Tikkun Magazine, November/December 1999
A Global Gamble
By S. George Philander
The debate about global warming is a debate about the outcome of a gamble. We are betting that the benefits of our industrial and agricultural activities will outweigh the possible adverse consequences of an unfortunate by-product of our activities, an increase in the atmospheric concentration of greenhouse gases that could lead to global warming and global climate changes. Some experts warn that we are making poor bets, that global warming has started and that disasters are imminent. Others assure us that the chances of global warming are so remote that the outcome of our wager will definitely be in our favor. The impasse is disquieting because the issue is of vital importance to each' of us; it concerns the habitability of our planet. How long will it be before the experts resolve their differences? How long before we must take action?
Some people falsely believe that global warming is a theory which has yet to be confirmed. They do not realize that scientists are in complete agreement that a continual rise in the atmospheric concentration of greenhouse gases will inevitably lead to global warming. The disagreements are about the timing and amplitude of the expected warming. It is as if we are in a raft, gliding smoothly down a river towards dangerous rapids and a waterfall, and are uncertain of the distance to the waterfall. If we know what that distance is then we can tackle the very difficult political matter of deciding on the appropriate time to get out of the water. But all scientific results have uncertainties, which lead to disagreements over plans for action. The result of such disagreements is usually the postponement of the political decision until more accurate scientific results are available - everyone knows that scientists should be capable of precise predictions - or until we are in sight of the waterfall.
We are reluctant to accept that some environmental problems are so complex that precise scientific predictions are impossible, that difficult political decisions are necessary in the face of scientific uncertainties. Consider the two main issues being debated: first, whether global warming is evident in the record of globally averaged temperatures to date; and second, whether the results from computer models of the Earth's climate are reliable.
We experience massive global warming each year as part of the regular seasonal cycle. From the winter solstice, December 21 onwards, the intensity of sunshine increases steadily. Temperatures, however, fluctuate considerably within seasons. Take, for example, the recent weather in Princeton, New Jersey. This past February, the temperature was so high that the forsythia started to bloom. The intensity of sunlight continued to increase thereafter, but March nonetheless brought some snow and even April was cool. Such fluctuations, known as the natural variability of our climate, can mask the transition from one season to the next, and they can also mask global warming associated with an increase in the greenhouse effect. That is why the unusually high temperatures of the early 1990s do not necessarily imply that global warming is under way. Similarly, should the next few years be unusually cold, it will not follow that the risk of global warming has receded. In the same way that we can not determine the transition from one season to the next by monitoring temperatures on a daily basis, so we can not determine the onset of global warming by monitoring temperatures on an annual basis.
To get at the bigger picture and alert us to global warming we have to rely on computer models that simulate the Earth's climate - just as we have to rely on a calendar to mark the change in seasons. The models reproduce many aspects of the climate realistically, but climate and global warming are such complex phenomena that the models fail to capture some features. Most members of the scientific community have sufficient confidence in the current models to accept the forecasts concerning future climate changes. A few critics focus on the models' flaws and cite those as the reasons for rejecting the models' results. These skeptics play a valuable scientific role by forcing a reexamination of assumptions made in the models, thus contributing to their continual improvement. However, the inevitable attention paid to these critics in the press is unrelated to the merits of their scientific arguments. Furthermore, such critics often neglect to point out that, because of the inevitable flaws, the models are as likely to underestimate as to overestimate the severity of global warming.
When we consider how extreme the effects of global warming are likely to be, we ought to pay attention to the geologic record, which contains valuable information about climate changes in the past. That record provides abundant evidence that this planer's climate is sensitive to small perturbations. For example, slight changes in the distribution of sunlight on Earth can cause climate changes as dramatic as recurrent Ice Ages. In spite of this evidence concerning our climate's sensitivity to perturbations, we are proceeding with the creation of a huge disturbance: a doubling of the atmospheric concentration of carbon dioxide, a powerful greenhouse gas.
Still, some experts argue that, until the uncertainties in the scientific results are reduced, we should not implement any policies for fear that those policies will put our economy at risk. Implicit in such statements are assumptions in the form of models that predict how the economy will respond to certain policies. The uncertainties in such economic models are far greater than those in climate models. Economics depends on human behavior, and determining whether a certain policy will benefit or harm the economy is even more difficult than determining how greenhouse gases will affect the climate.
The sooner we start doing something about global warming the better, because by the time that everyone agrees that global warming has started, it could be too late to do much about it. By starting early we can take a gradual approach, finding out which policies work, which do not.
Any policy should be carefully monitored to be sure it satisfies two conditions: (1) it should result in a decrease in the atmospheric concentration of greenhouse gases, and (2) it should not adversely affect the economy The results can be determined only after the policy has been in effect for a while. If it is successful, it should be continued; if not, we can try something else. We must avoid committing ourselves to grand plans that claim to solve the problem once and forever.
We can begin such a sensible plan on an individual level. Since the goal is to reduce the rate at which we inject carbon dioxide into the atmosphere, we should try to use less energy by using public transportation or driving fuel-efficient vehicles.
Every day, all of us - businessmen, politicians, military strategists - routinely make decisions on the basis of uncertain information, usually after we have familiarized ourselves with the available facts. Scientists can provide us with the facts concerning global warming. It is our joint responsibility to make policy decisions on the basis of those facts.
Philander, S. George. 1999. A Global Gamble. Tikkun 14(6): 22.