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Re: Global Warming or Global Cooling?
I may as well run up the "scientist" flag here. (On days when the stuff I design works, I call myself an "engineer"; today is not one of those days.)
Questioning the basic physics of greenhouse warming (CO[2] largely transparent to visible/shortwave infrared emissions from sun but a strong absorber in longwave infrared near color temperature of heated earth) is pointless, because you can measure these things in a terrestrial lab.
Citing the planet Mars as an example of a cool body with a mostly CO[2] atmosphere does not advance the argument, because both the distance from the sun matters as does the density of the atmosphere.
The sole technical weakness of attributing global warming to man-made CO[2] emissions, and of the long-range climate forecasts which motivate policy action to counter same, is well summarized in the point quoted above regarding the accuracy of climate modeling. If greenhouse heating caused by CO[2] were the dominant factor that determines Earth's surface temperature, and if it was a large effect, then there would be no debate (because we would already have cooked to death). We're trying to make long-range predictions about a 2nd or 3rd order effect. Think we'd notice if the sun's output changed by a factor of two? You better believe it! But what we're really talking about is what happens to a fraction of a fraction of the Earth's energy balance. The American Physical Society recently provided this tutorial on the "establishment" view on global warming. It points out that of the greenhouse warming believed to occur, the majority results from water vapor -- not carbon dioxide. So, we're talking about a change to a minority component of the greenhouse mechanism, which itself only affects a fraction of the energy lost to space.
Now, here's the problem. There can be no doubt that higher atmospheric CO[2] levels will result in greater greenhouse heating. However, since greenhouse heating is not the dominant mechanism that controls global climate, one has to try to predict whether this marginal change to the energy balance will net out to a big impact over time. From a policy standpoint, you'd also like to be able to answer "how bad?" and "how fast?". Trouble is -- the world is divided into physical systems with nice linear relationships that can be extrapolated far into the future, and those naughty chaotic systems with non-linear relationships and "sensitive dependence upon initial conditions" which defy long-range accurate forecast. Guess which type the climate is?
And this is where the climate scientists lose me. Without changing disciplines and spending a good year or so spinning-up on climatology, I'm not qualified to offer an "expert" opinion on the nitty-gritty details of the global warming theory. However, unless some rather basic mathematical facts have been rescinded while I wasn't watching, I am highly skeptical of the concrete predictions -- and even the confidence intervals -- quoted by the climatologists. The long-term effect of higher CO[2] levels could be far worse than they say, or laughably negligible (for instance because of changes to more dominant components of the Earth's energy balance, such as solar output). I'm afraid the policy dilemma is rather akin to Pasqual's Wager.
Originally posted by tastymannatees
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Questioning the basic physics of greenhouse warming (CO[2] largely transparent to visible/shortwave infrared emissions from sun but a strong absorber in longwave infrared near color temperature of heated earth) is pointless, because you can measure these things in a terrestrial lab.
Citing the planet Mars as an example of a cool body with a mostly CO[2] atmosphere does not advance the argument, because both the distance from the sun matters as does the density of the atmosphere.
The sole technical weakness of attributing global warming to man-made CO[2] emissions, and of the long-range climate forecasts which motivate policy action to counter same, is well summarized in the point quoted above regarding the accuracy of climate modeling. If greenhouse heating caused by CO[2] were the dominant factor that determines Earth's surface temperature, and if it was a large effect, then there would be no debate (because we would already have cooked to death). We're trying to make long-range predictions about a 2nd or 3rd order effect. Think we'd notice if the sun's output changed by a factor of two? You better believe it! But what we're really talking about is what happens to a fraction of a fraction of the Earth's energy balance. The American Physical Society recently provided this tutorial on the "establishment" view on global warming. It points out that of the greenhouse warming believed to occur, the majority results from water vapor -- not carbon dioxide. So, we're talking about a change to a minority component of the greenhouse mechanism, which itself only affects a fraction of the energy lost to space.
Now, here's the problem. There can be no doubt that higher atmospheric CO[2] levels will result in greater greenhouse heating. However, since greenhouse heating is not the dominant mechanism that controls global climate, one has to try to predict whether this marginal change to the energy balance will net out to a big impact over time. From a policy standpoint, you'd also like to be able to answer "how bad?" and "how fast?". Trouble is -- the world is divided into physical systems with nice linear relationships that can be extrapolated far into the future, and those naughty chaotic systems with non-linear relationships and "sensitive dependence upon initial conditions" which defy long-range accurate forecast. Guess which type the climate is?
And this is where the climate scientists lose me. Without changing disciplines and spending a good year or so spinning-up on climatology, I'm not qualified to offer an "expert" opinion on the nitty-gritty details of the global warming theory. However, unless some rather basic mathematical facts have been rescinded while I wasn't watching, I am highly skeptical of the concrete predictions -- and even the confidence intervals -- quoted by the climatologists. The long-term effect of higher CO[2] levels could be far worse than they say, or laughably negligible (for instance because of changes to more dominant components of the Earth's energy balance, such as solar output). I'm afraid the policy dilemma is rather akin to Pasqual's Wager.
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