University of Florida: Global Warming
Ancient global warming changed earth from icehouse to greenhouse - 12/17/07
Earth literally turned over a new leaf 15 million years ago when an earlier version of global warming changed large parts of the planet from lush forests to open grasslands, a new study by scientists at the University of Florida and other institutions shows.
In a portent of today's global warming, fossilized leaves tell the story of a carbon dioxide induced warm-up at the end of the Miocene age that melted much of the polar icecaps and led to the spread of animals that thrive in the wide open spaces, such as horses, camels and other grazers, said David Dilcher, a UF paleobotanist and one of the study's authors.
"Our findings clearly demonstrate that past climate changes were tied to carbon dioxide fluctuations in the atmosphere, which influenced the major vegetation patterns occurring on earth and in turn affected the evolution of major animal groups," Dilcher said.
The work by Dilcher, Wolfram Kurschner, a paleobotanist at Utrecht University in the Netherlands, and Zlatko Kvacek, a paleobotanist at Charles University in the Czech Republic, appears in a paper published this week in the online edition of the Proceedings of the National Academy of Sciences.
"The relevance for today is that the Antarctic ice sheets are reversing again," said Dilcher, who works at the Florida Museum of Natural History. "As carbon dioxide and other gasses increase in the atmosphere, we're emerging from a cooler or icehouse-type period into a greenhouse-type period with ice-free poles. The Earth is gradually going to undergo major changes just as we saw major changes in the upper Miocene Epoch."
While use of fossil fuels has been blamed for today's global warming, the likely source of this ancient episode was carbon dioxide belched from widespread volcanic eruptions in the Columbia River Flood Basalt region of the United States and in Central Europe, Dilcher said.
