Stories tagged global cooling

Jan
19
2009

It could always be worse.

Ice Sheet - Antarctica
Ice Sheet - AntarcticaCourtesy NASA

Some geologists think that 700 or so million years ago, the entire earth was one spherical skating rink. Called "Snowball Earth", it was a time when runaway ice caps covered the entire earth. They even covered the tropical oceans, making a mid-winter getaway to Hawaii less appealing, and possibly wiping out most of life on earth. The theory goes like this. Millions of years ago the sun was weaker than today. Ice started forming at the North and South poles, reflecting incoming sunlight back out to space and making it colder. So, the ice grew even more and so on in something called a positive feedback. Eventually, ice covered the entire planet, leaving rock types characteristic of glacial erosion in the tropics.

So, how do they think we got out? Well, all the time the earth was covered with ice, volcanoes were belching out carbon dioxide. Over millions of years, carbon dioxide is sucked out the atmosphere by breaking down rocks (it's much too slow a process to help us out in the current situation, though). Eventually carbon dioxide levels in the atmosphere reached many times what they are today, temperatures soared, and there was a global ice-out that's usually described as "catastrophic."

A careful review of the existing information by two scientists from Britain suggests that things may not have been so dire. Geological evidence suggests that some parts of the ocean were not covered in ice, though there was a lot of ice in the tropics. This new view means geologists and climate scientists need to re-think "Snowball Earth" and how it could have come about. Something to think about while you're trying to get the car started.