Have you ever seen a greenhouse? Most greenhouses look like a small glass house. Greenhouses are used to grow plants, especially in the winter. Greenhouses work by trapping heat from the sun. The glass panels of the greenhouse let in light but keep heat from escaping. This causes the greenhouse to heat up, much like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.
The Earth’s atmosphere is all around us. It is the air that we breathe. Greenhouse gases in the atmosphere behave much like the glass panes in a greenhouse.
Sunlight enters the Earth’s atmosphere, passing through the blanket of greenhouse gases. As it reaches the Earth’s surface, land, water, and biosphere absorb the sunlight’s energy. Once absorbed, this energy is sent back into the atmosphere. Some of the energy passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases, causing our world to heat up.
Green·house Ef·fect ['grEn-"haus E-'fekt]. A general warming effect felt on Earth’s surface, produced by greenhouse gases. These gases allow incoming solar radiation to pass through the Earth’s atmosphere, but trap heat by preventing some of the infrared radiation from the Earth’s surface from escaping to outer space. This process occurs naturally and has kept the Earth’s temperature about 60 degrees Fahrenheit warmer than it would otherwise be. Current life on Earth could not be sustained without the natural greenhouse effect. However, the greenhouse effect is becoming stronger as a result of human activities, which is causing the warming we have observed over the past century.
Green·house Gas ['grEn-"haus 'gas]. Any gas that absorbs infra-red radiation in the atmosphere. Greenhouse gases include water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), halogenated fluorocarbons (HCFCs) , ozone (O3), perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs).
Car·bon Di·ox·ide ['kär-b&n (")dI-'äk-"sId]. A heavy colorless gas (CO2) that does not support combustion, dissolves in water to form carbonic acid, is formed especially in animal respiration and in the decay or combustion of animal and vegetable matter, is absorbed from the air by plants in photosynthesis, and is used in the carbonation of beverages. CO2 is most important in a climate context because it acts as a greenhouse gas.
Ni·trous ox·ide ['nI-tr&s äk-"sId]. A colorless gas (N2O) that is an atmospheric pollutant produced by combustion. N2O is one of the greenhouse gas chemical compounds. N2O is also used in dental procedures and sometimes referred to as “laughing gas.”
Me·thane ['me-"thAn]. A colorless, odorless, flammable hydrocarbon (CH4) that is produced by the decomposition of organic matter, and other processes. Methane is a greenhouse gas; one molecule of methane is 25 times more effective at trapping heat than a molecule of carbon dioxide, when their effects are compared over 100 years.