Given that Genies exit bottles more easily than they enter them, what would your plan to prevent research/development/deployment look like, Ray?

Where are the politically plausible off-ramps here? Why would recalcitrant actors abide by a moratorium or ban? How would you make them comply?

Pretty cheap to deploy, including for Decentralized actors
Not a weapon, probably

But there are reasons to think that once you know something can be done, it's harder to prevent it being done. Perhaps especially in a competitive "grey zone" world.

and then made elsewhere, too.

The geoengineering case has similarities but differences, too.
Similarities:
Irreversible learning;
SRM looks attractive for at least some actors;
Competitive behaviour would likely follow;
Widespread negative externalities
Differences:

The issue reminds me of a point Schelling often made about nuclear proliferation - once you know how to do something, you can't unknow it, and incentives arise from this knowledge.

Some say that once Peirels had shown a bomb was possible, it was impossible that it not be made...

I don't know if that's true or not. It doesn't line up with the electoral calculus I've heard from National MPs over the years on climate change.

Starting from a position that they are insincere seems very Bluesky. Possibly detrend for that.

Yes.
It's hard to parse NZ First and ACT's posturing/positioning on the issue because small parties don't have to offer credible positions the way big parties do.

Well you never know - there are parties that talk about pulling out of Paris, and there are MPs who would prefer to do nothing - but my impression is that they're discussing cuts, rather than anything like those options.
Wellingtonians may know otherwise; but that's the strong impression I have.

Agree we made the issue much more salient.
I think this is a good thing, but among the GWP* haters are those who wanted to keep that buried and wanted everyone to just keep saying GWP100 was fine.
Other GWP* haters have different axes to grind - I think there are about 3-4 groups, approx.

As far as I can tell the issue being debated in NZ is whether CH4 emissions should be reduced by ~15% or ~25% by 2050 (or more). Some farming groups argue for "not reducing CH4 emissions" but I don't think this is under serious discussion in parliament.

We likely assign different credences to the "aim" - you may think it's a binding commitment, I may think it's an aspiration. We may well react differently when we fail in that aim, because we assign different weights to its credibility and moral force, its status as a promise, and so on.

They've made an agreement to "aim at holding temperatures..." I aim to stay sober tonight. At this point it seems feasible.

Splitting the bill for meeting the aim is a bit like a divorce settlement: the parties can agree on the estate, but may have very different ideas of how that's to be split.

How they think they contribute to meeting PA Article 2 very much is a normative choice.
Collectively they've agreed to something, but they haven't partitioned the mitigation required to get there.

Those are normative assertions. You're welcome to make them, and others are welcome to dispute them.

Those normative dimensions are separate from accurate treatment of what the emissions do to the climate - the GWP* science conversation is mainly about the latter, not the normative bits.

This is why we have been arguing that people should Indicate separate contributions of long-lived and short-lived greenhouse gases in emission targets... this completely avoids the conflation that Hannah is troubled by.
Ultimately the problem isn't GWP*, it's GWP100.

www.nature.com/articles/s41...

Lots of things are relevant to that further question, including reviewing how ETS treat EITE CO2 sectors - many of the same issues are at play here.
I don't mind too much where people land - but it is important that the arguments a proper airing, and that some enduring consensus gets built.

What ag folks have seized on is that net zero CO2 halts but does not decrease warming, and they argue (rightly) that gently decreasing SLCF emissions do the same.
This point is true whatever the metric.

Whether this is a good focal point for policy is a further question.

GWP* also more accurately reflects the warming from a pulse emission over time than do GWP20 or GWP100.

But this assumes its conclusion. Of course most the overshoot is from CH4 if you already assume massive CO2 reductions because you've told your IAM to do that. But wishing don't make it so.
Until we see real CO2 reductions, the Pierrehumbert 2014 argument seems pretty reasonable.

Separate treatment unscrambles the mess, by and large. Explicit targets based on tonnes CH4 for the ag sector would allow countries to make it clear and transparent how the sector contributes to warming over time.

GWP* also works at national scale, and any other scale, to reflect warming.

There is no good economic reason to use GWP100 to bundle LLCF and SLCF - actually the economic logic suggests separate treatment, in part because GWP100 fails to reflect marginal warming contributions.

Separate treatment is implied by the physical science of LLCF and SLCF, whether you use climate models or GWP*.

GWP100 has obscured this, unfortunately.

No, it doesn't.
GWP* accurately assesses warming from different sources.
Target choice can be informed by the realisation that net zero LLCF amounts to halting further warming, and small annual reductions in SLCF halt further warming.
But GWP* does not imply target choice.

There is no economic or policy logic for bundling long- and short-lived GHG. On first principles the idea fails.

This is why the GWP* folks have generally been arguing for separate systems.