1. Never stating their position in any concrete terms.
2. Adopting contradictory positions and never acknowledging this.
This make is hard to have a real debate with them because point 1 means you're never told what position you are debating against is, and point 2 means they are always a moving target jumping from nonsense point to point as you shoot each argument away.
You'll be hard pressed to find them making a factual assessment they can be held to, as does the IPCC. So the IPCC may say they think there will be a 2 degree rise over a set time and give the statistical probability that this forecast is accurate. Then they'll revise and amend that forecast as new evidence emerges. That's why it's a science.
By contrast the denialist talks of 'alarmism' and 'concern' other woolly terms that don;t really means anything tangible. They are deliberately vague emotional terms that allow them to escape making solid predictions over which they could be held to account. Denialism never seems to propose research methods that would show what is going on in the climate system - it always relies on cherry picking other peoples data and producing critiques of others hard work. There is nothing itself wrong with criticism - its an essential part of science. But after a while you want the people saying "that's wrong" over and over to show you how it's done right. After all, millions of dollars have been (and are) being pumped into denial by vested interests. Should be simple to fund a few bit of original research that says 'the temperate change will be X degrees over Y years...?
So why is this?
They have to have points 1 and 2 in operation else the carefully woven tissue of conspiracy and obfuscation would collapse under the weight of it's own contradictions. How do they do this? By making an emotional and not a scientific argument...
“…I’ve come to view “denial” as reflective of an individual values, rather than an emotional state they pass through. It is a culture war issue, in the same way abortion, stem cells, Sharia law and creationism have become litmus tests for conservative Christians, Muslims etc.
…Creationist reject evolution because it contradicts their literal reading of the bible. Ergo, thus *must* reject the science in order to affirm their tribalism and confirm their membership to the creationist “tribe”. It’s about outward signs of orthodoxy and inwardly managing ones identity.
Free market libertarians, culture warriors and ultra-conservatives see climate change mitigation as deeply threatening to their “choices” within the market and individual “liberty”.
If your committed to small government and limited intervention in the market, then things such as a carbon tax, ETS or regulation are anathema. After all, the “market” will fix this.
Why is also why you find conspiracy theories, crazy analogies in thier postings - indeed anything but rational thought. To understand them you also need to understand the conspiracy mindset and how it works.