Global Climate Change Economic Analysis Cage Match: Robin Robert Hansen Misreads Marty Weitzman

Robin Robert Hansen writes:

Robert Hansen's Blog: The Stern Review on the Economics of Climate Change: Blistering Peer Reviews: In the latest issue of the Journal of Economic Literature, two papers deliver devastating reviews on the Stern Review on the Economics of Climate Change... by serious, mainstream economists: William Nordhaus of Yale and Martin Weitzman of Harvard. These are not individuals and articles that can or should be ignored. Of course, they will be ignored by the mainstream media – while at the same time Al Gore’s receipt of the Nobel Prize carries the media day....

I have always said that my objections to the prescriptions of the most vocal climate change advocates are on three levels: one, the climate models depend too much on positive feedbacks that are not understood; two, the models have not really been tested, but instead are calibrated to the historical data; and three, even if one accepts the models, one then has to move into the economics of optimal policy, and there the best analysis suggests relatively modest reductions in carbon emissions for the near term. I like to ask environmentalists to summarize their prescriptions with the appropriate tax per barrel of oil: tell me what you think the price of oil should be increased by, in order to recognize the impact of carbon.

But back to the reviews of the Stern Review. So the Stern Review made big headlines when it came out, as it was commissioned by the UK government and was ostensibly a serious analysis of the economics of climate change. Both Nordhaus and Weitzman deliver fatal blows.... Weitzman says: "However, in my opinion, Stern deserves a measure of discredit for giving readers an authoritative-looking impression that seemingly objective best-available-practice professional economic analysis robustly supports its conclusions, instead of more openly disclosing the full extent to which the Review’s radical policy recommendations depend upon controversial extreme assumptions and unconventional discount rates that most mainstream economists would consider much too low...."

To summarize the contrast: The Stern Review calls for a carbon tax of $350 per ton of carbon in 2015. Nordhaus’ model, which has been peer-reviewed many times, calculates the optimal carbon tax in 2015 to be ONE-TENTH of that, or only $35 per ton carbon. I find it useful to put these quantities in terms of something we understand more readily: $350 per ton carbon converts to $1 per gallon of gasoline, while $35 per ton carbon converts to 10 cents per gallon of gasoline. We are talking big differences here.

So what is wrong with the Stern Review’s economics? It is real simple – they use an extremely low interest rate, close to zero. Everything follows from this, and in my opinion, the assumption is crazy....

Another point in this criticism is the essential inter-generational fairness issue. Per capita income worldwide has been growing at around 1.3% over many decades – and this is the number that the Stern Review uses. At that growth rate, per capital world consumption will grow from today’s $10, 000 to about $130,000 in two centuries. Which generation is the relatively poor generation? Are we so sure that we are impoverishing our children and our children’s children? What about all the new technologies, institutions such as democracy and market economies, physical infrastructure, and knowledge that we are bequeathing them? Do we not think that people 200 years from now will enjoy more leisure, better health, better technology, and generally be better able to pursue life, liberty, and happiness?

Read the articles, they are really convincing. For most of the media, of course, that will be too difficult. Much easier to report on Al Gore winning an Academy Award – oops, I meant a Nobel Prize.

When Robin Robert Hansen argues that we should do little about climate change in the near future because "the climate models depend too much on positive feedbacks that are not understood... the models have not really been tested," he makes the decisive error of failing, as Tyler Cowen puts it, to recognize that on this issue uncertainty is not our friend.

And this is how Robin Robert misreads Marty. Because Marty's major point in his review is that uncertainty is not our friend and that because uncertainty is not our friend the Stern discount rate is not crazy:

Marty Weitzman: There is a general point here and a particular application to the economics of climate change. The general point is that from experience alone one cannot acquire sufficiently accurate information about the probabilities of tail disasters to prevent the expected marginal utility of an extra sure unit of consumption from becoming unbounded for any utility function having everywhere-positive relative risk aversion, thereby effortlessly driving [the conclusions of] cost-benefit applications of expected utility theory [to an endorsement of the generalized precautionary principle]. The degree to which this kind of "generalized precautionary principle" is relevant in a particular application must be decided on a case-by-case basis that depends upon... a priori knowledge.... In the particular application to the economics of climate change, where there is so obviously limited data and limited information about the global catastrophic reach of climate extremes for the case T > 6 C, to ignore or suppress the signiÖcance of rare tail disasters is to ignore or suppress what economic theory is telling us loudly and clearly is potentially the most important part of the analysis. While it is always fair game to challenge the assumptions of a model, when economic theory provides a generic result (like "free trade is Pareto optimal") the burden of proof is commonly taken as resting on whomever wants to overturn the theorem in a particular application. The take-away message here is that the burden of proof in the economics of climate change is presumptively upon whomever wants to model optimal-expected-utility growth under endogenous greenhouse warming without having structural uncertainty tending to matter much more than risk. Such a middle-of-the-distribution modeler needs to explain why the inescapably-thickened tails of the posterior-predictive distribution... rare disasters under uncertain structure, [are] not the primary focus of attention and does not play the decisive role in the analysis.

So Weitzman concludes that good policy today:

combines the gradualist climate-policy ramp of ever-tighter GHG reductions... with the option value of waiting for better information about the thick-tailed disasters... fnding out beforehand [whether] we are on a runaway-climate trajectory... [confronting] honestly the possible options of undertaking currently-politically-incorrect emergency measures if a worst-case nightmare trajectory happens to materialize... having some semblance of a game plan for dealing realistically with what might conceivably be coming down the road... supplement mainstream economic analysis of climate change (and mainstream ramped-up mitigation policies for dealing with it) by putting serious research dollars into... contingency planning for worst-case scenarios.... It may well turn out that... early detection is impossible... too expensive... comes too late... so we should stop stalling and start making serious down payments on catastrophe insurance by cutting CO2 e emissions drastically. But these are conclusions we need to reach empirically.... Instead of declaring immediate all-out war on greenhouse-gas emissions as advocated by Stern, maybe we would do better by steadily but surely ramping up GHG cuts over the next decade or two while simultaneously investigating seriously the nature of the runaway-climate disasters.... We can always come back in ten or twenty years time and declare all-out war on global-warming emissions then if we then think it is the best option.... The Stern Review has its heart in the right place -- it is not nice for us to play the role of nature's grim reaper by bequeathing the enormously unsettling uncertainty of a very small, but essentially unknown (and perhaps unknowable), probability of a planet Earth that in hindsight we allowed to get wrecked on our watch. However, Stern does not follow through formally on this really unsettling part of the global warming equation.... I don't mean to imply that there is some off-the-shelf turnkey consensus model of the economics of uncertain catastrophes that the Stern Review was negligent in not using.... But I think progress begins by recognizing that the hidden core meaning of Stern vs. Critics... is] tails vs. middle and about catastrophe insurance vs. consumption smoothing.

Comments

[Tyler Cowen]

Keep in mind this guy is Robert Hansen, not my colleague Robin Hanson...

[ooops]

[Ken Houghton]

ROBERT Hansen (http://robertghansen.blogspot.com; Dartmouth B-School fake-libertarian-who-at-least-admits-it) is not Robin Hanson (http://www.overcomingbias.com/; GMU economics professor until he gets a real job).

Nor, presumably, is he the similarly-named Robert Hanssen(http://archives.cnn.com/2002/LAW/05/10/hanssen.sentenced/index.html), which may be a good reason to use his middle initial when referring to him. YMMV.

[Robert Waldmann]

I have two problems with Weitzman

first I don't agree that

"the expected marginal utility of an extra sure unit of consumption ...unbounded for any utility function having everywhere-positive relative risk aversion,"

utility equals the square root of consumption has constant relative risk aversion equal to 0.5. The maximum possible contribution of an extra unit of consumption is 1, that is increasing consumption from 0 to 1 adds one util which is finite.

Weitzman means that the derivative of the utility function must go to infinity as consumption goes to exactly 0. So ? A statement about a derivative can never tell us that we should be infinitely cautious. For example, it might be optimal to have consumption per capita 1 cent per lifetime. We will manage that no matter how much we mess up the world (if we do in the long run we and our species will all be dead).

There are mathematically convenient statements about derivatives. None of them has any relevance to the real world. All are statements about exactly what happens as something goes to exactly zero. In the real world this does not ever happen as noted by Heisenberg.

Also I agree with him that, in the economics profession, the burden of proof is on those who challenge claims like "trade is Pareto improving" . I add that proof is impossible, auxiliary hypotheses are always needed to turn the hypothesis of interest into a testable hypotheses. Thus the practice is that once some branch of economic theory attains the status of orthodoxy, it is not rejected as the result of empirical work. A worldview shattering event like the great depression might trip it up for a few decades, but that is not because of anything recognizable similar to scientific reasoning.

Weitzman seems to think that this is good thing.

Now other fields have theories which are highly respected. Those fields have theories which have made surprising true testable predictions. "Free trade is Pareto efficient" is not the sort of statement that can be tested without ESP as it is a statement about individual welfare. There is no evidence supporting that claim. There couldn't be. Also I don't know if MW is one of the advocates of free trade in heroin and Plutonium. If not, he is saying we must assume that a statement which we believe to be false in some cases, is true in all others unless someone manages proof without maintained assumptions (which is impossible).

I don't see how smart people like MW can take the economic profession's approach to economic theory seriously. It is a rare talent and highly rewarded.

[Bernard Yomtov]

"I like to ask environmentalists to summarize their prescriptions with the appropriate tax per barrel of oil: tell me what you think the price of oil should be increased by, in order to recognize the impact of carbon."

I quit taking Hanson seriously when I came to this sentence. What idiotic arrogance. Why should environmentalists have to summarize their prescriptions this way, any more than economists have to summarize theirs by providing detailed explanations of how power plants should be engineered?

[Pete]

Thanks. Nice to hear about these two articles. I'll look for them. Three things:
(1) My impression is that the feedback effects are somewhat better understood now (room for improvement of course).
(2) At least GCMs use some reasonably well-known geophysical and climatic processes in parameter choice and are compared to historical data and analyzed together with paleoclimatic data. Compare that with CGEs, which are totally unbelievable as tests of hypotheses and could be characterized as modeling with one data point.
(3) While I agree that the Stern Review didn't appear up-front with its crucial discounting assumptions, I don't think it's totally ridiculous to apply a relatively low discount rate. Please see Dasgupta "Discounting Climate Change" which does a nice job discussing issues with respect to both the pure time rate of discount and the consumption growth terms in the social discount rate (it's also a review of Stern). I find it a bit unnerving to assume a constant rate of pure time discount (for given per capita consumption levels), which can be taken to imply that we are (in the not-to-distant future) indifferent to human extinction much less the extinction of many other species.

[Rich Gibson]

"I find it useful to put these quantities in terms of something we understand more readily: $350 per ton carbon converts to $1 per gallon of gasoline, while $35 per ton carbon converts to 10 cents per gallon of gasoline. We are talking big differences here."

This sounds like an assertion that we can deal with the cost of carbon for somewhere between 10 cents and a dollar per gallon of gasoline.

I _know_ that I am terribly optimistic and naive, but frankly, the difference between the true cost of carbon mitigation being 10 cents versus one dollar per gallon of gasoline seems relatively unimportant to me.

Is the debate really over whether we should pay an extra 0, 10, or 100 cents per gallon to mitigate the effects of carbon?

[Eric Crampton]

I'd thought that the Witzman critique wasn't that zero discount rate was necessarily bad, but that in combination with the eta value it had to be. And that the case for abating carbon was entirely different from the one Stern makes: it's nothing about expected values, and everything about appropriate levels of insurance. They're very different arguments, and just because they reach similar conclusions doesn't mean that the Stern argument was right.

[Pete]

"I find it useful to put these quantities in terms of something we understand more readily: $350 per ton carbon converts to $1 per gallon of gasoline, while $35 per ton carbon converts to 10 cents per gallon of gasoline. We are talking big differences here."

Actually, I find $1 per gallon not too far off from what I'd like to see. If I set the pure time rate of discount equal to 0 and the overall discount rate equal to 2.5-3%, a rough calculation gets a gasoline tax of over 50-cent per gallon tax for climate change reasons. Add more for social costs associated with national security and... I don't really think 10-cents is necessarily the Holy Grail.

[zinc]

Rather than increase the price of gasoline, a terribly regressive method of helping y'all to sleep better at night, let's raise the funds through a "the special dead guy utils tax" on large estates.

Obviously these folks, rest their souls (assuming that they actually had a soul) garnered extra utils, which they don't need anymore, and caused more carbon dioxide pollution than the rest of us combined. So let's get off our fat tails and get those utils back. It's all for a good cause, just in case we're wrong and don't know it.

[AP]

If the potential downside to overreacting is that the economy doesn't do as well as it should, the potential downside to underreacting is human extinction. Unlikely as that may be, I'd take a fairly significant hit to my quality of life to see that it doesn't come to pass.

[bigTom]

Pete:
What is a CGE?
I strongly agree with your point number one. The feedbacks are relatively well understood, although it wouldn't be surprising if we missed one ot two. Again we think it is more likely to have missed a large positive feedback than a negative one. If I consider F to be a positive feedback then the amplification of warming by feedbacks scales as 1/(1-F). Current estimates of F are roughly .5. A factor of two mistake in F makes for a relatively small impact if the feedback is half of this value , but an infinite amplification results from a doubling. Any value of F greater than say .9 would be catastrophic.

$350/ton sounds pretty high to me. Carbon Capture and Storgae estimates are more like $100. It wouldn't make sense to charge significantly more than the cost of sequestration. Also a dollar raised by a carbon tax is not a subtraction of $1 from the world economy, but rather a redistribution of the dollar. Do note however than expressing a carbon tax as price/gallon of gas is deceptive. Percentage wise the carbon tax will be a considerably larger percentage increase for carbon intensive goods like electricity and steel.

I do agree that our response needs to be adaptive to new information as it becomes available. Traditionally politics has made that difficult to do.

I strongly endorse his endorsement for research into geo-engineering. A substantial part of the scientific community has an "its not nice to mess with mother nature" attitude about this. IMHO it is more than 50% likely that we will be driven to the point of trying geo-engineering. Better to have a significant longterm research base available when the time comes for this decision.

[Karl]

The option-value point potentially works in the opposite direction from how Weitzman describes it.

He's working off of the Dixit and Pindyck model, where an "option" is preserved by holding off on a commitment, hoping that, in the meantime, more information comes in that helps you decide whether to make the commitment or not. Weitzman implicitly follows Dixit and Pindyck, who explicitly define the choice to regulate an environmental problem as the commitment, so not regulating is the same as refraining from commitment waiting for more information. There's value in not regulating now, because that preserves the option of regulating later if you learn that you need to.

But in many environmental situations, NOT regulating is as much a commitment as is regulating. Every year that we don't commit to serious climate reduction, we DO commit to more suburban sprawl, an automotive fleet with average MPG of 25 rather than moving toward 40 or 50, new housing stock that's bigger than will turn out to be optimal once we decide that we really should be slowing down climate change, new housing stock with insulation that's suboptimal, etc.

Business-as-usual is itself a form of commitment. "Modest" measures (like a $1/gallon carbon tax) PRESERVE the option of getting further reductions with a lot less pain.

[Eli Rabett]

Weitzman starts from the right point. If you look at what Stern states will be the result of increasing greenhouse gas concentrations and what the IPCC predicts, they are pretty much the same. It starts to bite seriously at 3 C and is a serious disaster at 5 C. You can compare them at http://rabett.blogspot.com/2007/12/return-of-fat-bird-eli-and-ms.html

[Julian Elson]

Moreover, isn't one of the reasons that productivity has been growing steadily since the industrial revolution that neither our generation nor previous generations seriously have adopted "après nous, le déluge" as its slogan? If we establish, in all sectors of life (capital investment, environmental policy, research & development) that we should try to ignore the future and maximize current consumption for our generation, on the grounds that the future will be richer anyway, then it seems to me that the future probably won't be richer. After all, while per capita income growth may have been the norm in East Asia, North America, and Europe for some time, it hasn't been the norm for 99% of humanity's history, so simply assuming that we can change our society and economic model to ignore the future, and then still assume that the future will be better off, 'cuz hey, the future is destined to be better off, seems asinine.

[Bruce Wilder]

MW: ". . . unsettling uncertainty of a very small, but essentially unknown (and perhaps unknowable), probability of a planet Earth that in hindsight we allowed to get wrecked . . ."

Maybe I missed it, but why does MW think global catastrophe as a result of global warming has a "very small . . . probability"?

It seems like an oddly ungrounded, unqualified presumption.

Maybe, I don't understand the unstated counterfactual correctly.

I imagine that continually increasing the concentration of greenhouse gases in the atmosphere is a bit like stepping out onto the slope of a half-spherical dome from the top. Initially, the slope is gentle, but as one continues outward, the slope becomes steeper and steeper.

If one walks out far enough, one will slip and fall, and given the shape of the roof, continue to fall helplessly till one hits the ground.

Now, it might be that, if we knew the slope of the roof, and the force of our own traction, we could calculate how far we could walk out, without slipping and falling.

Now, is the "very small probability" the probability that we are treading on a domed roof? the probability that we will encounter some slippery oil spread on the roof, which will make a hash of estimates of traction? the probability that we won't notice the mistakes in our estimates of slope and traction, until we have already begun to fall?

[J Thomas]

"Rather than increase the price of gasoline, a terribly regressive method of helping y'all to sleep better at night, let's raise the funds through a "the special dead guy utils tax" on large estates."

I believe the concept here isn't just to raise money to spend on climate, but to systematicly distort the economy to reduce use of fossil fuels. We can burn a little bit of fossil fuel and keep CO2 in reasonable bounds, probably. At least it would increase very slowly. And if we slow down CO2 buildup we at least have a chance to find out what's going on before it hurts us too bad. So with a big enough tax on fossil fuels we'll have an incentive to find alternatives.

I'm concerned though that a big tax might leave consumers without the funds to pay for alternatives, and Congress would find ways to spend the money.

So I want to suggest again that we should give every registered voter (and maybe each citizen? And maybe legal residents? And possibly illegal residents ;) ) a federal debit card. And when we collect taxes from fossil fuel producers, every two weeks we split the income evenly among all the citizens and deposit it in their federal accounts. So we get all the effects of a tax to distort spending patterns, but we don't actually hurt consumers.

Say you normally spend $200/month on gasoline. It's a lot of money but you just grit your teeth and bear it. If, because of the tax, you're spending $400/month on gasoline but you get $200 from the government, then you don't have to do anything. Spend the extra money on gasoline and nothing's changed. But anything you do to reduce your gasoline use puts money in your pocket. Twice as much as it did when you only spent $200.

Businesses wouldn't get any tax refund, they'd pass their increased costs on to consumers. Businesses that find ways to make their products using less fossil fuel could make more profit or sell cheaper.

Systematically distort the economy to use less fossil fuel with a minimum of side effects. It amounts to a funds transfer from consumers who use more fossil fuel to consumers who use less. It would incidentally tend to amount to a regressive tax, because people who consume more will consume more fossil fuel and pay more hidden tax, but they'd get only the same refund as everyone else. People who consume more tend to be richer.

And all it costs is the funding to run the system -- to tax fossil fuels at their source, and to distribute the money.

We'd need some sort of arrangement for exports, so our exports wouldn't be penalised by a tax that foreign goods don't get.

[lgm]

I am not impressed when conservatives propose to ignore global warming because the science is not solid. This seems to be the excuse, not the reason, as they put greater stock in "science" that is far less solid.

In the case of Hansen/Weitzman, contrast: "I have always said that my objections to the prescriptions of the most vocal climate change advocates are on three levels: one, the climate models depend too much on positive feedbacks that are not understood; two, the models have not really been tested, but instead are calibrated to the historical data;..." -- Note, someone with no training in climate science feels qualified to give an expert opinion on amply peer-reviewed expert conclusions.

Now, to econometric modeling: "To summarize the contrast: The Stern Review calls for a carbon tax of $350 per ton of carbon in 2015. Nordhaus’ model, which has been peer-reviewed many times, calculates the optimal carbon tax in 2015 to be ONE-TENTH of that, or only $35 per ton carbon." -- As practicing economists, they must know that econometric models suck (an empirical fact). They are calibrated to historical data (like climate models). No amount of peer-reviewing will change that.

[lgm]

I am not impressed when conservatives propose to ignore global warming because the science is not solid. This seems to be the excuse, not the reason, as they put greater stock in "science" that is far less solid.

In the case of Hansen/Weitzman, contrast: "I have always said that my objections to the prescriptions of the most vocal climate change advocates are on three levels: one, the climate models depend too much on positive feedbacks that are not understood; two, the models have not really been tested, but instead are calibrated to the historical data;..." -- Note, someone with no training in climate science feels qualified to give an expert opinion on amply peer-reviewed expert conclusions.

Now, to econometric modeling: "To summarize the contrast: The Stern Review calls for a carbon tax of $350 per ton of carbon in 2015. Nordhaus’ model, which has been peer-reviewed many times, calculates the optimal carbon tax in 2015 to be ONE-TENTH of that, or only $35 per ton carbon." -- As practicing economists, they must know that econometric models suck (an empirical fact). They are calibrated to historical data (like climate models). No amount of peer-reviewing will change that.

[Matt]

Exactly the point. We are living under conditions of uncertainty, not risk. There is some chance--one we cannot quantify--that global warming will result in catastrophe, not cost or unpleasantness.

[Roger Albin]

For those interested in this debate, there are a pair of short recent relevant pieces in Science, one co-authored by Nordhaus, one co-authored by Stern. As a non-economist, I found both well written and well argued. On balance, I thought Stern had the better of the argument. He and his co-author make a very good methodological point about the nature of presently used discounting methods that supports his approach.

[Dallas Weaver]

One factor that seems to be overlooked in all the discussion relating time, money and risk is that the cost of impacting the atmosphere CO2 levels is a function of when and how fast you do it. The CO2 problem in the atmosphere is an inventory problem and when you are talking about emissions you are talking about rate of additions to the inventory. The cost of removing a ton of CO2 from a gas stream such as power plant flue gas depends upon the concentration of CO2 in the gas being scrubbed. The higher the concentration, the less it costs per ton removed. If we forget about the CO2 issue until the "black swan" or fat tail becomes evident, we could take all the existing CO2 sources to zero and still not impact the inventory of CO2 -- the climate driver. We would then have to remove CO2 from the atmosphere, where the concentrations are (even in the future) a factor of 100 to 1000 lower than the concentrations in stack gas, reformer gas, cement kiln exhaust, etc. That would increase the cost and energy consumption associated with removal by a corresponding very large factor. This is just pure mass transport theory as applied to a micro-economics problem and there is no way around the physics of the problem.

Unlike some other pollutants like methane, CO2 has a very long half life in the atmosphere. This means that the system has no reverse gear. With our limits to changing heavy industry fast, we don't even have good breaks, if we find that something is going to go drastically wrong with our planet.

You should note that the CO2 sinks like trees are only a short term option as the burn/rot rate approaches the growth rate with a net zero carbon inventory change (this is true for all aerobic biomass carbon storage pools like soil carbon, etc.). The oceans are a reasonably long term sink, but the turnover time is in the 10 century range so it will take a long time before the oceans come to equilibrium with our new CO2 levels.

[J Thomas]

Dallas, it sounds like you're knowledgeable about this topic.

Freeman Dyson has suggested that we can solve our emissions problem simply by increasing topsoil depth by 0.1" per year over half the landmass of the world. He says this would not be difficult.

http://www.edge.org/3rd_culture/dysonf07/dysonf07_index.html

What do you think of this idea?

[Ginger Yellow]

"Do we not think that people 200 years from now will enjoy more leisure, better health, better technology, and generally be better able to pursue life, liberty, and happiness?"

Not if they're underwater or homeless, no.

J Thomas: Dyson's proposal is insane.

"Changes in farming practices such as no-till farming, avoiding the use of the plow, cause biomass to grow at least as fast as this. If we plant crops without plowing the soil, more of the biomass goes into roots which stay in the soil, and less returns to the atmosphere. If we use genetic engineering to put more biomass into roots, we can probably achieve much more rapid growth of topsoil"

Maybe we can. We would also devastate crop yields, causing mass starvation, food riots and so on.

[piotr]

A non-economist take: it seems that the real horror is in spending money on something useful.

It is OK to spend a trillion or so on a war waged with imperfect inteligence.

It is OK to spend a trillion or so and produce a lot of bad loans in the process, so someone looses a trillion or so.

It is horrible to spend a trillion or so to decrease, and eventually, arrest, the climate change.

About regressive carbon taxes: you want poor folks to live in an energy efficient way, you must make the inefficient way hard to afford. It is very easy to balance regressive taxes with progressive distribution of benefits: this is what most Europe does. In Germany VAT on books and food is 9%, on the rest it is 19%, and the system manages to be progressive at the end of the day. And gasoline is at the moment ca. 8 dollars per gallon. Lower middle class uses public transit, walking and bicycles.

Clearly, something has to be done so the poor and lower middle class will be able to cope with new prices of fuel, basically, they need help in energy-saving investments. For example, inexpensive 80 mpg cars already exist (allegedly, they are not convenient but with a bit more cost and a bit less efficiency they can be convenient and run 70 mpg).

[J Thomas]

Hi, Ginger. I was thinking it was worth pilot projects in case it isn't all that bad. More topsoil is a good thing if it isn't too expensive, even if it doesn't sequester enough carbon to help much with climate change.

I was real curious about his estimates, too. If he's right about the amounts of topsoil, well, in 1970 we were estimating the USA had lost 3 inches of topsoil in the last couple of centuries. How much would global loss of humus contribute to the carbon problem? It could be a source that doesn't get counted with fossil fuels.

On the other hand, maybe he's way off when he estimates the amount of carbon in topsoil.

[James Killus]

I did a calculation a while back to see what level of carbon tax would fund the entire U.S. Federal government. It comes to just short of $1500 per ton.

Just sayin'.

[vtcodger]

***We are living under conditions of uncertainty, not risk. There is some chance--one we cannot quantify--that global warming will result in catastrophe, not cost or unpleasantness.***

Exactly!

A parable if I may.

The mayor of Lotusville and some consultants are examining a recently discovered leak in the Forlorn Hope Canyon dam which towers over the town. The gal from Strawhouse Brothers says in effect "It's not a very big leak and there are signs that it's been seeping here a long time. Stuff in some hydraulic cement and she'll be fine." She presents a 40 page report couched in polysyllables (Geologists love polysyllables and there is no known case of an engineer who can write comprehensible English) and a bill.

The dude from Brickhouse Brothers says "Yeah, it might have been seeping for a while, but there is a fair amount of water coming through that crack and it's only going to get worse over time. We think you should drain down the reservoir and rebuild the dam." He presents an incomprehensible 43 page report and a bill.

The mayor says "Thanks folks, but I you don't agree and I can't really understand what you are talking about, so I'm not going to do anything until I understand the problem better."

Four months later the dam bursts destroying most of the town, killing many of the inhabitants, and leaving half the survivors homeless. The mayor says "Who knew that dam might fail?"

The dam bursting is the case of climate is toggling the planet from the current state which has substantial ice caps at the poles to what we are very sure is the more normal state of ice free poles. If all the ice in the Greenland and Antarctic ice caps melts, quite a lot of land is going to disappear and a fair percentage of human infrastructure is going to be underwater. The cost is going to be horrendous.

[wood turtle]

If the normal state of the earth is ice free poles, then maybe the cedars of Lebanon will come back.

Some areas might benefit greatly from global warming, a more tropical earth might give way from deserts to fertile ground.