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Tip 30 - The Greenhouse Effect |
| Here's one way to understand the greenhouse effect: Think of a car parked in the summer sun. It gets incredibly hot inside because windows let the sunlight in but don't let heat escape. Our atmosphere is like that. It naturally keeps the Earth warm by trapping some of the sun's heat with a blanket of gases. The "recipe" for this blanket calls for fairly exact portions of water vapor, carbon dioxide (CO2), methane, and a few others. They each trap a fraction of the heat escaping from the earth. Too much of any one of them causes the atmosphere to get too hot. |
| HOW IT USED TO WORK Natural sources of extra "greenhouse gases," like volcanoes and animals, have always been balanced by natural absorbers of those gases, like oceans and trees. That's why our ancestors didn't cause global warming by burning wood -- they were just releasing CO2 that the trees had absorbed during their lifetimes, more or less. New trees took it up again, and everything was fine. |
| THE RICKETY BALANCE Now, humans have begun to upset that balance. Not only are we cutting down more trees than we're planting, but we're burning more and more fossil fuels-reserves of oil, coal and natural gas trapped beneath the earth. These fuels were formed from the remains of ancient jungles and swamps; it took them eons to absorb the CO2 that we release in a few seconds by burning them. Thanks to fossil fuels, the atmosphere now contains 25% more CO2 than it did a century ago. |
| SO WHAT? Scientists don't know exactly how much hotter this extra CO2 will make the Earth. But many agree it will warm the Earth overall-by 4° to 9° F by the year 2050. That may not sound like much, but it only took a rise of a few degrees to end the last Ice Age. This kind of warming could have disastrous effects. It could melt parts of the polar ice-caps, raising sea level by a few feet -- and flooding many of the world's major cities and harbors. It could lead to more scorching summers, droughts and deserts. And it certainly could change weather patterns in ways we can't foresee. It could be very hard for people to adapt to a several-hundred-mile shift in the Corn Belt, to say nothing of how hard it could be for animals and plants. |
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THE FIVE "GREENHOUSE GASES"- Carbon dioxide causes about 50% of the "greenhouse effect." The world's energy use produces about 20 billion tons of CO2 each year. Another 4 billion tons come from deforestation.
- Chlorofluorocarbons (CFCs), which are used as coolants in air conditioners and refrigerators, account for about 15-20% of the greenhouse effect. CFCs are completely artificial; they persist in the atmosphere for decades and contribute to ozone depletion too.
- Methane, the "natural gas" we use to heat our water and our homes, accounts for 18% of the greenhouse effect.
- Nitrous Oxide, a pollutant from cars and power plants, produces 10% of the greenhouse effect.
- Ozone, a component of urban smog, also contributes a tiny fraction to global warming.
HOW ENERGY AFFECTS THE GREENHOUSE- A typical household uses about 7,000-10,000 kilowatt-hours (kwh) of electricity every year. Each kwh we save keeps about 1.5 pounds of CO2 out of the atmosphere.
- Households use about 750 therms of natural gas a year, on the average. Some of it leaks out of pipes and contributes directly to the greenhouse effect. The rest produces CO2 when it burns -- about 12 pounds for every therm.
- The average car uses 500 gallons of gasoline in a year. Every gallon burned adds 20 pounds of carbon dioxide to the air.
- Even wasting water contributes to the greenhouse effect because of the energy it took to pump, purify and treat that water. According to the Natural Resources Defense Council, about 6 pounds of CO2 are emitted for every 1,000 gallons of water we use.
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| Acid Rain |
| Some of the rain that falls in the northeastern U.S. is nearly as acidic as lemon juice. In the Pacific Northwest, the rain and fog are not nearly as tart but still acid rain is an issue that concerns us as residents of the planet. Here's what causes it: |
| SULFUR OXIDES Sulfur makes up a small fraction of the coal and heavy oil used in some power plants. When these fuels are burned, the sulfur combines with oxygen in the air, forms sulfur oxides (SOx), and escapes up the smokestack. Electric utilities emit an estimated two-thirds of the nation's SOx. The contributions from each power company depend on the fuels they burn and the pollution controls they use. The majority of power Seattle City Light generates is hydroelectric. City Light owns a small percentage of one coal plant but the coal the utility uses to generate electricity contains very low levels of sulfur. |
| NITROGEN OXIDES Nitrogen oxides (NOx) also lead to acid rain. NOx emissions per individual car have been reduced sharply since the 1970s but the number of power plants and cars keeps growing.
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| HOW ACID RAIN OCCURS The SOx and NOx mix with water in clouds to form sulfuric and nitric acids, then fall back to earth in rain or snow, making lakes and streams too acidic for fish and other animals to survive. Plus, SOx and NOx attack forests and damage agricultural crops. |
HOW ENERGY USE AFFECTS ACID RAIN The fewer gallons of gasoline you burn, the less NOx comes out of your tailpipe. Your car emits most of its Nox in the minute after you first start it, before the catalytic converter has gotten warm enough to begin controlling it. So, in addition to saving energy, avoiding short trips in your car will also help control acid rain.
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| Urban Air Pollution |
| If you live in a big city, you may be accustomed to smog, but medium and small-sized cities are starting to have bad breath, too. The U.S. Environmental Protection Agency reports that more than 100 million Americans live in places where the air is unhealthy at least a few days a year. |
| GASP, CHOKE, WHEEZE As a result, more than 30,000 people in the U.S. die prematurely from lung diseases every year, according to the American Lung Association. The health costs from smog-related respiratory diseases in hundreds of thousands of people add as much as $90 billion to the country's medical bill every year. |
| INGREDIENTS: It takes several pollutants to form smog, including nitrogen oxides (NOx) and hydrocarbons (unburned or partially burned fuel). Both stem from the use of gasoline, natural gas and even things like paint thinner. Sunlight helps "cook" these chemicals into the blend we call smog. The simplest measure of smog is ozone (O3), which is useful high in the atmosphere but harmful to humans, other animals, plants and property down near the ground. |
HOW ENERGY USE AFFECTS THE AIR QUALITY- According to the Public Interest Research Groups, our cars, trucks and buses emitted 8.5 million tons of NOx and 6.5 million tons of hydrocarbons in 1986. Not surprisingly, everything we can do to reduce our consumption of gasoline or reduce the distance goods are transported helps to minimize NOx emissions.
- Utilities, oil and chemical plants account for about half the national emissions of NOx and hydrocarbons. But it's misleading to blame only these big entities for the problem; they produce energy, gasoline, plastics and other energy-intensive products because of our demand for them. By reducing our demand, we can reduce the severity of the problem.
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| Ozone Depletion |
The ozone layer is a thin, invisible shield of gases 6 to 30 miles above the ground. It protects us from the sun's ultraviolet light. But now, manmade chemicals containing chlorine and bromine have begun to attack the ozone layer. These are the chemicals:- Chlorofluorocarbons (CFCs) -- used as refrigerants and aerosol propellants, in foam plastics and some solvents. Includes Freon.
- Halons -- used in some dry fire extinguishers.
- Industrial solvents such as methyl chloroform and carbon tetrachloride -- used to clean electronic circuits, and greasy engine parts.
- CFC substitutes (HCFCs) -- increasingly used to replace CFCs in some products. They're not as strong but still harm the ozone layer.
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| OFF IN THE OZONE Since 1969, these chemicals have reduced the strength of the ozone layer above populated areas by 3 to 6%. This has already increased the incidence of skin cancer and cataracts among people living in high northern and southern latitudes. If ozone depletion continues at the present rate, the EPA estimates, up to 300 million extra cases of skin cancer could result in the U.S. alone over the next 180 years. |
HOW ENERGY USE AFFECTS THE OZONE LAYER- Most of what we can do to protect the ozone layer involves reducing our use of the chemicals listed above. But some energy-saving tips can also help the ozone layer. For example, a large percentage of CFCs are used in refrigerators and automobile air conditioners. By saving energy through wise use of these devices, we can minimize the need to refill them with new CFCs.
- When your air conditioner or refrigerator is drained of CFCs for servicing, it's important to capture them instead of letting them escape into the air.
- Many types of insulation (especially foam) contain CFCs. So if you insulate your home, it's critical to ask for cellulose, fiberglass or other CFC-free insulation. Otherwise, saving energy can actually harm the ozone layer.
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