Forwarding from another list. Darryl -------- Original Message --------
> >Methane's Impacts on Climate Change May Be Twice Previous Estimates >http://www.nasa.gov/vision/earth/lookingatearth/methane.html >07.18.05 > >Even on a cold winter day, standing inside a greenhouse can be >downright balmy if the sun is shining outside. The glass lets the sun's >warming rays in, but doesn't let as much of that warmth escape >outdoors. Our Earth is much like that greenhouse, where a mixture of >gases in our atmosphere acts together like a pane of glass, letting the >sun's rays in, and without letting as much warmth escape out to space. > >Singling out how much each greenhouse gas (GHG) contributes overall to >climate warming can be a tricky task. When it comes to measuring the >impacts of greenhouse gases on our climate, scientists typically look >at how much of each gas exists in the atmosphere. > >However, Drew Shindell, a climatologist at NASA's Goddard Institute for >Space Studies, New York, NY, believes we need to look at the GHGs when >they are emitted at Earth's surface, instead of looking at the GHGs >themselves after they have been mixed into the atmosphere. "The gas >molecules undergo chemical changes and once they do, looking at them >after they've mixed and changed in the atmosphere doesn't give an >accurate picture of their effect," Shindell said. "For example, the >amount of methane in the atmosphere is affected by pollutants that >change methane's chemistry, and it doesn't reflect the effects of >methane on other greenhouse gases," said Shindell, "so it's not >directly related to emissions, which are what we set policies for." > >Once GHGs like methane and the molecules that create ozone are released >into the air, these gases mix and react together, which transforms >their compositions. When gases are altered, their contribution to the >greenhouse warming effect also shifts. So, the true effect of a single >GHG emission on climate becomes very hard to single out. > >The leading greenhouse gases include carbon dioxide, methane, nitrous >oxide, and halocarbons. These gases are called â??well mixedâ?? greenhouse >gases because of their long lifetimes of a decade or more, which allows >them to disperse evenly around the atmosphere. They are emitted from >both man-made and natural sources. Ozone in the lower atmosphere, >called tropospheric ozone or smog, also has greenhouse warming effects. >In the upper atmosphere, ozone protects life on Earth from the sunâ??s >harmful ultraviolet rays. > >Some of the major investigations into the state of our warming planet >come from a series of reports from the Intergovernmental Panel on >Climate Change (IPCC) Assessment. These reports involved the work of >hundreds of climate experts. The reports rely on measurements of >greenhouse gases as they exist in the atmosphere, after they may have >mixed with other gases. > >Shindell finds there are advantages to measuring emissions of >greenhouse gases and isolating their impacts, as opposed to analyzing >them after they have mixed in the atmosphere. His study on the subject >was just published in the journal Geophysical Research Letters. > >According to new calculations, methane's effect on warming the world's >climate may be double what is currently thought. The new >interpretations reveal methane emissions may account for a whopping >third of the climate warming from well-mixed greenhouse gases between >the 1750s and today. The IPCC report states that methane increases in >our atmosphere account for only about one sixth of the total effect of >well-mixed greenhouse gases on warming. > >Part of the reason the new calculations give a larger effect is that >they include the effect methane has on air pollution. A major component >of air pollution is near-surface-level or tropospheric ozone, which is >not directly emitted, but is instead formed chemically from methane >other hydrocarbons, carbon monoxide and nitrogen oxides. The IPCC >report includes the effects of tropospheric ozone increases on climate, >but it is not attributed to particular sources. By categorizing the >climate effects according to emissions, Shindell and colleagues found >the total effects of methane emissions are substantially larger. In >other words, the true source of some of the warming that is normally >attributed to smog is really due to methane that leads to increased >smog. > >"If we control methane, which is viable, then we are likely to soften >global warming more than one would have thought, so that's a very >positive outcome," Shindell said. > >Sources of methane include natural sources like wetlands, gas hydrates >in the ocean floor, permafrost, termites, oceans, freshwater bodies, >and non-wetland soils. Fossil fuels, cattle, landfills and rice paddies >are the main human-related sources. > -- Darryl McMahon It's your planet. If you won't look after it, who will? The Emperor's New Hydrogen Economy (now in print and eBook) http://www.econogics.com/TENHE/ _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
