Scientists made an alarming discovery in the 1980s. They found out that the average temperature of the Earth's surface was slowly rising. This trend is called global warming. Today we know that global warming is increasing because more and more gases get into the atmosphere.
A greenhouse is a glass house in which plants grow. The glass lets light in and at the same time keeps heat from getting out. This heat keeps the plants warm, even when it is cold outside. The same happens to the Earth's atmosphere. It lets sunlight in and keeps carbon dioxide and other gases from getting out. We need these gases but too much of them trap more heat.
For a long time people on our Earth didn't think a lot about greenhouse gases. The situation changed when people started using more and more energy in the form of fossil fuels, like oil, gas and coal. We burn fossil fuels to power factories, run cars, produce electricity and heat houses. As fossil fuels burn they let carbon dioxide into the atmosphere.
During the last few decades people have also cut down many forests. Trees use carbon dioxide when they make their own food. Fewer trees mean that less carbon dioxide is taken out of the atmosphere.
Scientists have different opinions on how warm the Earth's surface will really get. The increase may be between 1.5° C and 6° C by the year 2100. Warmer weather will make ice caps and glaciers melt. Sea levels could rise dramatically. Plants, animals and people living in coastal areas all could be in danger. The weather may change in many areas of the world. Floods, droughts and damaging storms could be the result.
People in colder regions might welcome warmer weather but those who live in regions that are already hot may suffer from new diseases. At the same time some animals may not survive because they cannot adapt to the new environment. They could move to other places in order to live there.
Finding a solution to solve the world's biggest environmental problem is not an easy task. Although we need energy to make our economy grow there are things that could be done to fight off this problem. Carpools or travelling by public transport could take many cars off the roads. You could turn off lights, TV sets, computers and other electrical items if you don't need them. Companies have been spending a lot of money to produce items that use little energy.
We also need to use more alternative energy, like sunlight, wind power or wave power. Car companies have started to produce a new type of cars known as hybrids. It works like an electric car but also has a small petrol engine.
In 1997 over 150 countries signed the Kyoto Protocol at the United Nations Climate Conference. Industrialized countries should reduce their emissions of greenhouse gases. The United States which produces about 25% of all greenhouse gases has often made public that it will not support the agreement.