Human Factors Affecting Climate
Enhancing the Greenhouse Effect Naturally occurring greenhouse gases (such as water vapour, carbon dioxide, methane, and nitrous oxide) keep the Earth warm enough to support life. Scientific studies show that a variety of human activities release greenhouse gases. These include the burning of fossil fuels for electrical energy, heat and transportation. By increasing the concentration of present greenhouse gases and by adding new ones like CFCs, humankind is capable of raising the average global temperature.
Land Use Change As humans replace forests with agricultural lands, or natural vegetation with asphalt or concrete, we substantially alter the way the Earth's surface reflects sunlight and releases heat. All of these changes also affect regional evaporation, runoff and rainfall patterns.
Atmospheric Aerosols Humans are adding large quantities of fine particles (aerosols) to the atmosphere, both from agricultural and industrial activities. Although most of these aerosols are soon removed by gravity and rainfall, they still affect the radiation balance in the atmosphere. Whether this effect adds to or offsets any warming trend depends on the quantity and nature of the particles, as well as the nature of the land or ocean surface below. The regional effects, however, can be significant.