Geography

Greenhouse Effect (continued)


The carbon in the atmosphere guarantees one of the basic conditions for life on the planet: temperature.

The Earth is heated by infrared radiation emitted by the sun to a temperature of 27º C.

These radiations reach the surface and are reflected to space, carbon forms a protective bubble that traps some of these infrared radiations and reflects them back to the surface. This produces a 43 ° C rise in the planet's average temperature, keeping it at around 16 ° C. Without carbon in the atmosphere the surface would be covered with ice.

Excess carbon, however, tends to trap infrared radiation, producing the so-called greenhouse effect: raising the average temperature to the point where the ice caps covering the poles are reduced or destroyed.

Scientists are concerned about the increase in carbon dioxide in the atmosphere, which occurs at an average rate of 1% per year. Burning of vegetation cover in underdeveloped countries accounts for 25% of this increase. The biggest source, however, is the burning of fossil fuels such as oil, especially in developed countries.

Japan is the fastest growing country: from 1985 to 1989, its carbon dioxide emissions rise from 265 million tons per year to 299 million tons.

Research by NASA shows that the planet's average temperature has risen 0.18 ° C since the beginning of the century. In the 1980s, photographs taken by the Nimbus weather satellite over a 15-year period record the shrinking ice perimeter around the poles.

Assuming the greenhouse effect in action, scientists project a flood scenario: warming the air increases the evaporation of seawater, creates a greater volume of clouds, raises the level of rainfall and alters the wind regime. There would be heavy rainfall in today's desert areas, such as northern Africa and northeastern Brazil, and water would be lacking in fertile regions such as the Midwest.

The melting of the ice caps would raise sea levels by flooding islands and coastal areas. The Netherlands, Bangladesh, Miami, Rio de Janeiro and part of New York, for example, would disappear from the map.

Increasing global temperatures would also cause weeds and insects to multiply, and transfers of hot-weather pests - such as the central tsetse fly - to cold-weather regions. Absorbing excess carbon dioxide would make vegetation grow faster and take more nutrients out of the soil. According to these projections, temperate forests would survive only in Canada.

Ozone is concentrated in the upper layers of the atmosphere at 15 km from the surface and forms a kind of shield about 30 km thick, which protects the planet from the sun's ultraviolet rays. Reduction of the ozone layer increases exposure to lightning. ultraviolet radiation and is associated with the growth of skin cancer and eye diseases such as cataract.

For scientists, the hole in Antarctica delays the arrival of spring in the region and causes breaks in the food chain of the local fauna. It can help to increase the temperature and accelerate the melting of the ice caps.