Well, they make falsifyable claims all the time.
"Burning of fossile fuel --> more CO2 in the air"
"More CO2 --> more heat absorption"
"Higher temperatures --> increased melting of ice"
"Higher temperatures --> more water evaporation"
and so on
But is there even such a thing as a 'global average temperature'?
In reflecting on it, I see serious problems with that basic construction, on which many of these premises and arguments are based. Hence, I would reject 'science' which attempted to draw conclusions from such premises with demonstrable errors.
Let me put it this way: Anyone who does not understand what I mean in the above paragraph should definitely not be debating this subject.