Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon

Abstract

The application of isotopic tracers to paleo-climate investigations-including oxygen (delta O-18), sulphur (delta S-33) and carbon (delta C-13), integrated with Sedimentological and proxies studies, allows vital insights into the composition of early atmosphere-ocean-biosphere system, suggesting low atmospheric oxygen, high levels of greenhouse gases (CO2 + CH4 and likely H2S), oceanic anoxia and high acidity, limiting habitats to single-cell methanogenic and photosynthesizing autotrophs. Increases in atmospheric oxygen have been related to proliferation of phytoplankton in the oceans, likely about similar to 2.4 Ga (billion years-ago) and 0.7-0.6 Ga.