Tuesday, March 29, 2005
The Big Chill
Scientists at MIT and the Woods Hole Oceanographic Institution on Cape Cod say that ice ages, which come and go every 100,000 years, are driven by the tilt of the Earth's axis.
They say that the angle between Earth's equatorial and orbital planes, called obliquity, shifts between 22.5 and 24 degrees every 41,000 years. They built a model that shows that as the tilt increases and the planet tips to the side like a poorly balanced sinker, more sunlight can reach high latitudes and thaw glaciers.
Since Earth is tipped now at 23.5 degrees and moving up, danger is some cool weather may be heading our way. Praise global warming for each balmy day, the scientists say. "Without the much more rapid anthropogenic or human influences on climate, Earth would probably be slowly moving toward glaciation," they say in a press release.
One mystery remains: Since the tilt switches every 41,000 year, how come the ice age cycle lasts 100,000 years? The scientists propose that glaciers must first grow large before they are sensitive to tilt changes.
They say that the angle between Earth's equatorial and orbital planes, called obliquity, shifts between 22.5 and 24 degrees every 41,000 years. They built a model that shows that as the tilt increases and the planet tips to the side like a poorly balanced sinker, more sunlight can reach high latitudes and thaw glaciers.
Since Earth is tipped now at 23.5 degrees and moving up, danger is some cool weather may be heading our way. Praise global warming for each balmy day, the scientists say. "Without the much more rapid anthropogenic or human influences on climate, Earth would probably be slowly moving toward glaciation," they say in a press release.
One mystery remains: Since the tilt switches every 41,000 year, how come the ice age cycle lasts 100,000 years? The scientists propose that glaciers must first grow large before they are sensitive to tilt changes.
