No surprise here: Jet contrails affect surface temperatures

From Penn State

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. Video follows.

Jet contrails as seen by satellite. Credit NASA Langley Research Center

Jet contrails as seen by satellite. Credit NASA Langley Research Center

“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.”

“Certain regions of the U.S. have more favorable atmospheric conditions for contrails than others, “

said Jase Bernhardt, graduate student in geography.

For contrails to form, the atmosphere at the level the jet is flying must be cold enough that the moisture from the jet exhaust freezes into ice crystals. There also must be enough moisture in the air that the clouds that form remain in the sky for at least a few hours as persisting contrails.

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.

“Weather forecasting of daytime highs and lows do not include contrails,” said Carleton. “If they were included in areas of contrail outbreaks, they would improve the temperature forecasts.”

###

The National Science Foundation supported this work.

ADMONITION: Any mention of “chemtrails” in comments will be immediately sent to the bit bucket, as per our blog policy

104 thoughts on “No surprise here: Jet contrails affect surface temperatures

  1. Clouds and vapour trails lower surface temperature but warming increases clouds.
    Sounds like a self regulating system.

    • Self-regulating and forced. Finally mainstream gets one step closer to looking at the affects of high level cloud on climate.
      the effecs of contrails in lower stratosphere should lead to looking at the effects of major volacanoes on TLS
      https://climategrog.files.wordpress.com/2014/04/uah_tls_365d.png
      Then comparing ( inverted ) to the late 20th c. warming.
      https://climategrog.files.wordpress.com/2014/07/tls_icoads_70s-20s.png
      More detail discussion here:
      https://climategrog.wordpress.com/?attachment_id=902
      Part of the volcanic effect seems strongly related to ozone destruction
      Aircraft exhaust is not pure water vapour and CO2. Like all hydrocarbon fuels kerosene contains several pollutants like sulphur which remain in the stratosphere to create condensation nuclei. These will have a much longer lasting effect than the visibly obvious contrails that last at most a few hours.
      Much of the surface *warming* caused by major eruptions seems linked to ozone destruction in the stratosphere but also the processes that flush out the volcanic aerosols probably flush out some of the build up of stratospheric pollution too.
      Like every time they try to explain the pause, they end up explaining why the warming was not caused by CO2.

      • I note that the graph scale for the stratospheric temperatures is 5 times the scale for SST. About 10% of the IR TOA radiation comes from the high absorption part of the CO2 spectrum, which radiates at tropopause or
        stratrospheric temperatures. Any drop of stratospheric temperatures, whatever the cause, will significantly decrease IR radiation and “force” a rise of surface temperature that is an order of magnitude smaller but still significant compared to observations. This is due to the presence of CO2, but largely independent of CO2 concentration. The warming of 1980-1998 may be partly due do Ozone recovery or anything else that caused the drop in stratospheric temperatures.

    • Sorry no tin foil just some facts:
      Chemtrails […]
      [Per blog policy stated above … to the bit bucket… -ModE]

      • Sorry, but I don’t buy the chemtrail conspiracy theory, one of the issues being the altitude at which the alleged chemicals are released; for, if one wants to land a substance at a general location, one does not release the payload ten kilometers in the sky.

      • Moderator – I just noticed the admonition, so go ahead and delete my previous post also. Thanks.
        [Not needed. As the anonymous radio operator added in WWII, “All the world wonders … .mod]

      • But..but…but water vapor is a chemical! Hence they must be chemtrails used by the forces of evil to pollute our precious bodily fluids! [/sarc]

    • Hey, it worked! Of course no one else will be able to see this article as it originally appeared (all centered)…
      So, what this article lays out is a man-made counter to the natural warming of our planet, which could end up being a tipping point that leads to a new glaciation? Scary thought!

      • Doubtful, Earth climate too self-regulating for that. But a precipitous drop in Solar activity, maybe so.

  2. So when Al Gore and mindless celebrities cross the globe in private jets to oppose carbon usage, they actually cool the planet.
    Whoa. What irony

  3. Is this regional r global.?
    Do flight-routes systematically get colder than non-flight-routes?
    Hang on, flight-routes are in jet streams to save fuel. That’s a confounding factor.

  4. Sounds like excuse number 71 or 72 or whatever we’re up to now for why the world isn’t warming according to IPCC predictions; airline global cooling, and airliners freezing water vapor out of the atmosphere. No wonder we can’t find that tropospheric hotspot.

  5. well shat…..the discovered a cure for global warming……drill baby drill
    “this amounted to about a 6 degree Fahrenheit reduction in daily temperature range”

  6. …researchers have found that these elevated ice cloud trails can influence temperatures on the ground and affect local climate…
    ————
    As contrails are so evanescent, shouldn’t they say local weather instead of climate?

    • Weather is disturbances and short term changes within a climate system. ‘Climate’ can be viewed on many scales, from ground to thermosphere, ground to a few inches above, N. side of a tree vs. S. side of a tree, etc., etc. There is no ‘global climate’ per se, that is a term of distraction from real issues.

      • Types of Climate are typically determined by latitude and altitude. Smaller subsets usually determined by orographic effects, etc. If somebody asked me what is the climate of Earth, I’d have to say where on Earth? We’ve got a million of ’em(Climates).

  7. Every little bit (of real science) helps. Hopefully this will occur over some of those badly sited wx stations.

  8. More climate porn, was it really necessary for the researchers to include the 2nd tower hit.
    ……………I’m really biting my tongue right now.

    • I also wonder if the average has changed as well. A very good question.
      Contrails may not be as good at blocking incoming solar radiation as they are for blocking outgoing IR, have read some reports stating the warming due to contrails from a high flying aircraft is much larger than the warming due to CO2 emitted.

      • “Contrails may not be as good at blocking incoming solar radiation as they are for blocking outgoing IR,…”
        Here, try this. Go outside on a sunny day, stick your arm out, shoulder high with your palm down and ask yourself which warm first, your palm or the back of your hand.

  9. “In this respect, the contrail clouds mimic the effect of ordinary clouds.”
    Raise your hand if you are surprised.
    “Now researchers have found that these elevated ice cloud trails can influence temperatures on the ground and affect local climate”
    Affect local WEATHER. These idiots don’t even know what climate means.

  10. Well, this ice cloud hypothesis is counter to the Lindzen high ice cloud cirrus ‘adaptive infrared iris’ hypothesis for the tropics. One explanatory possibility is that latitude matters. Another is that one idea is just wrong (more likely contrails, since the paper’s data is so sparce and sketchy). The most likely possibility is, we just don’t understand enough yet about feedbacks to know one way or the other. Unless you are Pope Francis.

    • Why should Lindzen’s ‘adaptive infrared iris’ and contrails not both be in play? Neither forbids the other, and cause and effect are similar, and probably additive.

    • Well, this ice cloud hypothesis is counter to the Lindzen high ice cloud cirrus ‘adaptive infrared iris’ hypothesis for the tropics.

      Lindzen is talking about a natural process that acts as a feedback. Contrails are not natural and don’t act as a feedback.

  11. This article brings up a point about the discussion of how much warming we have seen. Since the problem seems to be how hot the Earth is getting, should we be looking at maximum temperatures and the increases in maximum temperatures. The increases in minimum temperatures make average temperatures higher and the anomalies based on average temperatures larger; but, is this important?

  12. Oh, be quiet folks.
    In the end, scientists would be brought to the scene, that without contrails there would have been no “Pause”.
    /sarc

  13. Interesting that a site such as this, which I read every day, should have verboten words. How about geological engineering, which is what serious researchers prefer anyway?
    60,000 times the accepted levels of aluminum in Shasta runoff at the headwaters of the Sacramento river.
    Very high levels all around california, in various lakes, rivers, etc. In arizona also.
    It is amazing to me that Anthony can put forth the truth on AGW, and yet, the other half of the story is verboten. When the gov pushes a big lie, you can be sure there are lots of facets to the propaganda, and one of them is practically always to cover something else up.
    This aint a conspiracy theory anymore. To much water and air analysis. And to top it off, Monsanto is developing lots of seeds that will grow in aluminum contaminated soils. what?
    Ah well, maybe a few people will get to read this.
    [And what list of words do you believe is verboten? There are a group that drop a reply into the “automatically moderated queue .. .But none of those are verboten per se. .mod]

    • Ah, take a look at what makes up rocks. Aluminum silicates dominate. ALL water has run over aluminum containing rocks. It is one of the more ubiquitous elements in the crust. Might as well be afraid of sodium …

      • People are afraid of Na. People are getting so silly, they call salt White Death, when quite the opposite is true. There are diets that cut salt to dangerously low levels, but sodium ions are used in many cellular processes.
        The symptoms of low sodium:
        “You may experience low sodium symptoms daily or just once in a while. At times any of these low sodium symptoms can be severe:
        Abdominal pain or cramping
        Bloating
        Body aches
        Changes in mood, personality or behavior
        Difficulty with memory, thinking, talking, comprehension, reading or writing
        Dizziness
        Headache
        Impaired balance and coordination
        Malaise or lethargy
        Muscle spasms
        Nausea with or without vomiting
        Serious symptoms that might indicate a life-threatening condition”
        And evidence that too much salt will decrease your lifespan is not reliable and has been called into question.
        http://www.webmd.com/food-recipes/20140402/cdc-salt-guidelines-too-low-for-good-health-study-suggests

      • …but “60,000 times the accepted levels of aluminum” What the heck does that mean? Accepted by whom. What is the harm. Water is healthy, yet if I drink 60,000 times the accepted intake of water, I will certainly die.
        I live in northern California, what am I suppose to be experiencing from “60,000 times the accepted levels of aluminum”, and is it good or bad?

    • Monsanto. There’s a clue right there. You know who the majority stockholders in Monsanto are? That’s right, members of the Trilateral Commission. The Elders of Zion own quite a bit of it too.
      I shouldn’t encourage him, now my sarcasm will be cited as fact and spread across the web.

  14. Ahh… since contrails would have increased consistent with the increase in flights over the last 2 decades, and the earth hasn’t warmed in the same period – this is another; “move along. nothing to see here” publication.. And in future,Bernhardt and Carleton bring your own paper and ink before you waste public money on another useless publication…

    • I see some of those in pretty much the same area of the sky a lot of times. I am not sure where the power plant is, but i know there must be one. The scale of the things is pretty vast.

  15. The high ice clouds actually let most of the sunlight in.
    They are thin and high and just scatter the sunlight so that it still reaches the Earth surface much more than they reflect the sunlight back to space without touching the surface.
    Jet contrails only form and last for any length of time in very rare special conditions such as deep high pressure systems.
    On average, the high ice clouds are supposed to hold more IR in from the Earth surface than they reflect sunlight back to space.
    On average, clouds reflect 44 W/m2 of sunlight and hold in 23 W/m2 of IR from the surface. Clouds are therefore a net cooling agent for the climate as a whole on the order of -21 W/m2. High thin cirrus and high thin jet contrails are supposed to be the opposite, providing a net warming effect to a few W/m2.

    • Clouds don’t ‘hold in’ IR radiation. IR radiation travels at the speed of light so it may ‘bounce around’ a bit and ‘take a few ricochets’ (or a million ricochets) but in an instant it’s gone into space.

      • It’s a tough concept, I know. But mainly it has to do with “ringing” the occasional CO2 or water molecule to produce sensible heat. According to Quantum Mechanics, (which is spectacularly accurate) some small percentage of IR photons will be absorbed on contact with these molecules while the rest will pass through. Kind of like a small percentage of photons will be reflected off of a piece of glass causing reflections while the rest pass through, making it transparent.
        Once a molecule has absorbed a photon, it will vibrate for a time and then possibly pass the heat to another molecule by collision, or re-emit the photon and return to its previous state (cool, if you will). That photon can be emitted in any direction and then will either be absorbed again, or finally find a clear path to space.
        This was demonstrated, though not explained, since quantum theory did not exist at the time of the first experiment, over a century ago. You could do it yourself with a glass tube, and the rest of his equipment.
        That the above is true does not mean that the planet faces a catastrophe. It certainly does not mean that the models are right. They appear to be wrong. It just means that you shouldn’t be repeating scientific nonsense and pretending it is “skepticism.”

    • Yes, just look at two sat pics – one in the IR ch and one Vis. You will see Ci cloud is far denser in on the IR pic. It is absorbing/emitting more at those wavelengths than the vis ones. hence you are seeing more SW passing through unaffected than LW. An example of the GHE.
      High clouds warm overall, reducing the diurnal range.
      Also yes, power station cloud (Cumulus) is common but they will serve to cool and are a tiny factor in comparison to worldwide contrails.

    • Bill Illis 6.30pm
      Your last line is interesting as I think this is an old statement:
      “High thin cirrus and high thin jet contrails are supposed to be the opposite, providing a net warming effect to a few W/m2.”
      From the article here:
      “They found that contrails depress the difference between daytime and night time temperatures, typically decreasing the maximum temperature and raising the minimum temperature. In this respect, the contrail clouds mimic the effect of ordinary clouds.”
      I remember reading the IPCC report on aviation after which I became very skeptical of the AGM argument. As AGW deals with humanly imperceptible changes in average temperature the statement about clouds ‘heating’ the earth’s surface did not make any sense to me as without exception I have never perceived a rise in temperature when any clouds come between me and the sun. The fact that clouds can trap heat cannot be divorced from the fact that clouds have prevented a larger amount of heat from getting to the ground in the first place. Otherwise we have found a way of making more energy from less!

        • Your standard IR thermometer works in the 8-14u atm window, but since it just collect IR (8-14u) photons, it doesn’t care where they come from. Pointed straight up on a clear winter night, mine has measured below it’s rated -60F, near -90F. Now, it doesn’t detect IR from the 15u Co2 band, so that would have to be added back(*more about that in a minute). On 50-60% rel humidity clear days the temp measured when pointed straight up (Tsky) it 90-100F colder than the ground. Scanning across a jet contrail, the temp will warm a few degrees, to maybe 5F warmer than sky with no contrails. The thicker the clouds, the warmer they are. The bottom of those thick puffy Cumulus can be 20-30F colder than the ground.
          Now I started using the ground for reference instead of the air, I don’t really think the air is the real player here, it’s the ground cooling through radiation to space, clouds reflect that IR, why they’re so warm. The air is just trapped between the heat source and the cold.
          Humidity causes Tsky to be warmer, reduces the difference between the ground (concrete sidewalk) to be less, 60-70F (as opposed to 90-100F), so a 90F humid day Tsky will be 20-30F.
          At night grass cools quicker than concrete, which if you live someplace that gets frost rings true, we see frost on grass, cars, frozen puddles when it’s 35F, but the roads don’t tend to have frost. And if you measure the temp, it takes the ground longer to cool, grass appears as if it’s a air gap insulation, same with snow, it too cools quickly.
          But, even when Tsky is way below surface temps, you can look at the nightly cooling rate (I have cheap weather station), it cools quickly as soon as soon as the sunsets, high cooling rates, until dew point get in the upper 80% to 90% rel humidity, then the rate slows.
          https://micro6500blog.files.wordpress.com/2015/03/relhumidity_withtemps.png
          You can see humidity hits 100% as it gets into summer, this also plays into humidity. As Willis talks about the humidity getting generated in the tropics moving poleward, this drys the air as it goes away from the tropics, every night some of that moisture is removed, and some ends up in the water table, the rest evaporates the next day, moves further until night, and so on.
          The ground and air temps drop until sunrise, then start to rise, which play into the length of day changes, if it cools all night, and in the summer the nights are shorter, someone clever can get detailed cooling rates due to changes in the length of day.
          * You can take a temp and use SB to turn that into a flux in W/M^2, which would the the BB temp the flux rate into the thermometer equates to based on 8-14u, then you can add the W/M^2 from Co2 to the BB temp flux, and the turn that back to a temp. Adding 3.7W/M^2 to -40F (mid 50F’s clear normal humidity day), changes the temp to ~-38.2F.

      • I am guessing that it means he is pointing an IR thermometer gun or something like it, at the sky and getting a higher reading than normal. You can get one at Home Depot.

        • I am guessing that it means he is pointing an IR thermometer gun or something like it, at the sky and getting a higher reading than normal.

          Yes, sorry busy day, took a while to write a reply.

          You can get one at Home Depot.

          No, The first one I got went to -40F, and the first time I pointed it up it read over range. then I found one that went to -60F and has a usb port so I can log it, unfortunately it only logs once per second, and only 4,800 time steps. But it still allows me to log the data, and the time so I can match it up with my weather station data.

  16. I have tried to find associated information on contrail persistance and the relative humidity change measured over the last 30 years. I know many are worried about ‘Chemtrails’ and I believe that at the altitudes most contrails occur this change in relative humidity may induce a longer persistance than what occured several decades ago. Does any data or chart show the relative humidity at the altitudes of 25 to 40 thousand feet over the last 30 to 40 years?

  17. CAGW’s professed ignorance of the net climate effect of cloud cover and CAGW models’ complete unskillfulness in cloud cover projections/formation is their get-out-of-jail-free card….
    When the CAGW hypothesis is inevitably disconfirmed, CAGW hacks will ultimately blame their cloud-cover “misunderstanding” for why CAGW crashed and burned so spectacularly, and will point to various IPCC reports and peer-reviewed papers proclaiming said “ignorance” as cover when testifying before the imminent Congressional and Senate hearings held to determine WHY the US and other countries blew $10’s of TRILLIONS on CO2 abatement and destroyed their economies for absolutely no reason whatsoever….
    And so it goes…..until it doesn’t…

  18. The heading photo by NASA showing contrails is without reference. By inference it will appear that this is a 24/7/365 day occurrence. What time of day and month was this and what were the atmospheric conditions?When the Icelandic volcano with the unpronounceable name (Eyjafjallajökull) erupted and grounded all planes in Europe some stated that we would witness clear blue skies which like snow would never be seen again. Well, when flights resumed there were, and still are, clear blue sky days, in fact apart from the cumulus clouds there is one right now here in southern UK.
    The first IPCC report on aviation said how contrails will ‘heat’ the surface of the earth. So now there is acknowledgement that contrails, which are artificially created clouds, behave just like clouds. No s**t Sherlock!

    • Stephen:
      ” Right now over the UK I can see one short contrail that is dissipating within seconds (4 to be precise). Engine technology keeps improving as it always has done and so it is rare these days to see a smoke trail behind an airliner.”
      They are not “smoke” trails. They are vapour trails. Comprising WV from the burning of aviation fuel. The WV condenses onto hydrophilic nuclei and form ice crystals -and will persist if the level that the plane is flying at is a) cold enough (~ MS40 ) AND b) the atmosphere is moist enough such that they don’t quickly sublimate/evaporate.
      I too have been observing this since the 70’s and later forecast them as an employee with the UKMO.

  19. “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.”
    This story agrees with John Christy’s prior studies on irrigation in the San Joaquin Valley.
    Daytime temperatures go down, nighttime temperatures go up, average temperatures go up, and the
    climate becomes more moderate, less extreme.
    http://wattsupwiththat.com/2010/09/12/christy-on-irrigation-and-regional-temperature-effects/

  20. It’s common sense that water reduces temperature variation. I live in a desert. The high yesterday was 95 F, low 68 F. That’s 27 F variation. Near the ocean, the temperature variation is less. Yet we need studies to get people to believe the obvious! No wonder people believe in CAGW. They lack common sense.

  21. I thought this older study would have been mentioned by now, but way back in 1980, scientists from the University of Illinois submitted to the NSF their report:
    EFFECT OF CONTRAIL CIRRUS ON SURFACE WEATHER CONDITIONS IN THE MIDWEST – PHASE I
    Stanley A. Changnon, Jr., Richard G. Semonin and Wayne M. Wendland
    ABSTRACT
    The effect of aircraft contrails on surface climate was assessed by first determining the density of jet traffic across a ten state area of the Upper Midwest, and comparing that distribution with observed changes of various meteorological parameters of the past 50 years […]
    Cirriform clouds increased in frequency from 1951 to 1978 according to standard surface meteorological observations. Frequency of clear days decreased over the 26 years at 10 of the 12 first order stations studied. The greatest decline occurred from Chicago to southern Iowa and from Chicago to southern Illinois.
    http://www.isws.illinois.edu/pubdoc/CR/ISWSCR-236.pdf
    (my bold)

  22. “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,”
    It’s good that the three day period in question was merely taken by this research team as “suggestive” and that they did a more extensive study, because in fact the apparent effect observed during that period was essentially spurious:
    http://www.int-res.com/articles/cr2004/26/c026p001.pdf
    “Several investigators have suggested that the airline shutdown following the 9/11
    terrorist attacks led to a reduction of jet contrails and an increase in the diurnal temperature range
    (DTR) across the US. Here, we use an air-mass approach to control for weather conditions across the
    country following 9/11 in order to more accurately assess the observed patterns in the temperature
    range. We indeed find a higher-than-average DTR shortly after the attacks, but we find that the
    unusually clear weather across the US more than accounts for the observed DTR.”

  23. Hmmmm, Contrails or Persistent Contrails or Chemtrails … OK , here is my question regarding the satellite image at head of this article, tell me now how long is a “normal” contrail at jet liner cruising altitudes? I understand them to usually extend about 2 miles behind a normal conventional jet liner or military jet. That said, when looking at the satellite image at the top of this post , tell me how long are those “contrails” as shown in the photo? Looks to me like they are hundreds of miles long. Explain how that is? Is this photo a time lapse over some 3 hrs or so? Or is it a snap shot of a few tenth’s of a second? If indeed it is a snapshot of less than a second , then those “contrails” are formed and visible for hundreds of miles, and just what kind of contrail does that? 2 miles long as visible contrail or 200 miles long? Why do some planes turn the contrails “on” and “off” as I have repeatedly observed for ten years now? Have fun ! Looking forward to some answers.

  24. Instead of this look at contrails, we should be also looking at whole atmosphere by altitude and other natural cycles. No doubt variance in solar irradiance and cloud cover impact lower troposphere temperatures more than CO2. IPCC idiots discounted the 11 year solar cycle since variance in radiation being W/m² hitting earth was too small. However we know low sun spot activity is associated with cold temperatures by Maunder Minimum 1645-1715, and Dalton Minimum 1790-1830, yet we have millenniums of data by isotopes going back before telescopes looking at sun by Vostok ice core for data the same. We are in solar cycle 24 which is half solar cycle 22, sun at low for normal turnover of poles. http://www.solen.info/solar/images/comparison_recent_cycles.png
    yet W/m² is not enough, but more weak magnetosphere of our sun shields us less and allows more cosmic radiation in from rest of space. This then reacts with things like sulfides in atmosphere seeding clouds, same effect cooling if volcano like Pinatubo, but on other end. CERN is doing interesting research. But if more cosmic radiation let in to earth by a weaker sun, then will seed more clouds, colder troposphere. If true, could only hope for some global warming by CO2, but that is a myth. I am waiting for “climate change” to morph into yet now better understood global cooling/ice age scare of 70s, yet warming would benefit humans more than cooling despite. Clouds-solar cycle link are more important than contrails.

    http://icecap.us/index.php/go/new-and-cool/cosmic_rays_hit_space_age_high/

  25. JPinBalt :
    Solar minima, whilst the only lowering the TSI by 0.1-0.2%, lowers the UV end of the solar spectrum by up to 30%.
    UV is intercepted by O3 in the Strat. In doing this it warms. In doing this it sets up a DeltaT between the Earth’s equator at pole in the NH winter. Weaker UV makes the strat colder over the equator. The stratospheric polar night jet is therefor weaker around the polar vortex. A weaker jet is a more meandering one. This allows the PV to more easily distrupted, and down-well winds to the Troposphere where a -ve AO (high pressure) is encouraged. This then pushes arctic air south in favoured areas -vis E US and Europe. There you have you LIA and Dalton Minimum. Couple the LIA longevity to the feedback of causing ocean currents to alter also.

  26. Why are they brown now? They used to be white. The sky is completely brown from contrails where I live.

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