Human-driven climate change has caused large and concerning temperature decreases in the stratosphere since at least 1986, according to a UCLA-led study published in the Proceedings of the National Academy of Sciences.
That sustained stratospheric cooling, the authors report, is evidence that the warming of Earth’s surface and lower atmosphere is not a natural occurrence.
In particular, the study confirms the effects of human causes on the overall climate: The temperature changes in the stratosphere were 12 to 15 times greater than what could have been caused by nature.
“This is the clearest evidence of a human fingerprint on the climate system I’ve seen in 30 years of atmospheric research,” said Benjamin Santer, the study’s lead author, a climate scientist at the UCLA Joint Institute for Regional Earth System Science and Engineering and the Woods Hole Oceanographic Institution.
The study, by researchers from UCLA and several other universities and institutes worldwide, is the first to search for human-caused climate change patterns in the middle and upper stratosphere. Those atmospheric layers — roughly 15 to 31 miles (about 25 to 50 km) above the Earth’s surface — rest above the elevations where most weather activity occurs. That high up, natural phenomenon like El Niño or La Niña have relatively little impact, which makes it easier to isolate the role of human influence, Santer said.
Human-driven climate change has already led to the warming of the Earth’s surface by 1.1 degrees Celsius since the late 1880s. (The Paris Climate Accords have set a target of not exceeding 1.5 degrees Celsius of warming to avoid the most dangerous climate consequences.)
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