Did megafauna extinction cool the planet?
Paris: 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 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 (CO2).
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 of 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 1.0 degrees Celsius (1.8 degrees Fahrenheit).
That would add up to a decrease of 9.0 to 12.0 C (16 to 22 F), a near-perfect match with the Younger Dryas cold snap.
"We find that the loss of megafauna could explain 12.5 to 100 percent of the atmospheric decrease in methane observed," the researchers said.
The theory is bolstered by the fact that the plunge in concentration was two-to-four times faster than the five other largest methane drops during the last 500,000 years, suggesting a unique confluence of factors.
"The megafaunal extinction is the earliest catastrophic event attributed to human activity," the study concluded.
"We thus propose that the onset of the `Anthropocene` [epoch] should be recalibrated to 13,400 years before present, coincident with the first large-scale migrations of humans into the Americas."
More from India
More from World
More from Sports
More from Entertaiment
- DNA: Harmful chemicals found in Maggi, Nestle India still in denial mode
- CM Kejriwal shortlists 39 'unwanted' IAS officers in Delhi
- Rajasthan: Gujjars revive reservation agitation, block rail track
- DNA: Modi-led NDA govt's hits and misses in one year
- J Jayalalithaa sworn-in as Chief Minister of Tamil Nadu
- Dr Subhash Chandra Show: Aspiring for more than what you have!
- ISIS to buy first nuclear weapon from Pak?
- Mumbai: CCTV captures assailant with gun at Film City
- Mathura SSP receives death threat letter, message for PM Modi
- BJP now central pole of Indian politics: Arun Jaitley
- Maharashtra FDA sends Maggi noodles for lab testing
- See what can Maggi do to your health!
- Watch: Fast N Facts @ 7:30pm
- Haridwar: Hotel Radisson Blu sealed for polluting Ganga
- Delhi: Two killed in road accident in New Ashok Nagar
- PM Narendra Modi graces Digvijay Singh's son wedding reception
- Goa Board SSC Exam Results 2015 announced
- Rahul Gandhi to pressurise govt to act on one-rank-one-pension issue
- ISIS close to buying nuclear weapon from Pakistan?
- Manohar Parrikar visits forward areas along LoC, reviews security situation
- There will be no delay in appointing CIC, CVC: Jitendra Singh
- Credibility of Prime Minister's Office restored by BJP, says Arun Jaitley
- ISIS justifies raping slave girls, says Michelle Obama is 'worth $40'
- Arvind Kejriwal to highlight AAP govt's 100 days work on Monday
- 'Unhappy' Celina Jaitley asks Sunny Leone to move out?
- BJP's plan for one-year celebration: 200 big rallies, 5,000 public meetings
- Video of cops dancing with woman goes viral, inquiry ordered
- IPL 2015 Final: Mumbai Indians vs Chennai Super Kings - Preview
- Heatwave leaves 153 dead in Telangana, Andhra Pradesh
- Jayalalithaa returns as Tamil Nadu CM: As it happened