Answer to the second question . . . temperature and relative humidity change daily, hourly, etc. Air mixes constantly. Thus the micro-environments for Trail formation and persistence changes dramatically from day to day even hour to hour at different altitudes. Usually contrails are visible only at higher altitudes where temperature are more extreme. . . which means only long haul commercial aviation will result in contrails. High performance Military aircraft engines are not designed to conserve fuel as much as to provide thrust and their vapor trails are released at higher temperature . . . resulting in different trail dynamics than commercial aircraft. Answer . . . it is complex and you need to know the temperature, altitude, relative humidity, and even the engine type before one can truly predict with confidence the likelihood of contrail persistence. In general long haul aviation is on the increase, high efficiency commercial engines are on the increase, and thus the number and frequency of persistent contrails and cirrus clouds resulting from the new activity have increased. So research into the climatic effects of cirrus cloud reflectivity (albedo effects) are on the increase.


Look at these Threads: Thread: Newest Chemtrail Poll (NOW): Choose the (best) reason for Chemtrails? . . . see results as they happen! . . . see results of last poll!!!
Thread: Chemtrail Poll . . . do you think chemtrails are real? See the Results NOW!


And come to the Chemtrail debate at 8:00 PM EST today.
I think 'The Debunkers' have had enough of Chemtrail talk on this thread. . .