The earth is getting hotter.

It sounded like nature's own apocalypse. *"The earth's temperature would rise, melting the icecaps, raising the seas, flooding the land. Arisona would turn into a rainforest and the agricultural Midwest Would become a desert." At least, that was how TV weathermen interpreted a report by the by the Environmental Protection Agency (EPA) on the "greenhouse effect" that would begin altering the earth's climate by the 1990s. The EPA predicted "catastrophic consequences" if contingency plans weren't made with "a sense of urgency".

Fortunately, the news improved later when the National Academy of Sciences said that although the greenhouse effect was very real, "caution not panic" was in order.

In fact, the science of the phenomenon is more interesting than frightening. *The greenhouse effect results when C02 and certain other gases in the atmosphere allow the sun's ultraviolet rays to penetrate and warm the earth but then absorb the infrared energy the earth radiates back into space - much as glass in a greenhouse effect does - forming a kind of "thermal blanket" around the planet. By burning huge amounts of fossil fuels, which release C02 into the atmosphere, man has raised the co2 level from 280 to 340 parts per million since I860. And continued use of coal and other fossil fuels is expected to double the concentration of C02 by the year 2050, elevating the earth's temperature by 3 to 9 degrees Fahrenheit. The greenhouse effect will mean much more than hotter summers and milder winters. It may alter rainfall, affect crop yields and eventually - as glaciers begin to melt - raise the level of the sea.

Both reports predict than the temperature change will be greater in the polar regions than near the equator. In general, they speculate that snowfall will begin later, the growing season will lengthen and higher latitudes will get less rain. The EPA says that the sea level will probably rise at least two feet before the year 2100, which could flood "many of the major ports of the world, disrupt transportation networks, alter ecosystems and cause major shifts in land development patterns".

Although use of fossil fuels is the main cause of the C02 increase, the government agencies don't advocate any sweeping changes in energy policies. Even a total ban on the burning of fossil fuels in the United States wouldn't have much impact, because the United States accounts for only 25 per cent of the world's total man-made co2 emissions. *A worldwide coal ban instituted in 2000 would delay the warming by about 15 years but is considered economically and politically unfeasible.

If we can't prevent the greenhouse effect, we can prepare for it. Suggestions include breeding plants that need less water, improving irrigation systems, and many others.

However not all experts are convinced that the heat is coming. Some think that the use of primary energy sources such as coal could decline 60 per cent by 2050 and, perhaps, "the opposite of the EPA scenario is true. If the rate of fossil-fuel use is going down, the amount of C02 we add to the air is getting less every year".

Дата добавления: 2015-11-14