Did Northern Hemisphere climate shifts in the past affect the climate in the tropics? For geologists who believe past global climate patterns may help predict future patterns, glaciers may prove to hold some answers.

As reported in the September 25, 2009, issue of the journal Science, a study led by Joe Licciardi of the University of New Hampshire found that glaciers in Peru expanded when glaciers in Europe and North America expanded.

Fluctuations in the North Atlantic regions were well recorded during the Little Ice Age. The North Atlantic glaciers had expanded to their most recent extents about 1650 to 1850. Licciardi collected samples from the moraines (rock and earth debris) left behind by retreating glaciers in Peru to document their fluctuations. (Peru has the world’s largest concentration of tropical glaciers.)

Advances in the technique known as surface exposure dating made it possible for the geologists to precisely date glacial fluctuations in the last thousand years.

Licciardi points out that the global pattern of glaciations was more complex than the north-south connection. In New Zealand, 7,000 miles from the Peru site, the glaciers had reached their peak long before the Little Ice Age.

With Peru’s climate now linked to northern Europe’s, the scientists plan to expand their research to other parts of the South American tropics. They hope to establish a regional pattern of glacial advances and retreats that can be compared with other places worldwide.

Most of the world’s glaciers are now retreating. “If the current dramatic warming projections are correct, we have to face the possibility that the glaciers may soon disappear,” said Joerg Schaefer, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory (LDEO) and co-author of the report. (A recent United Nations report says that current trends suggest that most glaciers will disappear from the Pyrenees by 2050 and from the mountains of tropical Africa by 2030.)

Regions that depend on glaciers for drinking water and for farming will be especially at risk as global temperatures rise.

The role of glaciers in shaping earth’s surface, leaving behind the moraines studied by geologists, and in influencing climate patterns is featured in the December 2008 issue and August 2009 issue.of Beyond Penguins and Polar Bears. In both issues, resources are provided to help K-5 students begin to become familiar with the earth sciences.