Global warming refers to the increase of the earth's average temperature due to increasing amounts of greenhouse gases in the atmosphere.
Scientists agree that the burning of fossil fuels like oil and coal causes greenhouse gases such as carbon dioxide to escape into the air and act like a warm blanket over the earth.
One way to reduce greenhouse gases is to reduce deforestation, the cutting down of trees. Trees soak up carbon dioxide from the air, so having lots of trees around is good for the atmosphere.
There are already some changes happening because of global warming. Sea level is rising and some animals are moving to new homes because their natural habitat is disappearing. If the warming gets worse, as scientists expect, there may be some kinds of plants and animals that become extinct.
There may be more storms and floods. Due to melting ice caps, sea levels may rise so much that people have to move away from the coasts. Some areas may become too dry for farming.
All humans contribute to global warming by burning fossil fuels when they drive a car, fly in an airplane, and heat or cool their houses.
The best way to help slow down global warming is to put less carbon into the air by using less fossil fuel - something that is easy to say, but hard to do!