The Home of American Intellectual Conservatism — First Principles

December 11, 2017

FEATURE ARTICLES
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On Climate Change
P. E. Hodgson - 02/13/09

On a much longer timescale, the mathematician Milutan Milankovitch identified cold and warm periods alternating every 100,000 years, with smaller cycles every 41,000 and 10,000 years. These cycles are attributed to perturbations of the sun’s orbit by the moon that cause the precession of the equinoxes and by other small effects due to the planets and are confirmed by world-wide measurements of glaciers, coral reefs, peat bogs, and polar ice caps.

There are thus many ways the climate can be changed in addition to the effects of the greenhouse gases. Careful scientific analysis is therefore needed before their contribution can be established. Many scientists worldwide are making detailed calculations using increasingly sophisticated models of the atmosphere. This is obviously a very complicated task. What, for example, do we mean by the temperature of the atmosphere? We can measure the temperature at a particular place and height, but this needs to be done over the whole surface of the earth and for heights up to several miles. The best we can do is to establish a grid of points and measure the temperatures at these points as a function of the time. Even a coarse grid contains millions of points and the calculations are very time-consuming even on a fast modern computer. The more accurate we want our calculations to be the longer they will take. In addition, the results may be very sensitive to the initial conditions; this is called the butterfly effect. The main uncertainty at present seems to be the effects of water vapour, which are greater than those of all the other gases combined. These are sensitively affected by changes in the cloud cover, which in turn changes the amount of solar energy absorbed or reflected.

The results of such calculations are published periodically by the Intergovernmental Panel on Climate Change, consisting of about two thousand of the world’s leading climate scientists, under the chairmanship of Sir John Houghton. [6] With many qualifications, the conclusion of their assessment is that there is good evidence that world temperature is increasing, and it is predicted that the average temperature will rise by about four degrees centigrade by the year 2100. In the same period the sea level will rise by about 60 cm, or by 40 cm if the carbon dioxide emissions are controlled. Such rises will eliminate many islands such as the Maldives in the Indian Ocean and will inundate much of Bangladesh and some of Holland. Already the sea level has risen by 0.1 to 0.2 cm per year during the twentieth century.

The connection between the rise in temperature and the rise in sea level has been attributed to the melting of the polar ice caps. However, the ice immediately around the North Pole and in the ice shelves around Antarctica is floating, and so when it melts, it has very little effect on the sea level, as Archimedes knew very well. There may however be some small effects due to differences in salinity between the ice and the sea. There are other effects of melting ice in Antarctica that are discussed below.

Another uncertainty is the effects of soot on global warming. This soot comes from the incomplete burning of coal, biomass, and diesel, and also from forest fires, domestic heating, and factories. It has been said to “mask” global warming and also that it “generates” global warming. It has been called “a cooling agent” and also “the biggest cause of global warming after carbon dioxide.” What seems to happen is that the soot shields the earth from the sun’s rays, thus making it cooler. It also absorbs some of the heat and re-radiates it into the surrounding air. Thus soot heats the air and cools the ground. Some scientists think that soot is the third most important contributor to global warming, after carbon dioxide and methane.

Catastrophic Events

In some respects the earth is a self-regulating mechanism so that any change initiates secondary changes that restore it to its original state. This idea has been developed by James Lovelock into the concept called Gaia (the Mother Earth). [7] The mechanism works for small changes, but he recognises that there may be changes that irrevocably flip it into another state. We are familiar with such changes, as for example when a bridge collapses under a particularly heavy load. If this happens to the climate, the results could be devastating for large numbers of people.

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