![]() Water vapor remains an uncertainty here, because more water vapor would also cause cooling, and our understanding of natural variations in stratospheric water vapor is quite poor. I will agree with the authors that stratospheric cooling (especially in the mid- to upper-stratosphere) is probably the best evidence we have of a human fingerprint on global temperatures, at least up where there is very little air, where no one lives, and where there are no observable resulting impacts on weather down here where life exists. ![]() So, why mention stratospheric cooling in the context of climate change?Ĭlimate researchers have been searching for “human fingerprints” of climate change for decades, something measurable that cannot be reasonably explained by natural variations in the climate system. So why haven’t we heard about this before in the news? Because it has virtually nothing to do with the subject of global warming and associated climate change. Richard Lindzen tells me he had references to stratospheric cooling in his 1964 PhD dissertation. Lower stratospheric cooling has been evident in our Lower Stratosphere (LS) temperature product for over 30 years (first published here). Observed stratospheric cooling, even in the middle and upper stratosphere, has been reported on for many years (e.g. The researchers’ first mistake is to claim they are reporting something new. ![]() The authors are taking advantage of the public’s lack of knowledge concerning the temperature effect of increasing CO2 in the atmosphere, making it sound like stratospheric cooling is part of the fingerprint of global warming. 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.“ 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. Including this information improves the detectability of a human fingerprint by a factor of five. This fingerprint, however, neglected information from the mid to upper stratosphere, 25 to 50 km above the Earth’s surface. “Differences between tropospheric and lower stratospheric temperature trends have long been recognized as a “fingerprint” of human effects on climate. The paper starts out summarizing the supposed importance of their work, which is worth quoting in its entirety (bold emphasis added): provocatively entitled “ Exceptional stratospheric contribution to human fingerprints on atmospheric temperature” goes where no serious climate scientist should go: it has conflated stratospheric cooling with global warming.
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