In the past century, the overall level of the sea has risen about 7 inches. Melting glaciers and higher ocean levels could mean that low-lying areas might flood, which could kill crops and some animal species. Another sign of global warming is a hole in the ozone layer over Antarctica. Ozone is mix of gasses in the atmosphere. This mix protects the Earth from the sun's rays.
Many people believe that global warming is making the hole larger.
The greenhouse gasses that cause global warming also warm up the atmosphere. This makes it easier for chemicals in the air to destroy the ozone layer. With less protection from the sun, people could face higher risks for skin diseases and blindness, plants and crops might die, and the Earth could get even warmer. Global warming can cause other environmental problems, too. Some places might have more rainfall, while others may suffer droughts.