Wayne - just a note - it's late. I am working on one more component of the process here and hope to get that information posted within the next week. Fortunately it's a relatively self-contained part of the picture but I have to review what I've collected and organize it before I post. I've had the material waiting on file for a month now and haven't been able to finish the job. But I will.
"By the 1980s the problem of global warming loomed so large that industry, and even some scientists, began casting about for engineering solutions. Here we are talking about true planetary engineering - changing the carbon balance on planet Earth in ways that will affect every living organism - and yet these engineering works were being proposed and tested in the absence of any global body to regulate and approve such activities.
For this reason, and because of an inherent distrust of such solutions, the response of most environmental groups to these initiatives has been lukewarm at best. Yet all would agree that we are facing a dire crisis that may require heroic actions to overcome."
More from "The Weather Makers" (Chapter 31):
"Air travel requires large amounts of high-density fuel of a type that at present only fossil fuels provide. It is also increasing in volume every year. In 1992 air travel was the source of two percent of carbon dioxide emissions. And in the US, where air traffic already accounts for 10 percent of fuel use, the number of passengers transported is expected to double between 1997 and 2017, making air transport the fastest-growing source of carbon dioxide and nitrous oxide emissions in the country. Across the Atlantic, by 2030, a quarter of the UK's emissions may come from air travel.
The cocktail of chemicals that comprise aircraft emissions work in somewhat opposite ways. Because most modern jets cruise near the troposphere, the water vapour, nitrous oxide and sulphur dioxides they emit have particular impacts. The nitrous oxide emitted by aircraft may enhance ozone in the troposphere and lower stratosphere, yet deplete it further in the upper stratosphere; sulphur dioxide will have a cooling effect.
What is emerging as a most important emission is water vapour, which can be observed as aircraft contrails. Under certain conditions contrails give rise to cirrus clouds. These clouds cover around 30 percent of the planet, and while the extent that aircraft contribute to cirrus cloud cover is uncertain, it could be as much as 1 percent which, because it is concentrated in the Northern Hemisphere mid-latitudes, may have a significant impact on climate. If aircraft were to fly lower, cirrus cloud formation could be cut in half and carbon dioxide emissions lowered by four percent, while average flight times in Europe would vary by less than a minute.
As mentioned earlier, the potential of these clouds to affect climate was demonstrated in 2001 between September 11 and 14, when the US air fleet was grounded. Average daytime temperatures rose abruptly by one degree Celsius, in such a manner as could not be explained by other factors. This suggests that contrails may be masking the impacts of warming caused by carbon dioxide. Perhaps we will need to main them while we reduce our carbon intensity. Equally, there seems to be no way at present to get aircraft to run on a less damaging substitute or fossil fuel. Without a return to the more leisurely days of travel by zeppelin, air travel will remain a source of carbon dioxide emissions long after other sectors have transformed to a carbon-free economy.
Transport accounts for around a third of global carbon dioxide emissions. Transportation by land and sea can easily be powered in ways that emit less carbon dioxde, and the technologies to achieve this either already exist or are on the horizon. Air transport, however, is fast growing and not likely to be fuelled by anything but fossil fuels. Thankfully, jet contrails contribute to global dimming, so it may be just as well that the jets keep flying long after wind-powered and solar-powered ships and compressed-air cars monopolise surface transport."