Global warming refers to an average increase in the Earth's temperature, which in turn causes changes in climate. A warmer Earth may lead to changes in rainfall patterns

What's been done about it? Global warming is a very difficult problem to fix. People are having a hard time agreeing on what to do about it. For example, everyone agrees that wasting energy is a bad thing to do. But some people think that the federal government should make laws about it, while other people think it should be up to each person or business to decide what to do.

Many states and businesses in the United States are not waiting until the federal government decides what to do. They have already started working on the problem.

What is Greenhouse? A greenhouse is structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. These structures range in size from small sheds to very large buildings. The glass used for a greenhouse works as a selective transmission medium for different spectral frequencies, and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away, in addition to the fact that infrared radiation cannot pass through the greenhouse glass.

How is it caused? Acid rain is caused by the release of the gases SO2 (sulphur dioxide) and NOX (nitrous oxides). The main sources of SO2 in South Africa are coal-fired power stations and metal working industries. The main sources of NOX emissions are vehicles and fuel combustion.

Why is it a bad thing? The world is now hotter than it has ever been since scientists started recording temperature. As the world gets hotter there will be more droughts in Africa and America leading to shortages of food. The slightest rise in the average yearly temperatures causes the polar ice caps to melt.

This will raise the sea levels causing flooding in low-lying countries like Bangladesh. All over the world the weather will be more violent, with in increase in typhoons, hurricanes and storms. This graph shows how the global mean temperature was rising over 20 years ago

FACT: - If the greenhouse effect did not exist at all the earth would be a frozen lifeless planet.

What is acid rain? The term acid rain is commonly used to mean the deposition of acidic components in rain, snow, fog, dew, or dry particles. The more accurate term is acid precipitation. Distilled water, which contains no carbon dioxide, has a neutral pH of 7. Liquids with a pH less than 7 are acid, and those with a pH greater than 7 are alkaline (or basic). Clean or unpolluted rain has a slightly acidic pH of 5.6, because carbon dioxide and water in the air react together to form carbonic acid, a weak acid. Around Washington, D.C., however, the average rain pH is between 4.2 and 4.4.

How is it caused? Sulphur dioxide and nitrogen oxides are the main pollutants that cause acid rain.

Why is it a bad thing?

How can we reduce it in the future? These pollutants are emitted largely by the combustion of fossil fuels. Reducing the use of fossil fuels therefore, including the use of electricity generated by coal- and oil-fired power plants, will help reduce acid rain-causing emissions. The following are some more specific suggestions on what you, as an individual, can do:

In the home

* Install a low-flow showerhead.

* Run the dishwasher only with a full load.

* Run the washing machine with a full load.

* If using an automatic dishwasher, let the dishes air dry.

* Hang dry some-or all-of the laundry.

* Buy energy-efficient appliances.

* Avoid the use of air conditioners altogether.

* Turn out the lights in empty rooms and when away from home.

* Consider installing compact fluorescent bulbs instead of high-wattage incandescent bulbs.

* Turn off the hot water tank when going away for extended periods of time.

* Install additional insulation on the hot water tank and pipes.

* Insulate and draft-proof your basement.

What's been done about it? In 1985 the governments of Canada and the seven eastern provinces joined forces to take action on reducing sulphur dioxide, the major contributor to acid rain. They launched a program to cut sulphur dioxide emissions in the eastern provinces in half by 1994. It was hoped that this action would reduce the deposition of sulphates in rain and snow in eastern Canada from levels as high as 40 kg per hectare per year (kg/ha/yr) to no more than 20 kg/ha/yr, a level that would cause considerably less damage to ecosystems.