3: increase in days over 100F.  Being hotter isn&#x27;t just an inconvenience: photosynthesis stops working efficiently when temperatures are over 100F (fun chemistry fact: chemical reactions are temperature sensitive; this is why your body tries to maintain a very narrow temperature range.  Otherwise, the chemical reactions all run at the wrong speed (or not at all), and the delicate balance of chemical pathways is disrupted).  So when temperatures get too hot, plants switch from photosynthesizing and storing energy to burning their stored sugars and respiring.  Forests begin emitting CO2 instead of consuming it; crops do not have the extra sugars to store as fruits and grains for us to harvest and eat.