How does excess Co2 effect the earth? We release Co2 and it absorbs a lot of heat. When it heats up the earth it melts things like polar ice caps. When polar ice caps melt it raises the oceans and floods places. Only the lowlands will get flooded and the highlands will stay dry but that’s only if the oceans don’t flood lots. When the places get flooded it kills trees by knocking them down. We need trees for oxygen and plants need Co2. That’s what I learned about Co2 and what its causes are.