Their last-ditch effort, then, is to try to argue that it's not anthropogenic and that therefore there's nothing we can do.
But if human activity isn't the major cause of the warming, it just means that we have to do even more to fix the problem.
If there is a natural increase in carbon gasses that is primarily responsible for the warming, then we have to cut human emissions to zero
and figure out a way to get rid of the gasses that are being produced naturally.
Whereas if the cause is mostly anthropogenic, then we only have to worry about cutting emissions, as that should let the problem clear up.
So as jar said, the best case scenario is a case where global warming is entirely caused by humans, because it requires less sacrifice and less effort on our part to fix than the alternative.
Jon
Love your enemies!