Some impacts from increasing temperatures are already happening:

• Ice is melting worldwide, especially at the Earth’s poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice.
• The number of Adélie penguins in Antarctica have fallen from 32,000 breeding pairs to 11,000 in 30 years.
• Sea level rise became faster over the last century.
• Butterflies, foxes, and alpine plants have moved farther north or to higher, cooler areas.
• Precipitation (rain and snowfall) has increased across the globe, on average.
• Spruce bark beetles have boomed in Alaska thanks to 20 years of warm summers. These insects have chewed up 4 million acres of spruce trees.

Other effects could happen later this century, if warming continues:

• Sea levels are expected to rise between 18 and 59 centimeters by the end of the century, and continued melting at the poles could add between 10 to 20 centimeters.
• Hurricanes and other storms are likely to become stronger.
• Species that depend on one another may become out of sync. Plants could bloom earlier than their pollinating insects become active.
• Floods and droughts will become more common.
• Less fresh water will be available. If the Quelccaya ice cap in Peru continues to melt at its current rate, it will be gone by 2100, leaving thousands of people who rely on it for drinking water and electricity without a source of either.
• Diseases will spread, such as malaria carried by mosquitoes.
• Ecosystems will change—some species will move farther north or become more successful; others won’t be able to move and could become extinct. Polar bears had gotten considerably skinner with less ice in which they live and fish for food. If sea ice disappears, polar bears might be extinct.