WARMING STUDY SENDS CHILL DOWN SPINE.

Byline: Lawrence Spohn Scripps McClatchy Western Service

A New Mexico geoscientist has uncovered evidence that Earth's past climate changed dramatically and quickly, and he says it should serve as ``a warning.''

``It should give us pause'' about how well we think we understand the Earth's climate, said Fred Phillips, a scientist at the New Mexico Institute of Technology and Mining in Socorro.

His long-term study of glacial deposits supports other contentions that thousands of years ago Earth experienced much wider average temperature swings than previously thought.

He suggested that today's theories and computer models for global warming may be too simplistic. They forecast a gradual warming of the Earth, rather than a warming punctuated with cool and very hot spells, which Phillips suspects is more likely.

Comparing the Earth to a greenhouse, atmospheric scientists say the sun's heat is being trapped in the atmosphere causing temperatures to rise very gradually. Carbon dioxide is the greenhouse glass. This gas, which traps the heat, is generated by fossil fuel burning in power plants and motor vehicles and other sources.

Scientists predict that even a few degrees rise in temperature would cause rising sea levels, coastal flooding and shifts in prime crop land. Even more pronounced heat waves could be even more devastating.

Experts have estimated that the Rio Grande basin would be among the hardest hit if temperatures do rise significantly next century. Substantial declines in precipitation and river flow would be prime effects in New Mexico.

Phillips' research does not directly address the controversial issue of whether the Earth is getting dangerously warmer and how fast. But Phillips, whose research ``goes in the opposite (colder climate) direction,'' said there is no reason to believe the same climate principles wouldn't apply.

The point, he said, is that while today's climate is comparatively stable and conducive to life, it wasn't always so and may not always be.

His research, along with that of others, shows that thousands of years ago a much colder Earth was a bit like someone with the flu, frigid one moment, feverish the next.

Mounting evidence suggests that shifts of 10 to 20 degrees Fahrenheit in average temperature occurred within decades or even years, not the centuries or millenniums once thought.

Using new technology, scientists are getting better at seeing back through the blurred picture of time.

For the past decade, Phillips has studied glacial moraines in California's Sierra Nevada Mountains using a new radio-dating technique he developed that uses radioactivity in surface rocks to date how long they've been there.

Moraines are the rocky rubble carved out of the landscape and deposited in piles or ridges by powerful ice glaciers as they moved down mountain valleys or across vast areas of land. Much of the Midwest is fertile crop land because ancient flowing glaciers dumped huge volumes of rich topsoil there that was scrapped out of Canada.

Phillips dated terminal moraines, which are large ridges of rocks and debris dumped at the edge of a glacier as it melts and retreats. His dates show that glaciers ebbed and flowed over the landscape periodically and that temperature changes were very abrupt.

Phillips' dating technique determines the amount of the radioactive isotope Chlorine 36 in the glacial moraine. That indicates the amount of time the rocks have been on the surface and allows Phillips to date each and every moraine in a series.

He found that the Sierra glacial advances are closely associated in time with what are called Heinrich events, which represent distinct warming periods during the 60,000-year-long Ice Age that ended 10,000 years ago.

Previous research had established the Heinrich, or warming, events based on findings in two other areas:

Sediment cores drilled from the bottom of the North Atlantic Ocean revealed a series of fine deposits called ``rock flour.''

Scientists say they had to be deposited by huge flotillas of icebergs that broke off the continental ice sheet and drifted out to sea where they melted, dropping rich glacial silt on the ocean floor.

Ice cores drilled in the Greenland ice sheet correlate with the ``rock flour'' ocean cores and show that temperatures warmed many degrees in only a few years.

While scientists believed these revealed global climatic events, they had said they could not rule out that they were merely regional effects.

A continent away, Phillips' rocks support the argument that the Greenland ice cores and the ocean cores do reflect global climate changes.