(3 of 4)
Despite concern about the harm that could be done by nuclear explosions in the atmosphere, scientists have yet to find any significant effect on climate. At present, many weather researchers are far more interested in the effects of sunspots, the fierce magnetic storms on the solar surface, which are often accompanied by the eruption of great flares of immensely hot gases. The streams of particles shot off during these episodes are already known to disturb the earth's magnetic field and disrupt communications. Astrophysicist Walter Orr Roberts, former director of the National Center for Atmospheric Research, thinks that they also may influence weather, at least temporarily. Among other evidence, he cites an apparent link between periods of minimum activity in the sunspot cycle and recurring droughts on the east side of the Rockies.
Still other climatologists suspect that global temperature changes could stem from wobbles in the earth's rotation that alter the amount of sunlight striking the surface. Some think that there may even be subtle changes in the earth's orbit, which would increase or decrease the distance from the sun.
However they explain the recent cooling, there are many observers who are not convinced that it is part of a long-term trend. Two Government experts, Donald Oilman and J. Murray Mitchell Jr., argue that it may only be a random fluctuation, rather than part of any fixed cycle. In fact until a few years ago, many scientists suspected that the earth would heat up, largely because of mankind's increasing output of carbon dioxide. A byproduct of fossil-fuel burning, the gas lets sunlight pass down through the atmosphere but prevents the escape of infra-red heat waves that are radiated from the earth's surface. Thus the gas adds to the planet's heat store.
To ease the adverse effects of changing climate, some people talk of "weather modification." Cloud seeding, for example, has been tried to release rains over parched fields. But the technique is still primitive and it raises serious political and ecological questions: if rain makers manage to bring water to one region will they be depriving another—perhaps in a neighboring country? The skilled plant breeders who created the Green Revolution can breed tougher grains to meet changes of climate. But these will take time to perfect, and their use will be limited unless science makes greater progress in long-range weather forecasting. Otherwise, farmers will not know which of the new seeds to plant. Unfortunately, even the best long-range weather predictions are notoriously inaccurate. Fluctuations in climate depend on so many variables—winds, temperature, rates of evaporation, etc.—that meteorologists have yet to formulate accurate mathematical models to show how all such factors affect one another.
Some new approaches promise help. As part of a multinational scientific program called NORPAX (North Pacific Experiment), Meteorologist Jerome Namias of Scripps Institution of Oceanography has been investigating unexplained links between ocean temperatures and weather. He has found, for instance, that the formation of hot and cold patches in specific parts of the Pacific appears to be followed by colder-than-normal winters in the Eastern U.S. and warmer-than-normal winters in the West. If enough patterns of that kind can be found, says Namias, they could tip off long-range trends.