Against Overstating or Understating the Case

The ethics of lying are easy; you're off the hook. You just make up whatever suits you and see what sticks.

The ethics of telling the truth are more complicated, especially if the purpose of your speech is to affect the opinions of the public.

Here's an interesting article on the Times of London that goes to this point.

Consider on the other hand this piece by Karl Wunsch from a couple of years back. I would consider the piece strictly speaking true but strikingly ineffective. He probably wanted to conclude with "you can never be 100% sure of anything" but noted that was a self-contradictory statement (What's the opposite of a tautology?) in that "never" expresses 100% certainty. So he backed off to "we have not as yet achieved 100% certainty about attribution", even though, well, you really can never get to 100% certainty in statistical attribution, can you? What he's left us with is a pile of doubt that Wunsch seems to have intended as a call to action!

Stop me if you've heard this one before.

So there are two managers who are balloonists for a hobby, and they get blown off track and a bit lost. So one of them yells at someone he sees down on the ground:

"Heyyy! Yes youuu! Wherre arre weeee?"

to which the reply comes back

"You're in a balloooooon!"

The balloonist shrugs and says ruefully to his companion "That must be an engineer. He responded exactly to my question, everything he said was precisely correct, and yet I am no better off than I was before."

Getting the right balance is not easy. Stephen Schneider got into terrible trouble (which has never entirely abated) with a sound bite that tried to make that point.

In the end, like an old person who is always too cold when the temperature is below 75 F and always too warm when it's above 70 F, the best you can do seems to be when both tendencies, toward precision and toward influence, are a little bit stressed.

All of which brings us back to Mamet's Law, the insight that started this blog in the first place.

"Law, politics and commerce are based on lies. That is, the premises giving rise to opposition are real, but the debate occurs not between these premises but between their proxy, substitute positions. The two parties to a legal dispute (as the opponents in an election) each select an essentially absurd position. "I did not kill my wife and Ron Goldman," "A rising tide raises all boats," "Tobacco does not cause cancer." Should one be able to support this position, such that it prevails over the nonsense of his opponent, he is awarded the decision. ...

"In these fibbing competitions, the party actually wronged, the party with an actual practicable program, or possessing an actually beneficial product, is at a severe disadvantage; he is stuck with a position he cannot abandon, and, thus, cannot engage his talents for elaboration, distraction, drama and subterfuge."

David Mamet in "Bambi vs Godzilla: Why art loses in Hollywood", Harper's, June 2005.

So the good news is that we are much smarter than the opposition. But the bad news is that we'd better be.

Dogs, SUV's, and Freaks

Ray's excellent takedown of Freakonomics in RealClimate has me shaking my head about people's abilities to discuss even the arithmetic, never mind the algebra or calculus or statistics, of global sustainability issues.

Of course, Ray is exactly right, not just in the substance, but in the fact that the substantial argument in question is elementary.

Now I am going to say something harsh, but I'm afraid it needs saying.

Anybody who writes on this stuff ought to be able to figure as much out on why the solar panel/albedo question is moot in a few minutes. I mean ANYBODY, not just economists, who writes on this stuff. To be clear that includes journalists. If you lack the skills to do the arithmetic, in my opinion you should not actually be writing on sustainability issues. Period. Also, if you missed the fact that any albedo effect is swamped by the greenhouse effect, if the question didn't instantly jump out at you on reading the claim, you should be asking yourself very seriously whether your grasp of climate change is sufficient to write about it.

The same holds for many other "consider a spherical cow" type questions. If you can't do math with large numbers you should find another beat. What you are doing is the opposite of helping. (That said, what am I to make of Joe Romm's "they are not black, they are blue!" response to the panel albedo issue?)

While I was pondering these matters, a tweet arrived from @Revkin way:

Your dog a bigger CO2 source than an SUV? http://j.mp/PetCarbon (Finally had chance to read; math seems to hold up?)

Well, at least there's that question mark, but as you can see, it generated a lot of retweets.



Best to nip this one in the bud. I found a very handy page for back-of-envelope energy calculations. Please let me know if you find errors on it, because I plan to refer to it a lot in future.

So, it claims that the energy of a human is about 100 watts (seems about right) and of a car going a sustained 40 mph is about 10000 watts (also seems believable; it's about 13.4 HP). So let's figure a dog is about a third of a human, consuming about 1/300 of the car. Roughly speaking, then, the energy of a dog day is equivalent to the energy of driving a car for about 5 minutes, or a big SUV for about two and a half.

So at first glance it appears that there's really no contest. Even though the referenced article presumed only 10,000 km per year (6300 miles) that's still about 20 miles per day which is a long way to drive in 2 and a half minutes, especially at 40 mph.

For this to come out in favor of the SUV, we need to get up to a half hour, (even leaving aside the manufacturing and ancillary costs which the original article claims). To do this, we have to make a very unfavorable comparison between food energy and petroleum energy, a factor of about 8.

Now, there are claims that the food we eat consumes about 400 gallons of gasoline per year. This is a few bucks a day, and sounds plausible to me. So about a gallon a day, or a third of a gallon for the dog, if the dog's consumption is equivalent. Which will get your SUV about 4 miles further. Still not enough to get the 20 miles though.

Then there's the fact that most of the meat your dog eats is by-product of meat production for humans, rather than independently produced. I'd argue that proportion is free, which greatly reduces the impact of the dog.

However, consider the cost of a meat-eating full grown adolescent child. You will find the child's food supply (or yours) is indeed comparable to the cost of a lightly driven SUV.

Texas Drought Abates

It's actually been raining quite a bit these last few weeks, and the outlook is for a wet winter on account of El Nino. Things are pleasant and green again, and we're hopeful for an especially colorful and cheerful spring next year. Nevertheless, it was the worst drought on record for several counties near Austin, though our own county (Travis) did not quite experience that.

There's a news report here and the state climatologist's report (PDF) here.



The image, from the state climatologist's report, shows 24 month precipitation surplus/deficit expressed as standard deviations at the peak of the drought. Darkest red shows 3 standard deviations, and corresponds to the areas of record-setting drought. At that moment, (late August) San Antonio had received less than two feet of rain over the preceding two years. In addition to the rainfall deficit, this drought was exacerbated by unusual heat.

Regarding climate change, the report is willing to take the bull by the (long) horns:

The drought intensified to exceptional status during late spring and summer 2009.
This intensification was associated with an upper‐level jet stream pattern featuring
troughs on the west and east coasts of the United States and a ridge across the
central United States. This weather pattern persisted for close to two months,
inhibiting convective activity and causing late spring storms to move farther north
than usual. The unusual, persistent jet stream pattern simultaneously led to
drought and heat in Texas and rain and cool weather in the Midwest and Northeast.
The extent to which this particular jet stream pattern was a random event or was
driven by particular patterns of sea surface temperatures is not known at this time.

Global warming has been identified as a possible cause of future extensive droughts
in the subtropics, including the southwestern United States. Computer models on
average project a precipitation decline of 5% over the next forty years. However,
long‐term precipitation trends across Texas remain upward. It is possible that the
present drought is the beginning of a long-term decline in rainfall, but it is also
possible that precipitation will remain steady or continue to increase. Based
on present scientific knowledge, it is not possible to say whether global warming
contributed to the present rainfall deficit. Indeed, whatever large‐scale processes
led to the overall upward precipitation trend may have caused rainfall to be greater
than it otherwise would have been.

Global warming has, however, contributed slightly to the severity of the present
drought through higher temperatures. Global temperatures have increase by about
0.7 °C over the past century, and long‐term temperature trends across Texas are
now at or above the sustained warm temperatures of the 1950s. It seems
reasonable to assume that present temperatures in Texas are on average about
1 °F warmer than they would have been in the absence of global warming. This has
increased potential evaporation and water demands by livestock and humans.
Thus, if a similar precipitation deficit had developed in the absence of global
warming, it would not have been quite as severe.

I'm not sure this is exactly the best way to describe the situation, ("global warming has contributed", argh...) but all in all I guess it's a good compromise between getting overly technical, being too vague, and also between being too strident, and being too indifferent.

Transition Towns: Mostly Harmless

I dabbled in the Transition Movement for a little while but quickly became disillusioned for exactly the reasons Alex Steffen describes in a controversial article on WorldChanging.

When I retweeted that article, gl33p, a buddy on Twitter, warned "Nonconstructive conflict on solution side limits network strength. Solidarity smart, no shortage of humans: nonzerosumgame", and I think that gl33p raises a good question.

It's clear that a focus on marginal backyard farming is not going to go far toward the massive reorganization of society that is needed. The question raised by this article is whether it does substantial damage. Should we be okay with the most idealistic and dedicated people focusing on a shabby sort of localism, because it offers some solace and some community? Or should we be concerned over the zero-sum game of attention being drawn away from the really big tasks of reinventing, well, everything, at scale?

It's a hard one. For me, thinking about the problem at scale and casting about for something to do about it is obviously the right thing to do. But then I'm a geophysicist. Most people, even those who see the great outlines of the problem, can't really begin to get a handle on the stocks and flows, the major risks and the minor ones, the tradeoffs and triages we will have to face.

I agree that there is something scary and off-putting about Transition, especially its accommodation to the paranoid survivalist streak in America. I also understand that many people just see a perfectly innocent revival of the hippie philosophy, and maybe Transition is that too.

So in the end, I just decided to put my attentions elsewhere, and not express my concerns. Had I done so, the concerns would be very similar to Steffen's. That said, I'm not entirely sure it was worth saying. I guess you pick your battles, and becoming too much like Totnes Town is hardly the biggest threat we are facing, you know?

On the other hand, the Totnes model really won't solve America's energy-intensive infrastructure, and won't make the southwestern urban landscape pedestrian friendly nor its climate conducive to casual gardening. Totnes has the advantage that it was a town in the first place.

Doing it Right

OK, so I griped about a graphically attractive but shallow effort to use information technology to communicate. Being negative isn't really enough, though, if you can avoid it.

Do I have any examples that I can be enthusiastic about? You betcha.



Update: Another excellent instance of web-based communication of complex concepts is here, this one regarding the relative sizes of very small objects. Others?

Web based tool

Do you like this?


I think it is high-design and low information. The thing is, at first glance it LOOKS like it could carry a lot of information, but on playing with it, one discovers that, alas, it doesn't.

Other climate science sites are high information and low design.

Of course, high information high design is the expensive quadrant, but it's the place to make progress on how people think.

Alex Steffen of WorldChanging Tweets

Vote Today on AGU Governance Changes

All members are being asked to vote on the changes that the Council has approved. The proposed changes expand the Council, focusing it on science, and they move the fiduciary responsibility for AGU to a newly created, smaller Board of Directors. The proposed Bylaws outline the working relationship between these two groups; the modifications bring AGU’s governing documents into alignment with District of Columbia requirements and reflect current practice in not-for-profit governance.

If you need more information before voting, the governance vote web page more fully explains all aspects of the proposed changes. There you’ll find FAQs, a video of AGU leaders talking about the proposed changes, and explanations of the specific changes in governing documents.

Political Theater or Just Plain Delusion?

Mr. Obama knows the difference between climate change theater and actual progress, as was demonstrated by this anecdote:

The debates unnerved both candidates. When he was preparing for them during the Democratic primaries, Obama was recorded saying, "I don't consider this to be a good format for me, which makes me more cautious. I often find myself trapped by the questions and thinking to myself, 'You know, this is a stupid question, but let me ... answer it.' So when Brian Williams is asking me about what's a personal thing that you've done [that's green], and I say, you know, 'Well, I planted a bunch of trees.' And he says, 'I'm talking about personal.' What I'm thinking in my head is, 'Well, the truth is, Brian, we can't solve global warming because I f---ing changed light bulbs in my house. It's because of something collective'."

That's exactly right, and that's pretty much the same point that Elizabeth Kolbert is making in her recent New Yorker piece Green Like Me.

Kolbert, author of "Field Notes from a Catastrophe", the best-written book out yet on global warming, is a treasure. She perhaps the best reporter in the catastrophic field in question. So when she writes, I sit up and take notice.

On the other hand, I'm sympathetic to "stunts", or political theater. Public behavior that causes people to question their own beliefs has a history that is hard to mock; arguably Mahatma Gandhi is the originator of what eventually became the Abbie Hoffman school of politics.

So I don't share Kolbert's implicit disdain for Alisa Smith and James MacKinnon:

Smith and MacKinnon also can’t find any local salt, so in the final scene of the book they make a twelve-hour journey—by car, by ferry, by steamer, and, finally, by rowboat. “A blue horizon, forever and ever to Japan,” they write. “The open Pacific Ocean rushing in as clear and clean as the air.” They fill a huge stainless-steel pot with salt water, which they carry back to shore and boil down. The journey is made to sound poetic, but from an ecological perspective it would have made a lot more sense for them to walk around the corner and buy some Morton’s.

MacKinnon wants us to know that he recognizes the futility of the undertaking. “I am acutely aware that efforts like the 100-mile diet are readily dismissed as ‘the new earnestness,’ which is currently enjoying a very temporary cool,” he writes. “And I am not deluded enough to feel that I’m making a difference or being the change I want to see in the world.” (The italics are his.) He is unwilling even to attempt a reasoned defense of the project: “My actions are abstract and absurd, and they are neither saving the rain forests nor feeding the world’s hungry.”

That is, they are play-acting and know it. This is productive behavior as a project, not as a lifestyle, and for a few people, not as a literal example for the world. The other players in Kolbert's story seem less clear on the concept. Please consider Kolbert's conclusion in the light of Obama's lightbulb complaint as well.

What makes Beavan’s experiment noteworthy is that it is just that—a voluntary exercise conducted for a limited time only by a middle-class family. Beavan justifies writing about it on the ground that it will inspire others to examine their wasteful ways. On the last page, he observes:

Throughout this book I’ve tried to show how saving the world is up to me. I’ve tried hard not to lecture. Yes, it’s up to me. But after living for a year without toilet paper, I’ve earned the right to say one thing: It’s also up to you.

So, what are you going to do?

If wiping were the issue, this would be a reasonable place to end. But, sadly—or perhaps happily—it isn’t. The real work of “saving the world” goes way beyond the sorts of action that “No Impact Man” is all about.

What’s required is perhaps a sequel. In one chapter, Beavan could take the elevator to visit other families in his apartment building. He could talk to them about how they all need to work together to install a more efficient heating system. In another, he could ride the subway to Penn Station and then get on a train to Albany. Once there, he could lobby state lawmakers for better mass transit. In a third chapter, Beavan could devote his blog to pushing for a carbon tax. Here’s a possible title for the book: “Impact Man.”

It's essentially a byproduct of American libertarianism, this idea that collective problems are the aggregate of individual actions, and that collective decisions are not important. It's delusional.

Perhaps Kolbert is less amenable to political theater than some of us, and is perhaps a bit harsher than she ought to be. Perhaps not. It really depends on how the various experimenters in reduced impact present their efforts to the world. It's fine to set an example by individual behavior. It can in fact be inspiring. But it isn't enough, it's very far from enough, and in the end it's just scratching the surface.

We need to live with less collectively, not just individually.

h/t Marion Delgado

The Geoengineering Quandary (In Living Color)

Following up from yesterday, we have a bunch of people being a little bit coy in response to a straightforward statement, Richard Branson's comment that "If we could come up with a geoengineering answer to this problem, then Copenhagen wouldn’t be necessary. We could carry on flying our planes and driving our cars."

Note that he didn't say all our problems would be solved. The finiteness of fossil fuels is obviously on deck. And while we might manage enough biofuels to keep our airplanes flying, that won't be enough to solve our problems. Still, there's little wrong with the substance of the assertion: if CO2 emissions could be made harmless, they would be harmless.

In response we have a chain of half-stated reactions:

David Roberts: "entrepreneur Sir Richard Branson said something heroically, world-historically stupid" and "The authors of the upcoming book SuperFreakonomics also think that geoengineering is a cheap, easy way to avoid the work of fashioning a more sustainable society." Branson is lumped in with Levitt and Dubner, a place one really doesn't want to be lumped these days.

(What David clearly means is that there are plenty more limits beyond this one, and finding a workaround to one limit without changing our behavior in the long run is not a happy ending, just a prolongation of the inescapable crisis. With this I am in total agreement.)

Keith Kloor: "The irony is that Roberts posts a set of global land use & ecological impact graphs to make his point that geoengineering won’t save humanity from all the upward trends in the graphs. So if every ecological and climate indicator demonstrates that the earth is becoming less livable because of increasing carbon dioxide concentrations and other global land uses, then is it realistic to take geoengineering off the table just because someone like Richard Branson makes a glib and simplistic statement?"

(I kind of agree yet again. Depending on what you mean, I don't think geoengineering should be off the table. Branson is advocating for biochar. Biochar should definitely not be off the table, and I don't think David Roberts wants it off the table anyway.

Where Kloor rubs me the wrong way is in his closing paragraph:

But the truth is that no matter happens at Copenhagen and in the U.S. Congress, some type of adaptation measures will be necessary. Roberts is a very smart guy, and I know he’s capable of chewing gum and talking about climate adaptation at the same time. The fact that he doesn’t want to likely results from his belief–which is shared widely by climate activists–that any discussion of climate adapation is an unwelcome distraction from the debate at hand on mitigation. Why there isn’t room for both discussions to occur beats me.

The idea that there is some sort of zero-sum game between "adaptation" and "mitigation" is really a very half-baked way of thinking about the problem. Forcing things under that rubric is simply a distortion.)

me: My coy statement was: "But what about geoengineering? Is David right? Is Richard Branson right? They are both right, as I'll explain later."

(In that article I tried to explain the very loose coupling between what is normally considered the mitigation community and the multitude of disparate adaptation communities, and the difference in scale of their problems. I explained that thinking of geoengineering as a part of "adaptation" was not splitting nature or the relevant intellectual communities at their joints. It's a very poor apprehension of the situation to find these communities as if they were in competition, and weaker still to assign geoengineering to the wrong side.

But what of geoengineering solutions? I am not in the least averse to using whatever tools we can bring to bear to manage the situation on the way to some sort of sustainability, a sustainability that I can't imagine really coming to fruition for a century or two, while the population slowly drops to a billion or a tenth of a billion.)

We need to use whatever works in the intervening generations. (It seems to me the 350.org folk are in agreement with Branson in supporting biochar as the nicest way to quickly bring the CO2 concentration down. So I can't see how David Roberts chooses to lump Branson in with the egregious Dubn and Dubner).

What works? Well, in addition to a rather ill-informed attempt to create a zero-sum game between "adaptation" and "mitigation" the press seems to be forming a rather confused idea of "geoengineering" (a trap into which Branson has inadvertently walked, though he will likely walk right back out none the worse for it personally), and unfortunately the scientific community writ large is contributing to the confusion on this matter.

Have a look at this figure, from the Royal Society report "Geoengineering the Climate", Sept 1 2009, via 2020Science


The above is from Royal Society’s much-anticipated report on geoengineering. As 2020science puts it:

Aimed at presenting “an independent scientific review of the range of methods proposed [for geoengineering the climate] with the aim of providing an objective view on whether geoengineering could, and should, play a role in addressing climate change, and under what conditions,” it provides what is perhaps the most authoritative and comprehensive assessment of the options to date… It dares to consider the option of actively engineering the climate on a planetary scale to curb the impacts of global warming, and advocates further research into geoengineering. In doing so, it will no doubt simultaneously enrage deniers of anthropogenic climate change, and those who fervently maintain that technological fixes are not the solution to the consequences of humanity’s excesses. ...Yet for anyone mature enough to consider the merits of evidence-based and socially-responsive decision-making, the report offers a clear and insightful perspective.

The figure speaks eloquently for itself. (I'd have made the size of the dots represent the potential scale of the effort, but that is somewhat subsumed under "effectiveness". Roof painting is fine, but of course there really aren't enough roofs to make a difference.) Rather, and somewhat counterintuitively, the size of a bubble indicates how quickly the approach could be brought online. Of course, this sort of chart subsumes a tremendous amount of debate and uncertainty, and is likely far from the final word on any of these approaches, but it's certainly interesting on its own.

Well, maybe not completely eloquently. "BECS" is "bio-energy with carbon sequestration".

What I'd like to point out is that there are two very different classes of strategy being discussed here: carbon sequestration strategies and radiative transfer balance strategies. It is easy to tell them apart. All the green dots (except for the low-effectiveness urban rooftop one) are carbon sequestration strategies. Those are considered safe. All the red ones are radiative transfer strategies. Those are considered high risk.

This is not a coincidence! These are really two very separate categories of idea! I am increasingly frustrated at the extent to which they are being confused. It amounts to retrograde progress in public understanding. Can we please distinguish between them?

Removing the carbon from the atmosphere solves the carbon problem. The climate disruption goes away. The direct ecosystem disruption goes away. The ocean acidification goes away. The cost is pulling out the carbon. The effect is that there is no extra carbon! It's pretty difficult in practice, but in principle it's a no-brainer!

Changing the radiative properties of the atmosphere is global climate engineering. It has numerous and extremely spooky consequences. It's like drinking more and more liquor every night and drinking more and more coffee every morning to compensate. You may crudely cancel out a few of the symptoms, but you're getting more and more unhealthy with every passing day, and anyway, plenty of the symptoms are still with you.

Part of this traces back to the earlier mistake of calling the problem "global warming" in the first place. Our problem is accelerating climate change, not global temperature. Global temperature is merely an easy-to-measure symptom (and is relatively easy to obtain from paleodata as well). No doubt it is an interesting quantity. But the change in global temperature is not the problem, and never has been. The problem is that the atmosphere is a forced fluid flow, and relatively small changes in the forcing can have very large changes in the flow as a consequence.

It is easy to counteract the changes in global temperature by cancelling out an inadvertent heating with a deliberate cooling. But it's really a desperation move. It might keep our ice sheets from falling apart, and that is a big goal, but it will add to climate change, not cancel it out!

Now, neither approach will solve all of our problems. But the sequestration approach will solve one of our problems, and it is a big one. If you don't believe in any of the sequestration approaches, you;d better take off that "350" cap, mate, because we need at least one of them to work if we're going to get to 350 before Greenland melts.

My bottom line, then, is all about nomenclature.

The "adaptation" community deals with local change on decadal time scales. The "mitigation" community deals with global change on longer time scales, and with forcing. There is no real competition between the adaptation and mitigation communities and certainly no zero-sum game. It's irresponsible to try to drum one up.

Technologies that can affect the forcing on a global scale are not really part of the adaptation conversation but rather part of the mitigation one. There are two main types of global strategy that don't address emissions directly: radiative and geochemical. The word "Geoengineering" is often applied to both but should probably only be applied to the radiative class of strategy.

Studying radiative geoengineering in this sense is probably justified, but anyone thinking that sort of geoengineering provides a free pass is indulging in childish wishful thinking. (One surely shouldn't publish a reputation-bearing book making such a case.) Also, of course these symptomatic approaches do not save the oceans from death by acidification, another environmental problem of the highest order.

Sequestration strategies are commonly lumped under geoengineering, but they are very different in strategy. They deal with the carbon problem itself, not just with one of its symptoms.

Solving the carbon problem will not suffice to bring us into balance with the world, but it will help a lot. It will help us survive to the day when we can achieve sustainability. If you dismiss every one of these ideas you need to hang up your "350" cap because we need at least one of them to work to get to 350.

PS - It's still a good idea to have a reflective roof if you are in a hot climate. It just won't fix global warming to any significant extent, okay?

PPS - Wow. A long article for a short attention-span world. David, can I borrow some puppies? (OK, I did some coloring, hope that helps.)

Update: A related conversation last January on Brave New Climate. A salient point for the Freakonomists out there from Prof. Brook:

Needless to say, no one would credibly argue that geo-engineering is a replacement for mitigation of carbon emissions. A business-as-usual scenario of coal burning, taking atmospheric CO2 to 750 to >1000 ppm (directly or via carbon-cycle feedbacks), will force the climate system so far out of whack that no ‘patch up job’ will be sufficient. No, the context under which geo-engineering might need to be considered is if a measured analysis shows that even with major emissions reductions, the impacts of committed warming will be so bad as to warrant using additional ‘terraforming’ of planet Earth. Are we at that point already? Dunno. But let’s have that risk assessment and necessary R&D done, just in case.

Needless to say? Nothing is needless to say anymore, apparently.

Update: Related article on RC. (With a link back to here, thanks!) The crucially relevant point which seems invariably forgotten by people who wish there were an easy solution so they could trumpet how blind we all are, is explained thus:

The point is that a planet with increased CO2 and ever-increasing levels of sulphates in the stratosphere is not going to be the same as one without either. The problem is that we don’t know more than roughly what such a planet would be like. The issues I listed above are the ‘known unknowns’ – things we know that we don’t know (to quote a recent US defense secretary). These are issues that have been raised in existing (very preliminary) simulations. There would almost certainly be ‘unknown unknowns’ – things we don’t yet know that we don’t know. A great example of that was the creation of the Antarctic polar ozone hole as a function of the increased amount of CFCs which was not predicted by any model beforehand because the chemistry involved (heterogeneous reactions on the surface of polar stratospheric cloud particles) hadn’t been thought about. There will very likely be ‘unknown unknowns’ to come under a standard business as usual scenario as well – another reason to avoid that too.

There is one further contradiction in the idea that geo-engineering is a fix. In order to proceed with such an intervention one would clearly need to rely absolutely on climate model simulations and have enormous confidence that they were correct (otherwise the danger of over-compensation is very real even if you decided to start off small). As with early attempts to steer hurricanes, the moment the planet did something unexpected, it is very likely the whole thing would be called off. It is precisely because climate modellers understand that climate models do not provide precise predictions that they have argued for a reduction in the forces driving climate change. The existence of a near-perfect climate model is therefore a sine qua non for responsible geo-engineering, but should such a model exist, it would likely alleviate the need for geo-engineering in the first place since we would know exactly what to prepare for and how to prevent it.

This is why all intervention has to be about reducing net carbon. Anything else is a desperation backstop and probably won't work for all sorts of reasons.

Update: RP Jr shows up to say that

"Here is what I have said recently (for example) on adaptation vs. mitigation:

"I think that mitigation policies should be completely decoupled from adaptation policies and they should proceed on separate tracks. They are not trade-offs but complements."

http://www.robertbryce.com/node/267

If this is his opinion I have indeed misrepresented it and apologize. I would like to register complete agreement with the above and regret any inconvenience. I have removed the reference to Dr Pielke's opinion within the text and apologize for my error.