CO2 Not the Only Greenhouse Gas
Global Warming Potential Gases Other Than Carbon Dioxide
Although Carbon Dioxide is the largest agent of global warming, there are other greenhouse gases. Methane, Nitrous Oxide and fluorocarbons all add to climate change.
In the ongoing debate on global warming and climate change one greenhouse gas, Carbon Dioxide has emerged as the chief culprit. This is so since CO2 makes up the largest percentage of man made greenhouse gas emissions. In the Energy Information Administration (EIA) “Emissions of Greenhouse Gases in the United States, 2001” report, man made carbon dioxide made up 84% of total greenhouse gas emissions.
But carbon dioxide is not the only greenhouse gas contributing to global warming. There are other gases, both natural and man made, that also add to the greenhouse effect. Some of these gases even have a greater global warming potential than carbon dioxide but because of their lower atmospheric volume their effect would not be in the same league as carbon dioxide. Non carbon dioxide greenhouse gases include water vapor, Methane, Nitrous Oxide, Ozone and Fluorocarbons.
Global Warming Potential
Gases contribute to global warming by both their ability to trap heat and their mean atmospheric lifetime. According to the Intergovernmental Panel on Climate Change (IPCC) report “Climate Change 2001: The Scientific Basis” the Global Warming Potential (GWP) of a greenhouse gas is measured against that of carbon dioxide which is given a GWP of 1. The report also gives figures for the mean atmospheric lifetimes of greenhouse gases, with the exception of CO2, which due to the complexity of the Carbon Life cycle, is not possible to measure accurately.
Aside from Carbon Dioxide the other greenhouse gases are:
Water Vapor
The IPCC report estimates that water vapor is responsible for 60% to 80% of the world’s greenhouse effect. This is termed the “natural greenhouse effect” since without it the Earth would be too cold to support life. The problem with this natural greenhouse gas is that the warmer the atmosphere gets due to rising CO2 levels, the more water vapor it can hold, thus compounding global warming.
Methane
Methane is emitted from livestock, agricultural processes, and organic waste decay. It is also created during the production and transport of coal, natural gas and oil. The IPCC report gives Methane a GWP of 62 over a 20 year period and its average atmospheric lifetime is 12 years. From these figures it can be seen that Methane is a powerful greenhouse gas, but according to the US EPA “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2003”, man made emissions of methane have decreased by 20%.
Nitrous Oxide
Nitrous Oxide is another powerful greenhouse gas, with a GWP of 296 over a hundred year period and a lifetime of 114 years, according to the IPCC report. It is a major component of fossil fuel burning and is also emitted during agricultural and industrial activities.
Ozone
The Ozone layer not only protects the earth from ultraviolet rays, it also acts as a natural greenhouse gas, but a study by the European Union entitled “Tropospheric Ozone in EU - The consolidated report” found that the production of ground level ozone has risen dramatically since the industrial revolution. This ozone is formed by the action of sunlight on hydrocarbons and nitrous oxide from the burning of fossil fuels. This ozone eventually finds its way to the troposphere and helps increase the greenhouse effect.
Fluorocarbons
Although the Ozone depleting Chlorofluorocarbons (CFC) were phased out under the “Montreal Protocol” the newer Hydrofluorocarbon (HFC) and Perfluorocarbon (PFC), brought in to replace them, are some of the strongest greenhouse gases known to man. In the IPCC report they have GWPs ranging from 300 to 10,000 with lifetimes of hundreds of years. These powerful greenhouse gases are used extensively in refrigeration and air conditioning and can enter the atmosphere when the units are damaged or being decommissioned.
Global warming and climate change are large and complex issues, with many factors playing their part. As the headline grabbing greenhouse gas, Carbon Dioxide tends to overshadow the less well known gases. People should be aware of their contribution to climate change and should deal with them accordingly.
