[Encyclios]

Effects of pollution on climate

The increase in the carbon dioxide content in the troposphere, as a consequence of the increase in fuel consumption and of the deforestation carried out to make room for new agricultural areas, is not insignificant, having passed, in the space of a century, from 290 to 320 ppm (parts per million) and predicted for the first decade of the XXI century with values between 375 and 400 ppm. Since it is above all the presence, even if on the whole modest, of carbon dioxide and water vapor in the troposphere that, retaining most of the flow of thermal energy radiated from the ground as a result of the phenomenon known as the greenhouse effect, regulates the temperature of the globe, a significant change in the percentage of carbon dioxide can not fail to have climatic repercussions.

For this reason, the increase of carbon dioxide in the atmosphere has been linked to the increase of the average world temperature during the hundred years before 1940. Since then, however, although carbon dioxide continues to be introduced into the atmosphere in increasing quantities, the average world temperature has shown a slight decrease that is interpreted as a consequence of the increased reflectivity, or albedo, of the Earth, due to the intensification of atmospheric cloudiness by fumes and dust produced by industrial and agricultural activities and volcanic eruptions particularly rich in dust (for example that of Pinatubo, in the Philippines, in 1991).

It must be remembered that the particles of smoke and dust, acting as condensation nuclei for water vapor, favor the formation of clouds that further increase the albedo. The effects of atmospheric turbidity are manifested especially in the lower layers and especially in highly industrialized areas with a significant reduction in visibility and increase in haze, fog, cloudiness and precipitation, to the point that industrial cities have more cloudy and rainy days than the surrounding countryside.

Because of the conflicting effects of increased carbon dioxide content on the one hand and cloudiness and turbidity on the other, and also because of the incomplete knowledge of the role of the many geophysical phenomena that intervene in the Earth’s radiation budget, it is impossible to establish with certainty the long-term consequences of these human-induced changes on the atmosphere.

Another consequence of pollution, with effects on climate assessed by scientists in a controversial way, is the accumulation of waste heat released into the atmosphere by various heat-producing activities: for some, the amount of heat administered to the environment is already greater than that disposable by irradiation in space and therefore the temperature is destined to rise with profound alteration of the climate within a few decades, for others the increase in heat can be compensated by activities that raise the albedo such as the expansion of concrete and asphalt surfaces in urban areas or the extension of deserts.

Ultimately, not much is known about the complex mechanism of interactions that regulate the physical environment and the extent of climate interference produced by atmospheric pollutants. Only the systematic monitoring of the dispersion and transport of pollutants, of the variations in the values of atmospheric turbidity, carbon dioxide and water vapor, and ultimately of everything that has an effect on the albedo, conducted on a global scale with the help of suitable meteorological satellites, will be able to provide more precise indications on the actual extent of the alteration of the physical environment.