FIGURE 1. Departure of average diurnal temperature ranges (DTRs) from the normal values derived from 1971–2000 climatology data for the indicated three-day periods in September 2001.
From the following article:
Climatology: Contrails reduce daily temperature range
David J. Travis, Andrew M. Carleton and Ryan G. Lauritsen
Nature 418, 601(8 August 2002)
doi:10.1038/418601a
These periods included the three days before the terrorist attacks of 11 September; the three days immediately afterwards, when aircraft were grounded and there were therefore no contrails; and the subsequent three days.
