Do we deny that climate is changing? No, of course not. Climate has always changed and is always changing. Our biggest sticking point is that somehow all climate change is being attributed to human activity, something that is ignorant at best and arrogant at worst.
I will be more than willing to agree that AGW exists if and only if the warmist camp were able meet the three requirements laid out by Robert Tracinski. By the way, these three requirements closely align with those of the scientific method, something that has been tossed aside by the warmists in their zeal to prove their point of view is the only correct one.
A clear understanding of the temperature record.Much of the Catastrophic AGW forecasts are made based upon assumptions that are not backed up with experimental data or through observations out there in the real world. They are assumed to be accurate by the warmists, therefore they must be right. The climate models they've been using were wholly incapable of accurately hind-casting climate, plugging data from the past into them and seeing if the model output matches what actually happened. Not one model even came close. So how is it they can place their faith in those same models to accurately depict what the climate will be like 100 or 200 years from now?
The warmists don’t just have to show that temperatures are getting warmer, because variation is normal. That’s what makes “climate change” such an appallingly stupid euphemism. The climate is always changing.
So to demonstrate human-caused global warming, we would have to have a long-term temperature record that allows us to isolate what the normal baseline is, so we know what natural variation looks like and we can identify any un-natural, man-made effect. A big part of the problem is that we only have accurate global thermometer measurements going back 135 years—a blink of an eye on the time-scales that are relevant to determining natural variation of temperature.
A full understanding of the underlying physical mechanisms. We have to know what physical mechanisms determine global temperatures and how they interact. The glibbest thing said by environmentalists—and proof that the person who says it has no understanding of science—is that human-caused global warming is “basic physics” because we know carbon dioxide is a greenhouse gas. Carbon dioxide is a very weak greenhouse gas and there is no theory that claims it can cause runaway warming all on its own. The warmists’ theory requires feedback mechanisms that amplify the effect of carbon dioxide. Without that, there is no human-caused global warming. But those feedback mechanisms are dubious, unproven assumptions.
The immense, untamed complexity of the climate is reflected in the poor performance of computerized climate models, which leads us to our last major hurdle in proving the theory of global warming.
The ability to make forecasting models with a track record of accurate predictions over the very long term.
We don’t know whether current warming departs from natural variation, nor have scientists proven the underlying mechanisms by which humans could cause such an increase. But even if we did know these things, we would have to be able to forecast with reasonable accuracy how big the effect is going to be. A very small warming may not even be noticeable or may have mostly salutary effects, such as a slightly longer growing season, whereas the impact of a much larger warming is likely to cause greater disruption.
Given the abysmal record of climate forecasting, we should tell the warmists to go back and make a new set of predictions, then come back to us in 20 or 30 years and tell us how these predictions panned out. Then we’ll talk.
(Note:Some formatting was changed in the quote because I kept having problems with the word processor app I use automatically making changes I didn't want, so after 20 minutes messing around trying to get things to look the way I wanted, I gave up and reformatted. -ed.)
Another thing that I find from the warmists that is difficult to take seriously is their belief that a warmer world would automatically be a bad thing. Geological and historical records imply just the opposite. The warmists assume a warmer world will have less arable land, that deserts will grow dramatically, and that everyone will die unless draconian measures are put into place. They will brook no dissent on this matter as they know it to be true, all without one shred of evidence to back up that belief.
Basing any actions upon conjecture and faith is dangerous, as history has shown us again and again. Show me the proof that what they say is accurate and true, and I will change my point of view. But I will not do so based upon the always questionable Precautionary Principle as more often than not the solution to the perceived problem is worse than the perceived problem itself.