Increases in tropospheric ozone are expected to result from increasing methane, nitrogen oxides, carbon moNO x ide, and hydrocarbon emissions. Some of the processes related to aviation emissions and their location in the atmosphere are shown in Figure 1-2 . The differing chemical and physical processes in the two regions must be taken into account. The troposphere is principally heated near the Earth s surface, and the temperature decreases with altitude. Warm, moist air tends to underlie cool, dry air, leading to frequent vertical turbulent motions that exchange air throughout this region.
Vertical motions are much slower here than in the troposphere.
The stratosphere is also much drier than the troposphere, and clouds rarely form at this level. Table 1-1 lists aircraft emissions that are important from an atmospheric perspective, with summaries of the roles that they play. The behavior of CO 2 within the atmosphere is simple and well understood. There are no important formation or destruction processes that take place in the atmosphere itself. The effect of CO 2 on climate change is direct and depends simply on its atmospheric concentration.