April 2010

My colleague (and blog contributor) Frank Ackerman has a new article on Grist that explains why the United States can’t afford to settle for the “social cost of carbon” estimate used in the fuel-efficiency and tailpipe emissions standards unveiled April 1.

As we outlined in our recent white paper, “The Social Cost of Carbon” (available on the E3 Network website), the $21-per-ton figure being used by the government as a “central estimate” of the damages caused by carbon dioxide emissions is based on flawed economics and questionable value judgments.

Frank’s article describes how the government came up with that number, and why the SCC is so important: It’s like a “volume dial” that determines how strict environmental standards should be. Even worse, as Congress considers a climate bill, the $21 SCC could be taken as the recommended level for a carbon tax or permit price:

If that happens, there is no way the United States could reach the widely discussed, science-based goal of cutting emissions by 80 percent by 2050, which would require a much higher price on carbon. Given how cost-benefit analyses dominate U.S. policymaking, a $21 SCC could have a devastating impact on environmental legislation.

It’s easy to think of the fuel-efficiency standards as yesterday’s news, and not discuss the SCC again until it comes up in Congress. But in fact, now is the time to do our homework and figure out what the true price of carbon should be – before that, too, is a done deal.

Paul Krugman’s excellent article in the New York Times Magazine this weekend contrasts a slow, incremental approach to greenhouse gas mitigation (such as William Nordhaus’ “climate-policy ramp”) to more rapid measures better fitting the urgency suggested by the climate science literature. Krugman dubs the latter the “climate-policy big bang.”

Krugman has done a nice job of describing some of the major points of disagreement within the field of climate economics. Here’s his view:

[T]he policy-ramp prescriptions seem far too much like conducting a very risky experiment with the whole planet. Nordhaus’s preferred policy, for example, would stabilize the concentration of carbon dioxide in the atmosphere at a level about twice its preindustrial average. In his model, this would have only modest effects on global welfare; but how confident can we be of that? How sure are we that this kind of change in the environment would not lead to catastrophe? Not sure enough, I’d say, particularly because, as noted above, climate modelers have sharply raised their estimates of future warming in just the last couple of years.

Krugman concludes that the “nonnegligible probability of utter disaster” should guide our climate policy, and that this “argues for aggressive moves to curb emissions, soon.”

Anyone who has been reading this blog will know already that I feel that the evidence of both the climate science and climate economics literatures overwhelmingly supports a big-bang climate-policy approach. It’s nice to know that Paul Krugman is a supporter of these views, and it’s even nicer to have his clear and influential thoughts on this reach such a wide audience.

Why would the Obama administration allow new drilling in U.S. coastal areas, and what will it mean for greenhouse gas reductions? My colleague Frank Ackerman has a posting on the TripleCrisis blog today on off-shore drilling, peak oil, and how they relate to a carbon tax:

Solving our energy problems, without a change in direction, will lead to increasingly costly and environmentally destructive production – either deep offshore, or deep in the rocks below existing communities and watersheds. We need a tax (or a fee resulting from an allowance system) on energy, to keep the cost to consumers high enough to encourage conservation, while holding the price for producers low enough to discourage the pursuit of the worst fossil fuel deposits.

This is another way in which the distributional consequences of carbon permit giveaways (i.e., who gets the revenue – see Alejandro Reuss’ Public Goods posting from earlier this week) differ from those of permit auctions. A cap and trade system will increase the price of oil exploration only if businesses have to pay for their permits; if permits are given to the largest polluters for free, there will be no incentive to limit fossil fuel extraction from areas where underground reserves are not very rich and the environmental consequences of extraction are enormous.

Most economic analyses of “cap-and-trade” policies – under which the government sets a target amount of emissions and then issues tradable permits totaling that amount – take it for granted that it would not make any difference, in the reduction of emissions, if the government were to sell the permits or give them away. A 2008 report on cap-and-trade climate policies from the MIT Center for Energy and Environmental Policy Research puts it like this: “Economic theory suggests that the method of distributing emission allowances, i.e., through grandfathering or auctioning, will not affect an individual source’s output decisions or emissions.”

If firms always make optimal decisions, maximizing their profits, as mainstream “neoclassical” economists assume they do, this conclusion should be correct. It shouldn’t make any difference to a profit-maximizing firm whether, by reducing its emissions, it avoids the cost of buying emissions permits or reaps the benefit of selling permits. Either way, it will reduce emissions as long as the cost of doing so is less than the price of the permit.

But are real-life firms really the perfectly rational profit maximizers of the neoclassical economists’ imagination? Some insights from behavioral economics suggest they may not be, and therefore that they may react differently to a policy that makes them buy emissions permits compared to one that gives them permits for free.


An Obama administration task force has recently proposed that $21 per ton is an appropriate “social cost of carbon.” (The social cost of carbon, or SCC, is an estimate of the damage caused – both today and in the future – by the release of an additional ton of carbon dioxide into the atmosphere; it’s a topic that I’ve discussed frequently in this blog (see here, here, and here). A bigger SCC means that the federal government is willing to do more to more to slow greenhouse gas emissions; conversely, a smaller SCC means that fewer emissions abatement measures will be considered “economical.”) In an Economics for Equity & Environment white paper, released today, Frank Ackerman and I discuss the very serious errors and omissions that have led to EPA, OMB and other agencies’ promotion of what is a very low SCC.

As our paper demonstrates, the calculation of the SCC is less science than alchemy. It is also – like much of cost-benefit analysis – a very strange way of making decisions. Cost-benefit analysis sounds like common sense: weigh the costs of an action against the benefits. A good policy will have net benefits; a bad policy, net costs. Simple.

Well, actually, no, not so simple. There are (at least) three big problems:

Problem #1: When it comes to the greenhouse gas emissions (and many other environmental issues) we can’t measure the costs and benefits with any accuracy. We’ve never filled the atmosphere with CO2 before. We’ve never tried to remove large quantities of CO2 from the atmosphere before. Some of the important consequences of climate change, such as the loss of human lives and risks of extinction of endangered species, simply don’t have meaningful prices (although economists have at times made up dollar values for them). And many of the costs of halting emissions and benefits of averting damages will occur well into the future. That’s a lot of uncertainty, which doesn’t tend to increase the accuracy of economic predictions.

Problem #2: Many of the costs and benefits will affect not us, but our great-grandchildren, and there is a fair amount of disagreement (a least among economists) about how to weigh these future impacts in the decisions we make today. Some (like me) say we should weigh all damages equally regardless of whether it is us or our descendants that suffer the costs. Others feel that future costs (and benefits) are worth far less than those that take place today.

Problem #3: While climate policy will benefit humanity as a whole, the costs of reducing emissions and the benefits of avoiding a climate catastrophe will impact different people differently. Most people will be net gainers from climate policy (more benefits than costs), but some will be net losers (more costs than benefits). This is true both across generations – future generations are the biggest net gainers from climate policy – and among the Earth’s population today. As a broad generalization, poorer people have more to gain from climate policy. The more one weighs the interests of the net losers compared with the net gainers, then, the less one will conclude that we should do to avert climate change.

In short, cost-benefit analysis is complicated, and its results are open to a lot of interpretation. Regrettably, that is how the U.S. government makes decisions about environmental issues. In a cost-benefit analysis of emission reducing policies, the social cost of carbon is the benefit from each one-ton reduction in carbon emissions (it’s the damage that doesn’t happen, and thus, a benefit). A bigger SCC means a bigger benefit from reducing emissions, making it more likely that any particular carbon reduction policy will pass muster as delivering greater benefits than costs.

There is no way to truly measure the SCC. (Seriously, all climate damages throughout time reduced to one figure in today’s dollars? If you really have faith in such a figure, I have a bridge in Brooklyn that I’d like to sell you.) The Obama administration should consider looking at the problem of emissions abatement from an entirely different angle: For example, by how much do we need or want to reduce U.S. emissions, and what’s the cheapest way to do that? Alternatively, how much can we afford to devote to insuring ourselves against the danger of catastrophic climate change? Decisions made from starting points like these are far more likely than cost-benefit analysis to result in a climate policy that is both effective and economical.