December 13th, 2009

A footnote to Mark’s post on uncertainty and the risks of global warming.”Hear, hear!” to his argument, but he understates the problem. This makes no difference to the logic, but a lot to the urgency. Mark (my italics):

The world – especially the much richer world of our great-great-grandchildren in 2100 – could adjust to a 3°, or even a 4°, increase in global average temperature, though at great cost in species extinctions, land area lost to rising sea levels (and therefore the forced migration of some large populations), and more extreme weather. That hotter planet would be, on average, a less pleasant place to live. But it would still be habitable.

But the climate scientists – the blue-ribbon Copenhagen Diagnosis group that issued an update to IPPC4 last month – don’t quite say this (again my italics):

Global mean warming of even just 1.5-2.0°C still carries a significant risk of adverse impacts on ecosystems and human society. For example, 2°C global temperature rise could lead to sufficient warming over Greenland to eventually melt much of its ice sheet (Oppenheimer and Alley 2005), raising sea level by over six meters and displacing hundreds of millions of people worldwide.

The difference between 2° and 3° C is important, for we have already used up half of the former and gone up 1 degree, and keeping to 2° implies peaking emissions in ten years or less (report page 51). The 2°C limit isn’t a scientifically based assurance of safety, but a horse-traded EU political target that may already be too generous. From the Copenhagen Diagnosis scientists again, page 50 (links and italics added):

…the group of Least Developed Countries as well as the 43 small island states (AOSIS) are calling for limiting global warming to only 1.5°C. The Synthesis Report of the Copenhagen climate congress (Richardson et al. 2009), the largest climate science conference of 2009, concluded that

Temperature rises above 2°C will be difficult for contemporary societies to cope with, and are likely to cause major societal and environmental disruptions through the rest of the century and beyond.

The only world we know to be safe is the one we evolved in, with zero anthropogenic emissions; heating it up beyond the small historical variation (well under ± 1°C, judging by the chart on the same page) is a risky venture into unknown feedback loops. Zero net emissions are what we have to go back to, with high technology replacing hunting and gathering. And there is no margin of safety for more dithering.

PS Trial comments policy

I’m not a climate scientist and I’m not running Climate Science 101 for denialists and amateurs here; this is a policy blog. Commenters are firmly invited to stick to the policy point. Comments that just try to challenge established climate science will be treated as trolling and gutted: please go to other fora to jack off. Corrections from qualified climate scientists, citing references in peer-reviewed journals, will of course always be welcome.

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15 Responses to “No safety margin”

  1. JohnN says:

    If you want a link for serious discussion by adults of the issues around climate change, try Real Climate:
    (also a good source for all that actual data that the deniers claim is hidden)

  2. JohnN says:

    Er, I meant that comment to be in the spirit of agreeing with the blog author’s wish to avoid science discussion here (and so here is where you could go if you wanted that) not as an implication that there were no adults here. Sorry.

  3. Finn says:

    The estimates for the cost of climate change slowing is estimated to be 1% world GDP or less (most economists claim less), whereas the cost of direct confrontation with the consequences of continuing to dump CO2 into the atmosphere is estimated to be 20% of GDP. How much richer must the generation that pays later be for that trade-off to be worth it?

    I got those numbers from here:

  4. Dan Staley says:

    Well, I just wrote a brief for a mayor that is in Copenhagen now about this topic (and about the CRIhack & Swift Boat campaign). The 2º is a political target that was likely chosen as a target temp that has never been seen since the retreat of the last glaciation. It is tough to find robust papers that give ecological reasons for a tipping point at 2º. Nonetheless, I’m an ecology guy and we should have started acting at least a decade ago to restrict CO2 emissions and land-use changes and promote white roofs etc.

    However, I fully agree that we should remain within the climate regime that modern society evolved in. Anyone purporting to promote policies such as Business As Usual is woefully undereducated in both Econ and Environmental History and thus should be ignored. 2º is a target we can all imagine and measure and follow. It very well may be that this temp, combined with all the other anthropogenic impacts will make our children and grandchildren miserable, so 2º is the max target for adaptive management. Much better – combined with the pipeline warming – is lower. Which means we need to begin very, very, very soon. 2010 at the latest.

  5. TomF says:

    “Comments that just try to challenge established climate science will be treated as trolling and gutted: please go to other fora to jack off.”

    Even more evidence that progressives are the most tolerant and open-minded members of society… so long as you agree with them.

  6. TomF: tough. As JohnN says, there are other sites where you can learn from and/or dispute with experts; Deltoid is another. I don’t propose to give space on my posts – I’m the host here, under Mark’s guidance, remember – to uninformed attempts to spread confusion. If you want to advocate policies tantamount to genocide, do it elsewhere.

  7. paul says:

    Finn: although 20% of GDP seems like an outlier, even a few percent of GDP lost would be utterly devastating, because GDP is so unequally distributed. The world’s low-income nations, according to world bank data, account for less than 1% of the world’s GDP. They’re also the ones least able to protect their citizen from the effects of climate change, so they can look forward to disproportionately large GDP costs. A loss of even 3-4% of GDP could simply wipe the lower-income nations out.

  8. MobiusKlein says:

    One possible policy reason –
    What is the probability of a Carbon Policy success? If it is low, then it may be better to treat the output as inevitable. Work on mitigation and such. A bad carbon policy could make life miserable now for poor countries, whose citizens can’t compete on a level Cap & Trade policy – they might be out-bid on every available scrap of CO2. And when some big country X cheats, all the other big countries opt out also. In the end, nearly the same amount of greenhouse gases have been emitted, but unrest and mistrust have grown.

    What to take from this? Make sure local policy changes aim at reduced carbon & energy use irrespective of global treaties.

  9. sd says:

    The argument that “there is lots of uncertainty about how big the impact of climate change will be, and that should make us MORE willing to spend a lot of money to avert it” is a strange one.

    Strange in that you could make damn near the exact same argument just about every potential threat that humanity faces, the cost of mitigating all of which would be well beyond the economic capacity of the world.

    We know that terrorists kill a lot of innocent people. We have no way of knowing how many terrorists there will be in 2109, so therefore we should spend X trillions of dollars to fight the growth of terrorism today.

    We know that a giant asteroid hitting the planet by 2109 would wipe out life as we know it. We have no idea how likely that is, so therefore we should spend X trillions of dollars to defend against asteroid strikes today.

    You get the picture. That’s why, within reason, the standard criteria for evaluating where we should invest resources is the expected future state. There are exceptions. We buy fire insurance, after all. But we buy insurance where there is a viable market for risk mitigation because lots of parties face the same risk but they won’t all be hit with an event.

  10. DanS – IIRC, the 2C figure isn’t just the highest since the end of the glaciation 13k years ago, but the highest since the glacial period began several million years ago. That’s why it’s dangerous – it gets us into a climate that hasn’t been experienced in millions of years, with poorly-understood effects. An excellent book, David Archer’s The Long Thaw, covers this issue.

    SD – you’re confusing uncertainty with no knowledge. We have no knowledge that terrorism will get worse and no reason to assume so. If we did think it could get worse with a wide uncertainty level, that would justify increased resource investment in response. (And we do know the odds of a life-extinguishing asteroid hitting the earth – it’s really really small, not growing, and not that wide an uncertainty level. City-killing asteroids are a little less well-understood but are a diminishing threat as we continue to discover and plot orbits of small asteroids.)

  11. Dan Staley says:

    Brian, I understand your point. My point is that there is nothing we have to date that says, say, 2º is a tipping point and we can’t go beyond this, etc. That is: there is no empirical basis to point to for the figure. But I counsel for action to prevent getting close. It is using multiple ways of knowing, not calling on empirical evidence.

  12. TomF says:

    James – I always enjoy reading all of the posts on this blog, including yours, even though I generally don’t agree with the policies advocated. I find you and your colleagues interesting, obviously well-educated, and knowledgeable about policy-related issues, although, as I stated, I often disagree with them. Advocating my own policies on this blog is never something I would think of doing – for two reasons – 1) this is a left-leaning blog, and you are entitled to your own private space to discuss your issues, and 2) this is a left-leaning blog, and you and your colleagues really aren’t interested in my opinion.

    That being said, my point (which I thought was a bit clearer but wasn’t) was certainly not that I was disappointed in the lack of opportunity to “challenge established science” or to “jack off” to my opinions, as you so eloquently put it. Any educated information I may have on that issue would be wasted here. Rather, my point was, and continues to be, that I found your sweeping disapproval and dismissal of anyone who would dare disagree with you to be pretty ironic for someone who claims to be of the more “tolerant” and “open-minded” persuasion.

  13. TomF: “your sweeping disapproval and dismissal of anyone who would dare disagree with you”: this allegation is demonstrably false. My post is a diaagreement with part of Mark Kleiman’s; where’s the sweeping disapproval? And have I swept away the comments in this thread that take issue with my specific arguments? I’m all for toleration of crazy and unpleasant opinions within the usual human rights limits; that does not require me to allow their advocates to interrupt and derail the conversations round my dinner table or in my blog. And FWIW I do think that climate change denialism (no global warming or if there is, no human agency) is now outside the range of civilised discourse: most of its advocatea are no longer arguing in good faith but self-recruited propagandists for a pathological and dangerous fringe ideology. Some people (like Tim Lambert) enjoy putting down cranks, I don’t. I reckon my trial comments policy has in fact raised the level of the thread, as quite a few reasonable people are glad of a space where their views won’t be lost in stale polemic.

  14. MobiusKlein says:

    How much value is there to a policy that moves from a 2°-8° world to a 1.5°-6° increase world. How much better is a 1.5°-3° increase world?
    I’m not sure there is a viable path to a 1.5° world that does not involve nuking coal power plants. I fear the carbon pushers will win the day by sheer inertia. (And please prove my cynicism wrong.)

  15. Barry says:

    TomF: “Any educated information I may have on that issue would be wasted here. Rather, my point was, and continues to be, that I found your sweeping disapproval and dismissal of anyone who would dare disagree with you to be pretty ironic for someone who claims to be of the more “tolerant” and “open-minded” persuasion.”

    Take your ‘educated information’ to RealClimate; once you’ve kicked their *sses, come back here and link to your victories.

    Shouldn’t take long, now, should it?