Look up, and watch humans change the weather

Posted at 11:55 AM on September 10, 2012 by Bob Collins (8 Comments)
Filed under: Science, Weather

For a short time today -- too short to get a decent picture -- the sky over Minnesota was wearing a pinstripe suit, thanks to the weather conditions that made obvious what is true all the time -- there's a highway over us.

Jet contrails only form to this degree in certain weather conditions.

Let's turn it over to Dr. Steve Ackerman at the University of Wisconsin for a proper explanation:

If you are attentive to contrail formation and duration, you will notice that they can rapidly dissipate or spread horizontally into an extensive thin cirrus layer. How long a contrail remains intact, depends on the humidity structure and winds of the upper troposphere. If the atmosphere is near saturation, the contrail may exist for sometime. On the other hand, if the atmosphere is dry then as the contrail mixes with the environment it dissipates. Contrails are a concern in climate studies as increased jet aircraft traffic may result in an increase in cloud cover. It has been estimated that in certain heavy air-traffic corridors, cloud cover has increased by as much as 20%. An increase in cloud amount changes the region's radiation balance. For example, solar energy reaching the surface may be reduced, resulting in surface cooling. They also reduce the terrestrial energy losses of the planet, resulting in a warming. Jet exhaust also plays a role in modifying the chemistry of the upper troposphere and lower stratosphere. NASA and the DOE are sponsoring a research program to study the impact contrails have on atmospheric chemistry, weather and climate.

Coincidentally, 11 years ago tomorrow provided some important data in the research of this question about whether contrails can influence the weather, the Christian Science Monitor reported...

Then Sept. 11, 2001 presented a unique opportunity to study what the sky looked like without airplanes and contrails. In the wake of the 9-11 terrorist attacks, the FAA prohibited commercial aviation over the United States for three days. That's when David Travis, an atmospheric scientist at the University of Wisconsin, Whitewater, thought to look at how temperatures might differ at temperature stations around the country.

He found that [PDF], for those three days, the average range between highs and lows at more than 4,000 weather stations across the US was 1 degree C wider than normal. In other words, contrails seemed to raise nighttime temperatures and lower daytimes ones.

But the real effect was in daytime highs, which were much higher. That would seem to indicate that, contrary to prevailing thinking, contrails might have a net cooling effect.

Certain areas seemed particularly sensitive to the absence of contrails. Because of unique climatic conditions in the atmosphere in these regions -- chiefly, moisture-laden air -- the Pacific Northwest and the Midwest are often covered by contrails. But when planes stopped flying right after 9-11, Travis also found that these areas saw the most dramatic increase in daytime highs.

It's unlikely much is being influenced, though, by today's contrails. They're evaporating fairly quickly, although several of them are faintly visible -- especially in southeast Minnesota -- in this satellite photo, taken around 10:15 this morning.

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Comments (8)

I remember wondering, and asking about this when I was little. Something to the effect of "If jets make clouds, can they cause rain?" I think I got some dismissive answer from whom every I asked (I think most children just accept that some times no one knows, and no one seems to care, no matter how important the topic seems to them at the moment.)

Later I remember being on a trip with my family, and my aunt some where that had a nuclear cooling tower (billowing out steam puffs at the time) my aunt referred to it as a "Cloud Factory". It probably sounded less frightening in her mind than "Nuclear Reactor" though I was concerned that if a factory could produce light puffy cumulonimbus clouds, what would stop some one from producing storm clouds... and if these factories did exist near the gulf, devastating hurricanes... seemed like a far more frightening concept to me at the time then what the reality was of a simple power plant.

Now I'm wondering if cooling towers have similar effects to contrails, or if they are releasing the moisture to close to the ground to have similar impact.

Posted by jon | September 10, 2012 12:52 PM

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They were everywhere over the Capitol this morning. I got some nice video I'll post to my Tumblr when I get home. It was about as many as I can ever remember seeing in the city. On the farm where I grew up the southern sky was filled with them in the winter as planes crossed the midwest. From Chicago to Denver, I assumed.

Posted by Kevin Watterson | September 10, 2012 1:15 PM

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// Now I'm wondering if cooling towers have similar effects to contrails, or if they are releasing the moisture to close to the ground to have similar impact.

sometimes in the winter we get some snow flurries around MPR; it comes from the District Energy cooling tower vapor.

Posted by Bob Collins | September 10, 2012 1:29 PM

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Prince says these are Chemtrails. He said this during an interview with Tavis Smiley. What does Prince know that we don't know... ;) ;)

Posted by Matt | September 10, 2012 1:41 PM

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As I was driving to work today, I was noticing the contrails, and this was at 7:00am. They were beautiful in the light of the rising sun, reminding me of the translation giving at the end of Koyaanisqatsi: "Near the day of Purification, there will be cobwebs spun back and forth in the sky."

Posted by Dylan Kvasnicka | September 10, 2012 2:11 PM

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One winter I drove through a tiny snowstorm outside of the Rock Tenn recycling plant at I-94 and 280 in St. Paul that was made from the steam coming out of their stacks. Made the highway unexpectedly slippery.

The great Boston band O Positive released an EP in the 1980s called Cloud Factory. (Always nice when I can plug a great Boston band!)

http://www.opositive.com/

Posted by Jeff | September 10, 2012 3:13 PM

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Not as cool as I thought. Didn't get them heading all the way south.

http://youtu.be/Ju8VTVwiIgc

Posted by Kevin Watterson | September 10, 2012 7:06 PM

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I have been contacted in the past by "chemical contrail" conspiracy theorists who believe there is a secret effort underway to change global climate via chemistry to either a) hasten or b) constrain the warming of our little blue marble.

Pretty crazy stuff, either way.

Posted by Robert Moffitt | September 11, 2012 7:49 AM

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