Chemtrails denier often use wiki definition of contrails
"Contrails (/ˈkɒntreɪlz/; short for "condensation trails") or vapor trails are long thin artificial (man-made) clouds that sometimes form behind aircraft. Their formation is most often triggered by the water vapor in the exhaust of aircraft engines, but can also be triggered by the changes in air pressure in wingtip vortices or in the air over the entire wing surface. Like all clouds, contrails are made of water, in the form of a suspension of billions of liquid droplets or ice crystals."
This definition give the impression that contrails is something similar to normal clouds.
But take a look at the first definition of contrails in Wiki:
"Contrails are condensation trails. Artificial clouds made by the exhaust of jet aircraft.
It had been hypothesized that in regions such as the United States with heavy air traffic contrails affected the weather reducing solar heating during the day and radiation of heat during the night. The suspension of air travel for 3 days in the United States after September 11th provided an opportuntity to test this hyposthesis. Measurements did in fact show that without contrails daily temperatures were about 1 degree (Farenheit) higher during the day and 1 degree cooler at night."
This definition clearly define contrails as problem, a pollution that will alter weather at least to reduce the temperature difference between day and night, which is a sign of green house effect.
The original definition mention this link:
abstract of article in Nature announcing research results of contrail temperature change study
The link no longer available, but an archive from 15th January 2007 at archive.org state:
"Nature 418, 601 (08 August 2002); doi:10.1038/418601a
Climatology: Contrails reduce daily temperature range
DAVID J. TRAVIS*, ANDREW M. CARLETON† & RYAN G. LAURITSEN*
* Department of Geography and Geology, University of Wisconsin–Whitewater, Whitewater, Wisconsin 53190, USA
† Department of Geography, Pennsylvania State University, University Park, Pennsylvania 16801, USA
The potential of condensation trails (contrails) from jet aircraft to affect regional-scale surface temperatures has been debated for years, but was difficult to verify until an opportunity arose as a result of the three-day grounding of all commercial aircraft in the United States in the aftermath of the terrorist attacks on 11 September 2001. Here we show that there was 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. 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."
At that time, contrails is serious concern. What about today?
Current Wiki also state that:
"Condensation from engine exhaust
The main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can raise the relative humidity of the air past saturation point. The vapor then condenses into tiny water droplets which freeze if the temperature is low enough. "
This definition along with earlier definition is not accurate, they are wrong. The important part during contrails creation is aerosol. The vapor will only make a droplet if there are particle they can deposit to. Bellow is how contrails creation step explained, from real contrails science book.
J. Schneider & Chr. Voigt - Physics and Chemistry of Aerosols and Ice Clouds, Chapter 8: Contrails and contrail cirrus (mirror link)
• Contrails consist of ice particles that nucleate primarily on aerosols emitted or formed in the plume.
• At initial stage contrails grow by deposition of exhaust water vapor.
• Later during their life cycle contrails grow by deposition of entrained ambient water vapor.
• Formation of contrails due to increase in RHI during isobaric mixing of the hot and humid exhaust gases with colder and less humid ambient air.
"Contrails (short for condensation trails) have been observed since 1915 (Schumann, 2005). The theory on the thermodynamic conditions causing their formation and decay was first described at the time of World War II (Schmidt, 1941). The strong increase in occurrence of contrails due to the strong increase of global air traffic has triggered intensive research in this field since the early 1990s, especially with respect to their present and future in?uence on global and regional climate (Meerkötter et al., 1999; Mannstein et al., 1999; Meyer et al., 2002; Marquart, 2003; Minnis et al., 2004).
Aircrafts add warm and humid exhaust air to the tropopause region. When the plume consisting of exhaust and entrained air cools, its relative humidity increases. If the ambient air is cold and moist enough, saturation with respect to liquid water is eventually reached. Soot particles from the combustion process and other condensation nuclei then start to accumulate water vapour and grow to little droplets which immediately freeze: the contrail is formed. The temperature and moisture limits are given by the Schmidt-Appleman Criterion (Schmidt, 1941; Appleman, 1953; Schumann, 1996). In warmer and moist surroundings contrails can also be initiated aerodynamically (Gierens et al., 2009; Kärcher et al., 2009). If the ambient air is supersaturated with respect to ice, the contrail can persist for several hours. Minnis et al. (1998) have observed life spans of more than 7 h for single contrails and 17 h for contrail clusters together with contrail widths of 15 km. Bakan et al. (1994) report contrail areas that could be tracked for more than two days. Nevertheless, a contrail usually loses its linear appearance at some point. After 1 or 2 h it can no longer be distinguished by its shape from a naturally formed cirrus cloud (Mannstein et al., 1999).
The most relevant parameters for the estimation of the climate impact of contrails are changes in cirrus cloud coverage and optical thickness, the resulting radiative forcing (RF) as well as possible effects due to changes in air composition and the in?uence on the hydrological cycle (Schumann 2005). Like thin cirrus contrails reduce both, the incoming short wave radiation and the infrared radiation escaping into space (greenhouse effect). The former effect leads to an in stantaneous surface cooling during daytime, the latter causes a warming mainly of the upper troposphere."
This clearly indicate that the scientist consider contrails as serious problem. Even if those scientist do not believe in chemtrails, they share the same concern with chemtrails believer. Chemtrails debunker / denier has contantly claim that contrails is just harmless water vapor. In this sense, chemtrails debunker is the one who deny the severity of problem caused by trails.
Either you believe in chemtrails or not, trails is a serious problem that must be solved right away.