And that isn’t the only example of CO2 not being helpful to plants. Each of our main crops have a temperature range that they can tolerate. When temperatures get too hot, their stomata close to prevent water loss, but at the same time photosynthesis is reduced which means the plant stops growing until temperatures cool off in the late afternoon. The midwest has already hit that limit for corn, which is the most heat tolerant of our primary crops, which means that production per plant is taking a hit. What is happening to soy beans is even worse.