Prehistoric Global Warming

[espritch]

It appears that humans may have been contributing to global warming for a very long time.

http://story.news.yahoo.com/news?tmpl=story&cid=624&e=1&u=/ap/prehistoric_pollution

According to the story, an investigation of air bubbles in Antarctic ice shows that humans may have been affecting global climate for the last 8000 years. The ice bubbles show an anomalous increase in atmospheric CO2 at that time which researchers think may be associated with the beginning of widespread land clearing for agriculture. An increase in methane shows up about 5000 years ago, possibly a result of rice farming. Increases in these greenhouse gases due to human activity may have prevented global cooling that climate models suggest should have happened at that time.

"You have 395,000 years of history, which sets some rules, and 5,000 years that break those rules," Ruddiman said.

 

[pupdog]

Going back a bit earlier, there may have be a greenhouse warming or 2 during the Cretaceous, according to an article in Science (I think 5 December. And other periods of increased warmth (greenhouse or otherwise) over the eons.

It was reported a while back how ice cores(?) recorded icreased atmospheric levels of metals and/or associated sulfur etc. associated with smelting during the rise of Roman industry.

 

[espritch]

Well, I'm pretty sure people didn't have anything to do with warming trends during the Cretaceous. I wonder if maybe dinosaurs did. A lot of the really big ones were plant eaters and probably produced a lot of methane. I remember watching a program where they talked about how gassy a brontosaurus would be. It was basically a great big gut full of digesting plant matter - kind of a walking fermentation vat. And methane is a greenhouse gas.

Of course I've also heard that the current ice age cycle was probably a result of the growth of the Himalayas. The rock exposed as these mountains grew started weathering and this process tends to trap CO2 reducing global temperatures.

 

[pupdog]

Sorry! I gave the wrong reference for the Cretaceous warming article. "Terrestrial Evidence for Two Greenhouse Events in the Latest Cretaceous" by Nordt, Atchley, & Dworkin, appeared in the December 2003 issue of GSA Today.

Carbon & oxygen isotope (from paleosols) data provided evidence for increased pCO-2 and rise in temperature. These increases may have been forced by degassing of CO2 by the huge volume of magma coming to the surface (the Deccan traps).