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July 20 (UPI) – A new analysis of satellite data revealed the atmospheric signature of seasonal changes caused by climate change.
Previous studies have revealed seasonal changes on the ground. As the planet warms up, animal migrations have shifted – birds are flying south and flowers are blooming earlier and earlier. Patterns of sea ice have changed, and hurricane and forest fire seasons have lengthened.
For the new study, scientists set out to find similar changes several kilometers above the surface of the Earth. Their effort, which included analysis of satellite temperature data collected between 1979 and 2016, marked the first time that scientists detected seasonal changes in the atmosphere.
According to their calculations, detailed this week in the journal Science, the changes being the product of natural variation – as opposed to anthropogenic climate change – is about five in a million.
"In the biological world, many people have sought and found these changes, so we decided to take a look at the satellite data," said Benjamin Santer, a scientist with Lawrence Livermore National Laboratory in California. "What we see is a profound proof of the human impact on the climate, not only in annual temperatures but also in the seasonal cycle."
Scientists have used computer models to simulate thousands of years of climate change. with and without increasing greenhouse gas emissions. The researchers then compared simulation predictions with satellite temperature data collected after 1979.
Satellite data was very similar to simulation predictions that included increasing greenhouse gas emissions. The most striking difference was found among the satellite data recorded above the land masses. Scientists have discovered that the difference between summer and winter temperatures has increased on average by 0.4 degrees Celsius over the last four decades.
"The Changing Seasonal Cycle Provides Powerful and New Evidence of a Significant Human Effect on the Earth's Climate" Press Release
More than anything, the results confirm what climate scientists already knew. But Santer hopes the results will hold skeptics out of the climate that climate change evidence is too dependent on ground measurements.
"I do not think it solves a major problem in atmospheric science, nor does it change anything about the climate system," said Dessler. "But it provides even more evidence that humans are altering the climate."
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