Ozone-rich air then flows in to replenish the ozone layer over the Antarctic. The enhanced springtime loss of ozone in the Antarctic started to occur late in the 1970s when the inorganic chlorine loading of the stratosphere was about 1.5 parts per billion. Hence, this value has been suggested as a target for reduction in chlorine loading. There are several factors that can change the balance between the energy absorbed by the earth and that emitted by it in the form of longwave infrared radiation. These factors, which include seasonal changes in solar radiation, changes in reflectivity of the earth's surface, and presence of aerosols, cause the radiative forcing on climate.
Temperature increases with altitude and vertical mixing is relatively slow.
Because they retain many of the desirable properties of CFCs and have much lower ODPs, HCFCs can be used to meet some of the societal needs and demands currently served by CFCs, while reducing the risk of ozone depletion. However, because they contribute some chlorine to the ozone layer, they may need to be used for only a transitional period until non-ozone depleting solutions are developed. Thus, HCFCs are recognized as transitional substances. The troposphere is the lowest layer of the atmosphere extending from the earth's surface to a height of 8 to 15 kilometers. The temperature of the troposphere decreases with height.