During dinosaurs' era

Feb 20, 2006 10:28 GMT  ·  By

Scientists are puzzled by a new finding about the extremely high temperature of the Atlantic Ocean during dinosaurs' times. The discovery could indicate that current climatic models grossly underestimate the future warming.

Karen Bice, a paleoclimatologist at Woods Hole Oceanographic Institution, and a multi-institutional team of scientists studied three long columns of sediment extracted from the seafloor off Suriname, on the northeast coast of South America. The sediments were extracted in 2003 by the drillship JOIDES Resolution, operated by the international Ocean Drilling Program.

The sediments are made of both carbon-rich organic matter and fossilized shells of microscopic marine organisms. They hold a record of tens of millions of years. By studying the shells the team determined that between 84 million and 100 million years ago, in an era when dinosaurs roamed the Earth, ocean temperatures in the region ranged between 33? and 42?C (91? and 107?F). The uncertainty of the estimates is +/-2?C. For comparison, the temperatures in the same region today range between 24? and 28?C (75? and 82?F). Most people find water more than 40?C to be very uncomfortable.

"These temperatures are off the charts from what we?ve seen before," said Bice.

By analyzing the organic matter from the sediments, the scientists also managed to estimate the amount of atmospheric carbon dioxide, the main greenhouse gas, during the same period. It was 1,300 to 2,300 parts per million (ppm), compared to 380 ppm today.

And now the real problem: When 1,300 to 2,300 ppm of carbon dioxide is introduced into current computer models that simulate global climate, the computed result does not give such ocean temperatures. "The climate models underestimate temperatures and the amount of warming that would accompany an increase in CO2 of more than 1,000 ppm above today?s level." Bice said.

So, what's wrong with current climate models? One guess can be that during past warm periods, oceans and wetlands may have released much more methane gas, the second greenhouse gas, to the atmosphere. Methane traps heat 10 times more effectively than carbon dioxide, but is present in much smaller quantities. What happened if more methane gas was present?

Well, even when extraordinarily high concentrations of methane are introduced into the climate model, it still fails to predict such exaggerated temperatures. The temperatures inferred to have actually existed 91 million years ago are simply off charts. This supports the idea that current climate models fail to estimate correctly the effects of increased greenhouse gas concentrations.

Still another alternative, that maybe could save the validity of the theoretical climate model, might be that the global temperatures during dinosaurs' time were not determined mainly by the greenhouse gases but by Earth's orbit.

"One of the most important impacts this evidence suggests is the change to the Earth' hydrologic cycle," Bice said. "Higher tropical temperatures will increase the intensity of hurricanes and winter storms. In addition, precipitation patterns will change, moving even more rain that now falls on the central U.S. - an area known as the breadbasket of the U.S. for its food production - to higher latitudes where the quality of the soil may not be as conducive to agriculture. Policymakers use these models to predict likely climate change with increasing CO2 levels, and if the models are not right, society is not well informed or well served."

The importance of this study is that on one hand it seriously questions the validity of current climate models and it suggests that global warming might be even a much bigger problem than previously estimated, and on the other hand it puts more weight on the theory that the dinosaurs have disappeared due to climate change.

Image credits: Tokoro Yukiyoshi