Climatic effect
 Scale and importance of the effect
Release of carbon dioxide by burning fossil fuels Increases the atmospheric absorption and emission of terrestrial infrared radiation (greenhouse effect), resulting in warming of lower atmosphere and cooling of the stratosphere. Global: potentially a major influence on climate and biological activity.
Release of chlorofluoromethanes, nitrous oxide, carbon tetrachloride, carbon disulfide Similar climatic effect as that of carbon dioxide since these, too, are infrared-absorbing and fairly chemically stable trace gases. Global: potentially significant influence on climate.
Release of particles (aerosols) from industrial and agricultural practices These sunlight scattering and absorbing particles probably decrease albedo over land, causing a warming and could increase albedo over water, causing a cooling; they also change stability of lower atmosphere; net climatic effects still speculative. Largely regional, since aerosols have an average lifetime of only a few days, but similar regional effects in different parts of the world could have nonnegligible net global effects; stability increase may suppress convective rainfall, but particles could affect cloud properties with more far-reaching effects.
Release of aerosols that act as condensation and freezing nuclei Influences growth of cloud droplets and ice crystals; may affect amount of precipitation or albedo of clouds in either direction. Local (at most) regional influences on quantity and quality of precipitation, but unknown and potentially important change to earth's heat balance if cloud albedo is altered.
Release of heat (thermal pollution) Warms the lower atmosphere directly. Locally important now; could become significant regionally; could modify large-scale circulation.
Upward transport of chlorofluoromethanes and nitrous oxide into the stratosphere Photochemical reaction of their dissociation products probably reduces stratospheric ozone. Global but uncertain influence on climate: less total stratospheric ozone probably allows more solar radiation to reach the surface but compensates by reducing greenhouse effect as well; however, if ozone concentration decreases at high altitudes, but increases comparably at lower altitudes, this would lead to potentially very large surface warming; could cause significant biological effects from increased exposure to ultraviolet radiation if total column amount of ozone decreases.
Release of trace gases (e.g., nitrogen oxides, carbon monoxide, or methane) that increase tropospheric ozone by photochemical reactions Large atmospheric heating occurs from tropospheric ozone, which enhances both solar and greenhouse heating of lower atmosphere. Local to regional at present, but could become a significant global climatic warming if large-scale fossil fuel use leads to combustion products that significantly increase tropospheric ozone levels; contact with ozone also harms some plants and people.
Patterns of land use, e.g., urbanization, agriculture, overgrazing, deforestation, etc. Changes surface albedo and evaporotranspiration and causes aerosols. Largely regional: net global climatic importance still speculative.
Release of radioactive Krypton-85 from nuclear reactors and fuel reprocessing plants Increases conductivity of lower atmosphere, with possible implications for earth's electric field and precipitation from convective clouds. Global: importance of influence is highly speculative.
Large-scale nuclear war. Could lead to very large injections of soot and dust causing transient cooling lasting from weeks to months, depending on the nature of the exchange and on how many fires were started. Could be global, but initially in mid-latitudes of Northern Hemisphere. Darkness from dust and smoke could wipe out photosynthesis for weeks with severe effects on both natural and agricultural ecosystems of both combatant and noncombatant nations. Transient freezing outbreaks could eliminate most warm season crops in mid-latitudes or be devastating to any vegetation in tropics or subtropics.

Table — Summary of Principal Human Activities That Can Influence Climate Change (source: Schneider, S.H. and R. Londer, 1984).