Claim: Global temperatures have fallen to a “30-year baseline” since 2016, far below
According to NASA, the average global temperature has increased by about one degree Celsius — about two degrees Fahrenheit — since 1880. Other independent, long-term climate datasets confirm that finding.
However, some social media users are circulating a blog post which claims that global temperatures are declining.
The blog link in a March 2 Facebook post reads, “Earth’s average temperature drops to a 30-year baseline of .71 °C (slightly more than a degree Fahrenheit) below 2016 peak.”
The blog argues that the finding challenges the idea of a consequent or dangerous global warming trend.
“In other words, it has become harder and harder to politically perpetuate the ‘catastrophic global warming’ narrative,” the blog reads.
The blog garnered hundreds of interactions on Facebook, Twitter and Reddit. ,
However, the blog is misleading. It cherry-picks data from shorter time frames that do not reflect the overall warming trend documented by many climate monitoring agencies. It also leaves out the key context that explains the declining trend over the years.
follow us on Facebook! Like our page to get updates on our latest debunks throughout the day
USA Today contacted the blog author and social media users who shared the claim for comment.
Blog reference hot, recent “foundational”
The blog references data from the University of Alabama in Huntsville (UAH) dataset, which reports temperatures recorded by instruments on a collection of satellites from the National Oceanic and Atmospheric Administration, NASA and European. UAH has data for 1978.
The blog says that the February 2022 temperature did not exceed the “30-year baseline” of the UAH dataset. This is accurate – with one caveat.
It is common for climate data agencies to report global temperatures as variations from a set baseline, rather than reporting actual temperature values. Different baselines may be used depending on both the agency and the context in which the data is being reported.
The UAH dataset currently reports monthly temperature changes compared to the 1991–2020 baseline.
This time frame – which itself reflects higher temperatures than in the pre-industrial era – is currently recommended by the World Meteorological Organization as the “standard reference”.
Fact Check: False claim that Arctic, Antarctic ice reached record highs
Despite the February 2022 result, UAH reports a February warming trend of about 0.16 °C per decade since the late 1970s, said John Christie, a professor and director of the Center for Earth System Science at UAH. told USA TODAY in an email. Overall warming was about 0.13 °C per decade.
Record-setting 2016 temperatures, presence of “downward trend” due to El Nio-Southern Oscillation
As noted in the blog, the global average temperature reported by UAH for February 2022 was about 0.7 °C lower than in 2016.
However, contrary to the claims of the blog, this finding does not contradict the overall warming trend reported by several climate science agencies.
That’s because, as global temperatures are rising due to human-caused greenhouse gas emissions, the climate is also subject to natural variability, NOAA climatologist Ahira Sánchez-Lugo previously told USA Today.
An example of this variability is the El Nio–Southern Oscillation – a natural phenomenon that can cause short-term warming or cooling of global temperatures.
These warming and cooling phases are called El Nio and La Nia respectively.
In 2016, a very strong El Nio contributed to record high global temperatures. Since then, the four La Nias have contributed to the comparatively low temperatures, Sánchez-Lugo said.
Even though the years after 2016 have been the warmest on record, the fact is that most are not as warm as 2016, resulting in what appears to be a “downward trend”.
Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, told USA Today that similar short-term “downward trends” in global temperatures occurred after the 1998, 2007 and 2010 El Nios. However, these were frequent warming trend fluctuations that continue to the present.
The existence of a statistically significant warming trend does not require that each month or year be warmer than all previous months or years, he said in an email.
Defending the blog post, author Cap Allen attributed temperature changes to less solar activity.
Elon told USA Today in an email, “Earth’s lower troposphere temperatures have declined dramatically since the 2016 peak, consistent with historically low solar activity, all the while increasing CO2 levels. ”
Some critics of the human-driven climate change concept say that fluctuations in the intensity of the Sun are actually responsible for global warming. However, over the past few decades the brightness of the sun has decreased while the temperature has increased rapidly.
According to both NASA and NOAA, solar fluctuations may account for only a small fraction of the warming since the pre-industrial era.
USA Today has previously addressed other social media posts that attempt to downplay the importance of global climate change by cherry-picking data.
Fact Check: Greenland is still losing ice; no reversal in trend
For example, social media users identified a “downward trend” in the NOAA data and claimed that climate change threats were exaggerated. As in this case, the trend was driven by 2016’s record high temperatures, which were followed by several La Nias.
Our Rating: Missing Context
Based on our research, we evaluate the claim that global temperatures have fallen to a “30-year baseline”, which has decreased significantly since 2016. The “30-year baseline” refers to a time frame already affected by global warming. A massive El Nio in 2016, followed by several La Nias, contributed to the appearance of a short-term “downward trend”, even as temperatures continued to rise overall.
Our fact-checking sources:
- Email exchange and phone interview with Ahira Sanchez-Lugo, February 24-25, USA TODAY
- Email exchange with Gavin Schmidt, March 15-22, USA TODAY
- Email exchange with John Christie, March 22, USA Today
- USA Today, March 1, Fact Check: Data from the Japanese Meteorological Agency shows warming over the Japanese island
- USA Today, March 9, Fact Check: Misleading data used in claim alleging global cooling trends
- NASA, accessed March 16, World of Change: Global Temperatures
- The Met Office Climate Dashboard, accessed March 16, Annual global mean temperature difference from pre-industrial conditions
- NASA, January 13, 2021 Tied for sixth warmest year in continuous trend, NASA analysis shows
- Six questions to help you understand the sixth warmest year on record, NASA, January 13, 2021
- NASA, accessed March 18, Carbon dioxide
- University of Alabama in Huntsville, accessed March 18, global temperature graph
- NOAA, accessed March 21, Global Climate Report 2021
- NOAA, accessed March 21, Global surface temperature departures (ºC), colored by monthly ENSO values
- NASA, accessed March 21, Global Temperatures
- The University of Alabama in Huntsville, accessed March 21, Global Temperature Report
- NOAA, August 10, 2017, International report confirms 2016 was hottest year on record for world
- NOAA, May 5, 2014, What is El Nio-Southern Oscillation (ENSO) for short?
- The Washington Post, Jan. 13, The past seven years have been the warmest in recorded history, new data shows
- IPCC, accessed March 22, FAQs
- NASA, September 6, 2019 What is the role of the Sun in climate change?
- NOAA, October 29, 2020, Couldn’t the Sun be the cause of global warming?
- NASA, accessed March 23, temperature versus solar activity chart
- World Meteorological Organization, May 5, 2021, updated 30-year reference period reflects changing climate
Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper facsimile here.
Our fact-check work is partially supported by a grant from Facebook.