Which two types of solar radiation are greenhouse gases unable to absorb?

• A. Visible light and shortwave infrared radiation
• B. Longwave infrared radiation and ultraviolet
• C. Visible light and ultraviolet
• D. Longwave infrared radiation and visible

Answer: (A)

Greenhouse gases trap heat by absorbing infrared radiation emitted by Earth's surface. The Sun’s energy arriving at Earth is mostly in the visible range, with some near-infrared and a bit of ultraviolet. These gases are largely transparent to visible light and ultraviolet radiation, so those wavelengths pass through the atmosphere with little absorption. Therefore, the two types of solar radiation they cannot absorb significantly are visible light and ultraviolet radiation. Their strong absorption bands are in the longwave infrared part of the spectrum, which is what keeps heat near the surface. (Some near-infrared absorption can occur for certain molecules, but it is the longwave infrared absorption that drives the greenhouse effect.)