Did paleolithic hunters cause global cooling?

 A recent article in New Scientist asks, "Did early hunters cause climate change?"  

"When hunters arrived in North America and drove mammoths and other large mammals to extinction, the methane balance of the atmosphere could have changed as a result, triggering the global cool spell that followed. The large grazing animals would have produced copious amounts of methane, a potent greenhouse gas, from their digestive systems. They vanished about 13,000 years ago."

The skeptics take issue with the paper for a few reasons.

  1. Temperature is highly correlated with methane, including during this period, and changes in temperatures could well be causing changes in methane levels (which fluctuate naturally).  Since most methane comes from fermentation in wetlands, temperature changes could slow or quicken the fermentation process.
  2. The methane drop is quickly followed by an even higher rise in methane.  It's not as if the megafauna came back to life, though it's possible that other factors caused the rise.
  3. Using the IPCC's own assumptions about methane forcing and the methane estimates in the paper, the estimated global temperature change from the mass extinction is 0.08 degrees C.  Yeah, so hardly anything.

Read the whole broadside here.  Note: the tone is less formal than an academic journal, but they open source their methods so anyone can check it.

 

(Thanks to @melbournian for the New Scientist article.)

Comments

 I read in SciAm a few years

Submitted by Levi on Tue, 06/01/2010 - 22:43.

 I read in SciAm a few years ago the proposal that it was burgeoning neolithic agriculture that cause the release of CO2 trapped in untilled that stayed an overdue ice age and continued refinement and modern industrialization only makes it worse.http://www.scientificamerican.com/article.cfm?id=how-did-humans-first-alte (gated)

I'm always amused and puzzled

Submitted by Christopher Ryan on Thu, 06/03/2010 - 09:30.

I'm always amused and puzzled by the wild overestimates of ancient humans' capabilities. A few hundred, maybe thousands, straggled into North America with spears and bad teeth and next thing you know, all the megafauna on the continent is driven to extinction! Wow, our ancestors were some tough (and hungry) brutes, right? They preferred to chase down those last few horses, camels, and mammoths, rather than net some salmon or rabbits. Megabullshit. It seems far more likely that the Younger Dryas was triggered by a massive meteor strike (and the data look pretty good): http://www.scientificamerican.com/article.cfm?id=did-a-comet-hit-earth-1...