posted 01-28-2002 10:29 AM            

"Climate and Choices
Climate is the result of the exchange of heat and mass between the land, ocean, atmosphere, ice sheets and space. As long as changes to the land, ocean, atmosphere and ice sheets stay below the thresholds I have just described, climate changes will happen slowly. But the climate will change rapidly if those thresholds are crossed. So rapidly that it would be impossible to rearrange agricultural practices quickly enough to avoid stressing world food supplies. So rapidly that many species would not be able to adapt, because their habitat, already greatly reduced by human activities, would be eradicated.

Human ingenuity would most likely allow us to adapt to a rapid change in climate, but we would pay a larger price than our civilization has ever known. Imagine the economic and social cost of moving, in a 20-year period, most of our agricultural activities 500 miles south of their current locations. Imagine the social cost and famine if agriculture could not be relocated quickly enough. Even a short-duration event such as the Dust Bowl years in the 1930s had a large influence on American society. The Little Ice Age, which caused major resettlement in Europe in the 15th and 16th centuries, is a more likely analogue of where we might be headed.

Some have proposed that we could counterbalance the greenhouse effect by manipulating the global exchanges of heat and mass. Methods that have been discussed include blocking the Strait of Gibraltar to change the salinity of the North Atlantic, USING AIRPLANE DISTRIBUTED PARTICLES or large orbiting sunshades to shade the earth, and fertilizing the ocean with iron to promote production of carbon dioxide-consuming biomass. But we have a poor record of managing even small ecosystems and lack a complete understanding of the ocean-atmosphere interactions that govern our climate. Intentionally manipulating climate would not only be costly and imprecise; it would also be impossible to benefit some regions without adversely effecting others. It would be a risky experiment on the only planet we can call home."

Source: http://www.sigmaxi.org/amsci/articles/99articles/Taylorthree.html

The entire article can be found at: http://www.sigmaxi.org/amsci/articles/99articles/Taylor.html

posted 01-28-2002 12:52 PM            

That's an excellent post. As our supercomputers get faster and we're better able to model such things as global climate, it's becoming increasingly obvious that a relatively small change in one climate driver (like cloud cover or direction of an ocean current) can possibly result in catastrophic changes to our climate.

Although I don't personally believe that contrails are anything but contrails, I thing that the sheer volume of such -- given the tremendous increase of airplane traffic worldwide -- has resulted in a significant increase in cloud cover. This could result in cooler days (since the clouds block a portion of the sunlight reaching the Earth's surface) and warmer nights (since the same clouds block the heat radiating back to space at night). I don't know what difference this decreased "temperature delta" might have on global climate, but my guess is that it wouldn't be good.

Regards,