Global warming is exactly what it sounds like: an overall increase in temperature of the earth. The earth goes through temperature fluctuations naturally over the course of several thousand years (ever heard of the Ice Age?). When the temperature begins to change faster, it becomes a cause for concern.
The primary cause of global warming is the greenhouse effect. Like global warming, this is a natural phenomenon. As sunlight hits the earth, some of the heat is reflected back into space, while some is absorbed by green house gases – naturally occurring atmospheric gases such as carbon dioxide and methane. Like insulation, the heated gas and atmosphere keep the earth warm enough to sustain life.
However, since the Industrial Revolution, human activity has caused the amount of green house gasses to increase. More gas means more heat from the sun is trapped on the earth, theoretically raising its temperature. Basically, it’s like adding more insulation to your home without lowering the amount of time you run your heater.
An increasing temperature on the planet can have disastrous effects in the long term. Widespread changes to earth’s climate would be expected to cause extreme weather and storms, massive ecological changes, and the extinction of many species.
Unfortunately, humans produce a lot of green house through power plants, automobiles, landfills, and even livestock cultivation. Anytime you reduce the use of any of these things, you are helping the environment. Whether you drive your car less, make sure the power plant doesn’t have to send as much electricity to your house, or just recycle, it all helps the earth in a big way!