Increasingly popular in US and UK politics, simply say something that is blatantly untrue, e.g. "The Arctic is cooling", "Greenland isn't melting", "No evidence CO2 causes warming," "Brexit will be good for Britain", etc ... 2/.
Show someone half the facts and conceal the other half, and lead them to an incorrect conclusion. e.g. "Many IPCC scientists say warming estimates are over-estimated" (ignoring that at least equal number would say the opposite). 3/.
It's easy to deceive with carefully chosen irrelevant truths, e.g. "CO2 is plant food", "there was more CO2 in the past", "water vapour's a more powerful GHG". All true but none challenge AGW in any way. 4/.
Choose the 1 piece of data that bucks a general trend. E.g. Sea level's falling in a few places where land is rising due to tectonics, 1998 was warmer than the next 7 years, Brexit will make one man (Jacob Rees-Mogg) better off. 5/.
The evidence for AGW is clear and overwhelming, so deniers will direct your attention as far from it as possible. "Mars is warming too!" "Al Gore flies too much!" "What about the starving Africans?" See also types 3, 7 and 8.
Deniers will present as fact the opinion of someone with no expertise in climate science, but maybe in another field, e.g. Nigel Lawson (politics), David Bellamy (Botany), or Matt Ridley (bankrupting Northern Rock bank). 7/.
The science of AGW is clear an unequivocal, but (thanks to deniers) the public has doubts. I a circular argument, deniers therefore use public opinion "Belief in climate science falling!" to further weaken trust in facts. 8/.
A form of misdirection (5). Deniers can't win on the science, so they divert to politics, e.g. "Wind farms are ugly!", "They want you to may more tax", "It's a Socialist plot!" Doing this reveals their actual motives! 9/.
Science needs mavericks, who challenge the consensus. An honest maverick searches for evidence, remaining quiet unless he finds some. Anti-AGW mavericks never have, but deniers still present their opinions as facts. 10/.
Invent something dumb your opponent said, then trash it. E.g. "They say melting sea ice will raise sea levels, but if you melt ice in water, then the level stays the same" (point is, it's melting ice ON LAND that raises sea levels. 11/.