photo #8640953

Beautiful texture to the sky with planes laying condensation trails (contrails) due to increased upper atmospheric moisture and freezing temperatures high aloft. These artificial ‘clouds’ are primarily water vapor. Chemically, (at less than 1% of a contrail) it contains trace elements of the exhaust CO₂, H₂O, NOₓ, SOₓ, etc. But the visible contrail cloud you see is overwhelmingly frozen water (99%+) — the pollutants are present only in trace amounts compared to the ice. These contrails can make a measurable difference in keeping temps a touch warmer at night due to some greenhouse effect and a touch cooler by day as it deflects the warming sunlight. After the tragedy if 9/11/2001, planes were grounded for 3 days and it allowed atmospheric researchers (led by David Travis, 2002) to do a “before and after” of jet contrails impacts on our temperatures. That the average daily temp range (difference between day high and night low) increased by about 2.0 °F across the continental U.S. during the flight ban! That was significantly larger than the normal variability for September and proof that jet activity can induce subtle weather impacts in high traffic areas: slightly cooler days and slightly warmer nights.