Significant uncertainties of climate change triggers

There might be feedbacks in the climate system that we aren't aware of yet.
The amount of carbon in the oceans and atmosphere changes suddenly and dramatically. The oceans are acidified and significant extinctions result. On land, global temperatures increase anywhere from five to nine degrees Celsius, causing widespread habitat disruptions. Despite the sudden onset of the event, its impact lingers for 100 thousand years.
his might sound like a worst-case situation for the current anthropogenic influences on climate, but it's actually an historic event that the public is generally unaware of: the Paleocene-Eocene Thermal Maximum, or PETM, which occurred about 55 million years ago. - Have you voted in the poll Global climate change (warming) ? -
That said, there are some significant uncertainties regarding the precise events that triggered the PETM. The change in the carbon cycle is indicated by a sudden change in isotope ratios; lighter-weight 12C became much more common, which suggests a biological source, but that's consistent with both deep ocean sediments and methane clathrates. More significantly, although we do know there was a sudden influx of carbon, we don't know how much in total wound up in the oceans and atmosphere.

By John Timmer

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