Last 50 years 'unusually warm', tropical glaciers melting rapidly finds research
June 27, 2006

Researchers studying ancient tropical ice cores have found evidence of two abrupt climate shifts -- one 5000 years ago and one currently underway. The findings, published in the current issue of the journal Proceedings of the National Academy of Science, may have important implications for immediate future since more than two-thirds of the world's population resides in the tropics.

Using chronological climate records retrieved from seven locations in the South American Andes and the Asian Himalayas, researchers from Ohio State University's Byrd Polar Research Center, the University of Texas; the University of Connecticut, and the University of Louisville found evidence that a massive climate shift to a cooler regime occurred just over 5,000 years ago, followed by a rapid reversal to much warmer temperatures in the last 50 years.

The scientists also say that most of the high-altitude glaciers in the planet's tropical regions are rapidly melting and will likely disappear in the near future. Glaciers and ice caps are retreating even in areas where precipitation is increasing suggesting that increasing temperatures and not decreasing precipitation as the most likely culprit behind the decline.

The researchers' records show that the past 50 years have been unusually warm.

"There hasn't been anything in the record like it — not even the [Medieval Warm Period 700 to 1000 years ago] ," said Lonnie Thompson, professor of geological sciences at Ohio State. "The fact that the isotope values in the last 50 years have been so unusual means that things are dramatically changing. That's the real story here."

Further, the emergence of 5,000 to 6,500 year old wetland plants around the margin of the Quelccaya ice cap in Peru, suggests that temperatures there are higher than any time in the past 5000 years.

Lonnie Thompson, professor of geological sciences at Ohio State.

Thompson says the research has important implications for global climate and human populations.

"Tropical glaciers are the ‘canaries in the coal mine' for our global climate system, as they integrate and respond to most of the key climatological variables — temperature, precipitation, cloudiness, humidity and radiation," he explained. "The uniformity of the climate in the tropics makes these kinds of records so critical since they tell us what is happening to global temperatures."

"What this is really telling us is that our climate system is sensitive, it can change abruptly due to either natural or to human forces," he continued. "If what happened 5,000 years ago were to happen today, it would have far-reaching social and economic implications for the entire planet.

"The take-home message is that global climate can change abruptly, and with 6.5 billion people inhabiting the planet, that's serious."

"Approximately 70 percent of the world's population now lives in the tropics so when climate changes there, the impacts are likely to be enormous," said Thompson.

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This article is based on a news release from Ohio State University.

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CITATION: (June 27, 2006).

Last 50 years 'unusually warm', tropical glaciers melting rapidly finds research.