Global warming is the long-term increase in Earth’s surface temperatures caused by human activities. This change is mainly due to the addition of heat-trapping greenhouse gases in the atmosphere such as carbon dioxide, methane, and nitrous oxide. These gases act like a blanket, trapping solar energy in the atmosphere and preventing it from escaping back into space.
Without the greenhouse effect, Earth would be much colder. But since the industrial revolution, when humans first began to use fossil fuels such as coal, oil and natural gas to power factories, heat homes and drive vehicles, the atmospheric concentration of these gases has risen rapidly. The result has been a rapid increase in Earth’s temperature and a range of other changes, including shrinking sea ice and glacier areas, loss of snow cover on land, rising sea level, and changing patterns of precipitation and extreme weather events.
These changes are occurring faster than ever before. And they’re more serious than many people realize. Rigorous analysis of all available lines of evidence shows that a large part of the observed temperature rise since the start of the industrial revolution is the result of human activities.
Scientists predict that global warming from greenhouse gases will continue and that climate disruptions such as wildfires, heat waves, droughts and floods will become more frequent and severe. Some of these changes are already happening: Arctic summer sea ice is melting; river and lake ice is breaking up earlier; and plant and animal geographic ranges are shifting.