An ancient coral reef in Papua New Guinea reveals that El Ninos and La Ninas, the pulses of warm and cold water in thePacific that cause extreme weather patterns such as droughts, floods and storms, have never been stronger than they are today.
So far, scientists have been unable to predict future El Ninos, meaning that they cannot prepare for weather emergencies. El Nino, the giant patch of unusually warm water, can disrupt fishing, produce rough weather on the West Coast of the U.S., and cause droughts in places like Indonesia. La Nina, which produces cold water, causes the terrible winter storms that batter the Northwest and the hot, dry summers of the Southwest.
An international team of scientists tracked El Ninos back 130,000 years by reading the annual bands in fossilized coral,which form much like the bands in tree trunks. Coral reefs near Papua New Guinea lie in an area that is stronglyaffected by El Ninos, making this coral an especially good indicator of past weather patterns.
Corals are small animals that build hard skeletons and live in colonies called reefs. Many swimmers and divers areunaware that coral are living creatures. They grow slowly and their skeletons record the current water temperature andsalinity. "This situation makes it possible to sample corals which grew during periods when climatic boundary conditionswere substantially different to those today," the research team wrote in a paper published in the journal Science.
Their research shows that temperature swings increase in warmer times, like those we're experiencing now, although Dr.Alexander Tudhope of the University of Edinburgh, said there was no way to tell if the recent period of sharp Pacifictemperature oscillations are related to global warming. El Ninos were about 50 percent weaker during the last ice age.
Dr. Tudhope did say that further greenhouse warming could cause further El Nino and La Nina temperature swings, bringingus more bizarre weather. "We' re already at the outward bounds of natural variability," he said, explaining that theglobal average temperature is now as warm as it has been for tens of thousands of years. "From here, we're going intouncharted territory really."
"The samples indicated that El Nino was never more intense than the events of the last hundred years," said David Lea ofthe University of California, who helped write the study. "Over the last 100 years we have very accurate records of ElNino, with 1982-83 and 1997-98 being the largest events on record.
"Of course, everyone wants to know if the intensity of these large events is somehow related to global warming. Ourdates suggest that the behavior of the tropical Pacific over the last 100 years is atypical, but it does not pinpointwhich factors modulate El Nino."
Centuries ago, El Ninos disrupted the weather every 2 to 15 years, but now they come more frequently. A La Nina event ishappening right now that is expected to last for several months.
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Also in The New York Times, Friday, January 26, 2001
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