Although the burning of fossil fuels has been humanity’s first attempt at changing the concentration of greenhouse gasses in the atmosphere, it’s not the first time the planet has experienced something of the sort. About 50 million years ago, the Earth saw a dramatic change in the atmosphere’s carbon isotopes, which implies a large influx of carbon dioxide and/or methane with biological origins. This event, the Paleocene-Eocene thermal maximum (PETM), was accompanied by a geologically sudden change in temperatures, major disruptions in ecosystems, and a significant extinction event.

The PETM could potentially inform us about some of the changes that may accompany the current rise in atmospheric carbon concentrations. Unfortunately, reconstructing an event that’s 50 million years old has proven pretty challenging; we’re still not entirely sure how much carbon was in the atmosphere before the sudden influx, or what the source of the additional carbon was. Nonetheless, a couple of papers published in recent weeks paint a potential picture of what might have taken place, although some significant uncertainties remain.

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Originally posted here:
Climate change in the Eocene: how’d all this carbon get here?