Tuesday, July 21, 2015

Judith Curry: Please save me from my belief in +10C of warming

Judith Curry has found a climate risk assessment report she likes, nay, loves. A red-letter day!
I haven’t found climate change risk assessments to be very satisfactory, for a range of reasons.  There is a new report out, entitled Climate Change: A Risk Assessment.  IMO  this is far and away the best risk assessment for AGW that I have seen. . .
Exciting! So what does the report say?
On a medium-high emissions pathway (RCP61), a rise of more than 4°C appears to be as likely as not by 2150. On the highest emissions pathway (RCP8.5), a rise of 7°C is a very low probability at the end of this century, but appears to become more likely than not during the course of the 22nd century. A rise of more than 10°C over the next few centuries cannot be ruled out.
So "far and away the best risk assessment for AGW" Curry has ever seen considers +7C "more likely than not" along a business-as-usual pathway and feels that +10C "cannot be ruled out." Since this would obviously be a catastrophic outcome, Dr Curry goes on to apologize to the scientists she has vilified and pledges to turn her blog over to serious scientific study of AGW and educating the public about these risks.

Kidding! Instead she closes her post with a frankly pathetic plea for someone to please find her a way out of the logical consequences of the report she's just endorsed:
The plausible worst case scenario is arguably where we should focus our efforts (both science and policy).  Working to falsify high values of RCP and sensitivity based on the background knowledge that we do have, should be a high priority.
So the takeaway is that the best risk assessment Dr Curry has ever seen considers +10C as a plausible worst case scenario. Said risk assessment recommends constructing policy around the plausible worst case scenario, and Curry agrees with that too. Her conclusion: I do not like where this science leads, so somebody find me some new science that leads us where I want to go (which is nowhere.)

If someone could find a way out of the logical consequences of her own beliefs and the basic science, she would be eternally grateful to you. In the meantime she will wait patiently and not draw any conclusions until the facts change (1).

1. This reminds me of how the early Zionists pledged their support for democracy -- but opposed democratic elections explicitly and violently during the days of the British Mandate on the grounds that they were heavily outnumbered by Palestinians and would lose them.

Since you can't ethnically cleanse the facts of radiative physics, the same strategy will probably not work for Judith.


  1. What are the policy implications of worst case (10C) vs most likely case (7C)? If we do manage to eliminate the worst case would this change the policy trajectory?


    1. The policy implicates of either +7C or +10C are difficult to quantify because such a world would be unprecedented as well as catastrophically bad for human welfare -- it's comparable to trying to specify the policy implications of global thermonuclear war.

      Growing food outside a greenhouse would be difficult or impossible over large regions of the earth. Significant areas of the planet would be lethal to human outside an air conditioned environment on hot days. All ice caps would be doomed, ensuring 65m of sea level rise, the only question being the timing of the loss.

  2. Huh. "Falsify" seems like odd language to use, for either a true scientific or policy inquiry.

    1. "Working to falsify high values of RCP and sensitivity based on the background knowledge that we do have, should be a high priority."

      It's as if she's directly addressing Nic Lewis.

    2. Unfortunately, I think what she said was exactly what she meant, Freudian slip though it may have been.

      I personally would not raise an objection if she said "I have a strong intuition that the upper bounds of warming are unrealistic, and I hope we're going to see science that supports my gut feeling."

      What I have a problem with is the reasoning which goes:

      1. I don't support action on global warming because the risk assessment is bad.
      2. Hey, this report does a great job of risk assessment, based on the state of climate science.
      3. The report implies we need to take strong action to mitigate global warming.


      4. We need some new climate science. I'll be waiting over here, patiently refusing to reexamine my beliefs, while you go find some.

      If she had said "Based on our best knowledge right now, we need to start mitigating climate change, although that calculation could change in the future if the upper bound of warming turns out to be less than we think" that would be rational and self-consistent. "Give me the best science and the best risk assessment, but not yet, Lord, not yet" is neither.

  3. JC should simply have said:

    "Working to further constrain the upper bounds of RCP and sensitivity based on the background knowledge that we do have, should be a high priority."

    Which makes perfect sense.

    But taking palaeoclimate evidence into account, that is unfortunately unlikely to get us off the hook.

  4. In the meantime she will wait patiently and not draw any conclusions until the facts change (1).

    I think she will actively try to make sure the world sees the maximum warming, whatever it may be (we don't know, it's uncertain).

  5. Judith is sounding like a hostage. Her intellect still tries to do science but she has fallen under the control of deep south conservatism which is holding her hostage. The result is cognitive dissonance and an indecipherable babbling sound flowing from her mouth.

    1. George...you nailed it. She is in the "land of denial" (I live in Atlanta as well....I should know). What she wants....is not going to happen. Of course, I am sure her "consulting practice" likely gets some $$$ from groups who love her bash Obama and climate scientists.

      She is having a BAD YEAR.....and it is getting worse.......

  6. In addition to what has already been said about Judith Curry's increasingly absurd intellectual contortions in her blog post I also note that she cites Dave Rutledge's work as evidence that RCP8.5 is not feasible. The problem is that Rutledge is a peak-fossil fuel man, who argues that there simply aren't enough fossil fuels to allow us to continue along RCP8.5. But if there are such serious constraints on FFs then we'd better be weaning ourselves off them anyway, so the BAU that Judith appears to think is so important for the well-being of humanity isn't a realistic option anyway.

    1. I was reading a little bit about this recently, and RCP 8.5 looks very realistic to me.

      RCP 8.5 involves a cumulative CO2 burden of 7,300 Gt.

      * 600 Gt have been omitted already.

      * 2,800-5,000 Gt are in our known reserves (an amount that can and has increased radically as technology and investment incentives change.)

      * 1,700 Gt are in the Northern permafrost, probably doomed under a BAU scenario. 2-3% is expected to emerge as methane, giving a CO2e on the century timescale of 2,550-3400 Gt.

      * There are large amounts of permafrost carbon in Antarctica, whose fate in a warmer world is unknown.

      * 2,000-10,000 Gt are in methyl hydrates, which Japan and China are already investigating the commercial extraction of.

      The airborne fraction over the coming centuries is a great unknown and even a relatively small increase could multiple the above numbers by x1.2 or x1.4.

      In summary, to think we can't get to 7,300 Gt of CO2e requires either a total lack of imagination or intensely motivated reasoning.

    2. Tracker, when you speak of reserves are you referring to resources that can be extracted at current prices or those that could be extracted if price were not a constraint? If it's the latter then I would agree with you. However, I would suggest that price is likely to be a pretty major constraint, as evidenced by the "peak fracking" now being seen in the U.S. despite the very large resources of tight oil and gas.

    3. The latter. While the economics are an important factor, the difficulty with classifying reserves according to how economically viable they are is that prices change over time, and in particular, market prices increase as scarcity increases. Economically viable reserves of oil, for example, are much greater when the oil price is $200/barrel vs $70/barrel.

      To some extent, at high prices consumers will substitute low- or carbon-free energy sources, or greater efficiency, but without collective political action, it is difficult to do that past a certain point. Solar and wind are intermittent, nuclear is unpopular, geothermal and tidal power are as yet miniscule in scale.

      While we focus a lot of our attention on cleaning up the electrical grid (very necessary attention too) electricity represents only 31% of US emissions. Transportation, industrial processes, heating and cooling and agriculture make up the rest. We have seen in the transportation sector, for example, that when prices rise people tend to grumble and pay them, rather than demand a vast new low-carbon transportation network.

      There is vast inertia within the economic system that in the past has made it easier to find and extract more fossil fuels, rather than transition to alternatives. I hope we overcome that inertia in the future, but RCP 8.5 is a realistic look at what may happen if we fail to.