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>There is a very clear causal explanation for why greenhouse gases do what they do I'm sorry, but it doesn't work that way. We have very clear chemistry/physi

by gd1 10y ago

>There is a very clear causal explanation for why greenhouse gases do what they do I'm sorry, but it doesn't work that way. We have very clear chemistry/physics on the composition of food, how it is digested, etc. But nutrition science is still an embarrassing shitshow. We have clear physics on how neurons fire, etc. but neuroscience is still in its infancy and psychology... well, it is psychology. Earth's climate is a large scale multi-variable control system with thousands of feedback loops. A good understanding of the physics that drive a single forcing doesn't really tell us shit I'm afraid. It is just as open to manipulation as these other fields.

selectron 10y ago
This sentiment is not correct - causal explanations do matter. The statistical evidence for global warming is not particularly strong, as temperature data is very noisy. If we didn't have a causal explanation there would not be a scientific consensus behind climate change. That adding greenhouse gases to the atmosphere changes the climate is more like gravity - we have clear physics on why things fall when you drop them, and if we somehow were adding mass to the center of the earth we know what effect this would have. More generally you are correct, we don't know exactly how much the earth will warm or if there are complicated feedback mechanisms in place that could cause this warming to speed up or reverse course. We can't even reliably say that next year will be hotter than this year (actually it probably will be cooler because this year has been unusually hot).
- gd1 10y ago
  Indeed, but it is really only the system response we are interested in. As you admit, a clear causal explanation for how a single input forcing is increasing doesn't automatically get us to a position where we can predict the overall system response. Or predict whether a given system response will have some positive or negative second order effect. We have a clear causal physical explanation that eating fat should make you fatter right? Are you willing to say that? Or would you qualify yourself - 'eating more fat will make you fatter in the absence of negative feedbacks (perhaps the fat reduces your appetite more than carbs or protein?) and assuming that all other inputs (exercise level etc) remain constant'.
  - deleted 10y ago
    [deleted]
jfoutz 10y ago
Really, all we have is how well a model predicts the future. there's a fairly sucky model from the 80's, [1]. Maybe it's totally wrong. Maybe it's just overfitting. But it's got a good track record, if underpredictive. I'm all for the idea that co2 doesn't effect temperature. I just haven't seen any models that show that. Furthermore, i haven't seen anything with any sort of a track record. I'm pretty sure Hansen's paper is pretty much the root of all modern climate modeling. I'm totally willing to stipulate that the whole field is wildly off track, but there's no evidence of that. The only thing we have is 35 year old models that seem to work. I mean, more specifically, aether was flat out wrong. it still had predictive power. Someday we'll have something more refined, or perhaps completely refuted. [1] http://www.realclimate.org/index.php/archives/2012/04/evaluating-a-1981-temperature-projection/ http://www.realclimate.org/index.php/archives/2012/04/evalua...
- gd1 10y ago
  Interesting. Compare the chart in the linked article with Hansen's own assessment that he put out in 2005 (third page): http://www.columbia.edu/~jeh1/2005/Crichton_20050927.pdf http://www.columbia.edu/~jeh1/2005/Crichton_20050927.pdf How do you reconcile those two? A lot seems to come down to centering decisions? Scenario A I believe is closest to the emissions path we are on.
  - jfoutz 10y ago
    My guess is, the pink band is current (er, 2011 versions) of what the global average temperature was. Which makes the 60's even cooler (heh). As with all things, it depends on how you measure. global mean global giss is here - http://data.giss.nasa.gov/gistemp/graphs_v3/ http://data.giss.nasa.gov/gistemp/graphs_v3/ So anyway, i'd agree the centering of zero sure could change things, but it sure seems like predictive power in the rates of change. Like, temperature isn't stable, it's not going down, it's going up and it looks like it's going up at about that rate. edit but that sort of goes back to the original point, all we really have is models. you held up physics as an example, but if we look at something like the gravitational constant, things are really screwy. As far as i can tell, 3 really first rate teams came up with 3 different answers - not even overlapping in the error bands. big G is obviously helpful, but it must be more complicated than we understand right now. I dunno. I kind of like the european model for chemical handling. Super toxic chemicals in tiny quantities aren't that big of a deal, maybe 50 people die, so it's not heavily regulated. Mildly toxic chemicals in large quantities, same deal. Maybe 50 people die. Large quantities of toxins are regulated in proportion to the risk. The point is, balancing the risk against the best current understanding really seems like the best that can be done.

by gd1 10y ago

selectron 10y ago

This sentiment is not correct - causal explanations do matter. The statistical evidence for global warming is not particularly strong, as temperature data is very noisy. If we didn't have a causal explanation there would not be a scientific consensus behind climate change. That adding greenhouse gases to the atmosphere changes the climate is more like gravity - we have clear physics on why things fall when you drop them, and if we somehow were adding mass to the center of the earth we know what effect this would have. More generally you are correct, we don't know exactly how much the earth will warm or if there are complicated feedback mechanisms in place that could cause this warming to speed up or reverse course. We can't even reliably say that next year will be hotter than this year (actually it probably will be cooler because this year has been unusually hot).

gd1 10y ago
Indeed, but it is really only the system response we are interested in. As you admit, a clear causal explanation for how a single input forcing is increasing doesn't automatically get us to a position where we can predict the overall system response. Or predict whether a given system response will have some positive or negative second order effect. We have a clear causal physical explanation that eating fat should make you fatter right? Are you willing to say that? Or would you qualify yourself - 'eating more fat will make you fatter in the absence of negative feedbacks (perhaps the fat reduces your appetite more than carbs or protein?) and assuming that all other inputs (exercise level etc) remain constant'.
- deleted 10y ago
  [deleted]

jfoutz 10y ago

Really, all we have is how well a model predicts the future. there's a fairly sucky model from the 80's, [1]. Maybe it's totally wrong. Maybe it's just overfitting. But it's got a good track record, if underpredictive. I'm all for the idea that co2 doesn't effect temperature. I just haven't seen any models that show that. Furthermore, i haven't seen anything with any sort of a track record. I'm pretty sure Hansen's paper is pretty much the root of all modern climate modeling. I'm totally willing to stipulate that the whole field is wildly off track, but there's no evidence of that. The only thing we have is 35 year old models that seem to work. I mean, more specifically, aether was flat out wrong. it still had predictive power. Someday we'll have something more refined, or perhaps completely refuted. [1] http://www.realclimate.org/index.php/archives/2012/04/evaluating-a-1981-temperature-projection/ http://www.realclimate.org/index.php/archives/2012/04/evalua...

gd1 10y ago
Interesting. Compare the chart in the linked article with Hansen's own assessment that he put out in 2005 (third page): http://www.columbia.edu/~jeh1/2005/Crichton_20050927.pdf http://www.columbia.edu/~jeh1/2005/Crichton_20050927.pdf How do you reconcile those two? A lot seems to come down to centering decisions? Scenario A I believe is closest to the emissions path we are on.
- jfoutz 10y ago
  My guess is, the pink band is current (er, 2011 versions) of what the global average temperature was. Which makes the 60's even cooler (heh). As with all things, it depends on how you measure. global mean global giss is here - http://data.giss.nasa.gov/gistemp/graphs_v3/ http://data.giss.nasa.gov/gistemp/graphs_v3/ So anyway, i'd agree the centering of zero sure could change things, but it sure seems like predictive power in the rates of change. Like, temperature isn't stable, it's not going down, it's going up and it looks like it's going up at about that rate. edit but that sort of goes back to the original point, all we really have is models. you held up physics as an example, but if we look at something like the gravitational constant, things are really screwy. As far as i can tell, 3 really first rate teams came up with 3 different answers - not even overlapping in the error bands. big G is obviously helpful, but it must be more complicated than we understand right now. I dunno. I kind of like the european model for chemical handling. Super toxic chemicals in tiny quantities aren't that big of a deal, maybe 50 people die, so it's not heavily regulated. Mildly toxic chemicals in large quantities, same deal. Maybe 50 people die. Large quantities of toxins are regulated in proportion to the risk. The point is, balancing the risk against the best current understanding really seems like the best that can be done.