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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Greenhouse Gas Is No Weakling
4 April 2012 1:27 pm
A simple interpretation of Antarctic ice-core records, the one preferred by global warming skeptics, portrays carbon dioxide as a weak, even inconsequential player in the warming that brought the world out of the last ice age. But the first continuous, near-global record of temperature as the last ice age ended now shows that carbon dioxide did indeed help warm the world.
The issue with Antarctic ice cores was that they recorded a rise in temperature ahead of the rise in carbon dioxide. How could the greenhouse gas be causing the warming, skeptics asked, if it wasn't in the atmosphere when the warming started?
But climate scientists know that no one region is representative of global climate trends. So Jeremy Shakun of Harvard University and his colleagues created a global temperature record. They combined 80 records of temperature over the past 22,000 years retrieved from around the world, ranging in latitude from Antarctica to Greenland. The seven types of records included ice cores whose oxygen isotopes record varying temperature. There were also pollen from lake muds and microfossils from ocean sediments, whose species and abundance reflect temperature.
Once a globally representative record came together, the data clearly showed carbon dioxide rising ahead of rising temperature, as it should if the greenhouse gas were helping drive the world out of the ice age. The warming of Antarctica ahead of carbon dioxide's rise was a red herring, Shakun and his colleagues conclude online today in Nature.
To see why, the researchers drew on a climate model as well as a variety of other climate records. They saw changes in the far north that triggered southward-marching changes in ocean and atmospheric circulation that eventually reached Antarctica. The immediate effect? There was an early warming as South Atlantic currents that normally carry heat away to the north stalled. But that warming came before the same changes triggered the release of much carbon dioxide from the deep ocean. As a result, Antarctic warming got a jump on the rest of the world, but carbon dioxide went on to warm the globe as a whole.
The new global temperature record "is quite an achievement," says Eric Wolff, a paleoclimatologist at the British Antarctic Survey in Cambridge, the United Kingdom. The early Antarctic warming "has been a thorn in the side of climate scientists," he says, but "one doesn't have to deal with that issue anymore."