What Are Greenhouse Gases? Some greenhouse gases (GHG's) occur naturally in the atmosphere, while others result from human activities. Naturally occurring GHGs include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases: Methane and nitrous oxide are two very powerful greenhouse gases, more powerful than carbon dioxide (CO2) in terms of global warming. Methane is a greenhouse gas that is 21 times more potent in global warming than carbon dioxide, nitrous oxide is 310 times more potent than carbon dioxide. In other words, reducing 1 tonne of methane has the same positive effect as reducing 21 tonnes of carbon dioxide. Reducing 1 tonne of nitrous oxide has the same positive effect as reducing 310 tonnes of carbon dioxide. These projects also promote cleaner air and water. Your money will support projects that reduce CO2 in the environment: Energy efficient renovation of multi-family and commercial buildings Forest restoration along the banks of pristine watersheds Enabling the use of low-carbon blended cements in public and private construction projects What are Greenhouse Gases? Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring GHGs include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases: Carbon dioxide (CO2 ) is released to the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned. Methane (CH4 ) is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. Nitrous oxide (NO2 ) is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels. Very powerful greenhouse gases that are not naturally occurring include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6 ), which are generated in a variety of industrial processes. Each greenhouse gas differs in its ability to absorb heat in the atmosphere. HFCs and PFCs are the most heat-absorbent. Methane traps over 21 times more heat per molecule than carbon dioxide, and nitrous oxide absorbs 310 times more heat per molecule than carbon dioxide. Greenhouse gas emissions are presented in metric tonnes of carbon dioxide equivalents (CO2e), which weights each gas by its GWP value, or Global Warming Potential. adapted from drivinggreen.com