Title: Climate Metastasis
Author: McLean Date: November 5, 2008
Metastasis for the Planet Year in, year out, as global warming progresses inexorably, the danger of positive feedbacks increases. Positive in this context means much worse news for the planet. The poster-child of a positive feedback is the ice albedo effect, where the progressive melting of ice cover, be it sea ice in the Arctic or ice sheets and glaciers on land. Ice reflects more heat back out to space than the darker water or land that is exposed as it gradually melts away due to global warming. Other feedbacks that have been observed include methane release from the melting of the permafrost found a few inches below the surface across Siberia an Alaska, and from methane from the melting of cathrates, methane frozen into ice found at the bottom of oceans. The nightmare scenario happens if the oceans change from being a net sink of CO2 to being a source. There are two factors; first there is a limit to the amount of CO2 that can be absorbed in the short term, say a hundred years or so – over a longer term the CO2 will be settled out of sea water as the calcium carbonate shells of marine animals. And as water warms, the amount of any gas that can be dissolved decreases, so leading to a release of CO2. This appears to be what happens in the interglacial warm periods, leading to rapid temperature rise and the melting of the great ice sheets of the Ice Ages. Anthropogenic global warming has another nasty surprise for us. Greenhouse gases work by trapping heat in the earth’s oceans and atmosphere, so that more heat is being absorbed than radiated back into space. Over time the planet will heat up, resulting in more heat going out into space, and equilibrium in the heat budget will be restored. The catch is that it will be centuries before this equilibrium is reached, largely because of the vast heat capacity of the oceans. So, like a cancer that can grow undetected until it reaches metastasis and spreads throughout the body and becomes untreatable, global warming may pass a point leading inevitably to catastrophic consequences before we are alarmed enough by the early symptoms to take action. This recent northern summer has seen symptoms of the first three positive feedbacks in the Arctic: ice albedo as the polar ice melts, permafrost methane release in Siberia, and cathrate methane release in the Arctic Ocean. Once metastasis has occurred, cancers are generally considered untreatable.
Section Climate Type Blog
Back