Oxygen gas in ice cores has shown evidence for abrupt climate change. Click on image for full size (97 Kb) Image Courtesy of Zina Deretsky/National Science Foundation

When the climate warmed relatively quickly about 14,700 years ago, seasonal monsoons moved northward. Prior to that, the monsoons were dropping more rain on the Earth's oceans at the expense of tropical areas, according to climate researchers.

In an article to be published in the June 12 issue of the journal Science, researchers from the Desert Research Institute in Nevada, the Scripps Institution of Oceanography and Oregon State University present their findings after comparing oxygen isotopes in air that was captured in ice cores and previously published data from ancient stalagmites found in caves. The research was supported by the National Science Foundation.

The ice cores, gathered from different locations in Antarctica and Greenland, contain air bubbles that were trapped as the ice formed over tens of thousands of years. By measuring the amount of certain oxygen isotopes in those air bubbles, the researchers were able to determine patterns in vegetation growth worldwide over that same span of time.

The researchers found that beginning about 14,700 years ago, the mixture of oxygen isotopes began to change in a way that suggests more vegetation growth, and this process continued for at least 200 years. The researchers then compared these findings with data from an earlier study that determined the amount of rainfall that fell in China over many millennia by examining stalagmites in caves. They discovered that this period of low vegetation growth corresponded with a time of reduced monsoon rainfall.

By climate standards, the researchers say, this shift happened abruptly over a few decades. They also caution that observations of past climate events may not be able predict future conditions. Given the vital roll that monsoons play in sustaining billions of people, however, this connection between climate change and monsoon patterns may be an ominous sign of what climate change in the 21st century may bring.

Text above is courtesy of the National Science Foundation

Oxygen gas in ice cores has shown evidence for abrupt climate change. Click on image for full size (97 Kb) Image Courtesy of Zina Deretsky/National Science Foundation

Researchers from the Desert Research Institute in Nevada, the Scripps Institution of Oceanography and Oregon State University have been comparing oxygen isotopes in air that was captured in ice cores to learn more about the climate of the past. They also looked at data from ancient stalagmites found in caves.

The ice cores were gathered from different locations in Antarctica and Greenland. They contain air bubbles that were trapped as the ice formed over tens of thousands of years.

The researchers found that the climate warmed about 14,700 years ago, and there was more vegetation growth for at least 200 years. The researchers then compared these findings with data from an earlier study that determined the amount of rainfall that fell in China over many millennia by examining stalagmites in caves. They discovered that this period of low vegetation growth corresponded with a time of reduced monsoon rainfall.

This shift happened over a few decades, which is a very quick time period for climate to change. The researchers warn that observations of past climate events may not be able predict future conditions. Given the important roll that monsoon rains play in sustaining billions of people, however, this connection between climate change and monsoon patterns may be an dangerous sign of what climate change in the 21st century may bring.

Oxygen gas in ice cores has shown evidence for abrupt climate change. Click on image for full size (97 Kb) Image Courtesy of Zina Deretsky/National Science Foundation

Scientists have been studying air that was captured in ice cores and ancient stalagmites found in caves to learn more about past climates. The ice cores were collected from different locations in Antarctica and Greenland. They contain air bubbles that were trapped when the ice.

They found that climate warmed very quickly about 14,700 years ago. When this happened, there were more monsoon rains and more vegetation growth for at least 200 years.

This shift happened over a few decades, which is a very quick time period for climate to change. The researchers warn knowing what happened to past climate may not help us predict future conditions. Monsoon rains play an important role in helping many people on Earth, so this connection between climate change and monsoon patterns may be an dangerous sign of what climate change in the 21st century may bring.