28 Feb 2008

Jurassic environmental change study will help with future climate prediction



In the current debate over the longer-term effects of 21st century global warming and climate change, research from The Open University (UK) is now providing some compelling evidence of what can happen when the Earth’s oceans and atmosphere become much warmer.

Open University graduate student Chris Pearce, together with supervisors Drs Anthony Cohen and Angela Coe, went back 183 million years to the Early Jurassic Period for information on how the Earth reacted in the longer term to severe environmental change. What happened on Earth during and after abrupt global warming over a time scale of approximately several hundreds of years included a substantial decrease in the oxygen content of the oceans and a significant mass extinction of marine and terrestrial species. These initial big changes appear to have occurred at rates that are similar to those occurring at the present day. The facts that they have gathered are being published today in GEOLOGY by the Geological Society of America and will provide essential information to help validate predictions about environmental change in the future.

The use of current computer models to try to predict the longer term course of future climate and environmental conditions is uncertain because of our relatively poor understanding of the great complexity of the Earth’s behaviour.

The Open University team examined and de-coded the geological record of the extreme environmental disturbance known as the Toarcian (Early Jurassic) Oceanic Anoxic Event. Their findings show that there was widespread decrease in the oxygen content of the oceans during this abrupt period of global warming. The researchers also demonstrate that the changes in seawater oxygenation at that time were periodic and were coupled with regular, large-scale fluctuations in the Earth’s global carbon cycle.

Dr Cohen commented: “These records have the potential to provide quantifiable information about precisely how the Earth responds to severe environmental change in the longer term. The precise relationships between the various expressions of this environmental crisis in the Jurassic, although it occurred a very long time ago in Earth’s history, can provide valuable constraints for testing the reliability of predictions about environmental change that will continue to occur in the future as a result of man’s activities.”

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