Ben Herman of the University of Arizona has responded to the post
with the following insightful information.
News Article “Aircraft Condensation Trails Criss-Crossing The Sky May Be Warming The Planet On A Normal Day More Than The Carbon Dioxide Emitted By All Planes Since The Wright Brothers’ First Flight In 1903, A Study Said On Tuesday”
“I read your recent post concerning the possible effects of contrails on global warming. While the effect of contrails in low humidity atmosphere may be something to think about, such is not the case. The water vapor trails only occur in a saturated, or near saturated environment, as witnessed by their presence being almost entirely limited to regions where cirrus clouds are present, or to regions in close proximity to cirrus clouds. The point here is, in such an environment, the water vapor and/or ice crystals already present are most likely absorbing a good deal of the IR radiation that would be absorbed by contrails in a dry environment. Therefore the increase of absorption is certainly quite limited. Of course a more thorough investigation of this is required for an accurate estimate of the actual effect of contrails, but this was apparently not considered, or at least not mentioned in the Reuter’s article you referred to in your blog.”