"Predicting is very hard, especially if it's about the future." …Yogi Berra
This fall marked the 70th anniversary of my entry into formal education. I started school at the height of the Great Depression; families were small, and only four of us were in first grade that year. It was a lucky break for the teacher, for there were six grades in the same room. I already knew my
numbers and could read stories if I had heard them often enough, so I spent most of my time listening to the lessons of the older kids. Science was especially fascinating. By the end of that year I had learned that the earth had gone through ages… a Coal Age, a Dinosaur Age, an Ice Age, a Stone Age and an Iron Age. I learned
that Columbus discovered America in 1492, but the Vikings would have been here first if their colonies in Vineland hadn't been destroyed by cold climate.
I was good at remembering facts, and over the next 12 years a lot of information got stored in my head, so people told me I was smart and should go to college. It was a rude awakening. I discovered that knowing facts was not the same as being smart; many of the "facts" I had accumulated were not really
true, or were limited to special situations. Instead of just spouting facts, I was expected to understand how things work. It came as a shock to learn that scientific knowledge is not permanent; it is always in a state of development, because as we study things we often find new information that doesn't fit old explanations.
When that happens, we must either change the old explanations or discard them completely and find new ones. This is why scientists call their explanations theories or models. A theory is simply how we explain something at the present time; it is not the final truth, because it is constantly being corrected and adjusted as we
discover new information.
Since theories explain how we think things work, they can be used to predict how things will work in the future. This the great value of science, and also its great weakness. These predictions are what will probably happen; they are not certainty, because at any time we may discover new information and
have to change the theory on which the prediction was based. Scientists understand this; the general public, it seems, do not. Hence, the problem. Most people want clear, simple answers. They do not understand science, but they know great discoveries have been made, so they expect scientists to foretell the future with
certainty. Thus when science has incomplete information and more than one theory is possible, demagogues or special interest groups can easily mislead the public by claiming all scientific predictions are worthless.
All of this was brought to mind by a coincidence early last month. I read an article in the Washington Post about recent discoveries which provide new evidence that carbon dioxide emissions are causing global warming. On the same day I chanced to pick up the Thurmont Times, which featured an opinion poll
on its website; one of the questions was, "Do you believe global warming exists?" It is a legitimate question; national polls have asked it several times in recent years. In a Fox News poll in 2007, 82% of the respondents believed in global warming, but only 68% believed CO2 was to blame. In a Yale poll this year, 80% believed
in global warming, but only 51% thought it is caused by human activities. In the Thurmont poll, only 43% believe global warming exists. Of course, whether our climate is really changing is not determined by polling the public; but unfortunately, how we respond to it as a nation may be. It is a classic case of trying to give a
simple answer to a complex question.
The Ice Age I learned about in first grade was first suggested in 1742 by a Swiss scientist named Pierre Martel, who noticed that glaciers were advancing, crushing villages in their paths and pushing large boulders down valleys in the Alps. He had seen such boulders much farther down the valleys, and
theorized that long ago it must have been much colder and glaciers must have covered much of Europe. More evidence accumulated over the next 150 years, and now we know that the earth actually went through several Ice Ages. The most recent one began a couple of million years ago and was divided into at least four alternating cold
and warm periods. The last great cold period ended about 11,000 years ago. Scientists have developed models that explain the cooling and warming of the earth fairly well over that long period of time. These models include changes in the heat output of the sun, which have been measured since the first satellites in the 1950s;
changes in the earth's orbit, caused by the gravity of the larger planets, Jupiter and Saturn, as they move closer or farther away from us in their own orbits; and changes in the tilt of the earth's axis, which cause the north pole to be pointed toward the sun at some times and away from it at others. These models provide a good
explanation of the last ice age and the warming that followed. They also agree with a cooling trend that began around 500 A.D.; it is now called the "Little Ice Age," and it caused the advancing alpine glaciers that Martel observed in 1742 and the destruction of the Viking settlements in Greenland.
There was no way to measure temperature accurately until1724, when Gabriel Fahrenheit and Anders Celsius independently invented thermometers by sealing mercury in a glass tube. Weather stations were established all over the world, and over the next century it became apparent that climate was getting
warmer. People began to ask why, and in 1824 Joseph Fourier suggested that carbon dioxide might cause a "greenhouse effect" by trapping the sun's heat in the atmosphere. The details of how this works were established by Svante Arrhenius in 1896. Meanwhile, more accurate measurements of CO2 were being made. In the 1880s, its
concentration in the atmosphere was 278 parts per million (ppm); by 1960, it had increased to 313 ppm, and the theory of greenhouse gases warming the atmosphere was in all college textbooks. Presently the concentration is 383 ppm, and its increase correlates well with the observed increase of global temperature.
The National Academies of Science of all industrialized countries have agreed that CO2 produced by burning fossil fuels is a major cause of global warming. A minority of scientists did not agree; several of them claimed that the warming trend that ended the last ice age is still going on. The new
discoveries described in the Washington Post confirm that the cooling trend that produced the "Little Ice Age" should still be going on if the sun's heat output and the earth's orbit and tilt were the only factors involved. But the fact is that the earth is getting warmer, and the warming trend began to accelerate around 1850,
just when atmospheric CO2 levels began to increase rapidly.
It will be interesting to see how this new evidence affects the national debate on CO2 emissions. I predict that some of the scientists who honestly opposed the CO2 effect will now accept it; a few will not, and in both cases they will have little influence on the debate. If you look at the sources of
comments on the internet you will see a preponderance of special interest groups… coal and oil companies, energy lobbyists, conspiracy theorists and the like… and self-proclaimed "experts" who make a lucrative income by speaking and writing in anti-environmental media. These sources will continue to court public opinion with
simplistic solutions to this complex problem, just as a few of their soul-mates continue to deny that smoking causes cancer. The real question is how long and how many of the voting public will listen to them. That, I will not attempt to predict.
Read other articles by Bill Meredith
