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The most direct way to find your question is to search for the name you used when you submitted it (first name, last name or both). If you did not include a name, then you can search using keywords from your question. Of course, since many weather-related terms are common to a lot of the questions we receive, this may turn up a number of others in addition to your own.

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Answer: There are many web sites and videos that posit a theory that a secret program to alter the climate, depopulate the planet or somehow control people through emission of chemicals is evident in the appearance of long white trails behind high-flying aircraft. However, pretty much every photo and video of the trails, the sky or the lingering cirrus cloud cover on these sites seems to show images of routine contrails (condensation trails), the likes of which have existed since the beginning of high-altitude flight operations. We've delved into this several times in the past few years on AskGreg, and rather than repeating the details here, you can look through those earlier responses by using the "Search for:" box at the top of the list of AskGreg questions. Just enter chemtrails or contrails there and click the find button to turn up those answers.
May. 4, 2013 | Tags: controversy

Answer: Although this isn't really something we have to be concerned about, it does make for an interesting thought experiment, one that has been addressed a number of times. If the sun just disappeared instantly, we would know it a bit over eight minutes later when its light ceased here, and at that same time earth would stop orbiting and begin to travel in a straight line through space. Of course, without incoming solar radiation the earth's surface would begin to cool rapidly, with some estimates indicating the average temperature would fall from the current 57 degrees or so to around freezing after a week, and after a year the average surface temperature would be on the order of minus 100 degrees F. Various forms of life would last for a great variety of different time periods depending on their typical current habitat and adaptations, along with the manner in which they gain life-sustaining energy. Small to medium sized plants, phytoplankton and so on would go pretty quickly due to the loss of photosynthesis, but large trees would continue to live off of stored sugars and water tapped from deep roots, at least until temperatures got cold enough long enough to freeze them to death. People could take advantage for a while of fossil, nuclear and geothermal energy sources to provide light and warmth, and perhaps to sustain some limited plant and animal growth for food, but this would surely become a great struggle in fairly short order for all but a relatively few enclaves. As earth continued to cool more slowly over hundreds and thousands of years, we'd reach a point where atmospheric gasses other than the water vapor we're accustomed to would begin to condense and precipitate out. If some humans were still around then, it would probably be a good bit tougher to keep going. Biologists considering this question do seem to think that one current form of life could continue on just about indefinitely, that being the ecosystem of organisms that live around geothermal vents in the deep oceans. That's in part because those organisms do not currently depend on the sun for sustenance, and also the oceans would develop an ice sheet that would greatly slow additional loss of heat from the deep water below. Areas near ocean floor vents would also continue to receive some of the heat generated by radiation and pressure from deep within the earth. That's a very brief overview of a few of the considerations of how such an even might play out. You can read some others, for example, at www.popsci.com/node/24698 and see a pretty entertaining video discussing some of these issues at www.youtube.com/watch?v=rltpH6ck2Kc.
May. 2, 2013 | Tags: astronomy, controversy, cool sites

Answer: Yours is the only report we've received of oddly colored frost or ice so far. In checking around with other employees, most of us have seen frost or ice covered windows a few times in the last month or two but the ice in question has generally appeared to be of the typical clear, translucent or white variety. We wondered if perhaps you or someone else may have run some blue-tinted washer fluid onto the windshield the evening before, which might account for such a coloring of the ice and frost. On the night in question, skies were partly cloudy in the evening and mainly clear the rest of the night with no precipitation reported, so the ice and frost would have had to be deposited directly from the air, unless you had a very low-probabilty encounter with a "blue ice/blue water" leak from a passing jetliner's waste system.
Mar. 9, 2013 | Tags: controversy, dew/frost

Answer: While the term superstorm became widely used by journalists, politicians and some others, most meteorologists refer to the storm as either Hurricane Sandy (during the time when it had tropical characteristics and sustained winds 74 mph or higher) or Post-Tropical Storm Sandy (covering the period when it had transitioned to a more extratropical structure). There is no definition that we're aware of for a superstorm, so that should probably be considered an informal/unofficial term that refers to an especially, large, intense or destructive storm.
Jan. 19, 2013 | Tags: controversy, hurricanes

Answer: That would be the correct interpretation - in other words "yes." (Sorry to everyone else about having no weather-related content in this answer, but every now and then it's fun to respond to a whimsical question like this one that ribs us a little for our on-air foibles!)

Jun. 13, 2012 | Tags: controversy

Answer: We aren't aware of any scientifically credible information to this effect, although it is easy to find many web sites that refer to assorted mystery planets, rotation-axis reversals, Mayan calendars ending in December 2012 (except that a different one was just found that stretches 7000 years farther in the future!), threatening comets and the like. A NASA site provides a reasonably good overview, in FAQ format, addressing some of these issues. You can find it at astrobiology.nasa.gov/ask-an-astrobiologist/intro/nibiru-and-doomsday-2012-questions-and-answers.
May. 21, 2012 | Tags: controversy, folklore

Answer: Hmm, it would seem the game writers were not aware that "cyclone" is probably too generic a term to use in that particular question. Hurricanes and typhoons are both cyclones, of the tropical variety. Other cyclones, such as subtropical and extratropical, also exist, with subtropical systems generally on the same size scale as tropical systems, and while extratropical cyclones are often larger than tropical cyclones, that is not always the case. In the past, much smaller circulations such as tornadoes and dust devils were considered cyclones (and cyclones was a popular term for tornadoes in the plains and midwest), but these days a reference to cyclones by a meteorologist generally refers to the much larger low pressure areas like those mentioned above. Perhaps the game writers figured that if someone knew typhoons and hurricanes are the same, they would have to choose cyclone since it is the only unique answer, but from a meteorological standpoint the question seems a little too ambiguous.
May. 12, 2012 | Tags: controversy, general meteorology

Answer: We certainly can't guarantee that every trail left by every airplane is a contrail, but we have noticed a very clear pattern in that the occurrence of a day with favorable weather conditions for numerous and lingering contrails, and upon which we see many of these contrails in the sky outdoors, or crossing the region on satellite imagery, will be followed in the next few days by several questions about chemtrails. This has definitely added to our sense that all of the chemtrail web sites out there have made a lot of people very sensitive to and concerned about simple contrails. It especially seems to capture people's attention when the contrails cross each other due to intersecting north-south and east-west flight paths, or when they are circular or elliptical, which can reflect the fact that there are some air traffic holding areas in our vicinity, in addition to more random occurrences of non-linear flight paths due to private or military aircraft operating in the area. As to your initial question, you can find a number of more in-depth discussions by using the "Search for:" box above the answers here and entering contrails or chemtrails, but the concise answer is that the duration and extent of contrails can vary greatly depending on the temperature and humidity of the air at flight level (colder and more humid equals longer duration, drier and less cold can result in no visible contrail production at all) and upon the winds, wind shear and stability at flight level (generally, less shear and greater stability increase contrail persistence and vice versa).
Apr. 8, 2013 | Tags: air quality, clouds, controversy

Answer: We take it that you are probably referring to linear or curved lines extending from high-altitude aircraft, in which case the cloud involved is typically composed of a combination of frozen droplets or directly deposited ice crystals that form as water vapor in aircraft exhaust mixes with very cold ambient air, and low concentrations of combustion by-products such as soot and oxides of carbon, nitrogen and sulfur. These are called condensation trails, or contrails, and they are quite common, existing in a variety of forms depending on the temperature, moisture, stability and wind shear characteristics of the layer of air in which the aircraft is traveling. In relatively dry and/or warm air, they can fail to form at all or can be so short-lived as to be nearly invisible, while in especially humid air they may be sufficiently persistent to spread, merge and form a layer of cirrus cloud covering much of the sky. Whether visible or not, the same exhaust products in roughly the same quantities are up there just about every single day.

Since we are not aviation forecasters, or military forecasters involved with projecting the visibility of high-altitude operations, we do not generally forecast contrail formation directly, although we do watch for conditions that can lead to the presence of significant high cirrus cloud cover, which often overlap those which would favor visible, or sometimes persistent and extensive, contrails.

The term chemtrails has been applied to these trailing clouds by some web site owners or contributors who believe materials other than exhaust products are being deliberately released by aircraft in what they purport to be covert and widespread government or corporate projects. After numerous years of inquiry and speculation, there remains no credible scientific evidence supporting this chemtrail theory.

It's also worth noting that we all routinely breathe particulates, gasses and volatile organic compounds from cars, buses, trucks, factories, power plants, dry cleaners and so on, along with variously allergenic pollens from trees, weeds and grass, that are at notably higher concentrations than anything reaching the surface from aircraft flying 20-40,000 feet above. Household cleaning products, various air fresheners, and other indoor allergens would also be at significantly higher concentrations. The point isn't to say that all these things are completely harmless, only that in a relative sense they would dwarf any combustion by-products from aircraft flying overhead.

Apr. 16, 2012 | Tags: controversy, weather & health

Answer: Your message was sent on Monday Feb 13th, and we recall that on that day, and the Wednesday that followed it as well, we noted atmospheric conditions that led us to include forecasts of significant high cloud cover and even a mention of potential for notable contrail formations. We aren't aware of any chemicals being sprayed by aircraft on those days, apart from those that are emitted as a byproduct of aircraft engine hydrocarbon combustion, such as particulates, carbon dioxide, some oxides of nitrogen and sulfur, and of course notable amounts of dihydrogen monoxide.

That last one of course is water, and forms the visible portion of a contrail that follows along behind an aircraft that is flying at an altitude with the appropriate combination of ambient temperature, pressure and relative humidity. Within a defined envelope of these parameters, mixing of the ambient air with the engine exhaust products (principally the water vapor, but with some potential influence from particulates acting as condensation or deposition nuclei), a highly visible linear cloud of water droplets and/or ice crystals can form. If there is relatively little turbulence and wind shear at flight altitude as well, the contrails can become quite thick, persist for a long time and stretch over many miles.

On the other hand, when conditions are not appropriate, they can be very short-lived or completely absent. It is also often the case that ambient conditions vary sharply in shallow layers aloft, so that the presence and character of contrails can change rapidly as aircraft either descend or ascend through horizontal layers of greater or lesser humidity, or pass at a single altitude through sloping layers. In either case, it can lead to the appearance of turning on or turning off a "sprayer," despite the fact that it is simply a product of the environmental conditions.

Adding to the potential confusion is the fact that under some conditions, persistent contrails can spread out into a partially man-made, partially natural cirrus cloud shield, or can mix with natural cirrus clouds, since the general conditions that support contrail formation are also more favorable for cirrus clouds to develop. Depending on the thickness and cloud particle size distribution of these clouds, they can produce rainbow-colored optical phenomena including halos, coronae, circumzenithal or circumhorizontal arcs, and iridescence. From your description, some of the clouds or cloud edges may have yielded iridescence on the day you wrote in. You can read more about this, and see some example photos, at www.atoptics.co.uk/droplets/irid1.htm (be sure to click the "more images" link at the left) and at atoptics.wordpress.com/tag/contrail-colours/ (scroll to the bottom of the page for some examples of iridescence occurring directly in contrails).

On the days in question, there actually were times before all the contrails formed locally that we could detect on satellite areas of both some natural cirrus cloud and numerous contrails upstream (due to greater humidity and especially cold air at those levels) that we expected to move over our area later. In each case, we saw the results overhead, but considered them to be simply a function of atmospheric properties at that time, combined with routine aircraft operations.
Mar. 2, 2012 | Tags: atmospheric optics, controversy, cool sites, weather & health