SYDNEY, Australia, February 22, 2002 (ENS) - Rising concentrations of greenhouse gases may have tipped the world into a changed climate pattern, research by two Australian government climate scientists indicates.
Links between a global climate change that began around 1970 and increasing greenhouse gas concentrations are the subject of investigation for Dr. Wenju Cai and colleague Dr. Peter Whetton with the Commonwealth Scientific Industrial and Research Organization (CSIRO).
The surface waters in the eastern Pacific Ocean, off the United States and Central America, have been warmer since the mid-1970s than at any time in the past.Temperatures of the ocean surface in this region have been up to 0.8 degree Celsius (1.4 degrees Fahrenheit) greater than they were in the first half of the 20th century.
Modelling the climate on specialized computer programs, Drs. Cai and Whetton from CSIRO Atmospheric Research have evidence that the change was caused by warm water in the oceans at high latitudes being carried to the eastern equatorial Pacific by deep ocean currents. The process takes about 30 years.
Using CSIRO's global climate model, the researchers have found that higher levels of atmospheric greenhouse gases may be the cause of the climatic shift in the Pacific.
"Our climate models are matching what we see in the real world," says Dr. Cai.
The six main greenhouse gases linked with global warming are carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride.
Carbon dioxide, the product of fossil fuel combustion emitted by motor vehicles, power plants and industrial facilities, is the most important greenhouse gas that traps the Sun's rays contributing to the potential for global warming.
The warmest year in the 1860 to present record occurred in 1998, according to records maintained by Members of the World Meteorological Organization (WMO). Nine of the 10 warmest years have occurred since 1990, and the global average surface temperature in 2001 was the second warmest on record.
Warmer conditions in the eastern equatorial Pacific are normally associated with El Niño events. These events occur every two to seven years, and normally lead to lower rainfall in eastern and southern Australia. The last El Niño occurred in 1997 and 1998.
While meteorologists say that El Niño events are a natural part of the climate system that have been affecting the Pacific Basin for thousands of years, they are dreaded for the droughts and severe storms that accompany them not only in the Pacific but around the world.
"The change doesn't mean that we will have more El Niño events, but those that do occur may be stronger," says Dr. Cai. He and Dr. Whetton have published their findings in the international "Journal of Climate."
This finding is in agreement with CSIRO's projections of likely changes to Australia's climate due to the greenhouse effect during the next 100 years. Scientists project warmer drier conditions for much of the country.
The Bureau of Meteorology Australia said Tuesday that an El Niño event this year is likely. "There has been strong sub-surface warming in the western and central equatorial Pacific during the past few months which may, given the appropriate triggers, lead to an El Niño event."
The austral autumn is the critical time of year for El Niño development, so climate scientists will be monitoring Pacific climate data even more closely than usual during the coming months.
Five of the 12 ocean forecast models surveyed predict the possible development of El Niño conditions between about April and September, Australian meteorologists said.