CO2 and Other Greenhouse Gases

Carbon dioxide (CO2) is the most important of many human-generated “greenhouse gases”—gases that are contributing to a gradual warming of the planet. These gases, many of which have always existed in the atmosphere, contribute to a balance of heat flows that has given us a relatively stable climate. Since the beginning of the Industrial Revolution, however, the concentration of CO2 in the atmosphere has grown from its historical average of 280 parts per million (ppm) to over 380 ppm and counting.

The atmosphere helps keep a balance between visible light and other high-energy radiation arriving at our planet from the sun and much-lower-energy heat radiating outward from the Earth’s surface. The atmosphere reflects some of this radiation, absorbs some, and allows some to pass through. Exactly how much radiation of each type is reflected, absorbed, or transmitted depends on what’s in the atmosphere.