I've spent the last few days participating in some online forums discussing Anthropogenic Climate Change and I've come up with a short list of what seems to me to be some of the biggest problems in the debate. Keep in mind that some of these issues can also be applied to any controversial, hot-button debate.
1. Appeals to Authority prove nothing and science does not run on consensus. If every scientist but one says that the sun moves around the Earth, the one who says the opposite is still right.
2. If Recorded Data plus Your Theory does not equal Observed Temperatures then Your Theory is wrong. Math does not make mistakes, but people who think they know more than they do make them often. No amount of "compelling evidence" can change this fact. In truth, if the math is wrong, this proves that you do not understand the "compelling evidence" as well as you claim.
3. If your own records and measurements show that the global mean temperature has been on a long-term warming trend for thousands of years then pointing out that the earth is still warming is not exactly Breaking News. Claiming that it will warm at an increased rate is not the same thing as demonstrating that it is warming at an increased rate.
4. Settled science stands up to scrutiny against all currently available data. It might be proven false (and become, once again, unsettled) with new data at some future time, but it cannot be shaky with current data and be considered "settled". Attempting to split hairs on the scientific definition of "proven" does not alter the scientific definition of "settled". The Laws of Thermodynamics are settled science. The Big Bang theory is not. Please take note of the differences.
5. If the centerpiece of your argument is "Anyone who disagrees with me is morally inferior" then there is probably something seriously wrong with your argument. The reality of "everyone with Opinion A is morally righteous and and everyone with Opinion B is morally inferior" is so vanishingly rare that this argument is almost never justified. By the same token, if your argument relies on "everyone who says X really means Y" then you are also most likely wrong. While some people do function this way, most people say things remarkably close to what they actually believe. When someone presents an argument for why they believe a certain way, pretending they have not done so - whether or not you agree with their opinion - does not magically justify your position.
6. You cannot justifiably demand that people only listen to respectable scientists and claim that anyone who disagrees with you is automatically not respectable. This is a form of circular logic and the only thing it proves is that you are not interested in honest debate.
7. Expecting people to accept your theory as evidence for your theory is also circular logic. If your evidence for catastrophe is modeled projections of what will happen, but these models are based on your theory, you don't actually have evidence. You have your theory, stated twice. We cannot debate your theory by first agreeing to assume your theory is correct.
8. Demanding that the people who are not arguing for radical and/or expensive change must prove you wrong really is not how this game is played. If you are the one demanding radical and/or expensive change then the burden of proof is on you to demonstrate that this change is justified. I do not have to prove that a multi-thousand-year trend will not dramatically change in the immediate future. You have to prove that it will.
9. Demanding that everyone change everything to suit your theory before you have proven your theory to be valid doesn't make much sense. Declaring the argument to be over when people are still asking for evidence doesn't prove anything. When your theory relies heavily on predictions that have repeatedly not come true and forecasts that cannot be tested, you might want to rethink declaring the debate to be over.
10. Claims that an increase in global mean temperature will have environmentally catastrophic results when the historical record demonstrates the exact opposite also doesn't make much sense. While there are certainly temperature thresholds that would be catastrophic, not even worst case scenarios in AGW predictions come anywhere close to those numbers. Most of the scientists involved freely admit that their worst case scenarios are highly unlikely, so arguing for even worse cases scenarios is irrational and dishonest. By that token, it is extremely dishonest to excoriate the other side for using inflammatory scare tactics when you are using inflammatory scare tactics yourself.
There you go, my Top Ten list for problems with the Climate Change debate.