Hot off the atmosphere: Based on daily values, the September average of CO2, measured at Mauna Loa was ~411.3 ppm; that's +2.7-2.8 ppm higher than last year.
Overall: still speeding in the wrong direction!
Overall: still speeding in the wrong direction!
Almost every year, September has the lowest monthly average CO2 concentration, due to its seasonal pattern. From here on, we'll see CO2 increasing towards a new 15-million year high in spring, probably peaking close to 420 ppm in May.
Re that seasonal pattern in atmospheric CO2: Overall, trees and plants take up CO2 in summer, and give back CO2 to the atmosphere in winter.
And since most of Earth’s landmass is in the northern hemisphere, this leads to a seasonal pattern in which CO2 in the atmosphere decreases from May to September/October, and then starts going up again.
And for fellow nerds: the seasonal decrease would last a little longer, and the increase a little shorter, if we weren't emitting CO2 all the time.
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