Today, global warming is a serious international problem that disturbs people of all ages and backgrounds. A report was recently published stating that global warming is natural, but most people are sure that this phenomenon is the result of human activity. First of all, one of the main causes of global warming is the emission of greenhouse gases. Greenhouse gases are in fact those gases present in the atmosphere which, by absorbing the thermal radiation emitted by the earth's surface, exert a covering effect on it. It is closely connected with the development of industry and the use of fossil fuels as energy sources. Important greenhouse gases directly affected by human activities are carbon dioxide, methane, nitrous oxide and chlorofluorocarbons (CFCs). Carbon dioxide is the most important greenhouse gas whose concentration in the atmosphere increases due to human activities. Methane is a component of natural gas. But its levels have increased directly with population growth. According to Desonie (2008), approximately 60% of the methane in the atmosphere today comes from rice production, waste processing and incomplete combustion of rainforest materials. Nitrous oxide is a minor greenhouse gas, but is also emitted by fossil fuels, forests and manufacturing. Chlorofluorocarbons (CFCs) are man-made chemicals that are considered non-toxic and non-flammable so they can easily be used in refrigerators and spray cans. However, CFCs are the most powerful gases that have extremely negative effects on the atmosphere, because they cause the destruction of the ozone layer that protects the planet from the sun's ultraviolet rays. The result of the increasing concentration of these gases is the warming known as the greenhouse effect. Second, changes in land use can alter the climate. As pointed out by Dale (1997), these include logging, slash-and-fire agriculture, urbanization and agricultural expansion. Slash-and-burn agriculture is a widespread technique especially in the tropics and consists of burning rainforest to create agricultural land or ranches.