Response to Global-Warmng Comments--Posner

These were a fine set of comments, and let me reply briefly to some of the major points made. One interesting suggestion is that a tax limited to net emissions would create a private market (contrary to what I suggested in my post) for devices for removing carbon dioxide from the atmosphere. A power plant, say, would willingly pay a license fee for such a device if the fee were less than the tax savings from being able to offset the plant's emissions by carbon dioxide that the device removed from the atmosphere. Another commenter points out, correctly but misleadingly, that water vapor in the atmosphere blocks more heat from the earth's surface than carbon dioxide does. That is true. But an increase in atmospheric temperatures brought about by an increased atmospheric concentration of carbon dioxide increases the amount of water vapor in the atmosphere (because warmer air holds more water), and thus has a multiplier effect. It is also true but, to me at least, not reassuring that climate has fluctuated a great deal in the course of the earth's activity quite apart from any human influences on climate. I am not reassured because a human-engendered increase in global temperatures could coincide with and reinforce a natural increase, rather than offsetting it. In this connection, I emphasize the possibility of a runaway greenhouse effect. Becker discusses the underlying problem in terms of multiple equilibria. A less technical way to describe it is in terms of tipping, feedback, or a "vicious cycle." For example, higher atmospheric temperatures cause melting of the permafrost in Alaska and Siberia, which releases methane (stored in great abundance in permafrost), which causes a further temperature rise, which causes more melting and so more release of methane. The fact that severe climatic effects might unfold quite rapidly is a reason not to be comforted by the argument that, after all, the earth might be better off if it were warmer--Greenland would once again be green, Siberia would support agriculture, and so on. If abrupt global warming destroyed tropical agriculture, it would take decades to relocate that agriculture to formerly frigid areas; the transition costs would be immense. It is thus the possible rapidity of extreme climate changes that worries me; and it also makes me doubt that we can count on technology to bail us out. In the long run, yes; but we are probably decades away from the development of economical technologies for arresting human-engendered global warming. We are thus in a vulnerable period in which technology-forcing taxes (or quotas, as discussed by Becker) may be a prudent response. Finally, the fact that abrupt global warming is less probable than gradual global warming is small comfort, because a proper cost-benefit analysis of safety measures takes into account not only the probability of a harm but also the magnitude of the harm should it occur.

Comments

[Eshan Shah-Jahan]

Focusing on net emissions is a step in the right direction, but a cap-and-trade system of emissions credits would be better. In this system, devices that sequester carbon dioxide could sell the credits to emitters.

Think of them as carbon cleaning services. The "Polluter Pays" principle dictates that if you make a mess, you pay to clean it up. So if you emit carbon dioxide into the sky, you should pay to have it taken out. Whether you pay the owner of a rainforest, a floating pool of algae or a machine, you should remove an amount equal to what you added.

Of course, we can't jump to zero net emissions immediately, so we would need some diminishing amout of transition credits. As these disappear, pressure (in the form of economic incentives) will mount to find solutions.

[GMB]

I don't think a runaway green-house effect is worth worrying about. Because from an analysis of the changing orbit of the earth around the sun we find that we are heading into a serious ice age in the medium term (that is to say over the next 1000-4000 years I think).

I think the right policy is the same regardless. I think we should be substituting towards non-renewable resources tax. Perhaps with a short-term focus on oil. Since we want to blow Jihadia our of the financial air, win this war, and get used to other energy sources.

I think its the same policy prescription either way. Since if the climate is due to overheat before the ice age closes in than tax substitution might mitigate this a little. Whereas if the Ice-Age does close without such interim overheating problems then our descendants might be grateful for some fossil fuels to be left readily to hand.

I think these trading systems are a bridge too far. Because particularly as proposed by Kyoto the money is supposed to wind up not in the consuming country. And it amounts to rewarding failure since in the medium term GDP growth and energy consumption are quite closely linked.

A much more doable international agreement is simply a diplomatic roll-out to try and get countries to substitute toward non-renewable resources taxes. But most particularly oil tax at first. Because we are not then handing cash over to socialists for their hopeless economic performance.

[James]

While it is true that human-created carbon dioxide could be augmenting a natural increase, it is also true that it could be preventing a natural cooling trend that might lead to worse outcomes than a warming trend. This is why I believe we need to spend more research on what a warmer or colder climate really means for the world.

I also don't see much danger of the "multiplier effect" simply because previous experience has demonstrated that the climate will fluctuate regardless of occasional spikes in the climate. History has featured numerous times when carbon dioxide levels have increased markedly over our current levels (through volcanic eruptions, for example), the temperature warmed, and yet eventually the trend reversed itself. Most likely this is because a warmer climate leads to longer growing seasons, allowing plants to flourish and eat up more carbon dioxide. Why we should assume that NOW is when the trend might be irreversible does not seem obvious to me.

[Palooka]

It seems both support and opposition to measures to limit global warmly is largely (and correctly) driven by how much faith one puts in the scientific "consensus" on this issue.

Several things give me great pause in taking this consensus seriously. Academic environmentalism has a history of crying wolf. First with the
looming "population explosion" and junk science on pesticides. I agree to a large extent with Michael Crichton, who in this speech (http://www.perc.org/publications/articles/Crichtonspeech.php), likened the environmental movement to a misguided and dangerous religion.

I also have trouble believing their modeling is of much utility in evaluating the dangers of CO2 emissions. In chaotic and exceedingly complex systems, where scientists can't even predict tomorrow's weather, I have serious reservations about putting hundreds of billions down a global warming toilet based off of their ever-changing modeling.

But, alas, I admittedly lack the necessary scientific knowledge to come to my own "expert" opinion.

Still, despite all my reservations, the building scientific consensus deserves attention. Let us assume the climate is in punctuated warming period, and that a significant portion of this is caused by human activity. Even if we are to have confidence in our answers on these exceedingly difficult questions, it does not follow that our resources should be spent on prevention rather than preparation for what may be an inevitable result.

The old addage "an ounce of prevention is worth a pound of cure" is often used in situations such as these. I am not so sure it's true in this case. Reducing our CO2 emissions enough to hault or substantially slow global warming will probably cost more than any country (not to mention the world as a whole) is willing to bear. Then we are left with half measures that cost hundreds of billions of dollars and effectively do nothing. Maybe those dollars would be better spent on preparing and planning for the results of a warming climate. Maybe, in this case, where we can do little to effect the ultimate direction of warming, we are better putting our resources in to adjusting and handling any ill-effect of global warming than in naively trying to influence its direction or pace.

[Jim S]

It's interesting that some obvious things haven't been mentioned here in terms of results of global warming. No realistic model says that we will have a nice even rise in temperatures everywhere. It's a system of energy balances after all. Energy comes in, energy goes out with the important question being how much of each. Even as things warm up there will still be temperature contrasts due to axial tilt and planetary orbit. Hurricanes will be likely to increase in number and severity. The same goes for tornadoes. Storms in general will have more punch to them because warmth is energy. Even blizzards in those areas still cold enough will get worse since the warm air meeting cold air can hold more moisture until it hits the colder air. If you think that insurance companies aren't worried about the long term possibilities...

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