IV.

Large-Scale Effects

The tall smokestacks used by industries and utilities do not remove pollutants but simply boost them higher into the atmosphere, thereby reducing their concentration at the site. These pollutants may then be transported over large distances and produce adverse effects in areas far from the site of the original emission. Sulphur dioxide and nitrogen oxide emissions from Britain and other industrialized countries of Western and Central Europe have caused acid rain in Norway and Sweden. The pH level, or relative acidity, of many freshwater lakes has been altered so dramatically by acid rain that entire fish populations have been destroyed. Sulphur dioxide emissions and the subsequent formation of sulphuric acid can also be responsible for the attack on limestone and marble at large distances from the source. There are also claims that acid rain has caused widespread damage to forests in Europe, but the precise role is unclear and earlier predictions of large-scale forest death are unfounded.

The worldwide increase in the burning of coal and oil since the late 1940s has led to ever-increasing concentrations of carbon dioxide. The resulting “greenhouse effect”, which allows solar energy to enter the atmosphere but reduces the reemission of infrared radiation from the Earth, may well lead to a warming trend that might affect the global climate and lead to a partial melting of the polar ice-caps. Possibly an increase in cloud cover or absorption of excess carbon dioxide by the oceans (in the so-called carbon cycle) would check the greenhouse effect before it reached the stage of polar melting. Nevertheless, many research reports released during the 1990s have indicated that the greenhouse effect is definitely under way and that the nations of the world should be taking immediate steps to deal with it. In June 1999 a massive cloud of air pollution, roughly the size of the United States, was discovered 1 km to 3 km (’ mi to 2 mi) above the Indian Ocean. The thick brown haze included soot, sulphates, nitrates, mineral dust, and significant amounts of gases such as carbon monoxide and sulphur dioxide. Scientists believe it was created by human activities, especially the burning of fossil fuels, and could have a significant impact on the regional and global climate, as well as plant and animal life.