Canberra, Friday 22 February 2002

Beliefs about global climate conditions rocked

A study by an ANU student has overturned longstanding beliefs about global climate conditions. Erica Hendy, a researcher from the ANU Research School of Earth Sciences, in collaboration with the Australian Institute of Marine Sciences, has found that ocean temperatures in the tropical Pacific during the 18th and 19th centuries were just as warm as the 20th century. Scientists had thought the 20th century was much warmer than the previous four centuries.

Ms Hendy's research will play an important role in modern climate modelling and will be published on a worldwide database. Climate modellers are severely hampered by not having real-world data from the Southern hemisphere and tropics to test possible climate scenarios. Australian research is making an important contribution in this respect.

Ms Hendy's study published in Science today, used corals growing since 1565 in the Great Barrier Reef to determine ocean temperatures. This 420-year temperature record, the longest ever produced from coral, includes a period known as the Little Ice Age from 1450 - 1870. During this time, rivers such as the Thames froze over, sea ice permanently surrounded Greenland and glaciers grew throughout the world. Until now, scientists have believed that temperatures during the Little Ice Age were cold around the globe.

"The cooling is well documented in the Northern Hemisphere, but we really didn't know what happened in the Southern Hemisphere or the tropics and assumed we'd find the same," Ms Hendy said. "Instead the coral thermometers report that at times in the 18th and 19th centuries the oceans were as warm as the late 20th century."

The breakthrough at the ANU uses the coral cores to monitor changes in both temperature and salinity - the keys to knowing what is happening in the ocean and atmosphere. "How salty the sea is tells us about the balance between how much rain is falling and how much water is evaporated and transported away," Ms Hendy said.

"The tropical ocean was saltier during the "Little Ice Age", which indicates stronger evaporation and movement of water vapour out of the region. This result helps to explain some of the climatic events occurring over the past 400 years. It is very exciting to see that the climate can operate so differently and change so rapidly before any possible human influence," Ms Hendy said.

"However, it should also make us more cautious with what we do in future because we don't want to tinker with a natural system that is so sensitive."

To view photographs taken during the collection of samples for this research go to <http://rses.anu.edu.au/egg/Pages/eggHendy.html> and click "Photo Gallery"

Contact: Erica Hendy (02) 6125 3348 or 0416 249 108 or
Genevieve Turville, ANU Public Affairs, (02) 6125 5575 or 0416 249 245

20/2002

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