The main cause of global warming is human pollution. Through burning coal, oil and gas, people have been increasing the greenhouse gases in the atmosphere, such as CO2. This adds to the power of the greenhouse effect, making the planet even warmer.

　　Many scientists believe that, if the warming is not stopped, there will be huge climate changes. The sea level could rise by one meter this century.

　　Should this come true, millions of homes will be swallowed up by the sea and the world will be flooded with “climate refugees (难民)” looking for somewhere to live.