I have identified three main techniques of climate denialism.
The first is: your opponent is presumed guilty until proven guilty.
The second is: focus on tone and not on substance.
The third is: make mountains out of molehills.
Did I miss any? The first two seem to be enough. The first forces your opponent to be either angry or defensive. The second takes that result and allows you to change the subject.
The third allows you to construct Gish gallops and paint the whole business with a false aura of controversy.