The internet is a chaotic system if you choose packets as your unit of granularity, and yet this message still came over the wire intact. The wiring inside a bomb impacted by an outside force is a chaotic system with plenty of uncertainty as to what's inside, but you would still be unwise to kick it. Gas flow in jet engines is a highly turbulent and chaotic system with measured temperature variation from the best models exceeding in many cases 20%, and yet jets will still fly.

You don't need a perfect model to arrive at an accurate prediction, you don't need a terribly accurate prediction in order to arrive at a general appraisal of a situation, and you don't even need a general appraisal of a situation to ascertain risk worthy of action.

Frankly, it should be probably be enough to say "we know that most of the energy the Earth receives is from the sun, and we know that most of the energy is dissipates is through infrared. We also know that the Earth is an extremely complex, strongly coupled, and chaotic system, in which the details of every component can never be known, and being able to predict with a high level of confidence what the effects of any major change would be is unlikely. Maybe we should probably stop fucking with the Earth's primary means of cooling?"

There is nothing wrong with skepticism, per se. Skepticism is a positive, and it is a very worthy thing to root out the bs from the science. But it must be weighed against two things: the need to come to some decisions in a limited timeframe, and the fact that people often managed to justify to themselves, using any means at their disposal, their continued action or inaction. Too often 'climate change skeptics' claim that due to unacceptable uncertainty, they're going to continue doing what they're doing -- or -- that it isn't happening at all -- or -- that it's just part of the natural variation, when simple physics tells us that if you significantly modify a primary means of forcing a system then at least something about it must change.