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Thursday, December 15, 2011
Global Warming and Positive Feedback Loops, in a nutshell
My comment on a yahoo news article announcing
Russian scientists have discovered hundreds of plumes of methane gas, some 1,000 meters in diameter, bubbling to the surface of the Arctic Ocean. Scientists are concerned that as the Arctic Shelf recedes, the unprecedented levels of gas released could greatly accelerate global climate change.
This is human caused. What it is is the beginning of a positive feedback loop. A few centuries of burning coal, oil, and natural gas have raised temperatures slightly. What happens when you raise the temperatures slightly is that things like glaciers and Arctic tundra melt. Once they get going they take off and don't stop. Like rolling a snow ball off the top of a mountain, or triggering an avalanche with a pair of skis, the initial push does not take a great deal of effort. But gravity and the nature of snow will do the rest of the work for you, to build a large, fast moving and potentially dangerous accumulation in a little period of time.
A lot of methane is in the Arctic tundra and under the Arctic ocean. Usually it stays trapped there. But if you let enough greenhouse gas into the atmosphere to start melting ice caps and permafrost, a lot more methane goes into the atmosphere, and now your curve towards higher temperatures starts becoming sharper, closer to an exponential curve, and there's no way to turn it "off", even if we went to zero carbon emissions tomorrow.
The retreat of sea ice offers another example of a positive feed back loop. Solar heat hitting the ocean water gets absorbed. Solar heat hitting ice gets reflected back away from Earth. When you melt the ice caps, now a lot of ocean that used to be ice is water. So the oceans are absorbing heat faster and holding it longer than they used to, which of course results in more ice caps melting.
Need a third? How about the gulf stream? Do you know what the difference is between Central Russia and Philadelphia? Not a lot in terms of latitude. But the Gulf Stream brings warm water to much of the US Eastern Sea board and Europe and that keeps those places warmer. It is possible that the melting of the ice caps will change temperatures and salinity levels that will end the gulf stream. That would be a third huge positive feed back loop that once kicked off, would not be possible to shut off, and would change temperatures in those areas very dramatically.
The past billion and a half years of earth's history have seen widely changing global temperatures and sea levels. The only problem with that is that our species evolved to thrive around certain temperatures and certain times, and now has given up much of its mobility in exchange for infrastructure and a devotion to geographically fixed private property. Sure, as a species, we survived the last ice ages. And you know what? The ice ages sucked. It was really cold. A lot of people froze to death. You couldn't grow food and living off of mammoths got really old after a while. Especially after we ran out of mammoths.
Now start looking at the difference in hunter gatherer societies that were affected by the ice age and our society. We have mortgages. Cultivated farm land. Sea level cities. We have trillions of dollars invested into certain sea levels, rain and weather patterns, and our ability to feed ourselves depends on that. When you start changing global temperatures and wind and rain patterns all that goes out the window, and you can start thinking about refugee crises that make Hurricane Katrina or anti-Mexican racism and scapegoating today look like a symphony of brotherhood.
Still don't believe in Global warming? Sweet. I have ski resorts in Taos and Flagstaff to sell you.