The Tropics Play A More Active Role Than Was Thought In Controlling The Earth's Climate

Oct 12, 2005

Researchers from the Universitat Autònoma de Barcelona and Durham University (UK) have discovered that a million years ago, global climate changes occurred due to changes in tropical circulation in the Pacific similar to those caused by El Niño today. Changes in atmospheric circulation caused variations in heat fluxes and moisture transport, triggering a large expansion of the polar ice sheets and a reorganisation of the Earth's climate.

The discovery, published in Geology, shows that local climate changes in the tropics can create more global climate changes, and emphasises the hypothesis that the tropics play a more active role than was thought in controlling the Earth's climate.

The planet enters and leaves glacial periods approximately every 100,000 years. However, a million years ago these cycles lasted only 40,000 years. Scientists have reconstructed the chain of climatic events that brought about a change in the frequency of glacial periods and that occurred alongside changes in sea temperatures in the Pacific Ocean and alongside significant changes to tropical climates.

The researchers have worked mainly with data obtained from the remains of marine organisms that have accumulated over time in the tropical Pacific. These fossil records show that approximately 1.2 million years ago, the difference in sea temperatures between the East and West Pacific began changing gradually over the course of 400,000 years.

In the equatorial regions surrounding Central America, the sea cooled; while around Indonesia, sea temperatures barely changed. This caused changes in atmospheric circulation, creating what is now known as the Walker circulation.

According to the researchers, these changes to tropical atmospheric circulation caused a change in heat fluxes and moisture transport to the polar regions. This brought about an increase in snowfall, enabling the ice sheets, particularly in the northern hemisphere, to expand and change in the frequency of glacial periods from 40,000 to 100,000 years.

Until now this expansion was thought to have been influenced only by the ice sheets themselves and by the ocean currents and the atmospheric circulation at high altitude in the northern hemisphere, as well as by CO2 levels in the atmosphere.

"Our results show that local climatic changes in the tropics can produce global changes," stated Antoni Rosell of the UAB, one of the authors of the research. "We are seeing that the tropics play a more active role than was thought in controlling the Earth's climate".

The two researchers, Antoni Rosell, a researcher of the Catalan Institute for Research and Advanced Studies (ICREA) for the UAB Institute of Environmental Science and Technology, and Erin L. McClymont, of Durham University (UK), currently at the University of Bristol, have published these results in Geology, the most important scientific journal in this field.

The uneven rhythm of the Earth's cooling process

The Earth has been passing through a cooling period for several million years. The process is not one of gradual, continuous cooling, but rather one of sporadic stops and starts. Professor Rosell's previous article, published in Nature, looked at one of these transitions. This transition was significant because it resulted in the cooling of large parts of the northern hemisphere, especially North America.

The latest article looks at another one of these transitions, this time in the more recent past and on a global scale. This transition is very important in climatology, as it coincides with a change in the frequency of glacial periods, the reasons for which are not fully understood. Although it was a change in the North Pacific that caused the northern hemisphere permafrost 2.7 million years ago, in the more recent case 1 million years ago, the origin of the permafrost was at the tropics.

Copyright 2005 by Space Daily, Distributed United Press International

Explore further: Short, sharp shocks let slip the stories of supernovae

Related Stories

Image: Cambodian rivers from orbit

7 hours ago

A flooded landscape in Cambodia between the Mekong River (right) and Tonlé Sap river (left) is pictured by Japan's ALOS satellite. The centre of this image is about 30 km north of the centre of the country's ...

Estuaries protect Dungeness crabs from deadly parasites

2 hours ago

Parasitic worms can pose a serious threat to the Dungeness crab, a commercially important fishery species found along the west coast of North America. The worms are thought to have caused or contributed to ...

Recommended for you

How bad can solar storms get?

May 22, 2015

Our sun regularly pelts the Earth with all kinds of radiation and charged particles. How bad can these solar storms get?

Mars rover's ChemCam instrument gets sharper vision

May 22, 2015

NASA's Mars Curiosity Rover's "ChemCam" instrument just got a major capability fix, as Los Alamos National Laboratory scientists uploaded a software repair for the auto-focus system on the instrument.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.