2 posts tagged “climate change”
For Project Syndicate...
What do we owe our great-great-great grandchildren? What actions are we obligated to do now in order to diminish the risks to our descendants and our planet from the increasing likelihood of significant global warming and its associated climate change?
Everybody--well, almost everybody: ExxonMobil, U.S. Vice President Richard Cheney, and their paid-for servants and deluded acolytes are exceptions or pretend to be exceptions--understands that when human burn hydrocarbons carbon dioxide goes up into the atmosphere, where it acts like a giant blanket, absorbing infrared radiation coming up from below and warming the earth.
Everybody understands that we really do not know how much global warming a given amount of extra carbon dioxide produces. We have models, we have forecasts, we have projections, but global warming might be a much smaller and might be a much larger problem than the central-case projections of climate models suggest. Everybody--well, almost everybody: ExxonMobil, U.S. Vice President Richard Cheney, and their paid-for servants and deluded acolytes are exceptions or pretend to be exceptions--understands that here uncertainty is not our friend, and certainly not an excuse for inaction. Uncertainty about its effects should lead us to do more to guard against global climate change than if we knew global warming would proceed exactly as the central-case projections forecast.
Everybody--well, almost everybody: ExxonMobil, U.S. Vice President Richard Cheney, et cetera, et cetera--understands that the world's governments, non-profit institutions, and energy companies ought to be spending a much bigger fortune than they currently are on research: research into technologies that generate power without adding carbon dioxide to the atmosphere, research into technologies that such carbon out of the atmosphere into forests or oceans, research into technologies that cool the earth by reflecting more of the sunlight that lands on us.
Everybody--well, almost everybody: U.S. Vice President Richard Cheney, et cetera, et cetera--understands that the burden of dealing with global climate change over the next two generations should be carried by the rich countries of the world. They got to take an easy carbon emissions-intensive path to industrialization and riches. It looks like China, India, and company will not be able to take such an easy path, and it would be unfair to penalize them for the loss of the easy hydro-carbon burning road.
Everybody--well, almost everybody, et cetera, et cetera--understands that now is the time to build the international institutions that will manage our reactions to global climate change over the next several centuries. Now is not the time to disrupt these institutions, or to prevent their creation.
What there is real dispute about is what else we should be doing right now and in the next decade. We economists like to think of things in terms of prices. And when we economists see something going wrong in the sense of having destructive side-effects, we like to tax it. Taxing it makes the individuals who are undertaking actions feel in their wallets the destruction they are causing elsewhere. Maybe the action is still worth doing, and maybe not. Imposing a tax--imposing the right tax--on those who are, say, driving low-mileage SUVs is a way of harnessing the collective intelligence of humanity to deciding in which case the bad side-effects are a reason to stop. But it has to be the right tax.
An SUV going ten miles in the city and burning a gallon of gasoline pumps about 3 kilograms--6.5 pounds--of carbon in the form of carbon dioxide into the atmosphere. Should the extra tax on this--and on all carbon emissions--appropriate for global warming be on the order of five cents a gallon, fifty cents a gallon, or a dollar fifty a gallon? Our views will change as we learn more, but at the moment whether the tax should be five or fifty cents a gallon hinges on a question of moral philosophy: how much do we believe that we owe our distant descendents?
Australian economist John Quiggin has a very illuminating discussion on his website <http://johnquiggin.com/wp-content/uploads/2006/12/sternreviewed06121.pdf>. The *Stern Review on Global Climate Change* (on the internet at <http://www.hm-treasury.gov.uk/independent_reviews/stern_review_economics_climate_change/sternreview_index.cfm>) which comes down more on the side of fifty cents a gallon, immediately, does so because they project that spending today to reduce carbon emissions is a very good investment for the future. If the world grows in per capita income at about 2% per year, a marginal expenditure of roughly $70 today in cutting carbon emissions would be worth it if it were to enrich the world of 2100 by about an extra $500 of year-2006 purchasing power, once all the damages to the world economy and environment from global warming, costs of adjustment, and so on are taken into account. This looks like a very good deal to Nick Stern and his team.
On the other hand, critics point out that the world today is poor: average GDP per capita at purchasing power parity today is roughly $7000. We expect improvements in and the spread of technology to make the world of 2100, at a 2% per year growth rate much richer than the world of today: $50,000 per capita of year-2006 purchasing power. We today can use the marginal $70 per capita, critics say, much more than the richer people of 2100 will need the $500 they would gain from not having to suffer from the effects of global climate change.
What critics don't often say is that the same logic applies to the world today. The U.S., Japan, and Western Europe today have average incomes of roughly $40,000 per capita. The poorer half of the world's population today have incomes of less than $6,000 per capita. I believe that the same logic which says that we today need our $70 more than the people of 2100 need an extra $500 also tells us that we ought to tax the world's rich in the OECD more and more to fund world development as long as each extra $500 in first-world taxes generates even as little as $70 in extra poor-periphery incomes. If we in the world's rich now are stingy toward the (likely to be much richer) future and want to leave them our environmental mess to deal with, we should be lavish toward our poor brothers and sisters today. If we today are stingy toward our poor brothers and sisters now, we should be lavish toward our descendents.
At least, that is what we should do, if our actions are based on some moral principle--rather than on the principle that what we have, we hold.
Partha Dasgupta Makes a Mistake in His Critique of the Stern Review
Partha Dasgupta makes a mistake. This is a rare, rare, rare event. Dasgupta writes, criticizing the Stern Review:
http://www.econ.cam.ac.uk/faculty/dasgupta/Stern.pdf: To give you an example of what I mean, suppose, following the Review, we set delta equal to 0.1% per year and eta equal to 1 in a deterministic economy where the social rate of return on investment is, say, 4% a year. It is an easy calculation to show that the current generation in that model economy ought to save a full 97.5% of its GDP for the future! You should know that the aggregate savings ratio in the UK is currently about 15% of GDP. A 97.5% saving rate is so patently absurd that we must reject it out of hand. To accept it would be to claim that the current generation in the model economy ought literally to starve itself so that future generations are able to enjoy ever increasing consumption levels...
In the "deterministic economy where the social rate of return on investment is, say, 4% a year" model that Dasgupta is using, the concept of "output" Y is Haig-Simons output--what you could consume and still leave the economy next year with the same productive capacity as it has this year. With that definition of output Y, with consumption level C, and with social rate of return on investment r, it is indeed the case that the growth rate g(Y) of a zero-population-growth economy is:
g(Y) = r(1 - C/Y)
Take the expression for the rate of growth of consumption g(C) as a function of the parameters δ and η:
g(C) = (r - δ)/η
And see that the assumed values for r, δ, and η give us a 3.9% per year growth rate of consumption. If you impose the steady-state requirement that the growth rates of consumption and output be the same, you do indeed get a 97.5% savings rate--that consumption is 2.5% of Haig-Simons output:
C/Y = .025
because with r=4% per year that is the only way to get g(Y)=3.9%
But suppose that you use a different concept of output--GDP--and say that productive capacity increases not just because you save some of GDP but also because of improvements in knowledge and technology g(A), so that:
g(Y) = r(1 - C/Y) + g(A)
with worldwide g(A) equal, say, to 3% per year. Then our g(C) equation still gives us a 3.9% per year total economic growth rate, but our g(Y) equation is then:
3.9% = g(Y) = r(1 - C/Y) + g(A) = 4%(1 - C/Y) + 3%
which gives us a savings rate not of 97.5% of Haig-Simons output but rather of 22.5% of GDP, leaving 77.5% of GDP for consumption.
A consumption-to-output ratio of 77.5% is far from absurd, and so Dasgupta's critique of Stern fails. His mistake is in failing to remember that in his model Haig-Simons output is very, very different indeed from standard reported GDP.
That being said, I agree with most of Dasgupta's major point: the action here is in the choice of the parameter η. I think it's appropriate to consider different ηs in the range from 1 to 5, and think the Stern Review should have done so.
(I'm also enough of a utilitarian fundamentalist to believe that the right value for δ is zero, and that Nordhaus's δ of 3% per year is unconscionable--it means that somebody born in 1960 "counts" for twice as much as somebody born in 1995, who in turn "counts" for twice as much as somebody born in 2020; somebody born in 1960 "counts" for 256 times as much as somebody born in 2160. That's not utilitarianism.)
