Reduced Cloud Cover, Not CO2, behind Warming

Written by Climate Discussion Nexus on September 28, 2024. Posted in Current News

In 2021 we reported on a pair of studies (here and here) that analysed satellite-measured data and found that clouds were not shielding the Earth’s surface from incoming solar radiation as much as they used to, causing an increase in heat absorption at the surface which accounts for much of the warming experienced in the past few years without reference to ‘greenhouse gases’

Speaking of which, an especially surprising feature of those studies was that while extra solar energy was accumulating at the surface, the total amount of longwave radiation at the top of the atmosphere was going up.

Why is that surprising? Because the crux of climate orthodoxy is that more CO2 (plus other ‘GHGS’) in the atmosphere is trapping more of that radiation and letting less of it escape back into space, thus heating the planet.

And now one of the teams is back with a new paper with updated data that shows… more of the same. Over the past 20 years the net inflow of energy into the Earth’s atmosphere has doubled, mostly because more is being absorbed at the Earth’s surface.

But at the same time more is being expelled by the atmosphere, opposite to what would be expected from increased ‘greenhouse gas’ levels. Yep, climate is complicated.

Let’s start by looking back at the second of the studies we mentioned in 2021, by Dubal and Vahrenholt. They presented a remarkable graph of cloudiness and outgoing longwave radiation (meaning thermal, and known as OLR) from 1980 to 2020:

Around 2000 there was a dramatic, mysterious drop in average cloud cover, which the authors attribute to oceanic changes in the Pacific region and which the standard climate models cannot begin to account for.

Since on the whole clouds reflect heat, with less cloud cover the Earth warms up. Meanwhile if CO2 is the “The Thermostat that Controls Earth’s Temperature” as NASA’s Goddard Institute for Space Studies infamously claimed in October 2010, trapping OLR instead of letting it escape, then as carbon dioxide increases in the air the OLR should be dropping.

In fact it has to be. But instead OLR jumped just as cloud cover plummeted, and has continued increasing ever since.

That chart of course only goes up to 2018. But in the new Loeb et al. paper the post-2000 data are shown as follows, with the red line in the top panel showing Absorbed Solar Radiation and the blue line OLR.

The green line in the bottom panel is the net effect of the two in combination, graphed along with gray bars showing the “Multivariate ENSO Index” (a measure of the intensity of an El Niño Southern Oscillation event) to demonstrate that they do not correlate with it:

The top panel shows Absorbed Solar Radiation or ASR, the amount of heat the planet is gaining overall, going up steadily for 25 years, which the authors attribute not only to reduced cover of certain kinds of clouds but also lower reflectiveness of other cloud types, and here again the authors tie it to oceanic changes in the Pacific region.

And the blue line in that panel might seem to show OLR decreasing, except that it’s counterintuitively measured as if you were upside down at the top of the atmosphere, indicating how much is being trapped so the line going down means more heat escaping to space.

What does this mean? We’re not the sort of simpletons who declare ‘the science is settled’, or think one study ends all controversy. We want more data and more analysis.

But the preliminary indication is that if Mother Nature flipped a switch 25 years ago that reduced cloud cover and warmed the planet, it wasn’t us that did it, and presumably she could flip it back any time and we’d see a corresponding cooling, especially since we really don’t know what that switch actually was.

P.S. While we like sunny and warm weather more than cloudy and cool, it would be worth witnessing such a reversal just for the perverse enjoyment of seeing the climate crowd blame that too on ‘greenhouse gases’ and claim they’d actually predicted it all along.

Heck, why not another man-made global cooling scare?

See more here climatediscussionnexus

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