The discovery of a bed of plants that lay frozen under a Peruvian glacier for thousands of years points to dire consequences from climate change today, according to Lonnie Thompson, a glaciologist.
Climate change 5,200 years ago - the age of the carbon-dated plants - was so swift and severe that the vegetation was caught under ice and snow and preserved. Prof Thompson, from Ohio State, spotted the plants two years ago as he walked along a high Andean glacier.
In 1991, hikers found the preserved body of a man trapped in an Alpine glacier and freed as it retreated. Tests showed the man - nicknamed Oetzi - became trapped and died about 5,200 years ago as well.
At this week's annual meeting of the American Geophysical Union, Prof Thompson presented evidence suggesting the climate shift 5,200 years ago was global.
In the UK, tree rings narrowed about 5,200 years ago, suggesting a dry period. The Sahara Desert at about the same time changed from a habitable region to a barren desert.
"Something happened back at this time and it was monumental," said Prof Thompson. "The evidence points to similar changes occurring in today's climate. To me, these are things we really need to be concerned about."