There was a study done in the US during the 9/11 shutdown. The effect of taking the aicraft out of the sky was to increase the daily variatoin in temperature by 5 degrees or so. (thats +5 in the day and -5 at night) because of the loss of cirrus clouds.
Furthermore, as Airforce one was the only thing flying they were able to track it by the moisture in the upper atmosphere. I remeber thinking during the shut down, MY GOD THE SKY IS BLUE for the 4 days of the shut down. Didn't see a single cirruc cloud. Aparrently it was that way all over the country.
Cheers
Wino