Causes of global warming

Carbon dioxide from power plants: In 2002 about 40% of US carbon dioxide emissions stem from the burning of fossil fuels for the purpose of electricity generation. Coal accounts for 93 per cent of the emissions from the electric utility industry. Coal emits around 1.7 times as much carbon per unit of energy when burned as does natural gas and 1.25 times as much as oil. Natural gas gives off 50% of the carbon dioxide, the principal greenhouse gas, released by coal and 25% less carbon dioxide than oil, for the same amount of energy produced.
Carbon dioxide emitted from cars: About 20% of US carbon dioxide emissions comes from the burning of gasoline in internal-combustion engines of cars and light trucks (minivans, sport utility vehicles, pick-up trucks, and jeeps). The United States is the largest consumer of oil, using 20.4 million barrels per day. If car manufacturers were to increase their fleets' average gas mileage about 3 miles per gallon, the US could save a million barrels of oil every day, while US drivers would save $25 billion in fuel costs annually.
Carbon dioxide from airplanes: The UN's Inter-governmental Panel on Climate Change estimates that aviation causes 3.5 per cent of global warming, and that the figure could rise to 15 per cent by 2050
Carbon dioxide from buildings: Buildings structure account for about 12% of carbon dioxide emissions.
Methane: While carbon dioxide is the principal greenhouse gas, methane is second most important. Methane is more than 20 times as effective as CO2 at trapping heat in the atmosphere. In the atmospheric methane have risen 145% in the last 100 years.
Nitrous oxide: Another greenhouse gas is Nitrous oxide (N2O), a colourless, non-flammable gas with a sweetish odour, commonly known as "laughing gas," and sometimes used as an aneasthetic. Nitrous oxide is naturally produced by oceans and rainforests. Man-made sources of nitrous oxide include nylon and nitric acid production, the use of fertilisers in agriculture, cars with catalytic converters and the burning of organic matter.
Deforestation: After carbon emissions caused by humans, deforestation is the second principle cause of atmospheric carbon dioxide. Deforestation is responsible for 25% of all carbon emissions entering the atmosphere, by the burning and cutting of about 34 million acres of trees each year. We are losing millions of acres of rainforests each year, the equivalent in area to the size of Italy.
City gridlock: In 1996 according to an annual study by traffic engineers (as reported in the San Francisco Chronicle December 10, 1996) from Texas A and M University, it was found that drivers in Los Angeles and New York City alone wasted 600 million gallons of gas annually while just sitting in traffic. The 600 million gallons of gas translates to about 7.5 million tons of carbon dioxide in just those two cities.
Carbon in atmosphere and ocean: The atmosphere contains about 750 billion tons of carbon, while 800 billion tons are dissolved in the surface layers of the world's oceans.
Permafrost: Permafrost is a solid structure of frozen soil, extending to depths of 2,200 feet in some areas of the arctic and sub-arctic regions, containing grasses, roots, sticks, much of it dating back to 30,000 years. About 25% of the land areas of the Northern Hemisphere hold permafrost, which is defined as soil whose temperature has been 32 degrees (F) for a period of at least 2 years.
Tundra: A name very suited to the environs of the arctic and sub-arctic, tundra means "treeless plain" in Finnish. The tundra is a biome (a major segment of a particular region having distinctive vegetation, animals and microorganisms adapted to a unique climate), home to about 1,700 kinds of plants, including shrubs, mosses, grasses, lichens and 400 kinds of flowers. About 50 billion tons of carbon is estimated to be held in a frozen state in the tundra, and now the tundra is beginning to become a source of carbon dioxide.