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The earth has warmed and cooled many times in its history. Isn't it reasonable to expect there is a natural negative feedback mechanism, and that this negative

The earth has warmed and cooled many times in its history. Isn't it reasonable to expect there is a natural negative feedback mechanism, and that this negative feedback mechanism will manifest itself and return the earth to equilibrium?

bdamm 12y ago
Those historical adjustments are on the scale of hundreds or thousands of years. Also, there has never been as rapid a rise in CO2 as there is right now. That might mean that the rise is too fast for the feedback mechanism to work. We just plain don't know, because I don't think anyone has identified the actual feedback mechanism chain.
- mathattack 12y ago
  We just plain don't know This is the key thing. We're just modeling, and models aren't so trustworthy over the long term when they're based only on past experience.
  - crusso 12y ago
    Models that don't prove their ability to predict are much worse than untrustworthy.
    - mathattack 12y ago
      It's false confidence (confidence intervals, assuming that distributions don't change, etc) that causes real problems. Never trust a novice running a regression. :-)
cma 12y ago
The feedback effect might be like the world is hanging on a pendulum, we can disturb it but it will always settle down back to the resting state. Or it might be like it is resting on a pedestal, disturb it some and it may wobble back into place, kick the shit out of it and it may fall over.
trhway 12y ago
>The earth has warmed and cooled many times in its history. yep, an it brought up and down massive civilizations. Roman Empire, Caliphates, Viking Age, Mongols, Medieval Europe/Black Death... somewhere here goes our current world order :)
j_baker 12y ago
There absolutely is a negative feedback mechanism. The question is whether that mechanism involves the destruction of humanity.
DennisP 12y ago
That used to be my hope. But it turns out that there's a lot of geological history we can look at, and it's not encouraging. What we see in the fossil record is the opposite: the planet warms a bit due to orbital variations or something, and positive feedbacks kick in that emit lots of CO2 and methane and tip the planet into a hot state. It happened fifty million years ago. There were crocodiles swimming at the North Pole, and very little life left at the mid-latitudes. Eventually, CO2 levels drop back down and the planet cools, but that's a much slower process involving things like rock erosion over millions of years. In the short term there are strong positive feedbacks...forests drying out and burning down, permafrost melting and releasing CO2 and methane, undersea methane ice destabilizing, etc. A great book that covers the geological evidence in detail, written for laymen, is Storms of My Grandchildren by James Hansen.

bdamm 12y ago

Those historical adjustments are on the scale of hundreds or thousands of years. Also, there has never been as rapid a rise in CO2 as there is right now. That might mean that the rise is too fast for the feedback mechanism to work. We just plain don't know, because I don't think anyone has identified the actual feedback mechanism chain.

mathattack 12y ago
We just plain don't know This is the key thing. We're just modeling, and models aren't so trustworthy over the long term when they're based only on past experience.
- crusso 12y ago
  Models that don't prove their ability to predict are much worse than untrustworthy.
  - mathattack 12y ago
    It's false confidence (confidence intervals, assuming that distributions don't change, etc) that causes real problems. Never trust a novice running a regression. :-)

cma 12y ago

The feedback effect might be like the world is hanging on a pendulum, we can disturb it but it will always settle down back to the resting state. Or it might be like it is resting on a pedestal, disturb it some and it may wobble back into place, kick the shit out of it and it may fall over.

trhway 12y ago

>The earth has warmed and cooled many times in its history. yep, an it brought up and down massive civilizations. Roman Empire, Caliphates, Viking Age, Mongols, Medieval Europe/Black Death... somewhere here goes our current world order :)

j_baker 12y ago

There absolutely is a negative feedback mechanism. The question is whether that mechanism involves the destruction of humanity.

DennisP 12y ago

That used to be my hope. But it turns out that there's a lot of geological history we can look at, and it's not encouraging. What we see in the fossil record is the opposite: the planet warms a bit due to orbital variations or something, and positive feedbacks kick in that emit lots of CO2 and methane and tip the planet into a hot state. It happened fifty million years ago. There were crocodiles swimming at the North Pole, and very little life left at the mid-latitudes. Eventually, CO2 levels drop back down and the planet cools, but that's a much slower process involving things like rock erosion over millions of years. In the short term there are strong positive feedbacks...forests drying out and burning down, permafrost melting and releasing CO2 and methane, undersea methane ice destabilizing, etc. A great book that covers the geological evidence in detail, written for laymen, is Storms of My Grandchildren by James Hansen.