By looking back, scientists see a bright future for climate change

04/14/04

New climate model predicted every major change

For scientists studying climate change, the past is often a key to understanding the future. Dake Chen at Columbia University's Lamont-Doherty Earth Observatory recently used more than a century of climate data to successfully test an improved model of ENSO, the El-Niño/Southern Oscillation that scientists believe is behind climate change in many parts of the world.

Chen and his colleagues report in the April 15 issue of the journal Nature that an improved climate model, known as LDEO5, for the first time predicted every major change in the temperature of the tropical Pacific Ocean over the past 150 years with up to two years of advance notice. In addition, their results suggest that ENSO is largely driven by internal relationships between ocean temperature and tropical winds rather than more unpredictable factors such as externally driven wind bursts, making the future of long-term climate prediction much more optimistic.

"No other model has been tested in such a long-term retrospective," said Chen, a senior research scientist at the Lamont-Doherty Earth Observatory, part of The Earth Institute at Columbia University. "In a two-tiered climate forecast system, a good first-tier forecast such as this is absolutely necessary for an accurate second-tier forecast of ENSO's global impacts."

El Niño and its opposite effect La Niña together make up the long-term variation in Pacific Ocean temperature that is thought to be behind events ranging from droughts in western Australia to changes in sardine catches off the coast of Peru. Together ENSO-related climate anomalies have been implicated in the deaths of tens of millions of people. Despite its importance, however, accurate predictions of ENSO have eluded scientists for decades and remain a goal of climate forecasters and public policy experts around the world.

Many theories describe ENSO as a chaotic and subsequently unpredictable force that governs water temperature in the Pacific Ocean between South American and Indonesia. Large-scale fluctuations in water temperature are believed to cause changes in tropical wind patterns that not only affect global climate patterns, but that themselves govern the movement of large masses of warm surface water across thousands of miles. Chen designed LDEO5 specifically to take into account the interrelated nature of the Earth's oceans and atmosphere and, using historical climate data, found that he was able to accurately predict the onset of large El Niño and La Niña events more accurately and with greater advance notice than any previous attempt.

Ultimately, Chen believes his model offers a strong case for a future when forecasters will be able to anticipate global climate change and climate-related disasters. "ENSO is by far the largest and most influential short-term climate fluctuation in the Earth's climate system," said Chen. "A better prediction of ENSO will not only benefit the tropical countries that are directly under the influence of ENSO, but will also improve our ability to manage disastrous floods and droughts in many parts of the world."

Source: Eurekalert & others

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