September 11, 2001 Airline Groundings: Contrails Affect Daily Temperature Range
All flights were grounded after the September 11, 2001 attacks on the twin towers. A team of NASA scientists noticed that it got much colder that night than usual. They came to the conclusion that cirrus clouds generated by aircraft contrails were trapping heat at night. This study changed world and sent the airline industry into a tail spin trying to figure out how to deal with their contrail conundrum. It is possible that aircraft contrail induced cirrus clouds are trapping more heat than their CO2 emissions meaning the airline industry could incur hefty carbon tax charges if they don’t create “less warming and more cooling clouds.”
Before 9/11/2001, one could make the argument that contrails creating clouds was just pollution. After this monumental study, scientists and geoengineers have been trying to figure out how to alter jet fuel> to create clouds that ONLY cool the planet and have no intention on stopping the creation of artificial clouds or removing these clouds all together.
David J. Travis, Andrew M. Carleton, and Ryan G. Lauritsen, 2004: Regional Variations in U.S. Diurnal Temperature Range for the 11–14 September 2001 Aircraft Groundings: Evidence of Jet Contrail Influence on Climate. J. Climate, 17, 1123–1134.
Contrails during day cause cooling because of reflecting of sunlight back into space. During night, they trap infrared heat causing heating. So it is a balance between the two time intervals. We would like to have more CICs (contrail-induced cirrus clouds) during day and none during night. FAA Scientist: We Want Clouds By Day, None By Night
If the time and place of seeding is selected with care, the climate effect of cirrus thinning can be enhanced. For that, only the long-wave warming effect of cirrus clouds should be targeted, and their solar effect should be avoided. This can be achieved if seeding is limited to high-latitude winters or to nighttime seeding.
Climate Change and Geoengineering: Artificially Cooling Planet Earth by Thinning Cirrus Clouds
No Planes, No Sounds, No Contrails
NEW YORK TIMES – Briefly Empty Skies Offer Climate Clues - October 30, 2001
CNN - 9/11/2001 study: Air traffic affects climate
The Globe & Mail - How Sept. 11 solved a weather mystery
Chicago Tribune January 8 2003 - Jet Trails fueling weather changes below, researchers say
Travis said he has mixed feelings about contrails. On the one hand they have been a prime focus of his research interest for the last 10 years. On the other hand they almost spoiled a recent vacation in the Pacific Northwest.
"There were so many contrails in the sky we weren't having any nice days," he said. "The contrails were making the days kind of gloomy and overcast. There aren't as many sunny days as we had when we were kids."
AUDIO: Interview with David Travis on 9/11/2001 & contrails - May 30 2002
VIDEO: 9/11/2001 & Contrails from Space by NASA Astronaut Frank Culbertson (4:45 minutes)
VIDEO: Jet contrails affect surface temperatures & 9/11/2001 - Penn State University - June 18, 2015
High in the sky where the cirrus ice crystal clouds form, jet contrails draw their crisscross patterns. Now researchers have found that these elevated ice cloud trails can influence temperatures on the ground and affect local climate, according to a team of Penn State geographers.
"Research done regarding September 2001, during the three days (following 9-11) when no commercial jets were in the sky, suggested that contrails had an effect," said Andrew M. Carleton, professor of geography. "But that was only three days. We needed to look longer, while jets were in the air, to determine the real impact of contrails on temperature and in terms of climate."
9/11/2001 & Contrails CSPAN VIDEO: 20:45 minutes
Daniel Lashof – Natural Resources Defense Council – Climate Center Science Director - January 30, 2007
Types of Contrails
Topic Number: 2 (version of 5 July 2013) Contrails and contrail impact on cirrus formation http://www.iccp-iamas.org/pdf/workshopPresentations/Topic2_final.pdf
CONTRAILS AND CIRRUS CLOUDS - Patrick Minnis – NASA Langley Research Center