Jet Contrails Affect Surface Temperatures

[OKIsItJustMe]

http://news.psu.edu/story/361041/2015/06/18/research/jet-contrails-affect-surface-temperatures

[font face=Serif][font size=5]Jet Contrails Affect Surface Temperatures[/font]

By A'ndrea Elyse Messer
June 18, 2015

[font size=3]UNIVERSITY PARK, Pa. -- 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.

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Bernhardt and Carleton looked at temperature observations made at weather station sites in two areas of the U.S., one in the South in January and the other in the Midwest in April. They paired daily temperature data at each contrail site with a non-contrail site that broadly matched in land use-land cover, soil moisture and air mass conditions. The contrail data, derived from satellite imagery, were of persisting contrail outbreaks. The researchers reported their results in a recent issue of the International Journal of Climatology.

They found that contrails depress the difference between daytime and nighttime temperatures, typically decreasing the maximum temperature and raising the minimum temperature. In this respect, the contrail clouds mimic the effect of ordinary clouds.

The researchers report that the "diurnal temperature range was statistically significantly reduced at outbreak stations versus non-outbreak stations." In the South, this amounted to about a 6 degree Fahrenheit reduction in daily temperature range, while in the Midwest, there was about a 5 degree Fahrenheit reduction. Temperatures the days before and after the outbreaks did not show this effect, indicating that the lower temperatures were due to the contrail outbreaks.

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[HassleCat]

1. Um... yes?

Contrails are clouds. Clouds affect surface temperature. When you read that part about the 6F temperature variation away from normal, just remember, it's highly localized, and not very frequent. Contrails are not propelling climate change or anything like that.

[OKIsItJustMe]

4. Yes, as it says, “… In this respect, the contrail clouds mimic the effect of ordinary clouds. …”

The effects of “contrails” on climate has been a source of a great deal of speculation. They amount to artificial clouds. So, what is their effect?

Here’s an item from a few years back…

http://www.nature.com/nclimate/journal/v1/n1/full/nclimate1078.html

[font face=Serif][font size=5]Atmospheric science: Seeing through contrails[/font]

Olivier Boucher

Nature Climate Change 1, 24–25 (2011) doi:10.1038/nclimate1078

Published online | 29 March 2011

[font size=4]Contrails formed by aircraft can evolve into cirrus clouds indistinguishable from those formed naturally. These 'spreading contrails' may be causing more climate warming today than all the carbon dioxide emitted by aircraft since the start of aviation.[/font]

[font size=3]Aviation is at present responsible for about 3% of all fossil fuel carbon dioxide emissions, but an estimated 2–14% of anthropogenic climate forcing. Furthermore, its contribution to climate forcing could triple by 2050, according to some scenarios. As such, mitigating the impact of aviation on climate has become a subject of considerable public and political interest. The debate is complicated, however, by the fact that aviation's climate impact results from a number of different factors, as well as by the large uncertainty in the effect that some of these factors have on climate. Writing in Nature Climate Change, Burkhardt and Kärcher present a global modelling study that quantifies the climate effect of 'spreading contrails' — the least well quantified of all the aviation-related climate-forcing agents.

Aircraft-engine emissions are mostly composed of carbon dioxide, water vapour, nitrogen oxides, sulphur oxides and aerosol particles. As well as the direct effect that these emissions have on climate, aviation has an added impact induced by the formation of condensation trails (contrails) in the wake of the aircraft. These line-shaped trails are formed by the mixing of hot, moist air coming out of the engine with cold ambient air. When the atmosphere is supersaturated with respect to ice, the line-shaped contrails can spread to form cirrus cloud, which has a warming effect on climate. Although there are robust case studies of this spreading phenomenon using satellite observations (Fig. 1), its relevance to the climate system remains unknown.

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Both ground- and satellite-based cloud observations have suggested a small but noticeable increase in cirrus cloud cover in regions of high air-traffic density relative to adjacent regions. However, contrail spreading is not the only mechanism that could explain this increase. It has also been suggested that aircraft-emitted aerosols could serve as ice nuclei and facilitate the formation of cirrus cloud. To understand the impact of aviation on climate, it is necessary to quantify the importance of these two mechanisms. This, however, is not a straightforward task.

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[Gregorian]

2. There isn't a lot of discussion of things like global dimming, which is kind of related.

Without some of these things global warming effects would be much worse. This has been verified during the few days that we stopped air flight after 911.

[arcane1]

3. The OP reminded me of an article on that post-9/11 testing

I can't recall where I read it though.

[OKIsItJustMe]

5. Yes, the item linked to references that research

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"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."

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