The word Contrail stems from 'condensation' and 'trail'. Aviationsmog (that's what it really is) is caused by airtraffic at great heights. Each day, jetengines of airplanes dump vast amounts of water (ice), CO2, soot particles (condensation nuclei), aërosols and chemical substances. Airtraffic thus not only alters the properties of the higher regions of our troposphere but also all the regions below, right down to groundlevel. This extra layer of man-made high-altitude smog probably infuences weather, climate and the quality and quantity of the sun's radiation that reaches the surface of Earth ("global dimming."). Aviation-smog is responsible for more clouds, rain, drought, bigger hailstones (megacryometeors), a stronger greenhouse effect (global warming), and, maybe, even gives extra power to hurricanes. Still, aviation-smog does not get the scientific and political attention it deserves
Meteorologists ignore contrails and aviationsmog, and their effect on sunlight, weather and climate!