Average stratospheric H₂O (left) and temperatures (right) for high CH₄ models all normalized to results from models using modern levels of CH₄. Nearly all models experience an increase in H₂O for the high CH₄ models due to the conversion of CH₄ into H₂O in the stratosphere. Planets around hotter hosts with higher O₂ show the largest increases as incident UV and O₂ are necessary for creating H₂O in this scenario. The excess H₂O impacts the temperature, providing stratospheric cooling in cases with large increases of H₂O. As the atmosphere is thin in the stratosphere heat radiating from H₂O can escape to space, causing an effect similar to stratospheric CO₂ cooling present on modern Earth.