Many scientists believe that human beings may be causing something just as dangerous like climatic changes over this century larger than any, since the dawn of civilization.
The principal change to date is in the balance of gases that form the earth’s atmosphere. These naturally occurring greenhouse gases, including carbon dioxide, methane, nitrous oxide and water vapour keep ground temperatures at a global average of 15oCelcius.
Without this natural blanket, the earth’s surface would be about 30oC colder than it is today, making the planet a freezing, barren, lifeless place similar to Mars. The greenhouse gases keep the surface warm.
The problem is that human activity may be making the greenhouse-gas blanket thicker. For example, burning fossil fuels throws huge amounts of carbon dioxide into the air; the destruction of forests allows carbon stored in the trees to escape into the atmosphere; and other activities such as raising cattle and plant rice emit methane, nitrous oxide and other greenhouse gases.
Until mankind began burning fossil fuels, greenhouse gases that occur naturally remained in relative balance. A Swedish chemist theorized that increasing amounts of carbon dioxide released into the atmosphere by coal-field industries would cause global warming.
The Inter-government Panel of Climate Change, set up by the UN General Assembly, has listed several likely negative outcomes of global warning: rise in sea levels, change in weather patterns bringing more floods or draughts to some areas, the spread of mosquito- borne infections, etc.
Measures worldwide are being taken to phase out chlorofluorocarbons and other man-made chemicals that deplete earth’s protective ozone layer. With such steps as these, some scientists now report that the earth’s ozone layer may well be on the way toward a recovery and balance of levels in the atmosphere.