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 This article incorporates text by Andrew Gettelman, Chieh-Chieh Chen, and Charles G. Bardeen available under the CC BY 4.0 license.

The recent Blue Angels show in San Francisco provided some nice examples of the ectoplasm effect described on this page. I'm wiki-challenged or I'd try to add one to the main page; here it is on Flickr:

http://flickr.com/photos/fitzhugh/263984025/ — Preceding unsigned comment added by 15.243.233.68 (talk) 19:18, 11 October 2006

ECTOPLASM? — Preceding unsigned comment added by 64.235.154.34 (talk) 10:07, 15 April 2015‎

I don't get it. Are there two causes for contrails? The article seems to say so. BeenAroundAWhile (talk) 06:57, 13 December 2017 (UTC)[reply]

Contrails are visible trails of condensed moisture in the atmosphere. They are associated with aircraft and rockets. So there is only one criterion for what constitutes a contrail. However, there are numerous phenomena that can cause a visible trail of condensed moisture in the atmosphere. Firstly, the long contrails we see at great height are caused by moisture from the engine exhausts. These contrails can extend over a great distance and can persist for many minutes. Secondly, short contrails that are usually only visible around aircraft near the ground can be caused by wingtip vortices from the wings (or propellers) of aircraft. These short contrails extend only over a short distance and rarely persist for more than a few seconds. Thirdly, a localized region of "cloud" above the wing of an aircraft is also condensed moisture in the atmosphere so it almost meets our criterion for a contrail. This cloud above the wing persists for such a short time it appears to be attached to the aircraft and follows it around. Dolphin (t) 12:59, 13 December 2017 (UTC)[reply]

Is "contrail" a neologism or a military phrase? Back in the 70s and 80s, they were called "vapour trails". I've only heard the phrase contrail for the last five or maybe ten years, right around the time the "chemtrail" conspiracy crap started to blossom.

Contrail seems to be a contraction. Even if this word has been accepted by the scientific community, the commonly used phrase vapour trail should still be mentioned, in bold, in the article lede. On top of that, the etymology of the word contrail should be explored in the article. --82.2.5.153 (talk) 12:37, 20 September 2018 (UTC)[reply]

In my opinion, the picture looks out of place in the 'See also' section of the article and should be re-located to a different section in my opinion. Xboxsponge15 (talk) 18:36, 15 November 2021 (UTC)[reply]

The pics are actually in the gallery section. Mobile devices or different browser sizes can sometimes alter the perception of a page layout. But I did remove one image in the 'see also' section since there isn't a need to illustrate See also items. - LuckyLouie (talk) 19:02, 15 November 2021 (UTC)[reply]

This article claims that up to 30% of jet exhaust can be unburnt jet fuel. I thought this seemed unlikely to be true, so I looked up the source (Ritchie et al. 2003). Sure enough, the paper says that, but it's not an original source. Ritchie et al. cite that figure from a 2nd paper (Kelly et al. 2003). However, this paper is not found in the bibliography at the end of the paper Ritchie paper. Therefore, there is no real source for the 30% figure that I can find. — Preceding unsigned comment added by 142.161.251.136 (talk) 05:09, 24 April 2022 (UTC)[reply]

Thanks - I deleted it Chidgk1 (talk) 12:36, 29 December 2025 (UTC)[reply]

“Impacts on climate” section before I changed it is below. Feel free to put back anything you think should not have been deleted

It is considered that the largest contribution of aviation to climate change comes from contrails.^[1] In general, aircraft contrails trap outgoing longwave radiation emitted by the Earth and atmosphere more than they reflect incoming solar radiation, resulting in a net increase in radiative forcing. In 1992, this warming effect was estimated between 3.5 mW/m² and 17 mW/m².^[2] In 2009, its 2005 value was estimated at 12 mW/m², based on the reanalysis data, climate models, and radiative transfer codes; with an uncertainty range of 5 to 26 mW/m², and with a low level of scientific understanding.^[3]

Contrail cirrus may be air traffic's largest radiative forcing component, larger than all CO₂ accumulated from aviation, and could triple from a 2006 baseline to 160–180 mW/m² by 2050 without intervention.^[4][5] For comparison, the total radiative forcing from human activities amounted to 2.72 W/m² (with a range between 1.96 and 3.48W/m²) in 2019, and the increase from 2011 to 2019 alone amounted to 0.34W/m².^[6] Contrail effects differ a lot depending on when they are formed, as they decrease the daytime temperature and increase the nighttime temperature, reducing their difference.^[7] In 2006, it was estimated that night flights contribute 60 to 80% of contrail radiative forcing while accounting for 25% of daily air traffic, and winter flights contribute half of the annual mean radiative forcing while accounting for 22% of annual air traffic.^[8]

Starting from the 1990s, it was suggested that contrails during daytime have a strong cooling effect, and when combined with the warming from night-time flights, this would lead to a substantial reduction in diurnal temperature variation (the difference in the day's highs and lows at a fixed station).^[9] When no commercial aircraft flew across the USA following the September 11 attacks, the diurnal temperature variation was widened by 1.1 °C (2.0 °F).^[10] Measured across 4,000 weather stations in the continental United States, this increase was the largest recorded in 30 years.^[10] Without contrails, the local diurnal temperature range was 1 °C (1.8 °F) higher than immediately before.^[11] In the southern US, the difference was diminished by about 3.3 °C (6 °F), and by 2.8 °C (5 °F) in the US midwest.^[12][13] However, follow-up studies found that a natural change in cloud cover can more than explain these findings.^[14] The authors of a 2008 study wrote, "The variations in high cloud cover, including contrails and contrail-induced cirrus clouds, contribute weakly to the changes in the diurnal temperature range, which is governed primarily by lower altitude clouds, winds, and humidity."^[15]

In 2011, a study of British meteorological records taken during World War II identified one event where the temperature was 0.8 °C (1.4 °F) higher than the day's average near airbases used by USAAF strategic bombers after they flew in a formation. However, its authors cautioned that this was a single event, making it difficult to draw firm conclusions from it.^[16][17][18] Then, the global response to the 2020 coronavirus pandemic led to a reduction in global air traffic of nearly 70% relative to 2019. Thus, it provided an extended opportunity to study the impact of contrails on regional and global temperature. Multiple studies found "no significant response of diurnal surface air temperature range" as the result of contrail changes, and either "no net significant global ERF" (effective radiative forcing) or a very small warming effect.^[19][20][21]

An EU project launched in 2020 aims to assess the feasibility of minimising contrail effects by the operational choices in making flight plans.^[22] Other similar projects include ContrailNet from Eurocontrol,^[23] Reviate,^[24] and the Ciconia project,^[25] as well as Google's 'project contrails'.^[26] Chidgk1 (talk) 12:50, 29 December 2025 (UTC)[reply]