The same media outlets and activist groups that spent 2023 screaming about record-breaking heat have gone conspicuously quiet. The reason is data that doesn’t fit the script, and University of Washington atmospheric scientist Cliff Mass laid it out in his blog.
Satellite measurements from the University of Alabama, Huntsville, which has tracked lower atmosphere temperatures since 1979, show a dramatic cooling trend over the past two years following a spike in 2023 that climate advocates trumpeted as proof of accelerating human-caused warming. Mass, one of the Pacific Northwest’s most respected meteorologists, pushed back on that narrative in a post on the Cliff Mass Weather Blog.
“The media and climate activists made a lot of false claims that the sudden warming in 2023 was due to human-emitted greenhouse gases, but have been very silent about the recent cooling,” Mass wrote. “Clearly, the cooling is not consistent with their ‘messaging’ about global warming.”
Hunga Tonga volcano, not carbon emissions, drove the 2023 global warming spike
The actual culprit behind the 2023 heat spike, according to Mass, was the massive 2022 Hunga Tonga volcanic eruption, which blasted enormous quantities of water vapor into the stratosphere. Water vapor is a highly potent greenhouse gas, and the eruption’s effects temporarily spiked global temperatures in ways that had nothing to do with carbon emissions.
“The rapid warming had nothing to do with human emissions, with the global temperatures naturally declining as the excessive water vapor was slowly removed from the system,” Mass wrote.
When a reader challenged his assessment of the Hunga Tonga eruption’s effects, Mass noted his depth of expertise on the topic.
“I have read them all,” he wrote, “over a dozen. In fact, the literature is divided, as many suggest warming as cooling. As you may know, I have written several papers on the impact of volcanic eruptions on climate and had an NSF grant on the topic.”
The March 2026 western US heat wave wasn’t caused by climate change, satellite data shows
The media’s most recent round of climate alarm centered on a significant March heatwave across the western United States, with outlets confidently attributing it to human-caused global warming. Mass looked at the same satellite data and found the story was far more complicated.
“These claims are easily disproved,” he wrote. “The heat wave was highly localized and some nearby areas were much colder than normal.”
Satellite temperature maps for March showed the warm anomaly over the western U.S. was offset by extreme cold across Alaska and northern Canada, a detail that received virtually no coverage.
Mass traced the cause to a perturbed upper-level atmospheric flow pattern over North America and was direct about what the science actually shows. “Research is very clear that global warming does not contribute to such a pattern,” he wrote.
Cliff Mass’s golden rule: the more extreme the weather anomaly, the less likely it’s caused by global warming
Mass wrapped his analysis with what he calls the Golden Rule of Climate Change, a principle that fundamentally undercuts the activist playbook.
“The more extreme the anomaly from climatology, the LESS likely it is that human-forced global warming is the cause,” he wrote. “This was true of the warming in 2023 and is true for last month’s warm event over the western U.S.”
For readers wondering where Mass actually stands, he was clear that he’s not dismissing climate science wholesale: “Human-caused global warming is real, but it is slow and modest in magnitude, and global in scope.”
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