surface temperature

The Earth's average surface temperature is regulated by a balance of solar and terrestrial radiation. Solar radiation, or shortwave radiation, has high frequencies and short wavelengths, close to visible light. Terrestrial radiation, or longwave radiation, has low frequencies and long wavelengths in the infrared part of the spectrum.1

About 30% of incoming solar radiation is reflected back into space by clouds, the atmosphere, or Earth's surface, a property known as Earth's albedo. The remaining 70% is absorbed by the atmosphere, clouds, or surface. To maintain thermodynamic equilibrium, Earth must radiate this absorbed energy back into space.1

The greenhouse effect further complicates this energy balance. Certain gases in the atmosphere, like carbon dioxide and methane, absorb some of Earth's outgoing infrared radiation. This absorption traps heat, leading to a warmer surface temperature than would exist without these gases. This natural greenhouse effect is essential for making Earth habitable.1

However, human activities, particularly the burning of fossil fuels, have increased the concentration of greenhouse gases. This "enhanced" greenhouse effect has the potential to significantly warm the atmosphere. Modern observations show a global surface temperature rise of about 0.9 °C (1.5 °F) between 1880 and 2012, with the last decade being the warmest on record.12