EFFECT OF PALEO-ATMOSPHERIC OZONE ON SURFACE-TEMPERATURE

Photochemical calculations indicate that the atmospheric O3 column was maximized when the atmospheric oxygen (O2) level was 10-1 of its present atmospheric level (PAL). For this O2 level, the O3 concentration maximum occurred about 10 km below its present peak. Coupled photochemical and radiative-convective calculations indicate that for this level and distribution, O3 may have increased the globally averaged paleosurface temperature by as much as 4.5°K. A major deficiency in our understanding concerns the exact chronology for the evolution of O2; i.e., according to various scenarios, O2 may have reached 10-1 PAL as early as 2 billion years ago or as late as 400 million years ago. © 1979.