Climate change refers to changes in seasonal temperature, precipitation, wind, and humidity for a given area. Climate change can involve cooling or warming.

Temperature readings taken around the world in recent decades, and scientific studies of tree rings, corals, and ice cores, show that average global temperatures have risen since the industrial revolution began, with increases accelerating over the past few decades. The overwhelming consensus among climate scientists is that most of the increase is due to human economic activity, especially the burning of fossil fuels and deforestation. These activities contribute to a build-up in carbon dioxide (CO2) and other gases in Earth’s atmosphere.

Our atmosphere is made up of gases, such as nitrogen, oxygen, and CO2, and water vapor, which act like a “blanket” draped around the planet. Some of these gases—such as CO2, water vapor, and methane—absorb heat, reducing the amount that escapes to space, and increasing global temperatures. This is what is called the “greenhouse effect,” and these gases are often referred to as “greenhouse gases.”

Without this process, the temperature of Earth’s atmosphere would average about 30 degrees Celsius (50 degrees Fahrenheit) colder than it is today, making it difficult for Earth to sustain life as we know it. However, if this blanket were to become too “thick,” with too many gases trapping too much heat, Earth would be uninhabitable. In the atmosphere of Venus, for example, a buildup of carbon dioxide has led to a broiling temperature of 500 degrees Celsius.