And also made European forests a net CO2 producer for the year, IIRC. Photosynthesis doesn't work well at high temperatures, so instead plants switch to respir

And also made European forests a net CO2 producer for the year, IIRC. Photosynthesis doesn't work well at high temperatures, so instead plants switch to respiration, burning their stored sugars for energy while taking in oxygen and releasing carbon dioxide. Which, you know, is why plants produce those sugars in the first place, not to magnanimously produce oxygen/scrub CO2 for us. Heat-waves, with lots of days over 40C/100F, will also wreak havoc on our agriculture.