A little more complicated than you say? A little more? I love the “it’s all simple, it’s just basic physics” tack that people take about climate science. The climate is the most complex, and most poorly understood, and largest, system that we have ever tried to model. No, it’s not “a little more complicated” than what you say, it’s immensely more complicated than our tinkertoy models.
Nor, as my citation showed, can the problem be fixed simply by improving the parameterization as you and Gavin claim. It is inherent in the models. Read the freakin’ citation. Turbulent systems are notoriously difficult to model, and resolution is one of the bugaboos of doing it.
[QUOTE=jshore]
The fact is that when at work I model the spectrum of a device, I will often use it to predict changes in the spectrum with device structure that are considerably smaller than the error between what my model predicts for the spectrum of a device and what the experimentally measured spectrum looks like. And, in fact, my predictions will almost invariably be correct.
One doesn’t have to get all the radiative processes down to lower than the 3.7 W/m2 change you are looking for. One just has to have reasonable confidence that the errors in those quantities don’t change by very large amounts as the perturbation we are studying (in this case, increasing CO2) is turned on. The fact that a variety of models (and generations of an individual model) with a variety of different parametrization schemes and a variety of different strengths and deficiencies all predict similar climate sensitivities (within an admittedly fairly broad range) is one piece of evidence that we can have confidence that this is so.
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And your evidence that gives you “reasonable confidence” that the cloud coverage doesn’t change by even 1% as the temperature changes would be … ???
jshore, a 1% change in clouds gives a change in radioactive forcing equal to a doubling of CO2. If you have evidence that there is no feedback that has a 1% effect on the clouds, bring it on. Richard Lindzens “Iris Hypothesis” has recently been supported by this paper. Is his hypothesis true? We don’t know. I know you don’t like to say that, but it’s the truth – we don’t know, just as we don’t know the size and in some cases the sign of a number of climate feedbacks.
And not knowing about this or a host of other feedbacks, your foolish assumption that not only the clouds but all of the climate is like your spectrum device, that it just sits stably or reacts predictably enough to ignore the huge model errors, is quite touching … but it is not science.
The models get the clouds wrong precisely because we don’t understand all the feedbacks, forcings, and resonances that affect the clouds. The idea that we can hold the clouds constant and thus derive the effect of increasing CO2 is laughable.
Yes, as you say, in a simple stable system which is well understood, it’s not necessary to get the details exactly correct. But the climate is a poorly understood, complex, chaotic, driven, constructal, optimally turbulent, multi-stable system, with dozens of forcings, feedbacks, and internal resonances, both known and unknown. It is made up of five subsystems (ocean, atmosphere, lithosphere, biosphere, and cryosphere) which all interact with all of the others in unknown ways. Correct me if I’m wrong, but I doubt very much if the same is true of the devices for which you are calculating spectra. You are analyzing a simple device built by humans, not an incredibly complex natural system. My guess would be that there is no significant turbulence in your system, for example, to take one of the many difference between machines and nature.
[QUOTE=jshore]
You may call that faith. Those of us who are actually trained scientists who have worked in other fields (where there is not so much of a politically-charged atmosphere) call it science.
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You would not fly in an airplane whose computer system had not been subjected to V&V and SQA. You would not ride in a subway whose computer system regularly had huge errors. But you want me to spend billions of dollars based on an untested, unreliable computer climate models … thanks, but I’ll pass until you subject the models to the normal scientific testing procedure that every other piece of mission critical software has to pass. That’s science, and we use it on everything from space probes to submarines.
Until the models are tested and verified, it’s not science, it’s just faith. Sorry to break the news, but your being a “trained scientist” doesn’t make you any less susceptible to faith than anyone else. Science is a way of looking at the world, not the result of a course of study. The fact that a person has a PhD in science does not necessarily make them a scientist.
w.
PS - the fact that a variety of models give us similar results for climate sensitivity only shows that they are tuned to reproduce the past climate record. Given the assumption that the temperature changes are due to CO2, even the simplest model will give that result. Here’s an extremely simple model – we assume that the post 1980 warming of 0.25° is all due to CO2. Given the change in CO2, that works out to about 2°C/per doubling. Does that prove anything about climate sensitivity? No, because we are assuming that all of the warming is due to CO2.