We must transition away from coal and oil as our main sources of energy if we are to avoid 'catastrophic' climate change.

The planet is already suffering from some impacts of global warming.

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.

Many species have been impacted by rising temperatures.

Some butterflies, foxes, and alpine plants have moved farther north or to higher, cooler areas.

Some invasive species are thriving. For example, spruce bark beetles have boomed in Alaska thanks to 20 years of warm summers. The insects have chewed up 4 million acres of spruce trees.

Other effects could take place later this century, if warming continues.

Sea levels are expected to rise between 7 and 23 inches (18 and 59 centimeters) by the end of the century, and continued melting at the poles could add between 4 and 8 inches (10 to 20 centimeters).

Hurricanes and other storms are likely to become stronger.

Floods and droughts will become more common. Rainfall in Ethiopia, where droughts are already common, could decline by 10 percent over the next 50 years.

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.

Some diseases will spread, such as mosquito-borne malaria (and the 2016 resurgence of the Zika virus).

Ecosystems will change: Some species will move farther north or become more successful; others won’t be able to move and will become extinct.

Wildlife research scientist Martyn Obbard has found that since the mid-1980s, with less ice on which to live and fish for food, polar bears have gotten considerably skinnier. Polar bear biologist Ian Stirling has found a similar pattern in Hudson Bay. He fears that if sea ice disappears, the polar bears will as well.