Among the many challenges to the dire predictions of global warming and climate change is the questioning of the accuracy of computer models that predict how bad it will get and when will it get there. The short answer is the models are good, not just good but very good. If we look back fifty years when computers were in their infancy and the models very crude we see a considerable congruency between what was predicted and what is happening.
Predictions about global warming are not new by any measure. As early as the beginning of the 19th century, over 200 years ago, scientists recognized that the atmosphere may be capable of trapping heat. Probably most important in the history of global warming and climate change is the work of Svante Arrhenius, a Swedish chemist. He was awarded the Nobel Prize in Chemistry for 1903 for his work in understanding certain features of chemical reactions.
Less well known at the time was his work examining the impact of Carbon Dioxide in the atmosphere on the climate. In 1895, Arrhenius presented a paper to the Stockholm Physical Society titled, “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground.” He mathematically modeled the impact of varying amounts Carbon Dioxide and water vapor in the atmosphere using only pencil, paper and a slide rule.
Climate modeling with computers in the 1970s vastly increased the predictive power but the computer models are only good as the assumptions going into the models. The modeling done and predictions made look good “in the rear view mirror.” There were over a dozen different models and some overestimated warming and some underestimated warming but over all they were surprisingly accurate.
The models erred due to unforeseen changes in the variables . As time goes on however, the unforeseen decreases with better understanding. One example is the NASA model by James Hansen that overestimated the heating. It was due to an unanticipated reduction of Chlorofluorocarbons in the atmosphere. This decrease came about due to an international effort to deal with the unrelated environmental issue of the Ozone hole.
The computer models calculate the heat input from the sun and output via radiation. Among the variables that impact these calculations are the amount of water in the atmosphere and whether it is in the form of vapor which warms the air, or clouds which reflect the sunlight, creating a cooling effect. The albedo of the planet, that is the reflectivity, is important and varies between land and and sea, and winter and summer due to snow and ice. The temperature of the oceans impacts how much of the greenhouse gases will be absorbed from the atmosphere because the solubility of gases in water is temperature dependent.
Climate modeling gets better by the day. There is no conceivable reason for the world’s scientists to act in concert to defraud the public. That is just silly. It does make sense however for those who profit from pollution to deny the pollution, or try to divert attention from the major culprit – burning fossil fuels.
Dr. Bob Allen, Ph.D., is Emeritus Professor of Chemistry at Arkansas Tech University.