http://www.nytimes.com/2005/01/02/books/review/02SINGERL.html?
pagewanted=1&ei=5070&en=76f9dac1d63616b8&ex=1168664400

Richard A. Posner, a judge on the United States Court of Appeals for the
Seventh Circuit, is the author of "Catastrophe."

'Catastrophe': Apocalypse When?

By PETER SINGER

Published: January 2, 2005

AN asteroid colliding with the earth could cause the extinction of our
species. Is this a risk worth worrying about? More important, is it a risk
worth doing something about? Richard A. Posner, a judge on the United
States Court of Appeals for the Seventh Circuit, who produces more books in
his leisure hours than most authors do working full time, thinks it is.

We should also, he argues, be doing more about other improbable
catastrophes. Global warming could cause the melting of icecaps, releasing
huge amounts of methane that accelerate further warming, forming a cloud
layer so dense as to block out heat from the sun and cause us to go into a
deep freeze. High-energy particle accelerators, used by physicists to
investigate the fundamental laws of nature, could produce particles that
create hyperdense ''strange matter'' that in turn might attract nearby
nuclei, thus growing larger and attracting ever more nuclei, until the
entire planet is compressed into a sphere no more than 100 meters in
diameter.

Not worried about these possibilities? Then what about the prospect of
bioterrorists genetically modifying an incurable strain of smallpox that
wipes out the human species? That might seem a more realistic scenario.

''Catastrophe'' lives up to its title. But it is no sci-fi potboiler, and
there will be no movie. Posner made his name defending an economically
rational approach to the law, and his new book is dense with complex
calculations of the expected costs of catastrophic events, and the amount
worth spending in attempts to avert them. The expected costs of a future
event are the costs of that event, if it should happen, divided by the
probability that it will happen. Thus, if I offer you $1,000 if a tossed
coin turns up heads, the expected cost of my offer is $500. (Suppose I
offer you $100,000 if a card drawn at random from a full pack is the ace of
spades. Would you prefer that offer to $1,000 tied to the toss of the coin?
Anyone interested in maximizing his assets would: the expected cost of that
offer to me -- and hence the expected value to you -- is $1,923.)

When a catastrophe is really catastrophic -- and Posner, it should be
emphasized, isn't writing about ''minor'' disasters like the terrorist
attacks of 9/11 -- it can have a significant expected cost, even if the
event is extremely improbable. Consider, for example, the risk that a high-
energy particle accelerator will produce a ''strange matter'' disaster. The
official risk-assessment team for one of these accelerators, at the
Brookhaven National Laboratory, offered a series of estimates, one of which
puts the annual risk of a disaster at one in five million. That seems a
very small risk. But since the disaster would kill six billion people, that
estimate gives it an expected cost of 1,200 lives per year. Even if the
risk is estimated more conservatively at one in a billion, it has an
expected annual cost of six lives. Would we build such an accelerator if we
knew that six people would die every year in which it operates?

In the third and most difficult chapter of ''Catastrophe,'' Posner explores
ways of calculating the costs of catastrophic risks and of possible
responses to them. He rebuts the claim that it is not cost-effective to do
anything about global warming, an argument that invariably relies on
heavily discounting disasters that will not occur for 50 or 100 years. We
may wish to invest money to generate wealth rather than spending it to
avert gradual global warming, but, as Posner suggests, the victims of the
warming are likely to be concentrated in poor countries and will not
necessarily benefit from the increased wealth generated by the richer
nations. (On the other hand, abrupt, spiraling global warming that flips
over into a deep freeze could kill us all, and then increased wealth will
not do us any good anyway.)

Any economic discussion of the expected cost of catastrophe must put a
dollar value on human life. Some will object to this in principle, but
unless we can agree on a figure, it will be impossible to decide what
expenditure is worth incurring, to build safer roads, say, or to keep
minute quantities of toxic chemicals out of our drinking water. Economists
working in this area usually investigate how much people are willing to pay
to reduce the risk of death -- for example, by buying safety devices for
their homes, or preferring to work in a safer occupation for a lower wage
than they could get in a high-risk occupation. The reduction in risk is
then multiplied by the sum the average person is willing to pay for it to
arrive at the value people implicitly place on their lives. Currently, most
government departments use a figure of around $5 million, give or take a
million or two.

One problem with this approach is that most of us assess large risks
differently from small ones. We may pay a steep price to reduce a risk of
one in a thousand to one in ten thousand, but we are not much concerned
about reducing a risk of one in a million to one in a billion. Yet a
rational person who is interested in continuing to live should be willing
to pay something for this reduction in risk. Clearly, these data show that
while people appear to be moderately competent at assessing large risks,
they are not very good at thinking about small risks. Posner, however,
mostly takes the data on their face, and suggests that the value of a human
life actually varies in accordance with the degree of risk we are
considering -- so that the loss of each human life in a highly improbable
catastrophe should be valued only at $50,000 instead of the $5 million that
it would be valued at if we were considering a more likely disaster. This
is bizarre. The real worth of our lives has nothing to do with the
probability of a particular cause of death.

IN short, Posner really has a much stronger case for saying we should spend
more to avert small risks of catastrophe than his own calculations
indicate. And the case gets stronger still if we take into account some of
the larger ethical issues he rapidly brushes aside, especially the question
of how we should view the fact that the extinction of our species would
prevent the existence of all future generations of human beings. Barring
catastrophe, our species may continue to exist for millions of years,
gradually overcoming our problems and achieving a level of happiness,
fulfillment and moral virtue -- including concern for the well-being of
other species -- that far exceeds anything we have yet known. Arguably,
this makes a catastrophe that causes our extinction a much greater tragedy
than the ''mere'' death of six billion people.

Posner's practical recommendations seem calculated to parcel out irritation
to everyone. Physicists will not like the doubts he casts on particle
accelerators. Liberals will be alarmed by his support for greater police
powers to counteract bioterrorism, including censorship of scientific
publications that could help terrorists devise new biological weapons.
Conservatives will dislike his support for taxes on carbon dioxide
emissions, and will be apoplectic at his proposal that we hand over some of
the nation's sovereign powers to an international environmental protection
agency to enforce an improved version of the Kyoto Protocol on global
warming.

As for ordinary readers, they will most likely be annoyed by the book's
frequent repetitiveness, particularly in the concluding chapter, and may
wonder what the two pages urging severe punishment for computer hackers are
doing in a book about catastrophes. (Did Posner lose part of his manuscript
to a computer virus?) Still, we would be well advised to set aside such
minor discontents and take the message of this book seriously. We ignore it
at (a small risk of) our (very great) peril.

Peter Singer is a professor of bioethics at Princeton University. His
recent books include ''One World'' and ''The President of Good and Evil:
The Ethics of George W. Bush.''

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