Global warming is actually the result of lots of complex ecological and chemical processes. Here is what you need to know: Scientists agree that global warming is occurring because of the dramatic increase of certain “greenhouse gases” that trap heat in the Earth’s atmosphere like a blanket. The main culprit is carbon dioxide, but other greenhouse gases like methane, nitrous oxide, ozone and halocarbons are contributing to global warming as well.
Most of these gases have been with us since the beginning of time as a part of the natural carbon cycle. They create the natural “greenhouse effect” which has sustained life and kept the planet from turning into a frozen wasteland. (You can read more about the Greenhouse Effect here.)
Too much carbon
But ever since we figured out how to burn coal and other fossil fuels (like natural gas and oil) to run our machines and cars, we’ve seriously tipped the scales by adding unnatural amounts of carbon into the atmosphere—more than what it can absorb. Fossil fuels are non-renewable, which means they cannot be replenished once they are removed from the Earth and burned.1 Every time we drive our car, turn up our heat or air conditioning, or turn on a light, we are burning fossil fuels and sending carbon dioxide into the atmosphere.
According to the U.S. Environmental Protection Agency (EPA), carbon dioxide was responsible for 83.9% of U.S. greenhouse gas emissions in 2005 (and burning of fossil fuels was by far the greatest source of carbon dioxide). And, around the world, we are cutting down too many forests, which also contributes to total global carbon dioxide emissions. (You can find out how forests reduce global warming here.)
What’s more is that all that carbon we’ve been overloading the atmosphere with isn’t going away quickly, not even if we completely stopped all greenhouse gas emissions today (an impossible scenario anyway). Carbon dioxide and other greenhouse gases can stick around in the atmosphere for 100 years or more.2
That means some of the effects caused by global warming are inevitable; but we can avoid some of the most dangerous and irreversible effects by reducing our heat-trapping emissions through solutions like energy conservation, expansion of renewable energy and slowing deforestation.
To determine how much a particular gas contributes to global warming, the IPCC devised a measure called the Global Warming Potential (GWP) to show its possible warming effect.
According to the Union of Concerned Scientists:
“To be able to compare the Global Warming Potential (GWP) of different gases, a base unit of CO2 is said to have the GWP of 1. The chart below shows, for example, that each ton of methane will have 21 times the global warming impact over a hundred-year period as a ton of carbon dioxide. Even though total emissions of chlorofluorocarbons are quite small compared with emissions of carbon dioxide, their impact is significant since their global warming potential is so large. And even bigger than that, scientists recently identified a rare and previously unreported gas—trifluoromethyl sulfur pentafluoride (SF5CF3)—that is long-lived (an atmospheric residence of several hundred to several thousand years) and may have a Global Warming Potential that could be as much as 18,000 times that of CO2. ....read more