The new finding has presented proof of human-caused climate change, demonstrating that specific signals from human activities have altered the temperature structure of Earth’s atmosphere.
Differences in tropospheric and lower stratospheric temperature trends have long been regarded as a fingerprint of human effects on climate.
“The incorporation of information from the mid to upper stratosphere, 25 to 50 kilometres above the Earth’s surface, improves the detectability of a human fingerprint by a factor of five”, said scientists.
The study published in Proceedings of the National Academy of Sciences (PNAS) said, “Enhanced detectability occurs because the mid to upper stratosphere has a large cooling signal from human-caused CO2 increases, small noise levels of natural internal variability, and differing signal and noise patterns”.
Day-to-day weather, interannual variability caused by El Nios and La Nias, and longer-term natural climate oscillation can all contribute to noise in the troposphere. The noise of variability is smaller in the upper stratosphere, and the signal of human-caused climate change is bigger, therefore the signal can be detected much more clearly.
The published paper reads, “Extending fingerprinting to the upper stratosphere with long temperature records and improved climate models means that it is now virtually impossible for natural causes to explain satellite-measured trends in the thermal structure of the Earth’s atmosphere”.
An adjunct scientist in the Physical Oceanography Department at the Woods Hole Oceanographic Institute (WHOI) in Massachusetts, US, and the lead author Benjamin Santer said, “This is the clearest evidence there is of a human-caused climate change signal associated with CO2 increases”.
Santer, who has worked on climate fingerprinting for more than 30 years, said, “This research puts to rest incorrect claims that we don’t need to treat climate change seriously because it is all-natural”.
According to scientists, this layer, from the mid to upper stratosphere, which the earlier studies had not studied in detail, can now be studied better because of improved simulations and satellite data.
“The new research is the first to search for human-caused climate change patterns in the middle and upper stratosphere”, the scientists said.
A professor in the Department of Atmospheric Sciences at the University of Washington, and co-author Qiang Fu said, “These unique fingerprints make it possible to detect the human impact on climate change due to CO2 in a short period of time (10 to 15 years) with high confidence”
Martin Professor of Environmental Studies at the Massachusetts Institute of Technology, and co-author Susan Solomon said, “The world has been reeling under climate change, so being as confident as possible of the role of carbon dioxide is critical”.
Susan Solomon further said, “The fact that observations show not only a warming troposphere but also a strongly cooling upper stratosphere is unique tell-tale evidence that nails the dominant role of carbon dioxide in climate change and greatly increases confidence”.
The lead author Benjamin Santer said, “This study shows that the real world has changed in a way that simply cannot be explained by natural causes”.
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