Did Mammoth Extinction Warm Earth?

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“Did mammoth extinction warm earth?” asks ScienceNOW 1 July 2010 and American Geophysical Union Press Release, 30 June 2010. Scientists from the Carnegie Institution for Science have studied pollen in sediments from the lakes of Alaska, Siberia, and the Yukon Territory, and concluded “that around 15,000 years ago—the same time mammoth populations dropped, and that hunters arrived in the area—the amount of birch pollen started to rise quickly.” The researchers looked at the feeding habits of elephants, and suggested mammoths would have been “great tree pruners” keeping the populations of trees down and maintaining the region as grassland. After the mammoths died out the trees would have grown larger and more dense, changing the landscape from a grassland to a forest. The forest would be darker in colour and absorb more heat from the sun.

The researchers used a climate simulation to estimate the effect of such a change on climate. The simulation calculated the vegetation change “would have warmed the whole planet more than 0.1 degrees Celsius (0.18 degrees Fahrenheit) over the course of several centuries.” Because mammoth extinction is believed to be caused by human hunting, the researchers claim this was the beginning of man-made global warming. The AGU press release goes on to say: “Only some portion—about one-quarter—of the spread of the birch trees would have been due to the mammoth extinctions, the researchers estimate. Natural climate change would have been responsible for the rest of the expansion of birch trees. Nonetheless, this suggests that when hunters helped finish off the mammoth, they could have caused some global warming.”

AGU

Editorial Comment: Did you note it was yet another computer simulation, rather than actual measurements that led to this conclusion? There is no doubt humans hunted mammoths, and may have contributed to their extinction. However, as the researchers admit, the change in global temperature was far more likely a part of a natural cycle of cooling followed by warming. It seems any excuse will do to promote the message of man-made global warming. (Ref. climate change, mammals, environment)

Evidence News 25 August 2010

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