Embracing (Climate) Uncertainty

In the public sphere, where the various running debates on climate science and climate policy are most fiercely fought, the uncertainty factor is often downplayed or glossed over. Subsequently, it gets little attention in the media.

And that’s a shame, because in the decision-making sphere, the uncertainty factor is very much on the minds of everyone from water managers in Denver to national security planners in the Pentagon. And they have to make some hard decisions, regardless of what happens with the energy/climate bill in Congress or treaty negotiations on the international stage. That’s because for both water managers and security planners (even though they work in very different arenas), there are huge unknowns with respect to the projected localized impacts of global warming.

So I think it’s notable that Gavin Schmidt highlights this issue over at Real Climate, with a new post that draws attention to this paper, called, “Options for Improving Climate Modeling to Assist Water Utility Planning for Climate Change.” Despite the wonky title, the paper is well worth reading for anyone interested in how the uncertainty factor is being grappled with at the ground level in water management circles. It’s also notable that Gavin chose to spotlight this clever play on a famous phrase, which is taken from that paper:

Grant us”¦
The ability to reduce the uncertainties we can;
The willingness to work with the uncertainties we cannot;
And the scientific knowledge to know the difference.

As I pointed out last week, it seems that national security experts are mouthing that same prayer. This is a good place for me to mention a recent paper that I’ve been meaning to discuss. It’s called, “Lost in Translation: Closing the Gap Between National Security Policy and Climate Science.” Here’s one passage that jumped out at me:

For the past 20 years, scientists have been content to ask simply whether most of the observed warming was caused by human activities. But is the percentage closer to 51 percent or to 99 percent? This question has not generated a great deal of discussion within the scientific community, perhaps because it is not critical to further progress in understanding the climate system. In the policy arena, however, this question is asked often and largely goes unanswered.

That brings me to one of the arguments that climate researcher Judith Curry has been making of late on this blog, which might best be summarized here:

we need to do a much better job of characterizing, assessing, and reasoning about uncertainty regarding this extremely complex system of climate science and the climate-science policy interface.

In other recent threads at this site, Judith has elaborated on where some of the key uncertainty lies and why it is necessary to engage forthrightly about it.

During some of this discussion, Judith laid out where she thinks people engaged in the climate debate line up on the uncertainty spectrum. Below is a slight modification of the categories she first mentioned here.


Regarding uncertainty, my take is that there are 5 different ways of dealing with it (an adaptation of Van der Sluijs):

1. Uncertainty denier ““ pretend it doesn’t exist, or underestimate it or try to keep the discussion away from the topic. Uncertainty denying or the “never admit error” strategy can be motivated by a political agenda or because of fear that uncertain science will be judged as poor science by the outside world.

2. Uncertainty reducer ““  “reduce the uncertainty” mantra, of the early IPCC reports and also the US CCSP Strategic Plan. A laudable goal, but reducing uncertainty will prove to be vain in the long run: for each uncertainty that science reduces, several new ones will pop up due to unforeseen complexities. Further there is a class of uncertainties (ontic or aleatory uncertainties) that are fundamentally not reducible.

3. Uncertainty simplifier ““ fit complex uncertainties into nice categories.  The subjective Bayesian approach of Moss and Schneider (expert judgment) fits here, this has been the uncertainty recipe for the IPCC 3rd and 4th assessment reports, e.g. the likely, very likely stuff. Uncertainty simplifiers, while they definitely pay attention to uncertainty, they tend to be inadvertent uncertainty minimizers.

4. Uncertainty detectives ““  well, all scientists should work hard to understand, represent, and reason about uncertainty (climate scientists generally don’t do a great job at this). The conflict is when political opponents seize on this uncertainty as an excuse for inaction.

5. Uncertainty assimilator ““ include uncertainty information in rational decision support systems and policies.

We need to get to #5.  This is not simple, since climate assessment (e.g. IPCC) is stuck in #3 right now.  My efforts to move it to #4 are being met with apparent calls to go back to #1.  We have to work our way through #4 before we get to #5.  Will #4 result in blood on the floor and more polarization?  On the contrary, it may actually enable the two sides of scientists to become less polarized, which will take some of the steam out of the political uncertainty embracers. Moving forward in the science requires #4#4 will also improve the policy and decision making process.


If various decision-makers (such as those water managers and security experts) are grasping for a handle on the uncertainties associated with climate change, then maybe it’s only a matter of time before our fractious public debates pivot on the collaboration between (#4) uncertainty detectives and (#5) uncertainty assimilators.

But to even get to that point might require a constant invocation of that Uncertainty Prayer spotlighted at Real Climate.

43 Responses to “Embracing (Climate) Uncertainty”

  1. Chris S. says:

    Keith I feel you may have missed one:
    #6 Uncertainty XXX (I’m not sure of the best way to term it): Those that claim that no action is possible given the current level of uncertainty. Perhaps this category is less prevalent in the scientific/decision making realms but it is one that is frquently seen in the blogosphere. It is also, evidently not a viable way to deal with it, but certain commentators seem to feel that it is the best way, at least until there is less uncertainty…

  2. Keith Kloor says:

    Chris S:

    Well, to start, these are Judith’s categories, not mine, though they seem about right to me. Indirectly, she addresses your point in #4.

  3. Andy says:

    Policymakers also have to address the uncertainty of whether a policy will work.  That is particularly relevant to carbon reduction.  How much must carbon output be reduced by what method in what timeframe at what politically acceptable cost?

  4. Tom Fuller says:

    There are people who do ‘what if’ scenarios dealing with uncertainty for a living.
    A policy guideline would start with the null hypothesis: What actions are beneficial to our lives, economies and the environment absent any harmful effects from greenhouse gases?
    The answer to that would be to improve energy efficiency and distribution for cost savings and pollution reduction, at a minimum.  It would also include adding intelligence to our electrical distribution network as it is upgraded (which needs to happen over the short term, as much of it is past its sell by date).  It would also include policy changes such as allowing aircraft to adopt direct descent, air traffic control improvements to reduce stacking over airports, and the reduction of no fly areas adopted during the Cold War for military reasons.
    You would then add in incrementally the impacts forecast for varying levels of temperature / sea level rise and put alongside mitigation and avoidance costs.  You would consider rebalancing fuel subsidies away from fossil fuels and towards renewables, harsher building codes to get structures away from threatened coastlines, research subsidies on more resilient crops, accepting the GMO form these would take, etc.
    You would also have signposts delineating when it would be appropriate to move from best case scenarios towards more problematic ones, the canaries in the coal mine that reasonable people on both sides of policy issues could agree on. That is, if they could agree.
    It could end up looking like a simple table in Word or Excel, with some gray areas for things that needed more robust political support than might be available.
    But I find it strange that this type of exercise, which happens frequently in the private sector, doesn’t appear to have been attempted on the ‘greatest challenge of our time.’ Or if it has that I haven’t seen it.

  5. Tom Fuller says:

    I amplify a bit on #4 here: http://www.examiner.com/examiner/x-9111-Environmental-Policy-Examiner~y2010m6d30-Global-warming-Policy-options-that-make-sense
    Don’t want to steal readers away from our host, but I wouldn’t mind some reaction.

  6. Bill Stoltzfus says:

    It seems from reading the 2 reports that what they want most is reduction in the estimate range as opposed to the uncertainty associated with the estimate.  An 80% chance of 50-60 cm of sea level rise would help them a lot more than a 99.9% chance of 20-90 cm SLR. 

    Right now I think there are too many options for how to mitigate/adapt/etc. because the impact ranges are so large.  Each of the options ‘could’ work if implemented in a particular way, but there is only enough money to choose one option, and from there we usually get gridlock. 

    The individual decision makers for the regional systems may have an easier time choosing and implementing solutions than countries as a whole, though–democratic bodies don’t usually lend themselves to quick, decisive action.

  7. Barry Woods says:

    In a very late submissionto the Muir Russell enquiry.  The following scientists seem very FAR from uncertain:

    Mann, Schmidt, Wigley, Trenbeth, Santer, Oppenheimer, Schneider,
    Huges, Bardley

    extract from submission:

    “As you are well aware, contrarians will seize on anything ““ from a snowstorm in Washington D.C. to any minor error in a thousand-page IPCC report ““ as “proof” that the entire body of scientific knowledge on climate change is a hoax.”

    To ensure that your findings do not fuel dangerous misconceptions, we feel it should be made absolutely clear ““ as every serious review of the stolen emails has already confirmed ““ that nothing in the emails calls into question the scientific consensus on human-caused climate change.”

    I think everyone here would acknowledge the problems at the IPCC, go beyond that of a minor (glaciers) error in a 1000 page report….
    Another Extract:

    Laboring under constant, intrusive oversight by hostile groups who harass scientists and interfere with their ability to carry out their research is another matter entirely. If CRU scientists felt besieged, it’s because they were ““ including, we now know, illegal spying on their private communications. Their emails and actions must be considered in this light.”

    Phil Jones would not share data a long time ago..
    They were planning on how to evade FOI requests, BEFORE, EVER receiving one, as evidence in their own emails…”

    Even Fred Pearce – The Climate files – hinks they were leaked, or even just a misplaced zip file containing, info prepared for an FOI release.

    This submission, is in my mind, trying to sway the enquiry, I hope that there words are looked at against the evidence to the contrary….

    The scientists, above EITHER:

    1)  believe every word that they are saying, ie the big oil/fossil fuel denial machine is out to get them (ie As Sir John Houghton, told me last month)

    2) Or it is a deeply cynical attempt to misdirect the enquiry..

    Personally, I believe it is 1), far from uncertainty, the scientists are so deeply certain, that they seem to modify events in their own minds to fit their own world view..

    I had no doubts when I spoke to Sir John Houghton that his words were sincere.  (link to his presentaion) in another thread – Keith Kloor has itas well)

    Uncertainty does not seem ”possible’ in their world view, it is a ‘risk’ to be avoided.

    Direct Link to the ‘teams’ submission to Muir Russell:


    Lots of comments about it allready

    Whatever Judiths’ and other efforts, this total certainty need to be continually questioned.

    Full submission

  8. Judith Curry says:

    I think Chris S #1 has a point, i did leave something out.  This has to do with making bad decisions in the face of uncertainty.  The “delayer” under uncertainty that Chris mentions is one.
    But on the other  extreme, there is an uncertainty “alarmist.”   Seems weird, but it is starting to pop up.  The first time I came across this was in the Discover Magazine interview with Mike Mann:
    “So when you take uncertainty into account, it actually leads to the decision that we should take action more quickly.”

    This statement seemed absurd to me, I assumed it was some sort of mistake.  Now I am hearing this more often, including Michael Tobis mentioning this on a recent thread.  What could possibly be the rationale for a statement like this.  The only thing I can think of is that it is a perversion of the precautionary principle.  So if a model comes up with an even scarier scenario as a new uncertainty is introduced into the models, then the burden of proof is on those who don’t want to act.

    Some criticisms from the wikipedia:

    “When applying this principle, it is recommended that society establish a minimal threshold of scientific certainty or plausibility before undertaking precautions. Normally, no minimal threshold of plausibility is specified as a “triggering” condition, so that any indication that a proposed product or activity might harm health or the environment is sufficient to invoke the principle. Often the only precaution taken is a ban on the product or activity.”

    “Critics of the principle argue that it is impractical, since every implementation of a technology carries some risk of negative consequences.”

  9. Judith Curry says:

    Barry #7:   The total certainty (or “fact”) they refer to is of the existence of the consensus.  Within the consensus statement (IPCC report) they do acknowledge uncertainty using the “simplifier” approach that drastically underestimates the actual uncertainty.
    The logical fallacies in this are obvious to me, anyways.  So the consensus group is less worried about me raising issues of uncertainty than my actually jumping off the consensus bus and joining the “very likely disgusted” group.

  10. Tim Lambert says:

    Judith, the reason why more uncertainty strenghtens the case for action has nothing to do with the precautionary principle. Martin Weitzman makes the case  here.  The basic idea is that costs do not depend linearly on temperature increases — the increase is more than linear, so greater uncertainty (“fatter tails” in the pdf) increases the expected cost.

  11. SimonH says:

    I can’t find reference to effectiveness uncertainties, unless I’m blind. Prescriptive or goal-oriented policy decisions also need to have solid analysis of the uncertainties of effect of any proposed actions. These also need assessing prior to action – in matters of climate, whether it be CO2 mitigation or investment in a particular renewable energy supply.
    You’ve fallen out of your plane and are now in the middle of a desert. You’ve determined that it is “very likely” that you will not be rescued before your water supply runs out, so you determine that a policy of action is required – to start walking. However, the choice of direction you should take has uncertainties attached and assessing those uncertainties is also a prerequisite to action.
    But the combination of uncertainties, both situation and prescription, amounts to the presence of a significantly greater cumulative uncertainty attached to any ultimately determined policy action.
    Or are we just talking about “action” being “move to consider policy”?

  12. willard says:

    Tim Lambert,

    Here is the author’s interpretation of the first theorem he discusses:

    > The Dismal Theorem makes a general point but also has a particular application to the
    economics of climate change. The general point is that Theorem 1 embodies a very strong
    form of a generalized precautionary principle for situations of potentially unlimited down-side exposure.

    Would you care to explain the first sentence of your comment to Judith in #10?

  13. Keith Kloor says:


    Tim Lambert raises an argument laid out nicely by Paul Krugman in his recent NYT magazine feature. Here’s the relevant passage referencing Weitzman:

    Finally and most important is the matter of uncertainty. We’re uncertain about the magnitude of climate change, which is inevitable, because we’re talking about reaching levels of carbon dioxide in the atmosphere not seen in millions of years. The recent doubling of many modelers’ predictions for 2100 is itself an illustration of the scope of that uncertainty; who knows what revisions may occur in the years ahead. Beyond that, nobody really knows how much damage would result from temperature rises of the kind now considered likely.

    You might think that this uncertainty weakens the case for action, but it actually strengthens it. As Harvard’s Martin Weitzman has argued in several influential papers, if there is a significant chance of utter catastrophe, that chance “” rather than what is most likely to happen “” should dominate cost-benefit calculations. And utter catastrophe does look like a realistic possibility, even if it is not the most likely outcome.

    Weitzman argues “” and I agree “” that this risk of catastrophe, rather than the details of cost-benefit calculations, makes the most powerful case for strong climate policy. Current projections of global warming in the absence of action are just too close to the kinds of numbers associated with doomsday scenarios. It would be irresponsible “” it’s tempting to say criminally irresponsible “” not to step back from what could all too easily turn out to be the edge of a cliff.

    Still that leaves a big debate about the pace of action.

    Do note that Krugman frames this line of reasoning around “in the absence of action,” which few people are arguing.  The big debate, indeed, is as he says about “the pace of action” (and I would also say what kind of action).

  14. Ron Broberg says:

    Yup. The broader the range of uncertainty, the more likely that raising CO2 will do nothing … and the more likely that it will include catastrophic scenarios.
    Those who hope that *simply* emphasizing uncertainty will reduce the need to react to CO2 emissions do so in vain – they also need to constrain uncertainty to a narrow band of possibilities that (hopefully) exclude catastrophic scenarios.

  15. Judith Curry says:

    Tim #10, thanks for bringing up Weitzman’s paper.  I agree that it is certainly important to look at the outliers or tail, I made this point in my op-ed response to Lomborg.  I agree with willard that the precautionary principle underlies alot of this analysis.
    The problem with Weitzman’s analysis is how far out on the tail you actually go.  First, he goes way beyond the PDF associated with the IPCC models.  But that is ok, since most statisticians would argue that the level of uncertainty is way to high and the ensemble sample too small  for a pdf of the  IPCC climate model runs to make sense.
    In conditions of deep uncertainty (e.g. the projections of climate ca 2100) as opposed to risk, evidence theory, possibility theory, and plausibility theory provide better guidance.  E.g.  a possibility distribution distinguishes what is plausible versus the normal course of things versus surprising versus impossible, without the pretense of a pdf.

    But back to how you deal with catastrophic possibilities or the plausible worst case scenario.   I really like this discussion of Weitzman’s paper, here is one quote:.

    “So then, how should we confront this lack of certainty in our decision logic? At some intuitive level, it is clear that rational doubt about our probability distribution of forecasts for climate change over a century should be greater than our doubt our forecasts for whether we will get very close to 500 heads if we flip a fair quarter 1,000 times. This is true uncertainty, rather than mere risk, and ought to be incorporated into our decision somehow. But if we can’t translate this doubt into an alternative probability distribution that we should accept as our best available estimate, and if we can’t simply accept “whatever it takes” as a rational decision logic for determining emissions limits, then how can we use this intuition to weigh the uncertainty-based fears of climate change damage rationally? The only way I can think of is to attempt to find other risks that we believe present potential unquantifiable dangers that are of intuitively comparable realism and severity to that of outside-of-distribution climate change, and compare our economic expenditure against each.”

  16. Judith Curry says:

    one other point, weitzman’s paper would certainly motivate alarmism as a strategy for implementing policy.  Come up with a scarier scenario, way out there on the tail, and the support for a precautionary policy should increase.

  17. Keith Kloor says:

    All: that discussion of Weitzman’s paper that Judith (#15) references is in a much more readable format here.

  18. Bishop Hill says:

    We should be investing a great deal of money in protecting ourselves against a possible asteroid strike.

  19. Keith Kloor says:

    I’m not sure if the Bishop is being wry or serious and thus in agreement with Ronald Bailey’s position here.

    Back to the topic of discussion: Bailey has also weighed in on Weitzman here.

  20. JohnB says:

    Firstly, “Hi Tim”. Nice to see another Aussie, even if he is from a State that can’t play Rugby. 😉

    I have two problems with using the “Precautionary Principle” as a call for action.
    1. As a salesman for years, I’ve used it far too often myself. In it’s simplest form “You could get hit by a bus tomorrow, so you should buy the Life Insurance tonight.”

    2. In the face of uncertainty, it is difficult to decide exactly what action to take. “Reduce CO2”, okay but how?

    Tim, you know that the party currently in Canberra have a very poor record on dams, so hydro is out. Labour would positively froth at the mouth if you use the “N” word. (Not to mention Bob Browns fit of apopolexy)

    Let’s try wind. Fine, but how many turbines will we need? More to the point, what if the Pielkes are close to the mark on “Land use change” as a major forcing?

    So we build wads of wind farms, (which any way you look at it will mean some major deforestation) wean ourselves off CO2 only to find that while we have reduced the CO2 forcing, we have increased the Land Use forcing and have got absolutely nowhere.

    Lots of spent money, lots of effort and zero effective result. It’s not that uncertainty says to take no action, it’s that uncertainty means we can’t logically and rationally decide which action to take. Taking an action, any old action could have very dire consequences in the long term. Are we willing to risk that just so that we can be seen as “doing something”.

    We did that by removing incandescent bulbs from the shops. We did something. Of course, the poorest in Australian society, those who can least afford it, now pay $4+ for a light bulb instead of 60 cents. But we “did something”.

    Can we play the “Do something, anything” game with the Climate?

  21. Ron Broberg says:

    Curry: <em>weitzman’s paper would certainly motivate alarmism as a strategy for implementing policy</em>
    We already have Fuller’s definition of ‘catastrophic‘ as ‘more dire than the IPCC.’ (my phrasing) Dr. Curry – do you consider the IPCC projections to be alarmist? Would advocating the use of IPCC projections as a basis for policy be alarmism?

  22. Judith Curry says:

    An important paragraph in Bailey’s article, which refers to issue raised by James Annan:
    “On the crucial issue of climate sensitivity, climate researcher James Annan at Japan’s Frontier Research Center for Global Change asks if the uncertainties Weitzman talks about aren’t just a reflection of our current ignorance, rather than some inherent feature in the climate system itself. Isn’t climate sensitivity an imprecisely known constant about which climate scientists can learn more, eventually converging toward a point estimate? If climate sensitivity turned out to be low, that would mean that future climate disasters were less likely. So instead of spending vast sums of money to cut carbon dioxide emissions, a better strategy would be fund research that aims to more closely specify climate sensitivity.”

    There is an issue of here of confusing epistemic and ontic (aleatory) uncertainty.  The epistemic uncertainty can in principle be reduced, e.g. by improved theories, better data, better models.  The ontic uncertainty (irreducible) in this instance relates to the fundamental chaotic nature of the climate system (this is why ensembles of simulations are done using the same model).   So if you consider the climateprediction.net exercise, the part where they vary model parameters is targeted at the epistemic uncertainty, whereas the variation of initial conditions is targeted at the ontic uncertainty.

    If all this sounds arcane, well it is, but it is important. Too often, the two kinds of uncertainties are confused or the distinction is ignored, and that can get us into trouble.  For example, specifically with respect to the sensitivity issue discussed by James Annan.  If model parameters and parameterizations are tuned by comparing a simulation with observations, the tuning is addressing both the epistemic and ontic uncertainties; this is why large ensembles are needed to optimize the tuning of model parameterizations against observations.  Otherwise you are likely to end up with a model that is too stable. which is not what is desired for a distribution of sensitivities.

  23. Judith Curry says:

    Ron #21, re IPCC WG1, i do not view this as alarmist.  I view much of what is in IPCC WG2 as alarmist.
    Re Weitzmann’s scenarios, he goes well beyond anything that the IPCC says has any likelihood at all.

  24. Bill Stoltzfus says:

    I have heard the catastrophe argument before, usually in the form of, “If there’s even a 1% chance of X, you buy insurance or you don’t do it.”  One person I read a lot of is Bruce Schneier, an expert on security, risk, and their interaction with computer systems.  Schneier believes that humans are very bad at assessing risk when it comes to low-probability/high-impact scenarios.  His essays here on the psychology of security are very helpful, and the first one, “Worst-Case Thinking Makes Us Nuts, Not Safe” discusses not only the precautionary principle but also Rumsfeld’s “unknown unknowns” in relation to this kind of thinking.
    On a related note, Gavin’s comment here (4th paragraph) about the GISS model sensitivity declining from the 1990’s to the present should be considered.  IIRC, all or most of the models now show a lower sensitivity than back in the 90’s, which seems to indicate that the possibility of catastrophic warming gets less the more we know about the climate.

  25. Andy says:

    As JohnB alludes, it’s not simply a binary question of action vs no action in the face of uncertainty or a non-trivial likelihood for catastrophe (which itself is a debatable point).  It’s really a question of how many resources to devote, where to put them, for how long – all of which will require sacrifice in other areas.  You can’t simply declare, which Weitzman seems to, that the possibility for a catastrophic outcome should essentially be treated by policymakers as if the event is probable.  Well, one can make such a declaration, but policymakers are unlikely to be convinced.

  26. SimonH says:

    .. if there’s a one-in-a-million chance of something happening… but Terry Pratchett correctly observes that one-in-a-million chances happen 9 times out of 10. 😉
    The precautionary principle is the primary domain of religious doctrines and life insurance corporations. Many who reject religion in modern westernised secular societies do so specifically because they understand – rightly or wrongly – that science operates on principles of proof and certainties; laws of physics, for example, distinct from religious doctrines pressing unproven and unprovable articles of faith. Faith, of course, is belief in the absence of absolute proof. Popular trust in the AGW meme hangs ultimately on the concealment of its uncertainties from the expanding body of purposefully secular thinkers.
    Scientific gnosticism – newly, explicitly but poorly parametrised by Prall et al in their PNAS paper – is being regarded by many sceptics (contextually speaking, agnostics) and deniers (heretics) as further evidence of the developing religion of climate science, where only the wisest witch doctors can be trusted to properly interpret the signs science – a science which demands penance and self flagellation based in no small part on predictions made by casting runes running computer models, and which seeks to find the path to the future in the noise of the dendrochronology – traditionally the domain of tarot card readers.

  27. SimonH says:

    Meh! My strikeouts got removed – signs vs science, casting runes vs running computer models.

  28. Barry Woods says:

    Strong stuff from Climate Audit, more uncertainty ref reconstructions:

    “I heard from a reliable source that, during the Oxburgh interviews, Phil Jones admitted that it was probably impossible to do the 1000-year temperature reconstructions with any accuracy.”


    I wonder where this will lead, Steve Mcintyre must be very, VERY sure to say it.

    Give that the ‘hockey stick’ was one of the key pieces of evidence, used to promote the ‘certainty’ of the settled science. It should be interesting..

    Even Michael Mann being uncertain about ‘the hockey stick’ recently on the BBC.

    “However, speaking to the BBC recently, Prof Mann, a climatologist at Pennsylvania State University, said he had always made clear there were “uncertainties” in his work.
    “I always thought it was somewhat misplaced to make it a central icon of the climate change debate,” he said.”

  29. Michael Larkin says:

    Climate, so I have been led to believe, is always changing regardless of any anthropogenic influence there might be. The null hypothesis, as I understand it, is that any changes currently in progress are overwhelmingly dominated by natural influences over which we have little or no control, and which aren’t necessarily well understood.
    I don’t know if that is so, but if it is excluded from consideration, then it seems to me there is a claim of no uncertainty about one thing: that any current changes are significantly, if not predominantly, affected by anthropogenic influences.
    I think this is a key point for an agnostic like me. Why is it taken as proven that any current climate change is at least significantly anthropogenic, with the main culprit being CO2? Has the null been disproved? If it has, and this is a genuine request, please let me know and if possible where to check. As far as I can see, if it has, then that would imply that we already know *all* the natural influences and have discarded their potential to predominate in recent times, based on unassailable data collected in scientific studies.
    I have so far not been convinced by the evidence about anthropogenic CO2. It may be a major culprit, of course, but I don’t *know* either way, and FWIW, I suspect no one on the planet does, however passionately they feel for or against. If my suspicion is correct, *doing* something seems a bit previous. And if the null is correct, then there’s sweet FA we *can* do about it.
    One day, whilst out in the garden, Joe notices that his neighbour, Fred, is casting pieces of bread on his lawn.”Why are you doing that?”
    “Oh, it’s to keep the tigers away.”
    “But there are no tigers in these parts!” protests Joe.
    “I know. Effective, isn’t it?”
    It wouldn’t surprise me if proponents on either side of the fence see parallels in that old saw with those on the other. Besides being a mere joke (but heaven knows, we sorely need some humour and humanity in the debate), it helps me keep detached from either side. With the benefit of hindsight, I can think of occasions when I have scoffed at the likes of Fred when it turned out he was right – bread did actually keep away the tigers; and of others when he was wrong, of course. But the point is, *at the time*, I most frequently didn’t know the truth of the matter. At the age of 60, I suppose I have finally learnt to cultivate a little patience and suspend judgement.
    Our species has always had a tendency to think that at any particular moment, it understands the current situation and how best to deal with it. However, seeing as we are Homo urgensis, we’ve made countless cock-ups when we acted precipitously on convictions we took as certainties that turned out to be crocks.
    Come on now, hand on heart, can we say we *know* what things will be like in five, ten, fifty, a hundred years from now? Even when we know there are things we don’t know, not to mention, very probably, things we don’t know we don’t know? Can we go ahead with policies that could have who-knows-what unintended consequences? I hear people muttering about how we’ve been 20 years discussing this issue, and it’s high time we made a move, but what’s 20 years? A blink of an eye in relation to climate issues, and it matters that recently the accuracy of data has been brought into question. Cynics may suspect this is the real source of the increasing urgency.
    I think we should decouple a rarely openly stated issue that permeates environmentalism: the feeling that how we live in the West is morally wrong. We are too materialistic, and have lost our way – spiritually, if that word dare be uttered. I personally have some sympathy with that view. But if it’s so, then it’s a moral and not a scientific question, and I think we should let morality explicitly drive it; and there’s no reason we couldn’t start a discussion about that now without climate issues in particular, or environmental ones in general, being a consideration, though there could be knock-on effects. That would be a direct and honest approach.
    There’s another tale with hairs on about a ne’er-do-well who crossed the border between two countries. One particular border guard, who knew him well, suspected he was smuggling, but when he searched the panniers of his bicycle, couldn’t find anything. Years later, when they met on neutral territory, the guard said him,”Come on, mate. I’m retired now and can do you no harm. Tell me what you were smuggling that time.”
    The rogue smiled and said, “The bicycle.”
    Morality, these days, is often frowned upon. We seem to have to conflate it with other issues, to smuggle it in rather dishonestly, to lay a guilt trip on people. And they may ask themselves, what is this? Science, or religion? I say, decouple the morality, and stick with the science. Of course, if one does that, then one necessarily has to be ruthlessly and clinically up front with the uncertainties. But what the hell, if there *are* uncertainties, why not?
    The biggest uncertainty, the elephant in the room, may be the null. “It must be CO2 because what else could it be?” – maybe it’s so, but forgive me if I’m not slavering over the prospect of possibly ill-considered and hasty action that in due course could turn out to have been totally over the top and responsible for an increase, rather than a decrease, in human misery.
    A man has an ardent female admirer, who wants him to propose. “If I fell in the river, would you dive in and save me?” she asks, fluttering her eyelids.
    “It depends;” he says, “can you swim?”
    Rescuing damsels in distress can be a risky business. What makes anyone absolutely sure that mother earth can’t swim like a mermaid? Have we truly investigated the question, or have we romantically assumed it’s a Dulcinea to our Don Quixote? Talking of tilting at windmills… but on second thoughts, that’s a separate debate.

  30. It’s the combination of uncertainty and knowing at least something about a credible threat that is at issue. Combine that with large inertia in the system, and we really start to have a tricky situation.

    If the uncertainty approaches ignorance and the chance of something happening approaches zero (as with Bishop Hill’s example of an asteroid strike), then of course nobody sane would advocate putting tons of effort and money into protecting ourselves.

    But if a particular threat is deemed credible, though uncertain, then the situation is entirely different.
    When driving in a snowstorm, most would deem it prudent to reduce speed, because of the enhanced uncertainty (as a consequence of reduced visibility).
    If there is no hint of a threat whatsoever, there is no need to prevent anything. OTOH, if one lets the mere presence of uncertainty prevent oneself to deal with the matter at hand, one would never leave one’s house in the morning.
    Michael Tobis wrote (and it’s a frequent theme on his blog, which those interested in the topic of uncertainty in climate science would benefit from reading):

    “if you believe that there is insufficient knowledge to project the evolution of the system for a century even crudely, I presume you would be very wary of changing its bulk radiative properties, right? If I were as contemptuous about climate science as you I’d be far more terrified of any global changes in concentration of radiatively active components than I am now.”

  31. Re: Bishop Hill et al., asteroid strikes
    “We should be investing a great deal of money in protecting ourselves against a possible asteroid strike.” — the Bishop
    Actually, not that much, though maybe 1000x more than now. One of the refs I read here a couple days ago said US spends about $1MM/yr, now, should spend around $1 billion per annum.
    The pertinence here is that a civilization-killer rock/iceball is inevitable — but (presently) we are helpless, even if one should be detected early. And a long-period comet on a collision course with Earth is (almost) undetectable until it’s a few months out — by present or any reasonably-likely near-future technology. It’s a non-negligible risk, and easily calculable — for a Western citizen, an order of magnitude more than the risk of dying in  an airliner crash, ims.
    So we need a defense system. The Hollywood H-bomb missile won’t work — it would convert a cannon-ball to a shotgun-blast, which might be worse.
    If it’s an asteroid, and detected early, a low-thrust ion engine attached to the asteroid could change its orbit enough to get us out of harm’s way. I think NASA has some plans to try this idea out.  The long-period comet is a lot tougher to deal with, especially if detection comes late (eg, for a Tunguska-size object, which is plenty big enough for multi-million fatalities, if it were to hit near a major city. The late Eugene Shoemaker suggested using a steam-generator to slow such a fragile object (visualize a loose mass of crushed ice). If there’s any testing of this idea scheduled, I don’t know of it.
    The point is, this is a quantifiable risk, and we can calculate cost-benefit ratios. Yet we spend 1/1000 of the amount that would give us reasonable protection against an event that will happen sometime (and a small fraction of what Western govts waste on crack-brain schemes every year).  The political implications for the likely success “precautionary principle” CAGW arguments are left to the reader.
    Cheers — Pete Tillman
    Consulting Geologist, Arizona and New Mexico (USA), with a long-time interest in large meteorite-strikes — I live about 90 minutes from Arizona’s Meteor Crater.

  32. Re #24, Bill Stoltzfus
    Thanks for linking the interesting  Bruce Schneier essay. “”My nightmare scenario is that people keep talking about their nightmare scenarios.” Indeed.
    Re: GISS model sensitivity declining from the 1990’s to the present: you’ve touched on a point that is one reason why many geologists find the CAGW catastrophist arguments laughably absurd. If the CO2 sensitivity mumbers were anywhere near the high end of the IPCC range, we wouldn’t be here to argue about it, because we’d be Venus. So, folks, it hasn’t happened in the past, and it won’t happen now. End of story. I’ll confidently bet any CAGW proponent $$LARGESUM that the sensitivity will ultimately be determined to be that contributed solely by CO2, or somewhat less. Positive-feedback systems, as all AGW atmospheric models use,  are inherently unstable, and our climate has been life-friendly for at least 3.5 billion years now — through catastrophic events that make a full-scale thermonuclear war look like popcorn. 
    Peter D. Tillman

  33. JohnB says:

    I missed that link the first time around. The essay beautifully encapsulates why I have such a strong gut reaction to the “Precautionary Principle”. It would be interesting to see someone try and refute the logic.

    Peter, I take it you also have been following the work of the Holocene Impact Working Group? Very interesting and not a little scary.

  34. kdk33 says:

    Bart (30)

    I’m surprised to learn that an appeal to ignorance is a frequent them on Michael’s site.  If Michael believes CO2 emmissions are dangerous, he is free to offer supporting evidence.  Appealing to a lack of understanding (ignorance) to bolster his position is just silly.

  35. #30,   Bart Verheggen
    #33, John B.
    The HIWG site is down at the moment, but a bit of Googling turned up some interesting new work that I wasn’t aware of:
    Burkle Crater, http://www.sandiegoaccountantsguide.com/library/Burckle-crater.php, is from an impact ca. 2807 BC, deep in the Indian Ocean. It generated truly enormous tsunamis, evidence for which is preserved in giant sandy chevron-shaped structures on beaches around the impact point, http://geology.com/news/images/madagascar-chevrons-usgs.jpg
    http://geology.com/news/labels/Oceanography.html (ccrool down to  “Chevron Structures Evidence of Frequent Meteor Impacts.”
    Another large impact ca. 12,900 yrs BP may have caused the puzzling, sudden  Younger Dryas cooling as we were emerging from the last Ice Age, and the mystifying megafaunal extinctions in the Americas, that are often (and implausibly) ascribed to overhunting by humans. http://www.pnas.org/content/104/41/16016.abstract
    So it appears that there have been at leas three major impacts in the last 13,000 years ago: Tunguska in 1908 was the third. This is an order of magnitude more than the current NASA model, and strongly suggests we’d best get the lead out. NASA estimates that, on average, a Tunguska-sized asteroid will enter Earth’s atmosphere once every 300 years, with an impact equivalent to (roughly) a 2-megaton H-bomb. Best not to be nearby then. http://science.nasa.gov/science-news/science-at-nasa/2008/30jun_tunguska/
    Cheers — Pete Tillman

  36. Keith, could you please look into blog software that allows editing, or at least previewing? And apologies to all: “ccrool” = SCROLL — etc etc.  AARGH!

  37. Peter Tilman,

    There are some people out there quite willing to bet on climate change, if you were to take a position of “no siognificant climate change”. See e.g. here. I hope you win!

  38. JohnB says:

    Peter, there is also chevron evidence on Groote Eylande in the Gulf of Carpentaria. There is more starting just north of Cairns and running all the way up the east coast of Cape York.

    I’ve been following the HIWG for a few years now and I’ve read a number of the papers involved. Dr. Masse also points to evidence in the not too distant past of a sky burst over South America. Legends tell of the land being shotgunned by meteorites over a large area.

    All in all, a very interesting area of research.

  39. #37 Bart Verheggen
    As you know, the climate is changing now, has changed (sometimes drastically) in the past, will change in the future. 
    My guess is that CO2 plays a smaller part in this than most climate scientists presently believe. It would be prudent to continue to study climate change, to encourage openness and sharing of research results, and to study adaptation options. Because the climate will change, whether or not people have much to do with it. And whether we’re ready — or not.
    Best regards, Peter D. Tillman

  40. Barry Woods says:

    Bart, if you are talking about the planets, natural processes that cause ‘climate change’ then I agree with you…

    If you are talking about, the additional co2 that man produces, on top of the natural co2, only, then I’m inclined to agree with 39#

  41. Well, then why not betting on it? See the link in my previous comment.

    Forest fires have always occurred naturally. Does that mean I cannot start a forerst fire? Wanna bet?

  42. Tom Fuller says:

    Well, last time I asked an honest question I got lambasted for being ignorant, but maybe things have quieted down enough on this thread for me to chance it.
    It would seem to me that the chances for a major strike on Earth from an extraplanetary object would reduce over time. Obviously not to zero, given the jostling and bumping around gravity provides to the junk in and near the solar system, but really, some stuff should fly away out of the solar system, some stuff has already hit various targets and done its damage, and the expansion of the universe should mean we are less likely to be hit by things wandering in from far off corners.
    Shouldn’t this be a diminishing risk?

  43. JohnB says:

    Tom, it is a diminishing risk over Geological time periods, but from our perspective the risk won’t change much over human history.

    Things wandering in to hit us isn’t the problem, we are a small target. However there is the problem of a wanderer doing damage in the Asteroid Belt and making some of them dangerous.

    One thing is certain. The probability that Earth will be hit by a dinosaur killer in the future is 1. It will happen, we just don’t know when.

    In 1994 we saw a string of 17 explosions rip across the surface of Jupiter, the impacts of Shoemaker Levy 9. Every one of those impacts was big enough to be a dinosaur killer if it had hit Earth.

    I’m a big supporter of Spaceguard. We have empirical proof that the killers are out there. We have seen in real time the destruction they represent. From our own history we can be pretty sure that we have been hit within recorded history.

    But it doesn’t take a dino killer to do great damage. Even a relatively mediocre meteorite in the right place could do immense damage. A water strike in the confined waters of the Mediterranean will cause untold damage and loss of life.

    The danger is very real, but if it makes you feel safer, the last I heard there was exactly 1 observatory in the entire Southern Hemisphere with time in their budget to look for “Earth Grazers”. There were 2, but the Australian Gov in a feat of monumental stupidity withdrew the funding about 4 years ago.

    Sleep well. 🙂

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