We experience massive global warming each year as part of the seasonal cycle. >From the winter solstice, December 21 onwards, the intensity of sunshine increases steadily. Temperatures, however, fluctuate considerably. They were so high in Trenton N.J. this past February 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 can also mask global warming associated with an increase in the greenhouse effect. That is why the unusually high temperatures of the early 1990's do not necessarily imply that global warming is underway. Should the next few years be unusually cold, then 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. The current debate about this aspect of global warming will probably be settled only after it is too late to do much about the problem.
To alert us of changes in the seasons we consult a calendar. To alert us of global warming we have to rely on computer models that simulate the Earth's climate. The models reproduce many aspects of the climate realistically but the phenomenon is so immensely complex that the models fail to capture some features. Most members of the scientific community have sufficient confidence in the models to accept the forecasts concerning future climate changes. A few critics focus on the flaws of the models and cite those as the reasons for rejecting the results of the models. These skeptics play a valuable scientific role by forcing a re-examination of assumptions made in the models, thus contributing to a continual improvement of the models. However, the attention paid to them in the press is unrelated to the merits of their scientific arguments. Furthermore, those critics often neglect to point out that, because of the flaws, the models are as likely to overestimate as underestimate the severity of global warming.
In our discussions of the likely consequences of the disturbance we are introducing to the Earth's climate, we ought to pay attention to the geological record which has valuable information about climate changes in the past. That record provides abundant evidence that the climate of this planet is very sensitive to small disturbances. 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 known sensitivity of the climate of the Earth, we are in the process of introducing a huge disturbance, a doubling of the atmospheric concentration of carbon dioxide, a powerful greenhouse gas. We are persisting with our efforts even though we are vulnerable to modest climate fluctuations, as demonstrated by the recent El Nino phenomenon.
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 models that predict how the economy will respond to certain policies. The uncertainties in such models of the economy 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.
We experience massive global warming each year as part of the seasonal cycle. >From the winter solstice, December 21 onwards, the intensity of sunshine increases steadily. Temperatures, however, fluctuate considerably. They were so high in Trenton N.J. this past February 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 can also mask global warming associated with an increase in the greenhouse effect. That is why the unusually high temperatures of the early 1990's do not necessarily imply that global warming is underway. Should the next few years be unusually cold, then 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. The current debate about this aspect of global warming will probably be settled only after it is too late to do much about the problem.
To alert us of changes in the seasons we consult a calendar. To alert us of global warming we have to rely on computer models that simulate the Earth's climate. The models reproduce many aspects of the climate realistically but the phenomenon is so immensely complex that the models fail to capture some features. Most members of the scientific community have sufficient confidence in the models to accept the forecasts concerning future climate changes. A few critics focus on the flaws of the models and cite those as the reasons for rejecting the results of the models. These skeptics play a valuable scientific role by forcing a re-examination of assumptions made in the models, thus contributing to a continual improvement of the models. However, the attention paid to them in the press is unrelated to the merits of their scientific arguments. Furthermore, those critics often neglect to point out that, because of the flaws, the models are as likely to overestimate as underestimate the severity of global warming.
In our discussions of the likely consequences of the disturbance we are introducing to the Earth's climate, we ought to pay attention to the geological record which has valuable information about climate changes in the past. That record provides abundant evidence that the climate of this planet is very sensitive to small disturbances. 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 known sensitivity of the climate of the Earth, we are in the process of introducing a huge disturbance, a doubling of the atmospheric concentration of carbon dioxide, a powerful greenhouse gas. We are persisting with our efforts even though we are vulnerable to modest climate fluctuations, as demonstrated by the recent El Nino phenomenon.
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 models that predict how the economy will respond to certain policies. The uncertainties in such models of the economy 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.
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