What atmospheric radiative effects, if any, do contrails cause? First of all, this question is not about the conspiracy theory based chemtrails as in the linked question, from the answers there and from the question Equation for predicting contrail formation I understand how contrails form and how they could be predicted.  Also, the evidence (as in the links and discussions within the answers to the linked questions, reveal that much of the chemistry of contrails is water and some soot.

Observations of contrails (from the ground and from satellite imagery) in the webpage Contrails by Professor Steve Ackerman of the University of Wisconsin, he notes that contrails


  rapidly dissipate or spread horizontally into an extensive thin cirrus layer.


and also states that


  NASA and the DOE are sponsoring a research program to study the impact contrails have on atmospheric chemistry, weather and climate.


Given it is long known that clouds affect the atmospheric radiation budget, is there evidence of atmospheric radiative effects of contrails?
We had a surprising opportunity to study this very question during the period of September 11-14, 2001, when all air traffic was grounded across the United States.

The research was inconclusive, but they found that there was a 1.8 degree celsius increase across the US during this time frame compared to the three days before and after that time frame.  However, this shift may have been coincidental.  It was found by others that this temperature shift was within the normal range for the time of year.

Ultimately, the question of whether these high-level clouds impact the weather and temperatures is still an open debate.



The source for this answer is from a Nature.com article.  However, they take their sources from the original research:


Travis, Carleton, &amp; Lauritsen showing contrails have an effect 
Hong, et al showing contrails do not have an effect