Climate change refers to the long-term shift in the world’s average temperatures and weather patterns, which can affect all aspects of nature and human society. It’s caused by humans increasing levels of heat-trapping greenhouse gases in the atmosphere by burning fossil fuels, including coal, oil and natural gas. These gases trap heat radiating from the sun and warm the Earth’s surface, with some effect also from aerosols that scatter or absorb solar and infrared radiation and from changes in water vapor and clouds.
The global temperature rise from these human-caused greenhouse gases has been much faster than scientists had predicted and is expected to continue. As the planet warms, glaciers and ice sheets melt, rivers and lakes break up earlier, and plant and animal species move to find new habitat or die off. Extreme events like flooding and wildfires increase, as do droughts. And sea level is rising.
These trends will be worse if we continue to emit greenhouse gases. Scientists agree that we must limit global warming to no more than 1.5 degrees Celsius in order to avoid the worst climate impacts and maintain a livable planet.
Everyone must take action to reduce their own carbon emissions. But wealthy nations that created most of the problem must do more than their share to cut them. Because of their lower incomes and weaker economies, developing countries may struggle to adapt to the harms they already face from climate change.