Forgot Password?
Home arrow GreeniacsArticles arrow Environmental News arrow Global Dimming Another Pollution Side Effect
Written by Miranda Huey   
Share |
Tuesday, 09 December 2008

Global Dimming: Another Pollution Side-Effect

Everyone's heard about global warming, but relatively few people have heard about global dimming. What is global dimming? Substantial parts of the world are actually dimmer, i.e., less light, darker, than they were several decades ago due to air pollution.1 The United States, for example, is about 10% dimmer, while parts of the former Soviet Union are actually about 30% dimmer. Even Antarctica has dimmed 9%.2 The culprit is two-fold. Burning coal, oil, and wood creates tiny visible particles, called aerosols, which seep into the atmosphere. Firstly, these reflect sunlight directly back into space. Secondly, polluted clouds contain more droplets than unpolluted clouds, leaving the earth with denser clouds which block off more sunlight.3 Because these pollutants tend to diffuse widely in the world's atmosphere, local pollution has become global dimming.4

One scientist, David Travis, verified the phenomenon in the days after September 11, 2001. Because of the terrorist attack, all airplanes in the U.S. were grounded for three days. Airplanes normally leave contrails, which can cover over half of the sky in certain areas. Travis observed that, after those three days, there were warmer days and cooler nights, exactly what one would expect without the insulating effect of aerosols. The temperature range increased over 1 degree Celsius, making it the largest temperature swing in the last thirty years. If this is the effect over the course of removing only one source of pollutant over the course of three days, global dimming's effect on the world could be greater than anyone ever realized.5

Global dimming may have already had devastating consequences. One of the first such consequences of global dimming may have been the 1984 Ethiopian famine. Before the 1970's, the Sahel had always had summer monsoons provide most of the water in the region. The sun would heat northern oceans, and a tropical rain belt would shift north to the Sahel. Starting in the 70's, the monsoons suddenly disappeared. A model which takes into account global dimming concludes that polluted clouds reflected enough sunshine back into space that the oceans were cooled, preventing the tropical rain belt from moving northward. As a result, 50 million people were affected. Now scientists are starting to fear that the same thing will happen in Asia, where billions of people's livelihoods depend on rainfall.6

On the other hand, for the past decade, scientists have also found evidence of the opposite phenomenon, global brightening. This happens when industrialized nations cut down their smog pollution, reducing aerosol emission and solar dimming. Unfortunately, while this alleviates the effects of global dimming, it accelerates global warming.7

However, global dimming is no solution to global warming. Firstly, the root causes of both global warming and global dimming are the same, burning coal, oil, and gas, causing them to happen simultaneously.8 Moreover, in spite of global dimming, the Earth's surface is still getting warmer.9 Additionally, carbon dioxide stays in the atmosphere for at least a century, while aerosols dissipate within a few days. Any global dimming solution to global warming would require exponentially more pollution to counteract the previous effects of greenhouse gases.10

Perhaps worst of all, global dimming is actually masking the true effects of global warming, which means that climate change is actually going to be much more drastic than reports previously predicted. While global warming has so far only seen a 0.6 degree rise, they predict that, if patterns keep going the way they have been, temperatures might just rise 10 degrees by 2100, making many parts of the world uninhabitable.11 Fortunately, if we curb our greenhouse gas emissions now, we may be able to curb the effects of both global dimming and global warming.

Browse all Greeniacs Articles Browse all Greeniacs Guides        Browse all Greeniacs Articles

5 Id.
6 Id.

Add your comment
RSS comments

Only registered users can write comments.
Please login or register.

Click here to Register.  Click here to login.

Last Updated ( Thursday, 10 February 2011 )


Green Facts

  • A single quart of motor oil, if disposed of improperly, can contaminate up to 2,000,000 gallons of fresh water.

  • Americans throw away enough aluminum to rebuild our entire commercial fleet of airplanes every 3 months

  • Due to tiger poaching, habitat destruction, and other human-tiger conflicts, tigers now number around 3,200óa decrease in population by about 70% from 100 years ago.

  • It takes 6,000,000 trees to make 1 year's worth of tissues for the world.

  • You will save 100 pounds of carbon for each incandescent bulb that you replace with a compact fluorescent bulb (CFL), over the life of the bulb.

  • Shaving 10 miles off of your weekly driving pattern can eliminate about 500 pounds of carbon dioxide emissions a year.

  • 82 percent of greenhouse gas emissions in the U.S. come from burning fossil fuels.

  • Glass can be recycled over and over again without ever wearing down.

  • Current sea ice levels are at least 47% lower than they were in 1979.

  • Rainforests are being cut down at the rate of 100 acres per minute.

  • Recycling 1 million laptop computers can save the amount of energy used by 3,657 homes in the U.S. over the course of a year.

  • In the United States, automobiles produce over 20 percent of total carbon emissions. Walk or bike and you'll save one pound of carbon for every mile you travel.

  • Americans throw away more than 120 million cell phones each year, which contribute 60,000 tons of waste to landfills annually.

  • In California homes, about 10% of energy usage is related to TVs, DVRs, cable and satellite boxes, and DVD players.

  • The World Health Organization estimates that 2 million people die prematurely worldwide every year due to air pollution.

  • States with bottle deposit laws have 35-40% less litter by volume.

  • A laptop consumes five times less electricity than a desktop computer.

  • For every 38,000 bills consumers pay online instead of by mail, 5,058 pounds of greenhouse gases are avoided and two tons of trees are preserved.

  • Refrigerators built in 1975 used 4 times more energy than current models.

  • Bamboo absorbs 35% more carbon dioxide than equivalent stands of trees.

  • A tree that provides a home with shade from the sun can reduce the energy required to run the air conditioner and save an additional 200 to 2,000 pounds of carbon over its lifetime.

  • Americans use 100 million tin and steel cans every day.

  • Every week about 20 species of plants and animals become extinct.

  • Recycling for one year at Stanford University saved the equivalent of 33,913 trees and the need for 636 tons of iron ore, coal, and limestone.

  • One recycled aluminum can will save enough energy to run a 100-watt bulb for 20 hours, a computer for 3 hours, or a TV for 2 hours.

  • An aluminum can that is thrown away instead of recycled will still be a can 500 years from now!

  • Turning off the tap when brushing your teeth can save as much as 10 gallons a day per person.

  • Less than 1% of electricity in the United States is generated from solar power.

  • Washing your clothes in cold or warm instead of hot water saves 500 pounds of carbon dioxide a year, and drying your clothes on a clothesline six months out of the year would save another 700 pounds.

  • A steel mill using recycled scrap reduces related water pollution, air pollution, and mining wastes by about 70%.

  • Plastic bags and other plastic garbage thrown into the ocean kill as many as 1,000,000 sea creatures every year.

  • Recycling 100 million cell phones can save enough energy to power 18,500 homes in the U.S. for a year.

  • You will save 300 pounds of carbon dioxide for every 10,000 miles you drive if you always keep your carís tires fully inflated.

  • Nudge your thermostat up two degrees in the summer and down two degrees in the winter to prevent 2,000 pounds of carbon dioxide from entering the atmosphere.

  • Youíll save two pounds of carbon for every 20 glass bottles that you recycle.

  • American workers spend an average of 47 hours per year commuting through rush hour traffic. This adds up to 23 billion gallons of gas wasted in traffic each year.

  • Recycling aluminum saves 95% of the energy used to make the material from scratch.

  • If every U.S. household turned the thermostat down by 10 degrees for seven hours each night during the cold months, and seven hours each weekday, it would prevent nearly gas emissions.

  • 77% of people who commute to work by car drive alone.