And wouldn’t it be wonderful if raising CO2 levels resulted in a net benefit? Certainly we’re required to look at all possibilities. But where you seem to err is in assuming that all possibilities should be given equal weight. Like any any company contemplating an investment, we as a society need to consider not just what the possibilities are, but also the likelihoods of their occurrence, along with the potential impact and cost if they occur (including possible tail-end outcomes). That’s basic decision analysis in a nutshell. And in evaluating the likelihoods, to whom shall I give greater credence? The voices of a few lone skeptics like yourself, or the collected pronouncements of 32 national academies of science along with numerous other scientific organizations in the fields of earth science, climatology, oceanography, paleoclimatology, and biology? After all, these are not priests issuing proclamations about the existence of God, but scientists trained in methods of critical inquiry. Could they all be wrong and the dissenters right? Sure. But I’m not going to bet the firm on it.

The fact is, there is nothing remotely skeptical about assuming the best case scenario is as likely as the worst case, and therefore that we shouldn’t be taking action to insure ourselves against possible negative outcomes. Making that argument makes your skepticism seem more like an affectation contrived to advance preconceived notions of what is in society’s best interest. Very little in common with the teachings of Pyrrho and Empiricus, much more like the blind optimism of Pollyanna.

You seem to have reverted to making the assumption that warming would put us at increased (rather than decreased) risk. If a warmer world might be better for humanity, and life generally, then how do you know in which direction the optimum is?

There is a risk associated with raising CO2 levels, and there is a risk associated with not raising them. Just as in Pascal’s wager there is a risk associated with being an atheist, and a risk associated with not being. You can’t say that going to church reduces the risk because you might have picked the wrong God, and while a partisan God may be willing to give a pass to honest atheists, they’ll condemn followers of their rivals. Or maybe is forgiving enough to grant atheists heaven too. One fallacy in Pascal’s wager is the false dilemma: the assumption that the two alternatives offered cover all the possibilities. Similarly with CO2 – you don’t know whether its cost is positive or negative.

First, I think you confuse prosperity with lack of vulnerability. Having more resources at your disposal may mean you can better deal with adversity when it occurs, but it doesn’t make you less prone to adversity. If your house is located in a floodplain or a region prone to wildfires, the fact that you may be wealthy does not in any way reduce the risk of losing your house. And, to carry the analogy further, if your wealth derives essentially from the fact that you live in a risk-prone area, there is no guarantee that the bargain is ultimately in your favor. It all depends on the potential benefits relative to the expected costs. Your argument is that sufficient wealth will allow us to deal with any contingency, but that equation becomes suspect if the means to obtaining that wealth itself opens us up to greater risks of negative contingencies.

In all of this we are dealing with varying degrees of uncertainty and risk. So when you state that the hypothesis that CO2 had a role in causing the PETM is unproven, one has to take that statement in the context of the balance of evidence, possible competing hypotheses, and ultimately – for the purposes of deciding today how to respond to the prospect of AGW – the risks and potential costs of tentatively accepting one hypothesis over another (including the null hypothesis). There is a basic question of presumption here. Various experts have deliberated over the possible causes and consequences of the PETM and decided there is sufficient cause to be concerned about the risk of human-caused contributions of a similar magnitude of CO2 to the atmosphere. (The fact that CO2 concentrations were higher prior to the PETM than they are today would in fact suggest that the proportional effects today may be even greater than they were then). So with all due respect to your name, why should I take your word that the PETM event “certainly doesn’t tell us what the effect of a 10 C warming would be today”? Have you tested and confirmed an alternate hypothesis? Or are you suggesting that we should for now simply accept the null hypothesis? That may be appropriate in the context of scientific inquiry. But in an economic and policymaking context, we are again back at Pascal’s wager – in the presence of bounded uncertainty, the only rational option is to weigh the possible costs and benefits associated with different possibilities and act accordingly. In that context, I cannot so easily dismiss the opinions of the experts.

Which brings us to the basic economic argument. Even if it were true that the “cheap energy we are using today will make our great grandchildren eight times wealthier than we are today” (a suspect assertion if I’ve ever heard one, especially since today’s energy expenditures are only about 8 percent of global GDP – I think you mean that total growth in GDP of around 2% per year would lead to that level of wealth, which is a very different assertion), that does not mean we can simply ignore the costs associated with using that energy. Risk is form of cost. As long as you accept that there is any risk in terms of disruption to human society associated with rising CO2 levels (whatever resources we may have in the future to deal with that risk), then the true cost of emitting CO2 is not zero. And as long as we continue to treat it as zero (by not taxing CO2, or imposing regulatory limits on its emission), then by definition we will be misallocating societal resources in a way that makes humanity worse off relative to an optimum mix of investments in fossil fuels and alternatives. Nobody – and I mean nobody – is advocating that we “stop development” as you say. That is a throw-away argument. The question is how to develop in an optimal way taking into account the various risks and uncertainties, costs and benefits associated with different deployments of capital and resources. To assume that that the science of climate change is “unproven” and that its potential consequences should be downplayed or dismissed (or, more precisely, not factored in any way into current investment decisions) is not a recipe for maximizing wealth. Quite the opposite. Only a fool would succumb to the temptation of building a house in the woods without considering (and insuring against) the risk of a wildfire, no matter what that house might promise in terms of future wealth and satisfaction.

Put another way, investments (including investments in nuclear technology) make perfect sense. But those investments will not occur “when the timing is right” if we do not also take steps now to impose a cost on CO2 emissions reflecting a reasonable guess at what the future costs of climate change might be. Only by internalizing that cost will can we realize an appropriate investment response in terms of timing and magnitude. R&D investment without accompanying price signals would be pointless. As pointless as investing in technology to reduce toxic waste would be if there were no cost or penalty associated with producing toxic waste (why else use the technology?) Maybe Lomborg’s economists are right about a 2040-2050 time horizon, but in fact they have very little basis for knowing (they’re not the ones familiar with and potentially investing in the technologies we’ll need). Better to trust the actual players in the market responding to an appropriate price signal. There were many built-in incentives to finding alternatives to horse transportation – among them the fact that people were immediately confronted with its unpleasant side-effects. No such built-in incentive for CO2. And again, nobody is now calling for an equivalent to banning horses!

Again, I’m talking about the parts on the edges, not the entire continental ice sheets. Only a small fraction of it.

Earth’s oceanic surface area is ~4e8 km^2. Neglecting density/volumetric differences between water & ice, it would take the equivalent of a block of ice 1 km high and 4e5 km^2 in area to raise the sea level by 1 m. Antarctica has ~18,000 of coastline, so that area would correspond to 22km inland from the coast. In other words, just the outer 2.2 cm of the 4 meters, or outermost inch of the 13 feet on your scale model has the capacity to raise the global sea level by 3 ft or so.

Is it the speeds you have a problem with? Poking around http://nsidc.org/data/velmap/ one can find many examples of rate measurements of hundreds of meters a year.

I don’t go much for just trusting experts. As you might have gathered from my name.

“With the current and growing global population, much of which is concentrated in coastal cities, such a rise in sea level would have a drastic effect on our complex society, especially if the climate were to change as suddenly as it has at times in the past.”

I mostly dealt with that in #33. The only thing I’d want to add is to say that our complex society is not fragile. Our complexity is because we adapt locally to suit the circumstances, to take advantage of opportunities, and to solve problems. Those are the benefits of prosperity. Five hundred years ago we would have struggled – and did, with famines common. Virtually everybody worked in agriculture, and even then could not guarantee enough to eat. Two hundred years ago with the industrial revolution in full swing, we coped a lot better, with more secure food supply, collected over a wider area and hence more robust, life expectancy going up, effort devoted to agriculture going down. An then in the 20th century things really accelerated, life expectancy and population rocketing, famine a distant memory for the west and far less common elsewhere, very little of our resources now needed for pure survival, and the resources and technology to respond quickly. We are far less vulnerable than we were. And the extension of that prosperity-fuelled adaptability is surely the best precaution we could take against whatever the future might hold.

The Paleocene-Eocene thermal maximum is not understood. It is true that it injected a lot of carbon into the system, although since CO2 levels were previously around 1000 ppm it didn’t make as big a proportional difference as you might think. Mentioning CO2 in that way gives the impression that it had something to do with the cause of it. This is indeed one hypothesis, but so far an unproven one. It certainly doesn’t tell us what the effect of a 10 C warming would be today. And while a lot of species moved habitat, there were relatively few extinctions, apart from certain classes of deep sea plankton.

That said, it does show that climate has changed throughout history and will undoubtedly happen again – whether CO2 has any effect on it or not. Being ready for it is a good idea.

“Fair enough, but if the “cheap” energy we are using today is in fact going to impose severe costs and hardship on future generations, then it is hardly “cheap.””

The cheap energy we are using will make our great grandchildren eight times wealthier than we are today, just as we are eight times wealthier than our great grandparents were. So that’s like everything we have today, multiplied by seven, that we’re going to take away from those future generations if we stop development. Like if our ancestors had believed Jevons and stopped burning coal, so we would all live today like they did in 1800. The only thing that is going to “impose severe costs and hardship” on future generations is cutting back on growth.

Bjorn Lomborg edited a book in which invited experts wrote essays, some of which proposed $100bn/yr investment. You say “even” Bjorn says so, but Lomborg always did go along with the official position on AGW. It’s always been a matter of principle for him, that he used in his books, that he went with whatever the official science and statistics said – his position always was that the official science and the statistics generally didn’t say what the environmentalist doom-sayers claimed they said. He would open himself to a charge of hypocrisy if he was to reject the official story as soon as he didn’t like the conclusion, so he doesn’t.

But for what it’s worth, I would also be sympathetic to the idea of significant investments in starting the transition, so long as they are genuine investments in the sense of giving a positive return on the money. If you was to propose developing nuclear power to get to the next generation of reactors, for example, I’d be right along side that idea. Moreover, I’m quite confident that we will invest, when the time is right and the technology is ready, and I would be frankly astonished if we were still using the same energy generating technologies in 50 years time.

The problem arises when you try to rush it, and make the jump too early. It would be as if the people of a century ago had predicted that the… ahem… ‘pollution’ produced by their horse-powered civilisation would overwhelm their cities in a few decades time, filling the streets nine foot deep, and had therefore instituted a campaign to immediately ‘ban the horse’. But their predictions never came to pass, and nobody had to ban anything.

Lomborg’s economists calculated a few years ago that the optimum time to take action on global warming would be around 2040-2050. At that point, further delay would cost as much as one would gain by waiting. I don’t buy economic models any more than I do climate models, but as Lomborg claims, that’s what the ‘official’ science actually says.

#37,

Did you try that scale drawing? Because I have a feeling that if you had, you wouldn’t have put it quite that way.

Let’s scale it down a millionfold. Now you have a sheet of ice about 4 metres across, and 3 mm thick. Imagine a big slab of flat concrete, 12 foot across and lay a 3 mm thick sheet of ice across it. Now try to imagine gravity causing it all to slide off. Those fast flow rates correspond to movements of about 1.5 mm/year in our scale model compare that to 4 metres. Does it seem reasonable?

can you say a little more about how you envisage this massive ice slide would work? What would trigger it, and what would drive it?
Gravity driven, triggered by increasing lubrication that overwhelms angle-of-repose stability. Or, perhaps rapid disappearance of sea ice which serves to block downward slides, as was discussed when the Larson B shelf disintegrated. The Columbia Glacier (AK) and in Jakobshavn in Greenland can clearly be seen sliding into the water in James Balog’s time lapse films:
http://www.youtube.com/watch?v=g4kha1RY-LM&feature=related and discussion at
http://www.pbs.org/wgbh/nova/extremeice/program.html

I’m not arguing that this would happen to the great ice sheets, just the parts on downward slopes with clear paths to the ocean. While that may be a small fraction of the total ice, its not negligible http://en.wikipedia.org/wiki/File:Antarctica_glacier_flow_rate.jpg shows a lot of fast moving ice, which has to be going someplace. I suspect that it could cause noticeable spurts in sea level rise against a slower background from meltwater. At some point, all potential sliding material would be exhausted once the glaciers no longer reach the sea directly. Then it would be back to melting and surface runoff rates, which would presumably be slower.

My point is, you can’t just assume that a rise in temperature must be catastrophic. If there’s something different about this warming compared to previous warmings that makes it so, you have to say what it is and why it makes a difference.

This is where the medium of commenting on blog posts is probably insufficient. There are of course numerous academic studies projecting the probable impacts of a rapid global temperature increase. Cf. the book Six Degrees: Our Future on a Hotter Planet by Mark Lynas for a layman’s treatment. Or, if you don’t trust model projections and informed speculation, try the recent statement from the U.K. Geological Society re evidence of the impacts of climate change from the geological record. It may be worth quoting a passage or two from this statement:

Life on Earth has survived large climate changes in the past, but extinctions and major redistribution of species have been associated with many of them. When the human population was small and nomadic, a rise in sea level of a few metres would have had very little effect on Homo sapiens. With the current and growing global population, much of which is concentrated in coastal cities, such a rise in sea level would have a drastic effect on our complex society, especially if the climate were to change as suddenly as it has at times in the past. Equally, it seems likely that as warming continues some areas may experience less precipitation leading to drought. With both rising seas and increasing drought, pressure for human migration could result on a large scale.

…and:

About 55 million years ago, at the end of the Paleocene, there was a sudden warming event in which temperatures rose by about 6ºC globally and by 10-20ºC at the poles. Carbon isotopic data show that this warming event (called by some the Paleocene-Eocene Thermal Maximum, or PETM) was accompanied by a major release of 1500-2000 billion tonnes or more of carbon into the ocean and atmosphere…. CO2 levels were already high at the time, but the additional CO2 injected into the atmosphere and ocean made the ocean even warmer, less well oxygenated and more acidic, and was accompanied by the extinction of many species on the deep sea floor. Similar sudden warming events are known from the more distant past, for example at around 120 and 183 million years ago. In all of these events it took the Earth’s climate around 100,000 years or more to recover, showing that a CO2 release of such magnitude may affect the Earth’s climate for that length of time.

The point is this is nobody is just “assuming” that impacts will be severe at the upper end of the expected range of warming.

As for the economic costs, you note that we should “bring all resources to bear – including and especially cheap energy” in combating poverty. Fair enough, but if the “cheap” energy we are using today is in fact going to impose severe costs and hardship on future generations, then it is hardly “cheap.” Assuming it is cheap is to engage (consciously or not) in a devil’s bargain. The economic forecasts of the cost of reducing emissions may be based on uncertain assumptions (they could hardly not be), but the reason the impacts would not be severe – and a couple percentage points off global GDP is hardly a large opportunity cost when you consider that global GDP in 100 years is likely to be far more than is needed to satisfy basic human needs – is that we are talking about a shift over time in the world’s energy-production and distribution infrastructure. It’s not as if we need to tear out every coal plant overnight – at least not today. But the longer we wait to put a price on CO2 so that we can start to internalize its potential adverse effects (and very real costs), the more drastic and costly it will be for us to reduce emissions and adapt to the effects in the future. Even Bjorn Lomborg now supports investments of around $100 billion per year to start the transition.

Interesting idea.

The Antarctic ice sheet is about 4000 km across and 3 km thick, and its weight pushes the ground below down to make a depression in the centre in which the ice rests, and the bedrock is by no means smooth. It’s worth drawing a scale diagram to get an intuitive idea of the shape. And to try to visualise those speeds of fractions of a km per year on the same scale, too. Ice doesn’t fracture but is ductile below the plastic limit, when the pressure exceeds a certain quantity. So, looking at that scale diagram, can you say a little more about how you envisage this massive ice slide would work? What would trigger it, and what would drive it?

I assume by glacial lubrication you mean the Zwally effect, when summer meltwater drains down moulins. I believe it has been proposed to explain some seasonality in a few particular cases, but in a lot of cases the acceleration of the glaciers doesn’t seem to be seasonal – they surge as often in winter as in summer – and so far as I know it has only been proposed for fairly fast-moving glaciers with a steep gradient and scoured-smooth base, I haven’t seen it suggested for slower-moving ice sheets proper on rough bedrock. It’s a genuine effect, but it’s unclear to me how important it is compared to other causes of changes of flow. I hear that it takes a lot of data processing to even detect it with any confidence in the noisy data, even for relatively fast-moving glaciers.

Moulins have occurred as long as there have been ice caps, so presumably the idea here is that they occur more often, or for longer? Would that not result in the same sort of things happening a little bit longer or more often, or are we critically close to some sort of major instability? If so, of what nature?

Ice doesn’t need to melt to raise sea level -it can just slide in and cause the same displacement. Looking at accelerating losses of glacial and sea ice, catastrophic or near-catastrophic ice slides don’t seem all that unlikely. Sub-glacial meltwater lubrication is now being implicated for acceleration. Its easy to imagine very non-linear scenarios. While Antartica is way below freezing, parts of the continental ice sheets are moving at hefty fractions of a km/year – only some needs to slide into the ocean to have an effect.

Higher than average sea levels also amplify storm surge concerns – recent events in a gulf coast city in the US comes to mind. The Mississippi River Delta, itself always receiving new silt from one of the biggest rivers in the world, didn’t offer much protection in 2005.

“For example, large numbers of refugees from high density coastal areas may overwhelm their own countries ability to house them.”

Over what time scale? A week? A year? Fifty years?

How often do people build new houses, and move house, anyway? Coastal erosion has always happened, and has necessitated a gradual shift of towns. As the global population expands, we will have to find new houses for a couple of billion more people as part of business as usual. And we have seen mass migrations and population shifts in the past even on short time periods (like with the creation of Bangladesh/Pakistan through partition), and global civilisation has survived it. Poverty, politics, and wars already cause all that, and one of the things we are hoping to get from economic development is a reduction in that sort of thing. It’s not a new thing that we have to adapt to, it’s arguably something that we might not end as soon as we had hoped.

As it happens, it’s extremely unlikely to happen to Bangladesh, because it’s mostly built on a river delta. Silt collected from all over the Ganges river basin is transported downstream until it reaches the sea, when it fans out and slows down, depositing the silt to form new land. River deltas are very flat and very close to sea level because the processes that form and maintain them keep them that way. As sea level rises, so will the land. The current coastline is already in equilibrium with the past century of sea level rise, with no more than small variations around the constant mean, and indeed at the moment the area of Bangladesh is increasing. Unless sea level rise accelerates dramatically, Bangladesh will be unaffected, and even if it does accelerate, it will reach a new equilibrium with a slightly smaller area. It isn’t going to vanish.

The same applies even more to developed nations, who have land reclamation technologies to use. The biggest risk to such communities is not sea level rise, but the short-sighted use of flood prevention technologies that break the cycle of the land formation process without putting anything in its place. The soft silt is always being compressed under its own weight, and without new silt from floods to restore its level, it sinks slowly below sea level. But again, this is an already existing problem that we have the means to address. It’s not something new.

And all of this is assuming that sea level rises more than the 1-2 foot predicted from a continuation of the current trend, which not even the IPCC are willing to claim.

Here’s an interesting map of Manhattan. I think it makes the point admirably.