Shade for the greenhouse

THE case for accelerated warming of the global climate is far from conclusive. But that shouldn't stop people from thinking more deeply about how they can support practical measures to moderate the so-called greenhouse effect. Current scientific thinking holds that heat-trapping gases are accumulating in the atmosphere at an increasing rate. One widely cited culprit is carbon dioxide, a major by-product of burning fossil fuels such as coal, oil, natural gas. Another is chloroflourocarbons (CFCs), which have already been implicated in the loss of ozone in the upper atmosphere.

The correlation between the growing concentrations of such gases and increases in the atmosphere's average temperature over the last century or so is too strong to be ignored, many researchers say.

But key questions remain unanswered or only partially answered: Are the rising temperatures due mainly to the greenhouse effect, or are they part of a broader, natural cycle in the Earth's climate? Could the current buildup of heat-trapping gases ultimately be countered by natural atmospheric processes, or by the complex interchange between the atmosphere and living organisms?

Despite the uncertainties, efforts to reduce man-made sources of greenhouse gases are needed. If scientists are right about the mechanism responsible for a trend toward a warmer global climate, action is called for now to stem the trend. If the scientists are wrong, people will still have taken actions that they ought to take anyway.

Several broad areas deserve attention. They include:

Research. Providing adequate and consistent funds for national and international research relating to the greenhouse effect should be a top priority. These projects include the upcoming Mission to Planet Earth, involving an international flotilla of satellites to study the Earth as a system from space.

International treaties. Nations that haven't ratified a recent treaty limiting CFC use should do so quickly.

Preservation of tropical forests. Safeguarding and restoring the world's tropical forests is vital. Their destruction compounds the carbon dioxide problem in two ways. Burning the wood, either as fuel or to clear farmland, yields carbon dioxide. It also reduces the amount of lush vegetation available to extract the gas from the atmosphere.

Transportation. In developed countries, increased emphasis should be put on mass transit where practical. In addition, fuel efficiency standards should be reviewed with an eye toward increasing mileage targets and accelerating the timetables for achieving them.

Electricity generation. Initial emphasis should be placed on making more efficient commercial and residential use of electricity. In the case of residential use, aid should be made available to low-income people, who may not be able to afford the up-front cost of improving efficiency.

Alternative sources of electricity, from better load management to wind generators should be supported where practical. Nuclear energy must be a key part of the energy mix, once manufacturers and utilities adequately address public concerns about safety and reliability.

These measures aren't new. The concepts harken back to the energy crisis of the 1970s, initially brought on by the Arab oil embargo. At that time the search for alternative energy sources was driven by concerns over the physical availability of supplies.

Today the search is increasingly being driven by similar concerns. But this time, the traditional sources of energy for human use may be rendered increasingly unavailable by the environmental consequences of using them.

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