Magnitude Of Recent Surface Solar Radiation Forcing Over US Is Tens Of Times Greater Than From CO2
By Kenneth Richard on 7. June 2021
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Over the US, the modest change in cloud cover from 1996-2019 predominantly drove the +11.77 W/m² surface solar radiation forcing during 1996-2012 (then -2.35 W/m² from 2013-2019). These “brightening” and “dimming” magnitudes easily overwhelm the values associated with an annual 2 to 2.5 ppm rise in CO2 forcing (0.2 W/m² per decade).
When cloud cover changes by even a percentage point or two from one decade to the next, the magnitude of the associated forcing can be compared directly to the impact of rising CO2 concentrations. And in a new study, Augustine and Hodges (2021) point out:
“Documented magnitudes of brightening are significant and much larger than the projected increase in downwelling longwave radiation (LW↓) expected for a doubling of CO2 since industrial times (~4 W/m²)”
Translated, the total projected forcing associated with a doubling of the CO2 concentration since 1750 (280 ppm to 560 ppm) is only 3.7 W/m² (Seinfeld, 2008).
