"Models for something that has never happened are notoriously incorrect."

I agree. But make the same point about the effects of AGW and people lose their cool.

AGW is happening now, so unfortunately we're getting the opportunity to test the models. And carbon levels, and climate, have both varied in the past, albeit a lot more slowly. Those variations can be used to tune some aspects of our current models.

It's a valid point of discussion, but unfortunately almost everyone opposed to climate action is anti-scientific and political in their motivations, and usually duplicitous about it. Which causes people to lose their cool.

Most actual climate scientists, on the other hand, are more than happy to entertain honest skepticism. It's integral to science.

> ... almost everyone opposed to climate action is anti-scientific and political in their motivations ...

I'd say that motivations are economic. And skeptical scientists and politicians are bought. It's the same strategy that tobacco firms used. Including the astroturfing.

My own objections to (some) climate change mitigations are philosophical.

In summary - models of the effects of AGW have proved largely useless in terms of predicting the impact of same, or even the existence of net negative impact.

So why are we proposing to spend vast sums of money, not to mention increasing the price of energy, to address this issue?

Actually, all large nuclear weapons states have agreed to do that, they just ignore their treaty obligations in perpetuity.

NPT:

"Article VI

Each of the Parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control."

I second this. To your question, I believe it's because the notion is multifaceted, and there are many reasonable answers. The most common being that we need nuclear weapons for deterrence (defensive) reasons, same as the reason for having a war machine or military alliances at all. A reason less touted is that we need it for offensive reasons, but then again, the best defense is offence so the two are difficult to clearly distinguish. Another reasonable argument against a ban regards enforcement: how to you enforce something from a position of weakness (having vowed not to use nuclear against a ban-breaker)? I could go on but the point is not that these reasonable objections are insurmountable obstacles, but rather that there are real difficulties that need to be addressed in order to avoid the nuclear havoc that otherwise seems a probable end result some time this century.

I don't think a world without nuclear weapons is actually safer.

Moreover, we seen/remember the world before nuclear weapons. Nowadays though, modern protection systems negate the effect. If something should be banned, it is "total nuclear umbrellas", so pushed by military countries.