Recent studies have shown that the earth is getting warmer. The scientists who carried out the studies say a large amount of CO2 in the asmosphere is the reason for the warming. CO2 is the gas which human and animals give off when they breathe. It is also produced when coal, oil and other things are burnt. Scientists have warned that this kind of burning is adding too much CO2 to the asmosphere. They believe the gas acts like a greenhouse--the grass-topped building used to grow plants in cold weather. They say that the gas is like the grass roof of a greenhouse, which lets in sunlight, but prevents heat from running away. As a result, they say the earth becomes warmer. One of these scientists, Dr.Hansen, says the weather will become so hot that some rivers will dry up. On the other hand, satellite pictures show us there is less ice in the Antarctic during the summer time than in earlier years. The heat would turn all the ice at both ends of the earth into water, making the oceans rise five to seven metres higher than they are now.