Airplanes May Affect Weather Patterns

blankmange writes "Wired is carrying an interesting piece: '...for three days starting last Sept. 11, meteorological researchers were presented with just such an opportunity when the FAA grounded commercial flights nationwide for three days following the terrorist air attacks. And now it has emerged that the American climate was indeed noticeably different during those three days without air travel.' Seems that what we do on the planet may have more effect than we may ever know."

Comments

clouds [contrails] and their effect on climate

[dolsen]

here's a nice image that illustrates (from low earth orbit) contrails over a large area (Nova Scotia, Canada, to be exact). at the NASA rapidfire site [bandwidth intensive] you can basically pick any day, choose an image over the northeast of the US [approx. 15:00 to 16:00 UTC normally] and it's a good bet you'll see lots of contrails. they have to have some impact on at least the local climate of the northeast. if you're in the mood for some light reading you can check out several NASA reference articles about clouds and their affect on climate:

• Changing Global Cloudiness Clouds are visible collections of small particles of water or ice, or both, suspended in the atmosphere. They are one of the most obvious and influential features of Earth's climate system. They are also one of its most variable components.
  
  Aerosols and Climate Change Aerosols are tiny particles suspended in the air. Taken as a whole these particles tend to cool Earth's atmosphere, and are an important factor in global change.
  
  Clouds and Radiation The study of clouds, where they occur, and their characteristics, play a key role in the understanding of climate change. Whether a given cloud will heat or cool the surface of the Earth depends on several factors.

there's also a good page on how ship tracks affect climate

oh yeah, the NASA press release about the contrail study...

Okay... some thoughts on all this...

[jellisky]

First of all, my biggest pet peeve: the difference between weather and climate. Yes, believe it or not, climate and weather are two very different terms. They should not be used interchangably, thankyouverymuch. Three days does not a climate make.

Now, to continue on that thought, it's interesting to think about the consequences of this "study". (The quotation marks are supposed to be there.) I cannot say what I really think of this "study" since I haven't read their results, but I cannot be that easily convinced that three days worth of data compared to years worth of data has any possible statistical significance, especially in something like diurnal ranges, which are 15-30 degrees C anyways. Show me three months and I might be convinced of a trend. I can name at least 10 different three-day weather features that could cause such a blip and that's just off the top of my head.

Next, IF this is true, then it only highlights something which has bothered me about climate modeling from the frickin' beginning: the role of clouds and how terribly they are handled in these (and all) models. Of course, this isn't the only problem I have with these modeling studies, but we won't enter that debate right now.

The type of cloud present has an effect on the net change in radiative flux. Deep, thick clouds (like cumulus) have a net positive change while thin clouds (like cirrus) have a net negative change. The thing, though, is that in balance calculations like these, there tend to be two effects, which are approximately equal and opposite in sign. So, you end up wondering how much of it is really real. (For example, the two terms might be 220 and -218, leading to 2 change... but if you're off by a little bit, those numbers might actually be 219 and -220, leading to a -1.) This is further compounded by the way models handle clouds, which is often routinely terrible (with respect to resolution, the actual physics involved in the cloud which can affect all the results, and many other factors).

To further put all this in perspective, let's assume the albedo (the amount of solar radiation reflected back to space by the earth which is largely a function of the cloudiness) of the earth increases by 1%. (It's currently around 30% in a climatological sense... even that number has an error bar of measurement around +/- 3%.) On average, that would mean that the earth would get 3.4 W/m^2 less radiation. (Daily and spacial average of solar radiation is about 340 W/m^2, again largish errors on this measurement.) This number is comparable to the change by doubling CO2 (about 4 W/m^2) and, as you can notice, opposite in sign. Of course, there's a huge extra batch of physics here that isn't even being considered like the change of the absorption of IR radiation from the earth by the clouds or the release of latent heat by the clouds or the feedback between warmer surface temperatures and clouds (which is barely understood since it's almost as complex a problem as the original)... Kind of makes your head spin to think about all these effects, doesn't it? And all of them are about the same order of magnitude by itself, i.e. about 0.5-5 W/m^2, both positive and negative. Let's also not forget that local effects, like all those new urban heat islands that have popped up around all our temperature recording stations that could very well explain that temperature rise in the last century or whatever, and that these effects are not put into these models...

Complex problem? You bet. Possible to understand? Eventually, I don't see why not. But, we can't sit back and keep using these antiquated ideas in these state-of-the-art models. As the old saying goes, "Garbage in, Garbage out." The effects of these contrails may be important, yes. I cannot debate that. However, to claim that off of whatever insignificant sample this is, or using any of the ideas we currently have, is ludicrous at best. Any imbecile with a computer nowadays can run a correlation analysis on data. But, to interpret it and explain WHY things are happening that way... that's the vital connection between statistical tomfoolery and real science. Then, to explain the dynamics and theory behind it all... that's the step to making a full fledged theory.

-Jellisky