Climate Clues

     IT'S A COMMONLY KNOWN FACT THAT IF YOU COUNT THE RINGS IN A TREE TRUNK
YOU CAN TELL HOW OLD THE TREE IS.  YOU CAN EVEN LEARN SOMETHING ABOUT THE
HISTORY OF THE TREE--A PARTICULARLY THIN RING MIGHT POINT TO A PARTICULARLY
HARSH WINTER FOR EXAMPLE.  WELL, THE LAYERS OF ICE IN A GLACIER CAN TELL THE SAME
KIND OF TALES, BUT THE HISTORY THERE CAN GO BACK MUCH FURTHER SAYS GEOLOGIST
JIM WHITE AT THE UNIVERSITY OF COLORADO.

     White: "In a recent ice core in central greenland, layers were counted back
40,000 years.  Some very dedicated people sat there and counted a long time. " 

      BY DIGGING OUT A LONG TUBE OF ICE AND COUNTING DOWN THE LAYERS,
GEOLOGISTS HAVE BEEN ABLE TO LEARN ALL SORTS OF THINGS ABOUT THE CLIMATE IN
CENTURIES PAST.  

     White: "Ice cores are an excellent recorder of past conditions. They are just snow,
so the dust in the atmosphere comes down and gets recorded, the gases that are in the
atoms get trapped in the snow. . .and they get incorporated into the ice core.  the . . .
composition of the ice tells us about temperature." 

     BY EXAMINING HOW TEMPERATURES CHANGED OVER THE YEARS, OR BY
DETERMINING THE LEVEL OF GREENHOUSE GASES LIKE CARBON DIOXIDE AND METHANE
ARE TRAPPED IN THE ICE, SCIENTISTS CAN GET A COMPREHENSIVE UNDERSTANDING OF
OUR EARTH'S PAST CLIMATE.  AND THAT'S CRUCIAL FOR SCIENTISTS WHO STUDY WHAT'S
GOING ON WITH OUR CLIMATE NOW, SAYS JOAN FITZPATRICK OF THE NATIONAL ICE
CORE LABORATORY.

     White: "In order for us to think about how the climate system behaves, we need to
have some information on how its behaved in the past. and ice cores are nature's finest
natural recording weather station."