You know, when the o2 level was 31%, dragonflies had a four-foot wingspan, and bats were the size of leer jets.
Perhaps we could start an AlGore movement, “Stop the Global Climate Change - Stop The Rise of Oxygen! Or GIANT bugs will get you! And bury you in a box!”
You jest, but that’s actually the upshot of a boost of carbon dioxide (if it were real). The green plants go YUMMIES and they put out oxygen in the sunlight.
Given current levels of solar radiation and vegetation, that’s what we’d get.