Did megafauna extinction cool earth?

The rapid decline of mammoths and other megafauna after humans spread across the New World may explain a bone-chilling plunge in global temperatures some 12,800 years ago, researchers reported on Sunday.
The 100-odd species of grass-eating giants that once crowded the North American landscape released huge quantities of methane — from both ends of their digestive tracks. As a heat-trapping greenhouse gas, methane is 30 times more potent than carbon dioxide.
It was not enough to trigger runaway global warming. But when all that gaseous output suddenly tapered off, it caused or at least contributed to a prolonged freeze known as the Younger Dryas cold event, they argue. If so, the “Anthropocene epoch” — the era of major human impacts on earth’s climate system — began not with the industrial revolution in the 1800s, but the large-scale influx of two-legged predators to the Americas more than 13,000 years earlier.
Calculations by a trio or researchers led by Felisa Smith of the University of New Mexico, published in Nature, show how all the pieces of this previously unsolved puzzle might fit together.
Extrapolating from data on cows and other modern-day ruminants, the scientists estimated the total methane output of pre-historic megafauna at nearly 10 trillion grams per year.
At the same time, ice-core samples reveal that an abrupt drop in atmospheric methane levels of 180 parts per billion by volume (ppbv) coincides with both, the virtual extinction of these gas-gushing herbivores and the onset of the deep chill that followed.
Greenland ice cores from other periods show that a reduction in methane levels of 20 ppbv corresponds to a reduction in temperature of roughly 1ºC. That would add up to a decrease of 9ºC-12ºC, a near-perfect match with the Younger Dryas cold snap.
“We find that the loss of megafauna could explain 12.5 to 100 per cent of the atmospheric decrease in methane observed,” the researchers said. —AFP

Post new comment

<form action="/comment/reply/14630" accept-charset="UTF-8" method="post" id="comment-form"> <div><div class="form-item" id="edit-name-wrapper"> <label for="edit-name">Your name: <span class="form-required" title="This field is required.">*</span></label> <input type="text" maxlength="60" name="name" id="edit-name" size="30" value="Reader" class="form-text required" /> </div> <div class="form-item" id="edit-mail-wrapper"> <label for="edit-mail">E-Mail Address: <span class="form-required" title="This field is required.">*</span></label> <input type="text" maxlength="64" name="mail" id="edit-mail" size="30" value="" class="form-text required" /> <div class="description">The content of this field is kept private and will not be shown publicly.</div> </div> <div class="form-item" id="edit-comment-wrapper"> <label for="edit-comment">Comment: <span class="form-required" title="This field is required.">*</span></label> <textarea cols="60" rows="15" name="comment" id="edit-comment" class="form-textarea resizable required"></textarea> </div> <fieldset class=" collapsible collapsed"><legend>Input format</legend><div class="form-item" id="edit-format-1-wrapper"> <label class="option" for="edit-format-1"><input type="radio" id="edit-format-1" name="format" value="1" class="form-radio" /> Filtered HTML</label> <div class="description"><ul class="tips"><li>Web page addresses and e-mail addresses turn into links automatically.</li><li>Allowed HTML tags: &lt;a&gt; &lt;em&gt; &lt;strong&gt; &lt;cite&gt; &lt;code&gt; &lt;ul&gt; &lt;ol&gt; &lt;li&gt; &lt;dl&gt; &lt;dt&gt; &lt;dd&gt;</li><li>Lines and paragraphs break automatically.</li></ul></div> </div> <div class="form-item" id="edit-format-2-wrapper"> <label class="option" for="edit-format-2"><input type="radio" id="edit-format-2" name="format" value="2" checked="checked" class="form-radio" /> Full HTML</label> <div class="description"><ul class="tips"><li>Web page addresses and e-mail addresses turn into links automatically.</li><li>Lines and paragraphs break automatically.</li></ul></div> </div> </fieldset> <input type="hidden" name="form_build_id" id="form-10accebe4009ad8d090faabe47fa666a" value="form-10accebe4009ad8d090faabe47fa666a" /> <input type="hidden" name="form_id" id="edit-comment-form" value="comment_form" /> <fieldset class="captcha"><legend>CAPTCHA</legend><div class="description">This question is for testing whether you are a human visitor and to prevent automated spam submissions.</div><input type="hidden" name="captcha_sid" id="edit-captcha-sid" value="80060263" /> <input type="hidden" name="captcha_response" id="edit-captcha-response" value="NLPCaptcha" /> <div class="form-item"> <div id="nlpcaptcha_ajax_api_container"><script type="text/javascript"> var NLPOptions = {key:'c4823cf77a2526b0fba265e2af75c1b5'};</script><script type="text/javascript" src="http://call.nlpcaptcha.in/js/captcha.js" ></script></div> </div> </fieldset> <span class="btn-left"><span class="btn-right"><input type="submit" name="op" id="edit-submit" value="Save" class="form-submit" /></span></span> </div></form>

No Articles Found

No Articles Found

No Articles Found

I want to begin with a little story that was told to me by a leading executive at Aptech. He was exercising in a gym with a lot of younger people.

Shekhar Kapur’s Bandit Queen didn’t make the cut. Neither did Shaji Karun’s Piravi, which bagged 31 international awards.