Inside the Earth's invisible blanket.
Much of the discussion about global warming centers around a phenomenon known as the greenhouse effect. Every day, the sun's rays enter the atmosphere, where their energy is absorbed by plants and in the Earth's surface and oceans, creating the conditions required for life on our world. At the same time, some energy from the sun is reflected back into space. However, just like the glass panes that trap heat and moisture within a greenhouse, our atmosphere contains carbon dioxide, methane, and other gases that prevent that energy from exiting back into space, resulting in a rise in temperature of the Earth.
Many different gases make up the Earth's atmosphere, the most abundant being nitrogen, oxygen, and argon. Greenhouse gases, including water vapor, carbon dioxide, and methane, form a small percentage of the overall atmosphere, yet they play an important role, trapping the heat required for life on Earth. However, too much of a good thing can have a negative impact.
In recent years, greenhouse gases have become strongly associated with global warming and the negative consequences of an overheating planet. But like all things in nature, greenhouse gases serve an important purpose. Without them, the Earth's temperature would be about zero degrees, instead of our current 57°F, according to the National Oceanic and Atmospheric Administration.
Water vapor (H2O)
Water vapor is the most abundant greenhouse gas in the atmosphere. The increase in water vapor concentrations may be the result of climate feedbacks that are related to the warming of the atmosphere. As the temperature rises, more water is evaporated from ground sources, such as rivers, lakes, and oceans. Warmer air can hold more water vapor, which can trap more heat. This creates a positive feedback loop. Whether created from simple evaporation from seas or lakes, or from industrial processes, water vapor is colorless, odorless and harmless.
Carbon dioxide (CO2)
Carbon dioxide is released into the atmosphere in a number of different ways, from volcanic eruptions and forest fires to the burning of fossil fuels, including coal, natural gas, and oil. Once carbon atoms combine with oxygen atoms in the air, they become carbon dioxide — a colorless, odorless, and non-flammable gas. Because carbon dioxide is a major component of greenhouse gases, carbon storage is seen as one tool that could be used to mitigate this effect.
Methane (CH4)
While low in concentration, methane accounts for approximately 9% of greenhouse gas in the atmosphere. Methane has a high heat trapping capacity, making it more effective at trapping heat than CO2 or water vapor. Produced when plants decay in areas with little to no oxygen, methane is a colorless, odorless, and flammable gas that comes primarily from landfills, rice paddies, livestock, and organic waste such as sewage, and from coal seams.
Chlorofluorocarbons
Chlorofluorocarbons are synthetic compounds that contain fluorine and carbon. They are easily converted from gas to liquid and vice versa. For many years, chlorofluorocarbons were a popular choice for aerosol propellants, cleaning agents, and the refrigerants found in many refrigerators and air conditioning systems. Because of their destructive effects on the Earth's protective ozone layer (which filters out the sun's ultraviolet light) and their high heat-trapping properties, their production was banned in the United States in the 1970s and most other countries after that.
Nitrous oxide (N2O)
More popularly known as laughing gas, nitrous oxide has been used in surgical and dental procedures for years because of its anesthetic and analgesic properties. In nature, this colorless gas with a sweet odor is released primarily from the ocean and bacteria in the soil. Other emissions also come from fertilized crops and the burning of fossil fuels.
