August 27, 2004 · Richard Posner
The following description of a recent conference on the world’s worst ills, featuring several economists who had been awarded the Nobel Prize in economics, enables me to sink global-warming skeptics and academic public intellectuals with only one salvo.
“An international panel of economists brought together to rank the world’s worst ills ended a weeklong conference in Copenhagen Saturday by listing HIV/AIDS, hunger, trade barriers and malaria as the world’s most pressing problems while relegating global warming to the near-bottom of the list. The eight economists at the Copenhagen Consensus � among them Nobel laureates Robert Fogel, Douglass North and Vernon Smith � were invited by maverick environmentalist Bjorn Lomborg to spend a hypothetical $50 billion in ways that would produce the most results. The panel unanimously gave HIV/AIDS top priority and recommended spending $27 billion to fight it, saying that although the costs were ‘considerable, they are tiny in relation to what can be gained.’ The issue deemed second in importance, malnutrition, was allocated $12 billion. The panel ranked trade liberalization third but allocated no funds to expand it. Fourth-ranked malaria received $13 billion.”
Each of these illuminati was paid $30,000 to attend the conference.
The AIDS epidemic is serious, but it does not threaten to destroy civilization; it is also readily controllable, without medical intervention, by avoidance of promiscuous sex. Malnutrition and malaria are serious problems too, but one effect of eliminating them would be to cause a population surge, which would in turn increase global warming, because added population means added energy demands (met primarily by burning fossil fuels) and added food demands (met in part by deforestation). Unlike AIDS, malnutrition, and malaria, global warming, especially if abrupt, could terminate civilization.
As I mentioned in a previous posting, the global climate equilibrium is fragile. In a period (known as the “Younger Dryas”) of only about a decade some 11,000 or 12,000 years ago, the earth’s temperature rose by 14 degrees Fahrenheit. The climate was very cold (it was the end of the last ice age) when the surge started, so no harm to human beings was done (rather the contrary); but imagine a similar surge today. Suppose the ice sheets that cover Greenland and Antarctica melted, raising ocean levels to the point at which most coastal regions, including many of the world�s largest cities, would be inundated. Or if the dilution of salt in the North Atlantic as a result of the melting of the north polar ice cap, the ice of which is largely salt free, diverted the Gulf Stream away from the continent of Europe. The dense salty water of the North Atlantic blocks the Atlantic currents from carrying warm water from the South Atlantic due north to the Arctic, instead deflecting the warm water east to Europe. That warm-water current is the Gulf Stream. If reduced salinity in the North Atlantic allowed the Gulf Stream to return to its natural northward path, the climate of the entire European continent would become like that of Siberia, and Europe�s agriculture would be destroyed.
Worse is possible. I mentioned in a previous posting the possibility of a runaway methane greenhouse effect, and here I add that it might be augmented by the effect of higher atmospheric temperatures in increasing the amount of water vapor in the atmosphere, because water vapor is another greenhouse gas. It is even conceivable that because increased rainstorms mean more clouds, and some clouds prevent sunlight from reaching the earth without blocking the heat reflected from the earth�s surface, global warming could (paradoxically) precipitate a new ice age�or worse. Falling temperatures might cause more precipitation to take the form of snow rather than rain, leading to a further drop in surface temperatures and creating more ice, which reflects sunlight better than seawater and earth (both of which are darker than ice) do. Surface temperatures might fall so far as to engender a return to �snowball earth.” The snowball-earth hypothesis is that 600 million years ago, and maybe at earlier times as well, the earth, including the equatorial regions, was for a time entirely covered by a layer of ice several kilometers thick except where the tips of volcanoes peeped through.
The hypothesis is controversial. It is unclear whether the conditions required for the initiation of snowball earth were ever present, and whether current or foreseeable conditions could cause such initiation. What is suggestive about the example is the ominous tipping or feedback effect that it illustrates (the domain of chaos theory). A relatively small change, such as an increase in rainfall caused by global warming, or an increase in the fraction of precipitation that takes the form of snow rather than rain, could trigger a drastic temperature spiral. The runaway greenhouse effect involving methane illustrates the same process in reverse, and, as in the rainfall example, one spiral can trigger the opposite spiral; that is the essence of a chaotic system.
The probability of abrupt global warming that would precipitate the disasters that I have described is unknown, but presumably small; yet economists know that to figure the expected cost of some risk, you must consider the consequences if a risk materializes, and not just the low probability that it will materialize. This point was missed by the “Copenhagen Consensus.” Nor is there any indication that the participants had studied the relevant science or conducted any cost-benefit analyses in deciding how to allocate their hypothetical $50 billion. Nor, I believe, were any of the economists experts in the economics of climate change. Economics is a large field, and the fact that one has received a Nobel Prize for work in economic history (Fogel), experimental economics (Smith), or the history of institutions (North) is no warrant of competence to opine on the economics of climate change.