I've looked at SPM.2 - and the two charts in that graphic top out at 2.5C - which obviously sets the mental alarm bells ringing.

I can't see anything that reflects your earlier claim of:

> ... the last IPCC report I read suggested global collapse was more on the order of 6 - 8 degrees.

I'll correct my claim: "the last IPCC report I read suggested that the 1.5C limit is based on local tipping points. From other papers I have read, tipping points for global collapse are more on the order of 6 - 8 degrees."

I couldn't find the 6-8C paper, but from memory the dictating factor was hydrate melting. I found this website which provides good summaries of the local tipping points. https://climatetippingpoints.info/2022/09/09/climate-tipping...

Do you know any references to global tipping points? When I first went looking for them it blew my mind that they were not easier to find in IPCC materials.

In the meantime I found this page, which answers this question explicitly. https://climatetippingpoints.info/2019/10/14/fact-check-will...

Agreed that it's hard to find definitive numbers, but given it's all projections and extrapolations, that's not hugely unexpected.

As a sibling commenter suggested, 'the science' is not saying the world ends once we get past 1.5 -- and to be fair to myself, that's not what I intimated - my language was unnecessarily cumbersome, but I was trying to point out that the consensus is we have some confidence of not having a cascade up to about that figure.

On that note, taking comfort from those higher thresholds & projections feels like hurtling past a 'Bridge Closed' sign at 100km/hr and taking instant but likely ephemeral comfort from the fact that sign wasn't so bad after all. If we hit 2-3 increase over the next few decades, even with moderate rises in climate-related casualties and costs, I expect there'll be even less appetite to address the problem.

Anyway, the two articles you've linked just now say much the same message:

" ... climate tipping point risks emerge above 1°C, become high around 2°C, and reach very high around 2.5-4°C. That means many tipping points are probably closer than we thought, and could start to be an issue even at today’s warming of 1.1-1.2°C."

Arguing about where the global collapse is guaranteed to happen does feel a bit deck-chair-ish.

I agree with everything you say, except for the part about discussing global collapse limits being deck-chair-ish. We are on a path to a lot of warming, where many of these local tipping points have and will become a reality. Having an estimate on when these effects combine to form a global tipping point is essential. It is essential because it informs how hard our policy response is. It is all well and good to try and aim for <2C warming but if we are obviously overshooting that mark, we need to know how far we can overshoot without passing a point of no return. If the consensus became that the trigger point for global collapse was imminent(say less than 10 years), we could plan a response that guarantees emissions reductions in 10 years regardless of the suffering caused (e.g. austerity to reduce energy use without consideration to poverty, banning ICE vehicles for non-essential purposes, sanctions for fossil fuel use). If we are incorrect and the trigger actually occurs in 100 years, we have just caused additional suffering by not planning our response longer. If humanity has an imminent existential risk, doing horrible things becomes morally justifiable (e.g. putting 4 billion people back in poverty). If we are 100 years off collapse, putting 4 billion people back in poverty is immoral without considering longer term solutions. Which path you choose is determined by our predictions for the future. Optimistically planning for <2C warming is good but unrealistic based on current trends. Unfortunately cheap energy is the basis of the world economy. Thus all solutions cause suffering for someone, whether by increased food prices, medicine prices, loss of jobs. Of course this has to be compared to the harms from climate change, but how can we make this comparison if we are ignoring the worst case outcomes (which I would argue are the more realistic cases)?

The fact that neither of us can find information on global tipping points in IPCC documents is to me a sign that the political aspect of the solution is not being done well. The IPCC essentially says "keeping warming <1.5C is essential" and "we are expecting more than 1.5C warming based on current trends" but then they make no estimates of the existential limits for the trajectory we are expecting. It mirrors my experience with environmental regulation. Policies where you can pollute, as long as the pollutant is kept at < X% concentration. But why X? What happens at X-1 or X+1? That is how engineering problems are tackled, but political solutions aren't as systematic. X is likely choosen not because that is the best outcome for society, but because a committee arbitrarily agreed that it is achievable. As we've both seen, the current IPCC limits are based on local collapse of systems such as coral reefs. But these systems are already being affected and are not expected to recover (based on the status quo). If that is the case, I think we should shift our focus from estimating the most warming we can have without _any_ negative effects (unrealistic) towards policies based on cost-benefit (pragmatic). Decarbonization in 10 years looks very different to decarbonization over 100 years. I'd prefer 10 years, but I don't want to ignore the people we will harm in doing so and I want to know what happens if we can't get our shit together in 10. We cannot make an informed decision unless we have limits which are not arbitrary and are realistic.

Edit: I thought I'd add a response to your bridge analogy. I think our current situation is like speeding towards a failed bridge where we can either ditch off the road down a cliff _now_, or go around the corner where maybe we can ditch into a bush. We need to know what is around the corner before we decide to go off the cliff. A real-world example for this: biofuels were pushed as an alternative to fossil fuels via subsidies, which caused minimal benefits to global warming but caused the worsening of starvation in the third world. If we had waited until better solutions were available or bad solutions were 100% necessary, we would have avoided suffering through starvation. Reflexively saying "we are in an emergency, quickly try solution <Z>" isn't useful unless we are sure that we are in an emergency (read: existential risk) AND we have confidence in solution Z improving the emergency. Doomerism breeds bad solutions and unnecessary suffering. Doomerism might be the right response, but the IPCC reports do not convince me of that.

Well, to all hand-wringing around seeking precision on threshold estimates - I'd throw back three points.

1) the precautionary principle,

2) empirical evidence abounds that budget projections are notoriously woeful - the '18% of GDP in 30y' relies on so much faith in multiple systems we already know are consistently out by factors of 2 or more, and

3) starting to fix this now would be lower overall cost, would incur near-immediate benefits, and would definitely court lower long-term risk.

Charles Stross's most recent blog post - the first three paragraphs - is not a unique analysis, but I feel describes the situation succinctly and accurately. Our (civilisational) resistance to addressing these issues are intentional and orchestrated, and 'a bit more data', or a more precise temperature rise we could cope with, are not the problem.

https://www.antipope.org/charlie/blog-static/2022/11/decisio...

I like this dialogue because you seem to be arguing in good faith, so I'll keep it going. 1) Precautionary principle needs to be _qualified_ by what you are cautious of. E.g. "I am being cautious about increasing global warming" or "I am being cautious about increasing human suffering" result in very different policy approaches. If we actually used the precautionary principle we wouldn't have burnt fossil fuels to begin with! 3) That is an assumption, it is _probably_ true, but I would prefer to see explicit reasoning (e.g. in an IPCC report), but as I mentioned before, IPCC ignores worst case scenarios in the delusional hope that we won't need to worry about them.

Charles blog post is a good example of articles discussing global warming that aren't very helpful. It is high-level, makes a lot of assumptions and seems disconnected from any actual solution. For example, PV is cheaper? That's very location-specific and depends on storage costs. Petrochemical exporters are Authoritarian?!? I don't think Australia, Canada, Norway or the USA fit this category. He doesn't seem to identify a problem besides propaganda, and he doesn't offer much in the way of a solution for this. He is a writer, so he sees the issue as a communication problem. That is just one facet, and he can't even suggest a solution in passing.

I don't agree that the precautionary principle needs to be qualified, or at least not constrained to a single axis - we want to exercise precaution about any changes (or any resistance to change) - with effectively a 'do no harm' focus.

Human suffering ... I don't know how you're measuring this, or projecting it from current state, but 2/3 of the planet are going to be in unimaginably dire straits once regular rainfall patterns change.

I think when we started burning coal in anger, say late 1600's, early 1700's - literally no one contemplated the potential for planet-scale effects, so I don't think that application of the PP applies. I think we're still pretty dumb and full of hubris, but we can contemplate these potential outcomes, and we know of many unintended outcome scenarios, so the PP is much more compelling now.

Charlie's not trying to solve climate change - just drawing attention to why it's not being addressed. Petrochemical exporters are rarely countries, but rather the oligarchs that own the materials. Here in AU we have a tiny handful, f.e. and I expect a similar situation elsewhere - so while the current political administration is nominally democratic, that's effectively irrelevant.

EDIT oh, regarding (3) that you responded to - I'd point out the myriad stats around fossil fuel vs renewables 'jobs', especially graphed over the past decade, and especially in the USA. I think we're now at a time where anyone claiming renewables aren't a better economic option for a society are the ones that need to provide citations.

I think a PP without qualification becomes so nebulous that it can't be used in anger. Like what is wrong with saying that the most precautious we can be is to turn off all fossil fuels immediately? Lets stop cement and fertilizer production while we're at it. Starvation concerns? Irrelevant because we're being Precautious(TM).

When are 2/3 going to be in dire straits? 10 years, 50 years, 100 years? It matters to our policy response, that is my whole point. Repeating "global warming bad" isn't wrong but it doesn't inform policy.

More jobs = better?! That simply means it takes more resources to produce the same output. That is efficiency going down and is not good for the economy. But that doesn't matter because using the PP means that economic health isn't important. THIS is why it is important that institutions like IPCC need to consider all possibilities. We can't tell if using more labour is a good thing unless we can compare it to the downside! If we limit our imagination to 1.5C warming, we are deluding ourselves.