You don’t “follow” me on the science, asking what it is about our limited ability to influence greenhouse gas levels that gives me “comfort.” Actually, it gives me angst. I worry that policymakers, influenced by Hansen et al., will try to do the undoable. If policymakers buy into the notion that we must reduce GHG levels to 350 ppm or civilization will perish, then in principle there can be NO LIMIT to the economic sacrifices they can demand of the American people (or, worse, people in developing countries).

Perhaps what you meant to question was my apparent lack of angst about humanity’s “uncontrolled experiment” on the climate system. Herewith a few responses:

(1) I acknowledge the reality of climate change risks, but alamists wildly exaggerate those risks and/or fob off airy speculations as scientifically-based predictions. The lack of warming of the past decade and the relatively low rate of warming of the past 30 years (~0.17C/decade) indicates a relatively low climate sensitivity. If I had to bet, I’d bet that 21st century warming is at the low-end of the IPCC forecast range.

I am also persuaded by Indur Goklany (“Is a Richer-but-warmer World better than Poorer-but-cooler Worlds,” Energy & Environment Vol. 18, nos. 7 and 8, 2007), that even if the Stern Review is correct about the economic impacts of a high-end 21st century warming, people in developing countries will still be much better off in 2100 than people in developed countries are today. Al Gore’s claim that global warming “threatens the survival of civilization and the habitability of the Earth” seems to me based on ideology, not science.

(2) Just as there are risks of climate change, there are also risks of climate change policy, and the latter are more hazardous to human health and welfare. Recall that the environmental movement’s first great crusade was against DDT. On the basis of pseudo-science (claims that DDT would cause cancer epidemics and wipe out avian life), the United States and many other nations banned DDT. The consequences were horrendous. Malaria, a disease that DDT had all but wiped out in many African countries, came back with a vengeance. Since the 1960s, some 40 million Africans have died who probably could have been saved by responsible use of DDT. A similarly large death toll could result if carbon tariffs prevent developing countries from exporting their products or investing in affordable, carbon-based energy.

(3) As Indur Goklany explains (“What to Do about Climate Change,” Cato Institute Policy Analysis No. 609, 5 February 2008), targeted investment (“focused adaptation”) to solve underlying health and environmental problems that global warming might exacerbate and broad-based economic development could save many more lives at far less expense than would cap-and-trade or carbon taxes.

Yes, I’m aware that Hansen has published studies estimating climate sensivity partly based on paleoclimate research. However, Hansen did not reference those studies in his testimony. He provided no specifics, nor did he attempt to explain how paleoclimate research supports his estimate of climate sensitivity. So I saw no reason to say more about this subject than Hansen did.

As noted in my column, John Christy presented quantative evidence that the model projections Hansen used in 1988 to launch the global warming movement overshoot actual temperature trends. Hansen invoked “paleoclimate information” not to rebut Christy’s testimony, but to avoid having to discuss it. Rather than debate climate sensitivity with Christy, Hansen advised the Committee to ask the National Academy of Sciences to tell Congress what to think. This appeal to authority rather than to evidence is contrary to the spirit of science.

Is a carbon tax preferable to cap-and-trade? In the abstract, yes, but in the real world, it all depends. A very high carbon tax would be more economically damaging than a very modest cap. To be politically sustainable, either carbon caps or taxes would require enactment of carbon tariffs, which could lead to trade wars and worse.

If carbon taxes are high enough, they kill coal–Hansen’s avowed goal. But that would send electricity prices through the roof, with potentially devastating effects on productivity, GDP growth, and wages, easily swamping the dividends that more or less offset consumer losses from higher gasoline prices and household energy bills.

BTW, surely you are aware that Hansen has earlier offered extensive information that paleoclimate records indicate that long-range climate rsponse to a CO2 doubling is on the scale of 3 degrees C. Did you miss that? Or were you more eager to say that Hansen’s reference to more recent studies about facts some how implies that Hansen is “dissing” models? What’s the point anyway, other than point-scoring – if facts appear to indicate that long-term sensitivity is relatively high, should we be ignoring that and placing our faith in models instead? Should facts not further inform models, or policy-makers?

Second, while you note Hansen’s attack on cap & trade and his “tax and dividend” proposal “quite clever”, you fail to offer any opinion on the realative merits of these quite different proposals. Instead, you offer some sniping criticisms of tax and dividend, as if you are hoping that the consequence will be that the Obama administration, Dems and rent-seekers generally will turn away from climate policy altogether. But isn’t that nothing but wishful thinking, and shouldn’t libertarians and others who prefer to avoid the monstrosity of cap & trade be trying to encourage the efforts of those whose proposals would be much less economically damaging? Isn’t Hansen’s proposal far preferable over cap & trade, and the kind of industrial planning that Jon Adler says is inevitable from the EPA under EPA vs. Massachusetts without legislative action?

Exxon and a host of others (as noted at the blog posts linked at my name) have come clearly down in favor of carbon taxes over cap & trade; perhaps you may at some point care to favor us with your own comparative views.

It seems to me that Hansen’s proposal is clearly preferable; it could be easily implemented and monitored, would not involve large new bureaucracies, would be much more transparent and less susceptible to rent-seeking, would provide market signals on GHGs while having no fiscal impact, would be grounded in the principle that the atmosphere is owned by citizens and not government (or by corporations that are given or purchase rights to emit GHGs), and, by being refunded per capita to citizens would be generally progressive.

Third, as for your criticisms of Hansen’s proposal:

- carbon taxes will hit coal use more heavily than petroluem or natural gas, so focussing first on “pain at the pump” smacks of pandering, especially as revenue recycling may eliminate the pain completely;

- older, dirtier coal plants are already uneconomic and generate tremendous costs to health and property that are not costed to producers or consumers; taxing carbon is a great way to end some of the nonsense incentivized by the CAA. Your speculation about power supply and electricity prices is nothing more than speculation, but oil and gas-fired plants could be brought on line relatively quickly;

- as for the “green stimulus” effect, it is ironic that you fail to see that the fact that “There is no guarantee people will use their dividends to buy hybrid cars, energy-efficient appliances, or green energy” is in fact an argument IN FAVOR of rebated carbon taxes as opposed to cap and trade, as the first allows much greater economic freedom and is thus more conducive to wealth creation. Further, not only is dividending the tax proceeds a great way to make sure that the government doesn’t have an even larger pot to dole out mandates, subsidies and other goodies to favored industries, but the right could trade its acceptance for such a tax for elimination of existing subsidies to ethanol and solar.

- your point about labor productivity is fair, but it ignores the social cost of carbon. Has forcing polluting industries for the ’60s on benefitted society and improved productivity as a whole the whole? Or is it simply more important to allow certain classes of producers and consumers to profit while continuing to shift costs to others?

- as for “massive” transfers, this is all “would” and “could” without any backing, and it completely ignores all of the massive wealth transfers involved in the way we presently regulate power generation and energy (and have refused to regulate GHGs). I’m happy to have more information, but let’s not forget that the whole purpose is to have a closer alignment between profits/benefits and social costs.

It should be noted that the human and domesticated animal populations of the globe were substantially lower in 1750 than they are today. Therefore, even if fossil fuel combustion ceased, dramatic human and domesticated animal population decreases would be required to permit stabilization of the atmospheric concentration of CO2.

IEA has estimated the investment required to reduce annual CO2 emissions by 50% by 2050 would be $45 trillion. It is reasonable to assume that the remaining 50% would be more difficult and more expensive to eliminate. That’s $100+ trillion, or approximately $2.5+ trillion per year over the period. The US share of that investment would be $700+ billion per year, assuming that we were not also expected to provide a share of the funding for the developing world.

The massiveness of this prospective monstrosity makes me wonder why we are paying any attention at all to the relatively trivial “porculus” bill, which is supposedly a “one time thing”.