Thanks for posting this, Richard. One thing I'll say is that you were talking to a reasonable person, and so you could have a reasonable conversation. There's a group of people who would fall into the "lukewarmer" category, and I would classify myself as one of them. I would also classify Kirsty in the same group. We believe that the climate has been warming, and that some of that may be due to CO2. However, on the lukewarmer spectrum, I see Kirsty leaning towards rather more influence of CO2 than I do.
I've stopped seeing it as a scientific issue. I think it's more one of politics, power and religion. The fact we're losing organised religion doesn't mean that we're losing the religious impulse, which in the formerly mostly Christian West revolves around guilt. In former times, guilt was focussed on personal sin, but as that's waned, it's shifting more towards collective sin. We might not know exactly what we have to feel guilty about, but are looking for some object upon which we can focus guilt, and have increasingly zeroed in on environmental issues.
I'd say that the new "original" sin is perceived as our collective tendency to trash the environment. Because we're in the forefront of technological advance, we see ourselves as being mostly responsible for the problem. However, we forget that if it weren't us, it'd doubtless be someone else, and that although we've affected the environment in deleterious ways, we've also improved a lot of things too.
We've exaggerrated how much we can influence things globally, and become blind to the fact that things aren't nearly as bad as they are perceived. The great barrier reef is actually doing well, so are the polar bears, the glaciers aren't all melting, and the seas are rising at the same rate as they've been doing for quite some time; but if one focusses on the negatives, things seem much worse than they actually are. The real sin may actually be one of hubris, in believing we can have much more of an influence than we do.
The great advantage for the doomsayers is that climate is complex; nobody can definitively say what all the parameters are and how they act, and if some insist that anthropogenic CO2 is paramount, it's very difficult to prove them wrong. In the end, the only proof that could satisfy might well come with the passage of time. If in 10, 20, 30 years things haven't changed as predicted -- may even have started to go in the opposite direction (cooling) -- then the AGW scare will abate and people will have to find some other object on which to focus their guilt.
I see the climate scare as being tied in with identity politics, because that too involves (weaponising) guilt: for being white, for example. It's reversing the hierarchy of elitism: you're most worthy if you're a black female transgender person, slightly less if you're a black female "cis" person, and so on until we get to the bottom of the pile where all the white cis men reside. Worthiness depends on the degree of victimhood, apparently, and of course no white men can possibly be a victim, suffer any kind of injustice or affliction.
Much as I appreciated your chat with Kirsty, I've yet to see any reasonable discussion between people firmly on both sides of the argument. It's not, I think, that those who think it's a lot of fuss about nothing aren't prepared to meet and debate, but that those on the other side aren't. And that as much as anything gives the game away. Why are they afraid to debate? Why are so many of their efforts focussed on actively preventing debate? Could it be that's because they aren't as sure of their convictions as they make out? That at some level they might suspect their arguments don't hold water?
It's the same with the identity politics -- having "safe spaces", preventing contrarians from speaking, doxing people, cancelling them, getting them fired from their jobs, and so on. Guilt is, circuitously, generating intolerance, to the extent that increasingly the intolerant have even started to turn on those who five minutes ago were considered to be in the same group. I can't see it lasting indefinitely; I certainly hope it doesn't.