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The amount of global warming we're experiencing is still a matter of debate, and certainly the specific climatic responses are mostly unknown. One day it's "we'

The amount of global warming we're experiencing is still a matter of debate, and certainly the specific climatic responses are mostly unknown. One day it's "we'll see increased hurricane activity due to global warming", and then it's 180 degrees around to saying that hurricane activity will decrease. My point isn't to deny global warming, but to show that we don't really understand very well how climate works. We may be on a deadend path right now. But people who want a radical change -- whether it's one of the suggestions in this article, or simply an enormous decline in CO2 emissions -- may turn us off that dead end, but they do so by closing their eyes and hitting the gas pedal simultaneously. Nobody really knows where we'd wind up. The article points out that the effects may be uneven. But I think it's worse than that. Returning CO2 levels to historic lows, or blocking solar radiation, might not be able to return the system to its original state: these reactions may not be reversible. Our environment has many factors that keep us at equilibrium, and many of these things have been working diligently to take up slack. Why should we think that these things will simply unwind back to their original state?

anamax 17y ago
> Returning CO2 levels to historic lows, or blocking solar radiation, might not be able to return the system to its original state: these reactions may not be reversible. I thought that it was generally agreed that CO2 levels had been much higher in prehistoric times. If so, it's unclear why recovering from lower levels in the future would be irreversible when we got here from there before.
- encoderer 17y ago
  As I understand it, the oldest record we have of past CO2 levels is glacial ice cores that go back about 600k years. In those, at least, CO2 has never been higher than today.
  - jibiki 17y ago
    It is hypothesized that Earth's atmosphere initially contained much higher % C02. "Based on today's volcanic evidence, this atmosphere would have contained 80% water vapor, 10% carbon dioxide, 5 to 7% hydrogen-sulfur, and smaller amounts of nitrogen, carbon monoxide, hydrogen, methane and inert gases." http://en.wikipedia.org/wiki/Earth%27s_atmosphere#Earliest_atmosphere http://en.wikipedia.org/wiki/Earth%27s_atmosphere#Earliest_a...
- CWuestefeld 17y ago
  Well, surely the CO2 level itself could be reversed. But what other elements of the system's equilibrium will be changed in the meantime. For example, the actual amount of temperature increase observed is less than the CO2 level increase would suggest. Suppose that whatever agency has tempered the temperature increase has "woken up", and continues to do so as CO2 decreases. Then a return to "proper" CO2 levels (if you can call any level proper) would mean serious global cooling. And this might not be evident until it's too late. Of course, I'm making that up, but there's no reason to think that it's implausible.
  - anamax 17y ago
    > Suppose that whatever agency has tempered the temperature increase has "woken up", and continues to do so as CO2 decreases. Why is that a reasonable thing to suppose? We're assuming that we got to here from there before. Why is it reasonable to assume that we can't do so again? Yes, maybe something else has changed, but shouldn't you at least go to the trouble of identifying actual possibilities instead of just assuming that they exist?
    - CWuestefeld 17y ago
      There are any number of processes that will occur easily in one direction, but can have... dramatic... results in the other direction. Consider, by analogy, breaking H2O into hydrogen and oxygen, vs. recombining them. Or, for more fun, consider a girl wearing a skirt, jumping on a trampoline. The process of going up is ordinary, but what happens on the way down is quite a bit different. It's easy to dream up scenarios in the environment that might work this way. Algal blooms that have been pushed along by increased CO2 will affect the equilibrium between other types of sea life -- plankton up the line through large predatory fish. Moving up the food chain, creatures use input food less efficiently (carnivores need to kill much more food by mass than bunnies). So the algae enables plankton, which in turn feeds mackerel which in turn enable more sharks, but turning it around, as the algae recedes, the mackerel are pressured by the already-larger shark population, so they may well be decimated by the CO2 decrease. (I don't know if this specific example is correct -- it’s certainly oversimplified -- but the concept is certainly conceivable). Reiterating: it’s very complex, we don’t really know.
anamax 17y ago
> The amount of global warming we're experiencing is still a matter of debate, and certainly the specific climatic responses are mostly unknown. Not really. According to the measurements that showed warming up to 2000, atmosphereic temps been mostly stable to slightly declining since 2000. Of course, the interesting question is what's happening to the oceans, since they have far more heat capacity than the atmosphere.

anamax 17y ago

> Returning CO2 levels to historic lows, or blocking solar radiation, might not be able to return the system to its original state: these reactions may not be reversible. I thought that it was generally agreed that CO2 levels had been much higher in prehistoric times. If so, it's unclear why recovering from lower levels in the future would be irreversible when we got here from there before.

encoderer 17y ago
As I understand it, the oldest record we have of past CO2 levels is glacial ice cores that go back about 600k years. In those, at least, CO2 has never been higher than today.
- jibiki 17y ago
  It is hypothesized that Earth's atmosphere initially contained much higher % C02. "Based on today's volcanic evidence, this atmosphere would have contained 80% water vapor, 10% carbon dioxide, 5 to 7% hydrogen-sulfur, and smaller amounts of nitrogen, carbon monoxide, hydrogen, methane and inert gases." http://en.wikipedia.org/wiki/Earth%27s_atmosphere#Earliest_atmosphere http://en.wikipedia.org/wiki/Earth%27s_atmosphere#Earliest_a...
CWuestefeld 17y ago
Well, surely the CO2 level itself could be reversed. But what other elements of the system's equilibrium will be changed in the meantime. For example, the actual amount of temperature increase observed is less than the CO2 level increase would suggest. Suppose that whatever agency has tempered the temperature increase has "woken up", and continues to do so as CO2 decreases. Then a return to "proper" CO2 levels (if you can call any level proper) would mean serious global cooling. And this might not be evident until it's too late. Of course, I'm making that up, but there's no reason to think that it's implausible.
- anamax 17y ago
  > Suppose that whatever agency has tempered the temperature increase has "woken up", and continues to do so as CO2 decreases. Why is that a reasonable thing to suppose? We're assuming that we got to here from there before. Why is it reasonable to assume that we can't do so again? Yes, maybe something else has changed, but shouldn't you at least go to the trouble of identifying actual possibilities instead of just assuming that they exist?
  - CWuestefeld 17y ago
    There are any number of processes that will occur easily in one direction, but can have... dramatic... results in the other direction. Consider, by analogy, breaking H2O into hydrogen and oxygen, vs. recombining them. Or, for more fun, consider a girl wearing a skirt, jumping on a trampoline. The process of going up is ordinary, but what happens on the way down is quite a bit different. It's easy to dream up scenarios in the environment that might work this way. Algal blooms that have been pushed along by increased CO2 will affect the equilibrium between other types of sea life -- plankton up the line through large predatory fish. Moving up the food chain, creatures use input food less efficiently (carnivores need to kill much more food by mass than bunnies). So the algae enables plankton, which in turn feeds mackerel which in turn enable more sharks, but turning it around, as the algae recedes, the mackerel are pressured by the already-larger shark population, so they may well be decimated by the CO2 decrease. (I don't know if this specific example is correct -- it’s certainly oversimplified -- but the concept is certainly conceivable). Reiterating: it’s very complex, we don’t really know.

anamax 17y ago

> The amount of global warming we're experiencing is still a matter of debate, and certainly the specific climatic responses are mostly unknown. Not really. According to the measurements that showed warming up to 2000, atmosphereic temps been mostly stable to slightly declining since 2000. Of course, the interesting question is what's happening to the oceans, since they have far more heat capacity than the atmosphere.