The greenhouse effect

Presumably, by now, you’ve heard of something called the “greenhouse effect.” (If you haven’t, we’ll pause briefly while your next-of-kin checks to see if you’re still breathing.)

The term “greenhouse effect,” as usually used today, refers to the predicted gradual warming of the Earth due to an increase in various gases in the atmosphere, primarily due to man’s activities. There is considerable debate as to just how serious this warming is going to be–and whether it has begun yet. (Despite the warmth of the ’80s in our part of the world, the most recent and most accurate study of the Earth’s temperature, carried out by satellites over the last decade, shows no evidence of global warming or cooling.)

However, in a broader sense the greenhouse effect has been at work for eons, which is a good thing, because if it hadn’t been, we probably wouldn’t be here. That’s because the greenhouse effect is what keeps the mean surface temperature high enough (currently it’s 17 degrees) for life to thrive.

About 40 percent of the energy we receive from the sun is shortwave radiation, to which the atmosphere is transparent. This radiation warms the ground, which radiates heat back at a much longer wavelength. Most gases are transparent to this longer-wavelength radiation, but not all. The so-called greenhouse gases, especially carbon dioxide (though others are also involved), absorb it, instead–and heat up, warming the other gases in the atmosphere at the same time.

The amount of carbon dioxide in the air and the mean surface temperature are far from carved in stone. The surface temperature has, in the past, been both so much colder that much of the planet was covered with ice, and so much warmer that even near the poles sub-tropical flora and fauna flourished.

However, the current increase in carbon dioxide is quite rapid, and due almost entirely to human activities, especially the burning of fossil fuels. It’s estimated carbon dioxide levels are 25 percent higher now than they were in 1860. Some scientists predict that by 2050 this increase in carbon dioxide could boost global mean temperatures from two to five degrees.

Considering Saskatchewan winters, that doesn’t sound so bad. But look at some of the possible consequences: shifting weather patterns could bring drought to once-fertile areas (like Saskatchewan?) and heavy rains to fragile deserts; run-off from melting glaciers and the expansion of warming seawater could raise sea levels six feet, inundating low-lying coastal areas and islands; hurricanes could increase in frequency and severity.

Probably some parts of the globe would actually benefit, but the atmosphere is so incredibly complex that there is no way of predicting the precise effect on any area–just as no one can accurately predict the weather more than a few days in advance.

This should mean that all countries have an equal stake in dealing with the problem. While it is generally conceded it is impossible to halt the greenhouse effect, it can be slowed, “simply” by cutting fossil fuel usage.

Of course, that’s not really simple at all. Developed countries such as our own aren’t anxious to give up the comforts and conveniences purchased with high energy usage, and less-developed countries are understandably unhappy with suggestions that they should not be allowed to follow the same industrialized route to prosperity as the developed nations.

Still, there are steps to be taken. Energy conservation techniques such as were all the rage during the 1970s’ energy crisis should be continued and expanded. Just because oil is currently cheap is no reason to burn it profligately. To do so could be costing us a lot more than just a few dollars.

On a broader scale, countries must develop energy sources other than coal and oil. Natural gas, for example, produces half as much carbon dioxide per unit of energy as coal, and solar power, wind power, geothermal power and nuclear power, though they have their own problems, produce no greenhouse gases at all.

Some scientists are already thinking of more direct methods of attacking the problem–and before dismissing them as wildly farfetched and hopelessly expensive, consider the cost of building coastal walls to keep out the rising ocean.

Plant more forests, says George Woodwell, director of the Woods Hole Research Center in Massachusetts. About 1.86 million square kilometres of new forest (4.5 times the area of California) would take care of a third of the carbon dioxide problem (assuming we stop cutting down the forests we already have).

Spread phosphates in the ocean, or use large orbiting reflectors to beam extra sunlight into the polar seas, to promote blooms of phytoplankton, suggests climatologist Roger Revelle of the University of California in San Diego. Phytoplankton use carbon dioxide in photosynthesis, then when they die take it with them to the ocean floor, where it remains for centuries.

Volcanos cool the earth by spewing sulfur dioxide, notes Wallace Broecker, a geochemist at Columbia University; we could load the upper atmosphere with sulfur dioxide, using a fleet of 700 jumbo jets working around the clock for year after year after year. (Aside from the logistical problems, this has one other slight disadvantage: sulfur dioxide promotes acid rain.)

There are other suggestions: painting every roof on every building on Earth white to reflect more sunlight, for example, or building giant orbiting parasols (10 million square kiometres’ worth) to block out the sun, or…

Or maybe we should just look harder for alternatives to fossil fuels and use less of them in the meantime.

Sounds a lot simpler, doesn’t it?

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