Global warming is a rise of temperature in the earth's atmosphere. As the earth warms, it may lead to changes in rainfall/snow patterns, a rise in sea level, and impacts on plants, wildlife, and humans.
The Greenhouse Effect
When sunlight reaches the earth, some is reflected back to space, but most of the sunlight travels to the atmosphere, until it hits the earths surface. The sunlight warms up the earth's land and oceans making the earth give off energy. This energy can be absorbed by some of the gases in the air, but the difference is that the energy is harder to escape into space. When humans pollute the air the level of greenhouse gases increase. Making the energy even more difficult to escape into outer space. Which in turn traps the heat, warming up the earth.
Polar Ice Caps
As a result of global warming, the polar ice caps as a whole is shrinking (melting). The image to the left shows that since 1979, the area of permanent ice cover is reducing at a rate of 9.8% each decade. Scientists predict that if this continues, summers in the Arctic will be ice-free by the end of the century. For example, the Ward Hunt Ice Shelf, the largest single block of ice in the Arctic, had been around for 3,000 years. In 2000 the Ward Hunt Ice Shelf started cracking and within two years, it split all the way through and is now breaking into pieces.