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I always wonder why there is never any mention of non-linear dynamics and chaos theory in discussions of climate change and, especially, mitigation. We've chan

I always wonder why there is never any mention of non-linear dynamics and chaos theory in discussions of climate change and, especially, mitigation. We've changed a few variables in a complex and sensitive system by introducing a lot of greenhouse gases into the atmosphere. Temperatures appear to be rising in approximate correlation to the concentration of those gases. It's naive to expect that taking out the CO2 or - God forbid - pumping out sulphur dioxide particles is going to have any predictable effect.

thrownaway2424 12y ago
I think we have an extremely robust understanding of exactly what would happen from reducing atmospheric CO2. You seem to be overstating the danger of that one. There is a lot of unknown territory around things like dumping iron into the seas, or spraying salts into clouds. Nobody knows all the pitfalls there. There are other avenues with less possibility of side-effects, e.g. launching something into space to partially block the sun would have a direct impact.
- gtt 12y ago
  Is it based on first-hand experience with atmospheric models or something related? If so, could you elaborate where robustness comes from?
  - marcosdumay 12y ago
    It's based on first-hand experience with an atmosphere with less CO2 than the current one. Like what everybody here had yesterday, for example. Of course, things never change back to exactly what they were in the past. But to state that the risk of that option is similar to doing a completely new experiment on a global scale is insane. Also, I always love those people that say that, since we've made Earth a worse heat sink, we should compensate by making the Sun a worse heat source. First principles do not go away just because you have a chaotic system.
- scrumper 12y ago
  I'm not sure those other avenues (like blocking the sun) would have less possibility of side effects. Light & IR energy reaching the earth is just another variable that would change, again perturbing a very complex system.
waps 12y ago
So there's 2 different things : 1) chaos theory This is an existential problem for climate theory. If you believe in statistics' mathematical foundation, then climate theory is wrong. Why ? Because the time series that are being used as the basis of the models do not satisfy the central limit theorem, ergo you cannot even correctly measure the climate (because no finite amount of measurements will ever be complete enough to give an accurate measurement of the whole system). Of course this is a mathematical argument that few people even understand. And it is extremely pedantic (like stating that in particle physics there's 2 contradicting theories, ergo we have no working theory), but in some ways this is correct. The reply, when honestly discussed, is that chaos theory in practice applies to half the things you might measure in the real world, and disallows the use of statistics to predict the future. But ... those predictions "work". Just look at the numbers ! (In my opinion those numbers in fact they do exactly what chaos theory says they should, they work in the short term, fail in the long term. See for example the first few IPCC reports, and note that their predictions were wrong. The more recent ones are right - so far). Utilitarianism in action. Of course the utility of climate theory varies, from genuine interest in the future evolution of the planet to political reasons. It will come as no surprise to anyone, these days, if one states that the vast majority of people have only political reasons - both on the left, right, green, red, blue, ... sides of the aisle. 2) mitigation Mitigation would move us from a situation where "nature" is doing the damages, more or less randomly, to a situation where you can directly point at a specific human being/country that did the damage. Given that most world leaders are lawyers, this is seen as extremely undesirable. Right now climate changes are the result of a "generic" action executed mostly by Europeans that are long dead. Hell, their 90% or so of their grandchildren are dead. If America were to directly change the climate, and as a result, say, the region around Delhi/Beijing/... changes into a desert ... Even if it present global advantages.

thrownaway2424 12y ago

I think we have an extremely robust understanding of exactly what would happen from reducing atmospheric CO2. You seem to be overstating the danger of that one. There is a lot of unknown territory around things like dumping iron into the seas, or spraying salts into clouds. Nobody knows all the pitfalls there. There are other avenues with less possibility of side-effects, e.g. launching something into space to partially block the sun would have a direct impact.

gtt 12y ago
Is it based on first-hand experience with atmospheric models or something related? If so, could you elaborate where robustness comes from?
- marcosdumay 12y ago
  It's based on first-hand experience with an atmosphere with less CO2 than the current one. Like what everybody here had yesterday, for example. Of course, things never change back to exactly what they were in the past. But to state that the risk of that option is similar to doing a completely new experiment on a global scale is insane. Also, I always love those people that say that, since we've made Earth a worse heat sink, we should compensate by making the Sun a worse heat source. First principles do not go away just because you have a chaotic system.
scrumper 12y ago
I'm not sure those other avenues (like blocking the sun) would have less possibility of side effects. Light & IR energy reaching the earth is just another variable that would change, again perturbing a very complex system.

waps 12y ago

So there's 2 different things : 1) chaos theory This is an existential problem for climate theory. If you believe in statistics' mathematical foundation, then climate theory is wrong. Why ? Because the time series that are being used as the basis of the models do not satisfy the central limit theorem, ergo you cannot even correctly measure the climate (because no finite amount of measurements will ever be complete enough to give an accurate measurement of the whole system). Of course this is a mathematical argument that few people even understand. And it is extremely pedantic (like stating that in particle physics there's 2 contradicting theories, ergo we have no working theory), but in some ways this is correct. The reply, when honestly discussed, is that chaos theory in practice applies to half the things you might measure in the real world, and disallows the use of statistics to predict the future. But ... those predictions "work". Just look at the numbers ! (In my opinion those numbers in fact they do exactly what chaos theory says they should, they work in the short term, fail in the long term. See for example the first few IPCC reports, and note that their predictions were wrong. The more recent ones are right - so far). Utilitarianism in action. Of course the utility of climate theory varies, from genuine interest in the future evolution of the planet to political reasons. It will come as no surprise to anyone, these days, if one states that the vast majority of people have only political reasons - both on the left, right, green, red, blue, ... sides of the aisle. 2) mitigation Mitigation would move us from a situation where "nature" is doing the damages, more or less randomly, to a situation where you can directly point at a specific human being/country that did the damage. Given that most world leaders are lawyers, this is seen as extremely undesirable. Right now climate changes are the result of a "generic" action executed mostly by Europeans that are long dead. Hell, their 90% or so of their grandchildren are dead. If America were to directly change the climate, and as a result, say, the region around Delhi/Beijing/... changes into a desert ... Even if it present global advantages.