Duncan - The problem with the thinking on greenhouse gases is that we are looking at ground level, whereas the reasons for this change are tens of thousands of feet above ground level.
Annual CO2 emissions: The U.S. produced 4,433,057 kilotons of CO2 in 2010 (26.43 per cent of global production) versus 499,137 kilotons for Canada (1.59 per cent). It is generally accepted that emissions from aircraft account for between two and four per cent of the total. The National Aerospace Laboratory predicted in 1990 that this figure could rise to 15 per cent of total global production. This meansthat as a minimum, aircraft produced 88,661.14 kilotons of emissions in the U.S during 2010, versus 9,982.74 kilotons in Canada. Most of the following is taken from carbonindepenant.org or the Intergovernmental Panel on Climate Change (IPCC): "Aviation has effects on climate beyond that resulting from its CO2 emissions, including effects on tropospheric ozone and methane from its NOx emissions, water vapour, particle emissions and formation of contrails/enhanced cirrus cloudiness."A 2006 column by George Monbiot stated: "Aviation has been growing faster than any other source of greenhouse gases. Between 1990 and 2004, the number of peopleusing airports in the U.K. rose by 120 per cent, and the energy the planes consumed increased by 79 per cent. Their carbon dioxide emissions almost doubled in that period - from 20.1 to 39.5 mega tonnes, or 5.5 per cent of all the emissions this country produces. Unless something is done to stop this growth, flying will soon overwhelm all the cuts we manage to make elsewhere." Emissions in the stratosphere are believed to be two to four times more harmful than emissions at ground level.The aircraft industry is predicted to quadruple by 2050. You can't plant trees at 35,000 feet.Ian KimmDuncan