By analysing a warming event 55 million years ago, geologists have an analogy to current climate change conditions, they claim.
Pushing global temperatures past a certain threshold, or tipping point, is likely to trigger a series of positive feedback mechanisms leading to the release of large quantities of greenhouse gases and even more rapid warming, the geologists said at the 34th International Geological Congress, being held in Brisbane, Australia.
“The PETM [Paleocene-Eocene Thermal Maximum] was a short term, very rapid, very extreme warming,” said David Greenwood, a paleoclimatologist from Brandon University in Canada. “Because it’s a short term event, it offers some insight into the kind of warming we’re experiencing now.”
Catastrophic change in carbon cycle
A drastic increase of greenhouse gases in the atmosphere at the end of the Paleocene and the beginning of the Eocene, about 55 million years ago, caused an increase in global temperatures by about 6ºC, which was sustained for nearly 150,000 years.
It is unclear what caused the initial warming, but it resulted in a catastrophic change in the global carbon cycle, said Gabriel Bowen from the University of Utah in Salt Lake City, USA. This would have triggered a series of additional, positive feedback mechanism that exacerbated the warming. These could have included the release of carbon from thawing permafrost soils, reduced growth of biosynthetically active plants or changes in the burial rate of carbon in the soil.
“This combination of feedbacks sustained atmospheric carbon dioxide levels at high levels for a period of tens to hundred thousand years,” said Bowen. “If those same feedbacks come into place, then this initial perturbation [of the carbon cycle] that we’re having right now through the burning of fossil fuels may have a much longer timespan than we’d like to.”
1) Catastrophic? For whom? What, were there warming induced mass extinctions then?
2) The theorizing by scientists part is not the part that makes it science.
“If” when applied to speculation regarding the hypothesized mechanisms (about which they admittedly know nothing – “It is unclear what caused the initial warming”; “a series of additional, positive feedback mechanism (sic)… could have included the release of carbon from thawing permafrost soils, reduced growth of biosynthetically active plants or changes in the burial rate of carbon in the soil” ) amounts to a rhetorical shoehorn for wedging in the justification for solicitation of the next research grant.
This isn’t science, it’s total guesswork. I laugh at all this talk of large positive feedbacks. Any physical system with such feedbacks are inherently unstable. Since the environment has been stable for the last 500 million years or so, neither getting stuck in a perpetual ice age nor frying from pole to pole, it is not possible for these positive feebacks to exist. And without them there is no catastrophic warming.
Where in the galaxy was the solar system when this occurred?
It need not have been caused by anything on the planet—it could
have been caused by an external change—-perhaps by
a “hole” in the GCR flux resulting in substantially less cloud cover.
Track it back.
The tipping point was a 6C rise in 20,000 years? The we had 150,000 years of global warming followed by an ice age. And this is something we should stay up late at night and worry about? Bravo Sierra.