The past five years have been the hottest on record. Scientists say that human actions are largely to blame. People rely on fossil fuels—like coal, oil, and natural gas—to power cars, businesses, and homes. But burning these fuels produces greenhouse gases that trap heat in Earth’s atmosphere, causing global temperatures to rise (see The Greenhouse Effect).
Higher temperatures are melting glaciers and ice sheets. That meltwater drains into the ocean. At the same time, ocean waters are heating up, which causes them to expand. As a result, the sea’s volume has increased. That’s causing more flooding in low-lying coastal areas. Some island communities are already relocating because their homes are now underwater.
A warmer world has led to more extreme weather too. Hurricanes, which are fueled by warm ocean waters, are becoming stronger. Heat waves are becoming longer and more severe. Intense heat is often accompanied by droughts. These long periods without rain can destroy crops and deplete reservoirs, increasing the risk of food and water shortages. The hotter it gets, the more extreme these phenomena become. “The impacts of climate change just get worse with higher temperatures,” says Natalie Mahowald, a climate scientist at Cornell University in New York.