Greenhouse Gases: Ozone

Smog in Los Angeles

Ozone in the lower atmosphere is a component of smog, a severe type of air pollution. This low-altitude ozone is a greenhouse gas formed by nitrogen oxides and volatile organic gases emitted by automobiles and industrial sources. In contrast, the ozone in the upper atmosphere occurs naturally and forms the ozone layer, which shields life on Earth from the Sun’s harmful ultraviolet radiation.

        Ozone is both a natural and human-made greenhouse gas. Ozone in the upper atmosphere is known as the ozone layer and shields life on Earth from the Sun’s harmful ultraviolet radiation. This ozone is formed by the action of ultraviolet light from the Sun on molecules of ordinary oxygen. Some chemical compounds are known to destroy ozone molecules in the upper atmosphere. This can break down, or deplete, the ozone layer. Depletion of the ozone layer actually causes a slight cooling, offsetting a small part of the warming from greenhouse gases.

        However, ozone in the lower atmosphere is a component of smog, a severe type of air pollution. Nitrogen oxides and volatile organic gases emitted by automobiles and industrial sources combine to form the ozone in smog. This ozone is a poison that damages vegetation, kills trees, irritates lung tissues, and attacks rubber. It is also a greenhouse gas that contributes about a fourth as much as carbon dioxide to global warming. Unlike the greenhouse gases discussed above, which are well-mixed throughout the atmosphere, ozone in the lower atmosphere tends to be limited to industrialized regions.