by: Sayer Ji
July 16, 2012
In the three days that followed the 9/11 terrorist attacks, when all commercial flights above the continental US were suddenly suspended, a veil was lifted on the profound, though until that point unconfirmed, effects that aviation-associated artificial clouds are having on our planetary environment.
In the August 2002 edition of Nature, which is ranked the world’s most cited interdisciplinary journal, a report was published titled “Contrails reduce daily temperature range,” where scientists discuss how “a brief interval when the skies were clear of jets unmasked an effect on climate.”
Three Days Without Contrails
The post-9/11 grounding of all commercial aircraft resulted in the sudden disappearance of condensation trails (contrails) from jet aircraft across the entire United States. According to theNature study, the potential of contrails “…from jet aircraft to affect regional-scale surface temperatures has been debated for years…,” but it was not until the three-day grounding period that doubts concerning the existence of the phenomenon could be put to rest.
The Phenomenon: A 1.8 Degree Celsius Increase In Temperature in North America
The study found “…an anomalous increase in the average diurnal temperature range (that is, the difference between the daytime maximum and night-time minimum temperatures) for the period 11-14 September 2001.”
They go on to explain: “Because persisting contrails can reduce the transfer of both incoming solar and outgoing infrared radiation and so reduce the daily temperature range, we attribute at least a portion of this anomaly to the absence of contrails over this period.”
They arrived at their measurements by analyzing maximum and minimum temperature data from approximately 4,000 weather stations through the conterminous United States (excluding Hawaii and Alaska) for the period 1971-2000, and compared them to the three-day post-9/11 grounding period.
They found an increase in the diurnal temperature range (DTR) of approximately 1.1 degree Celsius over normal 1971-2000 values, and an increase of 1.8 degrees during the grounding period in contrast to the adjacent three-day periods analyzed when DTR values were near or below the mean.
This is a highly significant finding as “The increase in DTR is larger than any during the 11-14 September period for the previous 30 years…,” and since “…the 11-14 September increasing DTR was more than twice the national average for regions of the United States where contrail coverage has previously been reported to be most abundant (such as the Midwest, northeast and northwest regions).”