Hi John , Inconveniently, they do both. They reflect and scatter incoming solar radiation (cooling effect) but also absorb outgoing longwave (warming). At night they are purely warming, but during the day the net effect can be either - depending strongly on whether there are clouds beneath them (decreases cooling benefit), the surface albedo (sea is dark so contrail benefits are greater), and the surface temperature. Kärcher wrote an excellent review article in 2018 (Formation and radiative forcing of contrail cirrus) covering the degree of uncertainty in all this - since we have very poor records of total coverage and properties, the exact balance between warming and cooling is also highly uncertain.
Regards, Seb On Sun, Jul 14, 2019, 08:40 john gorman <[email protected]> wrote: > The report that got me into this was a research paper showing that the > lack of contrails just after 911 allowed a warming of the atmosphere. So I > came up with an idea to increase and simulate the cooling effect of > contrails. At the time I had never heard of the this group or the word > geoengineering. > > > > I now see in a recent post that contrails warm the earth. > > > > Which is correct? > > > > John Gorman > > > > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/geoengineering. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/5d29a2ee.1c69fb81.57666.3e93SMTPIN_ADDED_MISSING%40gmr-mx.google.com > <https://groups.google.com/d/msgid/geoengineering/5d29a2ee.1c69fb81.57666.3e93SMTPIN_ADDED_MISSING%40gmr-mx.google.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/geoengineering. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAGb9uZsZgCSSaugj_KU8P%2BFt%2Ba14pBpAkzG1Gr3KJY%2BrDCbXQg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
