« Home | There Has Been No Global Warming for the Past 70 Y...//-->  »

Thursday, October 19, 2006

Oceans Temps, Solar Cycles Linked

By Paul Recer

Saturday, March 05, 2005

Associated Press
posted: 10:10 am ET
16 November 2001

WASHINGTON (AP) _ The brightening and dimming of the sun may account for a 1,500-year cycle of cooling and warming on parts of the Earth, a study of ice in the North Atlantic suggests.

Researchers found that a very slight difference in the amount of solar energy reaching the Earth can have a powerful chilling effect on the climate: ice builds up in lands bordering the North Atlantic, the average temperature drops in Europe and North America.

``Whether the whole Earth is affected, we don't know for sure yet, but it is certainly implied,'' said Gerard C. Bond, a researcher at the Lamont-Doherty Earth Observatory of Columbia University in Palisades, N.Y.

``The effect does extend from the high northern latitudes down, maybe even to the tropics,'' said Bond, first author of a study appearing Friday in the journal Science.

The cycle of sunlight intensity roughly follows a 1,500-year pattern, based on analysis of the past 12,000 years. But the difference from the top of the cycle to the bottom is very small, with less than a 0.1 percent difference in energy levels, he said.

Bond and his colleagues believe this is enough to trigger severe climate changes, such as the Little Ice Age, a 490-year period starting in 1400 that dramatically chilled Europe and the North Atlantic.

``The climate system is extremely sensitive to weak forces, such as solar variability,'' Bond said. ``That should make us that much more worried about greenhouse warming.''

Greenhouse warming is thought to be caused by an increase in the atmosphere of carbon dioxide from the burning of fossil fuels, including oil, gas and coal.

The study is an effort to determine if small changes in sunlight over centuries can cause the Earth's climate to warm or cool. Other experts working on the same problem said Bond and his team have made a strong case.

``It shows that the connection is real,'' Jeffrey Park of Yale University said in Science. To David Thomson of Queen's University in Ontario, Canada, it seems like ``a fairly convincing case.''

Bond and his colleagues analyzed small bits of rock that were dropped to the Atlantic floor after being carried to sea by icebergs that broke off glaciers in Iceland and other northern islands.

The rocks fell as the icebergs melted, Bond said. Thus, the farther south the rocks fell, the farther south the icebergs drifted, providing a measure of ocean temperature.

To determine when the rocks were dropped, researchers dated the age of shells deposited at the same time and place.

The 1,500-year cycle of warming and cooling corresponds to data from tree ring studies, another way of measuring the sun's strength over time.

Bond said the sun, at its most energetic, strengthens the Earth's magnetic field, which blocks more cosmic rays, a type of radiation streaking in from deep space.

When cosmic rays hit plants, they cause the formation of certain isotopes, such as carbon-14, that can be measured in ancient tree rings. A tree ring rich in carbon-14 suggests an inactive sun, for example.

Measurements of the iceberg drift and the tree rings showed a similar cycle, Bond said.

``The connection we observed is that the increases in icebergs and drift ice occur at the same times as the increase in (carbon-14), which means the sun was weaker,'' said Bond.

He said the findings also agree with studies that measured the chilling of the Earth based on the advance and retreat of alpine glaciers in Europe.

Bond said the Earth's temperature is still recovering from the Little Ice Age, when ocean temperatures dropped by two to three degrees. That change was enough for ice to jam most of the North Atlantic, closing many ports in the winter and affecting the weather throughout Europe. Rivers that never freeze in modern times were routinely used then for ice skating, Bond said. This means the temperatures SHOULD be going up.

Based on the 1,500-year cycle, Bond said that the Earth's next little ice age could occur about the year 3100, plus or minus 500 years.

E-mail this post

Remenber me (?)

All personal information that you provide here will be governed by the Privacy Policy of Blogger.com. More...