The majority of the scientific community believes that global warming is a real threat to the world as we know it today. They believe that global warming mostly results from the emissions of carbon dioxide and other greenhouse gases from human activities such as industrial processes, fossil fuel combustion, and deforestation.
There are many causes of global warming. One cause is carbon dioxide that is made from the burning of fossil fuels from power plants for the purpose of electricity generation. Coal makes up 93% of these emissions. Coal emits 1.7 times more carbon per unit of energy when burned than natural gas and 1.25 times more carbon than oil. Consequently, natural gas gives off 50% less carbon dioxide for the same amount of energy produced. Another cause is carbon dioxide that is made from the burning of gasoline in internal-combustion engines of cars, minivans, sport utility vehicles, pick-up trucks, and jeeps. Poor gas mileage is considered the main culprit here. According to the Environmental Protection Agency's 2000 Fuel Economy Guide, a new Dodge Durango sports utility vehicle (with a 5.9 liter engine) that gets 12 miles per gallon in the city will emit around 800 pounds of carbon dioxide over a distance of 500 city miles; this translates to 19.6 pounds of carbon dioxide emitted into the air for every gallon of gas a vehicle consumes.
Another cause of global warming is carbon dioxide that is made from commercial trucks, contributing another 13% of U.S. carbon dioxide emissions.
Carbon dioxide that is made from airplanes is another cause of global warming - the United Nation's Intergovernmental Panel on Climate Change estimates that aviation causes 3.5% of global warming, with a projection that it will rise to 15% by 2050.
Another cause of climate warming is carbon dioxide that is emitted by the structure of buildings, accounting for another 12% of carbon dioxide emissions.
Methane is another cause of climate warming, as methane is the second most important greenhouse gas after carbon dioxide. According to the IPCC, methane is 20 times more effective than CO2 in trapping heat in the atmosphere. US Emissions Inventory 2004 levels of atmospheric methane have risen 145% in the last 100 years. Sources of this rise in methane include rice paddies, bovine flatulence, bacteria in bogs, and fossil fuel production.
Another cause of global warming is nitrous oxide, a colourless, non-flammable gas with a sweetish odour. It is naturally produced by oceans and rainforests, while it is also artificially produced in nylon, nitric acid production, agricultural fertilizers, cars with catalytic converters, and burning organic matter.
Deforestation is also one of the causes of global warming, the second-leading cause only to carbon emissions. Deforestation is responsible for 25% of all carbon emissions entering the atmosphere, as 34 million acres of trees are burn and cut each year. The destroying of tropical forests alone emit hundreds of millions of tons of carbon dioxide into the atmosphere each year.
City gridlock is another global warming cause. According to an annual study by traffic engineers from Texas A&M University, drivers in Los Angeles and New York alone waste 600 million gallons of gas annually while just sitting in traffic. That translates into around 7.5 million tons of carbon dioxide that is emitted into the atmosphere. And remember, just two major U.S. cities are named, not to mention the rest of the U.S. and the world.
Another global warming cause is just the amount of carbon already in the Earth's atmosphere naturally, as 750 billion tons of carbon are present. Add in another 800 billion tons of carbon that is dissolved in the surface layers of the world's oceans.
As you can see, carbon dioxide, methane, and nitrous oxide are the major causes of global warming. You can also see there are many sources of these gases, especially carbon dioxide. Much work needs to be done in order to address all the causes of global warming.