This absorption and radiation of heat by the atmosphere-the natural greenhouse effect-is beneficial for life on Earth. The energy that radiates back toward Earth heats both the lower atmosphere and the surface, enhancing the heating they get from direct sunlight. When they absorb the energy radiating from Earth’s surface, microscopic water or greenhouse gas molecules turn into tiny heaters- like the bricks in a fireplace, they radiate heat even after the fire goes out. From the surface, this energy travels into the atmosphere where much of it is absorbed by water vapor and long-lived greenhouse gases such as carbon dioxide and methane.

The absorbed solar energy heats our planet.Īs the rocks, the air, and the seas warm, they radiate “heat” energy (thermal infrared radiation). Of the remaining 70 percent, most is absorbed by the land and ocean, and the rest is absorbed by the atmosphere. Roughly 30 percent of incoming sunlight is reflected back into space by bright surfaces like clouds and ice. Temperatures are certain to go up further.Įarth’s temperature begins with the Sun. The global average surface temperature rose 0.6 to 0.9 degrees Celsius (1.1 to 1.6° F) between 19, and the rate of temperature increase has nearly doubled in the last 50 years. Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century primarily due to the greenhouse gases released as people burn fossil fuels. How does this warming compare to previous changes in Earth’s climate? How can we be certain that human-released greenhouse gases are causing the warming? How much more will the Earth warm? How will Earth respond? Answering these questions is perhaps the most significant scientific challenge of our time. But in the past century, another force has started to influence Earth’s climate: humanity Climate has changed when the planet received more or less sunlight due to subtle shifts in its orbit, as the atmosphere or surface changed, or when the Sun’s energy varied. Throughout its long history, Earth has warmed and cooled time and again.

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