Influence of Atmospheric Composition on Climate

Climate may be defined as the aggregate of all physical atmospheric properties and conditions. As such, it is absolutely clear that the chemical 

Carbon dioxide is not the only gas that can influence terrestrial infrared radiation, and infrared absorption is not the only way that composition influences climate. Other gases that are important for their infrared absorption, sometimes known as greenhouse gases, include CH4, CCI2F2 (CEC-12), CECI3 (CFC-11), N2O, and O3. Taken together these other species are about of equal importance to CO2. That 

The condensed phases also are important to the physical processes of the atmosphere however, their role in climate poses an almost entirely open set of scientific questions. The highest sensitivity of physical processes to atmospheric composition lies within the process of cloud nucleation. In turn, the albedo (or reflectivity for solar light) of clouds is sensitive to the number population and properties of CCN (Twomey, 1977). At this time, it appears impossible to predict how much the temperature of the Earth might be expected to increase (or decrease in some places) due to known changes in the concentrations of gases because aerosol and cloud effects cannot yet be predicted. In addition, since secular trends in the appropriate aerosol properties are not monitored very extensively there is no way to know 

As such, it is absolutely clear that the chemical composition of the atmosphere as well as the physical characteristics of condensed phase trace species are of leading importance as determinants of climate. A well-known example is the increase in the temperature of the Earth s surface due to the absorption of infrared radiation from the Earth s surface by CO2 in the air (see box). Without CO2, the Earth s surface would be several degrees cooler than at present, depending on cloud cover, water vapor, and other controlling factors. Of course, there is substantial concern over the secular increase of CO2, which will double from its pre-industrial level by the early to mid-twenty-first century. 

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