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New Study Shows Three Abrupt Pulses of CO2 During Last Deglaciation
vinces99 writes A new study shows that the increase of atmospheric carbon dioxide that contributed to the end of the last ice age more than 10,000 years ago did not occur gradually but rather was characterized by three abrupt pulses. Scientists are not sure what caused these abrupt increases, during which carbon dioxide levels rose about 10 to 15 parts per million – or about 5 percent per episode – during a span of one to two centuries. It likely was a combination of factors, they say, including ocean circulation, changing wind patterns and terrestrial processes. The finding, published Oct. 30 in the journal Nature, casts new light on the mechanisms that take the Earth in and out of ice ages.
"We used to think that naturally occurring changes in carbon dioxide took place relatively slowly over the 10,000 years it took to move out of the last ice age," said lead author Shaun Marcott, who did the work as a postdoctoral researcher at Oregon State University and is now at the University of Wisconsin-Madison. "This abrupt, centennial-scale variability of CO2 appears to be a fundamental part of the global carbon cycle."
Previous research has hinted at the possibility that spikes in atmospheric carbon dioxide may have accelerated the last deglaciation, but that hypothesis had not been resolved, the researchers say. The key to the new finding is the analysis of an ice core from the West Antarctic that provided the scientists with an unprecedented glimpse into the past."
"We used to think that naturally occurring changes in carbon dioxide took place relatively slowly over the 10,000 years it took to move out of the last ice age," said lead author Shaun Marcott, who did the work as a postdoctoral researcher at Oregon State University and is now at the University of Wisconsin-Madison. "This abrupt, centennial-scale variability of CO2 appears to be a fundamental part of the global carbon cycle."
Previous research has hinted at the possibility that spikes in atmospheric carbon dioxide may have accelerated the last deglaciation, but that hypothesis had not been resolved, the researchers say. The key to the new finding is the analysis of an ice core from the West Antarctic that provided the scientists with an unprecedented glimpse into the past."
"However, the researchers say that no obvious ocean mechanism is known that would trigger rises of 10 to 15 ppm over a timespan as short as one to two centuries."
We're way, way, way beyond 10 to 15 in 200 years.
Who said the CO2 causes anything?
The article and summary use the words "contributed to", which we know will be true - as a greenhouse gas, any increased CO2 will amplify and contribute to further warming. Doubtless there are other causative factors involved (e.g. Milankovitch cycles), some of which may well have occurred before the CO2 release.
The interesting question is, what triggered the CO2 pulses?
Why would anyone engrave "Elbereth"?
[quote]How do we know the CO2 spikes caused the warming? Perhaps the CO2 resulted from increased biological activity occuring as a result of the warming. [/quote]
CO2 is a warming gas in the atmosphere; in the absence of any other changes, adding CO2 will warm the atmosphere. However, as the article notes, we don't know what caused the quick ramp-up of CO2, and we *do* know that other factors (both cooling and warming) were in play. We also know that over time the atmosphere warmed enough to end the ice age in question.
What is safe to say is that CO2 has a warming effect, which could be counterbalanced *and* added to by other factors. It's the overall balance of these things that tilts the scales one way or another. CO2 is just one piece.
But it's not mistaking correlation for causation to note that adding CO2 to the atmosphere will result in increased warming. That's just basic physics. The fact that it could be offset by something else is immaterial to your point.
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