Even at “just” $45 trillion, the opportunity costs for that money are enormous. I’ll leave it up to you to imagine just what could be done with all of that money, but even a fraction of it could make huge improvements in the human condition on Planet Earth – for all manner of issues which we know with absolute certainty to be both real and dangerous. No need to play any “what if” games with them.

Even the climate modellers will tell you that the biggest area of uncertainty in their models is how clouds are handled. What they won’t tell you is what a *huge* problem that is, because they are the main driver in terms of “climate sensitivity”… whether the feedback is positive, neutral, or negative. They currently all assume it’s significantly positive, magnifying the effects of CO2 by 2, 4 or even 6 times. But some scientists have seen evidence that it may actually be negative (which is certainly vastly more common for natural systems than positive feedback). If they’re right, a doubling of CO2 in our atmosphere (without any change in solar irradiance) would only increase the temperature by about 0.3C. Sorry, that’s all way too uncertain for me to sign up for spending $45+ trillion to try and “solve”.

Under his argument, you could posit any threat and demand action because if we’re wrong in the end we are all screwed. Whether global warming is real is very, very important to how we react to it.

Besides, modern civilization is the cleanest environment of all. We in the first world don’t have to deal with mass filth and plagues because we destroyed on the nature that was causing it. Clean does not necessarily mean natural.