Greenhouse Gases
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Global Warming categories:
>Greenhouse Gases
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Our nearest neighbor, Venus, serves as a stark warning of a runaway greenhouse effect. Often called earth's twin because of its similar size and mass, Venus is uninhabitable with a surface temperature of 867° F and an atmosphere that is 96.5% carbon dioxide.
courtesy: NASA If the world continues on a "business as usual" path (no emissions reductions), by 2100 carbon dioxide concentration will likely be over 1000 parts per million! |
Greenhouse Gases
| The earth has a natural energy balance: the amount of incoming solar (ultraviolet) radiation must equal the amount of outgoing (infrared) energy emitted back to space. Greenhouse gases trap heat in the atmosphere by absorbing and re-emitting outgoing energy back to the earth's surface. As these gases accumulate, the atmosphere must heat up to increase outgoing radiation and restore the energy balance – a process known as the greenhouse effect. |
| Below are some of the major greenhouse gases,
given their potent heat-trapping qualities and their high
emission rates:
Methane (CH4) is emitted during the production and transport of fossil fuels, rice cultivation, animal husbandry, organic waste decay, and from natural sources such as wetlands. Liquid methane is commonly known as natural gas, used to power stoves and furnaces.
Nitrous Oxide (NOx) sources are agricultural emissions (nitrogen is found in fertilizer), as well as fossil fuel and solid waste combustion.
Some of the most potent greenhouse gases are synthetic industrial chemicals not found in the atmosphere before the twentieth century. These include hydrofluorocarbons (HFC’s), perfluorocarbons (PFC’s) and sulfur hexafluoride (SF6). Also belonging to this group are chlorofluorocarbons (CFC’s), famous for their ozone-depleting properties, which are to be phased out under the Montreal Protocol. HFC's became a substitute for the illegal CFC's, and are mainly used in refrigeration, air conditioning and foam insulation. PFC's are emitted during the manufacture of Teflon products and semiconductors. They persist for over 50,000 years, and are therefore considered permanent additions to the atmosphere. SF6 is used in electrical insulation, and is emitted during the installation and disposal of these materials.
The atmospheric concentration
of each of these has increased dramatically since the Industrial Revolution, when
fossil fuel burning and chemical emissions began en masse. These
increases are a scientific fact and are NOT a matter of debate.
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Carbon Dioxide (CO2). Increased
concentrations are largely due to fossil fuel burning (power
plants, transportation, industrial processes), as well as the
destruction of forests and other plant life, which remove carbon
dioxide from the atmosphere. 
|
Greenhouse Gas |
Current level |
Pre-Industrial level (1750) |
Unit |
|
Carbon dioxide |
377 |
280 |
ppm (parts per million) |
|
Methane |
1745** |
700 |
ppb (parts per billion) |
|
Nitrous Oxide |
314** |
270 |
ppb (parts per billion) |
|
CFC-11 |
268** |
0 |
ppt (parts per trillion) |
|
CFC-12 |
533** |
0 |
ppt |
|
SF6 |
4.2** |
0 |
ppt |
** based on 1998 measurements (source: Intergovernmental Panel on Climate Change)
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Click the icon below (and then hit the magnifying glass to zoom) to get an idea of just how drastically our atmosphere has changed and will change, when compared to the steady global CO2 concentration of the last 1000 years.
Now click here to see that carbon dioxide concentration remained relatively steady over the last 400,000 years (never exceeding 300 ppm), according to ice cores sampled from Antarctica. But in only the last 150 years, it has moved way out of that window to 377 ppm.
Finally, carbon dioxide, temperature and sea level continue to rise even after we’ve decreased our emissions to zero. This fact emphasizes the importance of acting NOW, given the response lag already built into the climate system – meaning that the greenhouse gases we put into atmosphere today will affect us for centuries to come.
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Online sources for greenhouse gas information:
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USGCRP Atmospheric Composition Slightly more technical page with greenhouse gas research news
Global CO2 is measured atop Mauna Loa in Hawaii
The Pew Center's Greenhouse Gas Page Quick facts and figures on global and U.S. emissions |
News about greenhouse gases, with updated measurements
Get the basics on greenhouse gases and the carbon cycle here
Other Gases: HFC's, PFC's and SF6 Great resource from the Department of Energy |
Our global warming hub was written and compiled by Diana Leonard.
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Why are some gases "greenhouse", while others are not? Greenhouse gases are comprised of molecules that are large enough to interact with the longer radiation waves that are emitted by the earth. But they are too large to interact with the tiny ultraviolet waves arriving from the sun.
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Annual carbon dioxide emissions (tons per person)
United States 20.2 Australia 18.3 Canada 16.5 Russian Federation 9.7 Japan 9.4 United Kingdom 9.2 Italy 7.5 Sweden 5.8 China 2.7 Peru 1.0 Vietnam 0.8 Ethiopia 0.1
source: United Nations Statistics Division |
