Greenhouse Effect
The earth's climate is driven by the balance of energy or heat added by the sun and lost by the earth. The primary energy is lost through heat radiation, much like the heat you feel coming from a stove. Several gases in the atmosphere, called greenhouse gases, can reflect some of this heat back to the earth. This effectively warms the earth and may alter the climate over time as these gases increase in concentration.
A greenhouse gas indictor is derived from two basic properties of each gas. The first is its ability to reflect heat. The second is how long the gas remains in the atmosphere, that is, how long it may act to reflect heat. These properties are then compared to the properties of carbon dioxide and converted into carbon dioxide equivalents. Then the individual equivalents are added together, for the overall greenhouse gas indicator score that represents the total quantity of greenhouse gases released. Most of the methods used in Life Cycle Impact Assessment (LCIA) are based on the International Panel on Climate Change (IPCC).
To interpret the greenhouse gas indicator, an important variable is the time horizon used (e.g., 50 or 500 years). Short horizons tend to emphasize gases with short residence times in the atmosphere, like methane. In addition, the indicator does not consider the effects of clouds and aerosols in reflecting the sun's heat and reducing the warming.
A greenhouse gas indictor is derived from two basic properties of each gas. The first is its ability to reflect heat. The second is how long the gas remains in the atmosphere, that is, how long it may act to reflect heat. These properties are then compared to the properties of carbon dioxide and converted into carbon dioxide equivalents. Then the individual equivalents are added together, for the overall greenhouse gas indicator score that represents the total quantity of greenhouse gases released. Most of the methods used in Life Cycle Impact Assessment (LCIA) are based on the International Panel on Climate Change (IPCC).
To interpret the greenhouse gas indicator, an important variable is the time horizon used (e.g., 50 or 500 years). Short horizons tend to emphasize gases with short residence times in the atmosphere, like methane. In addition, the indicator does not consider the effects of clouds and aerosols in reflecting the sun's heat and reducing the warming.