contrails courtesy of NOAAEarth Day is this Thursday. Everyone can participate in a scientific experiment by counting the number and type of contrails in the sky. Unless you are a conspiracy theorist contrails, a condensation of condensation trails, are formed when the water vapor exhaust of jet engines freezes in the cold air in which jets travel. Contrails have a small warming effect on climate and also diminish the daily temperature range - the difference between a day's high and low temps. This year the GLOBE program is working with NASA scientists and students around the world in a Contrail Count-a-thon. Although intended for students, anyone can participate – even Gothamist readers! All you need to do is download a worksheet and count the number and type of contrails between 11 a.m. and 1 p.m. The forecast doesn’t look too promising. If Thursday turns out to be overcast, Gothamist will have lunch, drink a refreshing beverage, and turn our gaze downward.