a (El Ni?o-Southern Oscillation)
NOAA, accessed Sept. 11, National Time Series (August)
NOAA, accessed Sept. 11, National Time Series
NOAA, accessed Sept. 11, Global Time Series
The Conversation, July 31, 2020, John Tyndall: the forgotten co-founder of climate science
UCAR, accessed Sept. 11, History of Climate Science Research
The Royal Society, March 2020, If the world is warming, why are some winters and summers still very cold?
Yale Climate Connections, Dec. 15, 2020, Global warming is real, so why is it cold outside?
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This article originally appeared on USA TODAY: No, hot August in 1983 doesn't expose climate 'hoax' | Fact check
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