The uncertainty of climate science: In the twenty-five years since I became a science journalist, I cannot count the number of high profile press releases and scientific papers that I’ve read claiming that the increase in aviation and the resulting contrails from airplanes was going to be a major contributor to human-caused global warming. According to the models, the increase in contrails was increasing the high altitude cirrus cover, and thus in a variety of ways acting to warm the planet.
Well, a paper just published in Geophysical Research Letters took a look at the effect the sudden and almost complete cessation of aviation during the 2020 COVID lockdowns had on high altitude cirrus clouds. If the models were right, the lack of air traffic should have caused a reduction in cirrus clouds, thus demonstrating the models were correct.
The models were wrong, once again. From the abstract:
We find that, despite the very large reduction in air traffic, neither cirrus cover nor temperature ranges changed by enough to be detectable relative to the year-to-year variability of natural cirrus. Comparing the satellite observations to previous model-simulated aviation cirrus, we determine that any aviation-induced change in cirrus would have a much smaller magnitude than would be inferred from climate model simulations. These results suggest that the warming effect of cirrus clouds produced by aircraft may be smaller than previously believed. [emphasis mine]
In other words, air traffic apparently has no impact on the high altitude cloud cover. The models that said this traffic was a contributor to global warming were 100% wrong. It apparently is not.
Of course, there remains some uncertainty even with this result, as it is for only one year. The effect of air traffic on clouds could have been disguised in 2020 by the natural fluctuations normally seen from year to year, though the paper’s authors think not.
Assuming this data is confirmed, the authors also concede that the plans to mitigate contrails by rerouting planes so that they do not all fly along the same routes could be very counter-productive. It will cause those detours to burn more fossil fuels, while changing nothing in the cloud cover in the upper atmosphere.
Ah, the law or unintended consequences once again rears its ugly head. Too bad global warming activists never seem to admit it exists, even though it constantly bites them in the rear, time after time after time after time after time….