1) where can we find a completely accurate (or even reasonably accurate) climate model? Even pro-AGW climatologists would shy away from claiming that they have one. Point is, the science is not "settled", unless everyone is agreeing on the mere fact that climate does change over time (which, seriously, no one credibly argues against).
Lets be clear here. "Pro-AGW climatologists" is a redundant phrase. In the *scientific* community (Ie not in the blogger peanut gallery), theres no more "ANTI-AGW" climatologists then there are "Creationist biologists". A very very tiny minority of mostly unqualified right-wing think tank employees at best. But actually nobody is "Pro AGW". Nobody wants this. My sister has been working on the hydrological parts of the modelling for the past decade and she utterly hates the science because the implications are so dismal. But its what needs to be done. Its like saying Oncologists are "pro cancer".
That humans are causing climate change isn't a debate anymore. Hasn't been for a long time, the science is fundamental and would require major revisions to fundamental science that we'd have to throw away 50+ years of scientific progress across the board. A whole new system of chemistry, a whole new physics going back to the 1800s (When scientists first started warning about the 'greenhouse effect' after discovering CO2's infra-red properties in the lab) , a whole new system of optics to account for why CO2 appears to be creating banding in the infra-red spectrum, it just goes on and on.
There are two things required for AGW to be false.
1) A mechanism that is stopping the CO2 humans are putting in from following the laws of physics by trapping IR light and introducing energy into the atmosphere.
2) A mechanism that is making measuring devices pretend that physics is still working as expected.
Perhaps when man makes CO2 its different to natural CO2 and instead of creating heat it creates some sort of strange particle that causes physicsts to lie, like orgone energy.
Does this sound strange? Well it exactly how strange science needs to get for AGW to be false. At this stage, scientists are happy to use the standard scientific model that says if you have a theory that predicts an effect and then the effect turns up in the observation, its a good bet the effect is true.
As for models, well yes, they are not without peril, however certain things can be predicted with certainty.Namely If you introduce x amount of CO2, it will trap in y percent of Infra red (and certain other spectra) light that is passing throught the atmosphere at the time. Since we have a good understanding of how much CO2 is in the air (We've more or less doubled it), we can do a back of the napkin calculation to work out how much energy is being added to the climate system. Remember, this is 1870s science here, nothing is controversial about this, and it can be verified in a high school laboratory.
The question then is how this energy manifests. The options are by heat (Warming) , by kinetic manifestations such as increased winds, cyclones, hurricanes, etc, by increased pressure gradients, such as the one that caused the huge chill over winter in the US, and so on.
Thats what the models are trying to work out. Whatever the case is, we know that the very minimal baseline is still pretty bad.
More to the point, the state of the art in modelling is that our models can attach error bands to the predictions. So "We think this is 80% likely to happen, give or take 5-10%" Currently we're pushing close to 100% certainty give or take a few percent. Not quite the sigma-5 type certainty of 'we've proven it" (Although we *HAVE* proven AGW), but pretty damn close.
At this stage its highly unlikely that the least-bad models will turn out over-done, and we can safely say with certainty that SOMETHING is going to happen.
Thus the precautionary principle states that even taking into account the small likelyhood we are wrong about it, we've got to do something, as long as the something isn't worse. Climate engineering might be worse, much worse even. Economic intervention however definately won't be (In fact most academic economists think climate intervention would have beneficial effects on the economy)
