"We know the gathering greenhouse will be warm, but this new information confirms that the contrast between the rainy season and the dry season will increase dramatically," says Greg Retallack, whose study indicating that a troubled greenhouse is brewing is published in the April issue of the journal Geology.
In this case, the word "troubled" refers to the stormy conditions shown to have been in play during a well-known greenhouse event some 55 million years ago during the late Paleocene epoch. Retallack explored the relationship between seasonality and rainfall in soils, then applied the same techniques to buried soils spanning the ancient greenhouse event.
"This is known to have been a time of high atmospheric carbon dioxide from studies of the breathing pores in fossil leaves," he explains. "At that time, Wyoming warmed from a mean annual temperature of some 55 degrees to a summer-like 65 degrees Fahrenheit. Rainfall in Utah jumped from 16 inches per year to 26 inches per year. As a result, sagebrush deserts of the western U.S. were transformed into sub-humid woodlands."
Retallack agrees with previous research indicating that the cause of the late Paleocene greenhouse spike, which lasted less than half a million years, was a catastrophic release of natural gas from undersea ices and permafrost.
"In a remarkable parallel to modern hydrocarbon pollution of the atmosphere, this natural methane oxidized to carbon dioxide and created a global greenhouse event," he explains. "The past methane outburst dwarfed even human consumption of hydrocarbons, and there is a danger that another similar outburst could be triggered by warming of polar and submarine ice due to human activities. Our little warming push could repeat the troub
Source:University of Oregon