Carbon dioxide did not end the last Ice Age


A new USC study shows that Deep-sea temperatures rose 1,300 years before atmospheric CO2 rose, ruling out the greenhouse gas as driver of meltdown, says a study in Science.

Carbon dioxide did not cause the end of the last ice age, a new study in Science suggests, contrary to past inferences from ice core records. “There has been this continual reference to the correspondence between CO2 and climate change as reflected in ice core records as justification for the role of CO2 in climate change,” said USC geologist Lowell Stott, lead author of the study, slated for advance online publication Sept. 27 in Science Express. “You can no longer argue that CO2 alone caused the end of the ice ages.” Deep-sea temperatures warmed about 1,300 years before the tropical surface ocean and well before the rise in atmospheric CO2, the study found.

The finding suggests the rise in greenhouse gas was likely a result of warming and may have accelerated the meltdown – but was not its main cause. The study does not question the fact that CO2 plays a key role in climate. I don’t want anyone to leave thinking that this is evidence that CO2 doesn’t affect climate,” Stott cautioned. “It does, but the important point is that CO2 is not the beginning and end of climate change.” While an increase in atmospheric CO2 and the end of the ice ages occurred at roughly the same time, scientists have debated whether CO2 caused the warming or was released later by an already warming sea.

The best estimate from other studies of when CO2 began to rise is no earlier than 18,000 years ago. Yet this study shows that the deep sea, which reflects oceanic temperature trends, started warming about 19,000 years ago. “What this means is that a lot of energy went into the ocean long before the rise in atmospheric CO2,” Stott said. But where did this energy come from” Evidence pointed southward. Water’s salinity and temperature are properties that can be used to trace its origin – and the warming deep water appeared to come from the Antarctic Ocean, the scientists wrote. This water then was transported northward over 1,000 years via well-known deep-sea currents, a conclusion supported by carbon-dating evidence. In addition, the researchers noted that deep-sea temperature increases coincided with the retreat of Antarctic sea ice, both occurring 19,000 years ago, before the northern hemisphere’s ice retreat began.

Finally, Stott and colleagues found a correlation between melting Antarctic sea ice and increased springtime solar radiation over Antarctica, suggesting this might be the energy source. As the sun pumped in heat, the warming accelerated because of sea-ice albedo feedbacks, in which retreating ice exposes ocean water that reflects less light and absorbs more heat, much like a dark T-shirt on a hot day. “The climate dynamic is much more complex than simply saying that CO2 rises and the temperature warms,” Stott said. The complexities “have to be understood in order to appreciate how the climate system has changed in the past and how it will change in the future.”

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September 27, 2007 5:50 pm

It seems pretty obvious to me that as things warm up, like flourishes, and CO2 increases from the flourishing life, among other things. The cause and effect is totally reversed. Why do the alarmists not see that every piece of data tells them CO2 doesn’t drive climate?

Larry Sheldon
September 27, 2007 6:54 pm

“Why do the alarmists not see that every piece of data tells them CO2 doesn’t drive climate?”
There is no grant money in that!

September 27, 2007 7:00 pm

We’ve known since the 80s (SPECMAP Project) that earth’s orbital parameters drive glaciation by altering the albedo as the 100K obliquity, 40K tilt, and 23K precession cycles interact. IIRC, the estimate was about 30-50%. Feedbacks and solar variation account for the rest and work on shorter time scales. This study his hardly news except for some of the details.

Evan Jones
September 27, 2007 7:05 pm

I thought it was the tilt-wobble dance that created ice age cycles and that this was well known and undisputed. So why would anyone have thought that CO2 was a driver, here?
We already knew CO2 increase followed a dozen or so centuries after the warming-start. And there is still evidence here that CO2 may have acted as a secondary driver.
If the heat began with deep-ocean warming, then how did it “get there” from the axis wobble/tilt? SR on Antarctica in the spring? (Not sure I see the connection).
I can’t find anything I can really get my teeth into, here.

September 29, 2007 3:13 pm

My only problem with this paper is as you say. I’m not sure anyone was claiming that a rise in C02 caused the end of the previous ice age.

October 2, 2007 3:47 am

Evan, BCL
Check out Ruddiman’s papers on the climateofthepast website. This was definitely a touted theory.

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