Effects of ozone levels on climate through Earth history

Molecular oxygen in our atmosphere has increased from less than a part per million the Archean Eon, to fraction of percent Proterozoic, and finally modern levels during Phanerozoic. The ozone layer formed with early Proterozoic oxygenation. While itself only minor radiative climatic effects, accompanying important consequences for Earth climate. Using Community System Model (CESM), 3-D general circulation model, we test effects various on Earth's When CO2 is held constant, global mean surface temperature decreases decreasing ozone, maximum drop ~3.5 K at near total removal. By supplementing GCM results 1-D flux calculations, are able which changes responsible this change. We find that change caused mostly by stratosphere being much colder when absent; makes it drier, substantially weakening greenhouse effect. also examine effect structure upper troposphere lower formation clouds, circulation. At low both high clouds become more abundant, due tropospheric stability. These generate opposing short-wave long-wave forcings nearly equal. Hadley jet streams strengthened, while stratospheric polar jets weakened, latter direct consequence temperatures. This work identifies major impacts an piece evolution atmosphere.