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Ice cores taken from a remote South American glacier in the Peruvian Andes are revealing a year-by-year tropical climate history over nearly 2,000 years, according to a study released Thursday.

Researchers at The Ohio State University retrieved the cores from a Peruvian ice cap in 2003, and then noticed some startling similarities to other ice cores that they had retrieved from Tibet and the Himalayas. Patterns in the chemical composition of certain layers matched up, even though the cores were taken from opposite sides of the planet.

In a paper published today in Science,  Ohio State University Professor Lonnie Thompson and his team shows that the 1983 and 2003 cores faithfully preserve a year-by-year record of tropical climate 18 centuries long, extending back to the year 683 with annual resolution and a little less perfectly back to almost 200. Thompson calls it "the longest and highest-resolution tropical ice core record to date."

The ice core has alternating light and dark layers record the wet and dry seasons at the top of the world - light from snow and dark from dust during the dry season.

"We have an annual resolution going back 1,300 years, and that's almost unprecedented," said Ellen Mosley-Thompson, a paleoclimatologist at Ohio State University and study co-author. Only a few ice cores from polar regions have longer annual resolutions, she said. (This resolution means they can see what the climate was like for each year.)

The cores provide a new tool for researchers to study Earth's past climate, and better understand the climate changes that are occuring today.

"These ice cores provide the longest and highest-resolution tropical ice core record to date," said Lonnie Thompson, distinguished university professor of earth sciences at Ohio State and lead author of the study.

"In fact, having drilled ice cores throughout the tropics for more than 30 years, we now know that this is the highest-resolution tropical ice core record that is likely to be retrieved."