Global warming has long been considered as the culprit for extinctions--the surprise is that much less carbon dioxide gas in the atmosphere may be needed to drive an ecosystem beyond its tipping point than previously thought.

"Earth's deep time climate history reveals startling discoveries that shake the foundations of our knowledge and understanding of climate change in modern times," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which partially funded the research.

Jennifer McElwain of University College Dublin, the paper's lead author, cautions that sulfur dioxide from extensive volcanic emissions may also have played a role in driving the plant extinctions.

"We have no current way of detecting changes in sulfur dioxide in the past, so it's difficult to evaluate whether sulfur dioxide, in addition to a rise in carbon dioxide, influenced this pattern of extinction," says McElwain.

the rest...

http://www.nsf.gov/news/news_summ.jsp?cntn_id=115009&govDel=USNSF_51

Bottom line - truth is, the so called "experts" do not know what the he!! is going on...

grz-