[saN]

If this is in the wrong section, feel free to move it.

I heard that a scientist at the University of Wisconsin did a study on the global temperature after the attacks of 9/11. It showed that temperatures were rising the very few days after 9/11 because no airplanes were flying. Has anyone heard of this?

[Borek]

Yep. IIRC there were some changes in the mean daily temperature in US as there were no condensation clouds (or whatever they are called, vapour trails?). But I think temperatures observed were slightly lower, not rising.

[constant thinker]

I've heard them called condensation trails, vapor trails, and contrails with the latter being the most common.

Borek, I happen to remember that the mean averages were lower also.

[syko sykes]

It would make sense that the temperatures were slightly lower because no CO₂, was being emitted from the planes. However, a few days isn't a large enough sample to have any statistical significance so you can't necessarily link the slight variance in temperature to the airplanes.

[Borek]

It wasn't CO₂, contrails are kind of clouds, cloud cover prevents heat loss from the earth surface, No clouds, it gets colder. No idea where do you live, but here in Poland the most cold nights in winter are almost always those with beautfull, starry sky.

[constant thinker]

No idea where do you live, but here in Poland the most cold nights in winter are almost always those with beautfull, starry sky.

It's the same over here in the Northeast of the U.S.

[Borek]

No idea where do you live, but here in Poland the most cold nights in winter are almost always those with beautfull, starry sky.

It's the same over here in the Northeast of the U.S.

Hardly surprising. But for someone from Florida, or Australia, it is exotic like heatwave for Eskimo

[lemonoman]

contrails are kind of clouds, cloud cover prevents heat loss from the earth surface, No clouds, it gets colder.

Compare with Ash clouds from volcanoes, which cause a cooling effect because they directly block sunlight from reaching the earth.

I just felt like sharing that...lol

[Borek]

To make things harder to describe/grasp cloud presence changes planet albedo, thus changing amount of heat reaching planet surface. As amount of clouds depends on humidity, and humidity depends on amount of heat reaching waters (thus it depends on albedo), whole system is very difficult to model.

[Donaldson Tan]

No clouds, it gets colder. No idea where do you live, but here in Poland the most cold nights in winter are almost always those with beautfull, starry sky.

During day time, a large cloud coverage results in a cooler day because the cloud reflects heat from the sun. While this happens, the ground absorbs heat from the sun during the day. At night, the group reemits the heat absorbed during the day and the large cloud coverage would reflect the heat back to the ground.

Hence, a cloudy sky results in warmer nights and cooler days.

[Sam (NG)]

No clouds, it gets colder. No idea where do you live, but here in Poland the most cold nights in winter are almost always those with beautfull, starry sky.

During day time, a large cloud coverage results in a cooler day because the cloud reflects heat from the sun. While this happens, the ground absorbs heat from the sun during the day. At night, the group reemits the heat absorbed during the day and the large cloud coverage would reflect the heat back to the ground.

Hence, a cloudy sky results in warmer nights and cooler days.

Hence the weather in England is f&#^$*@ Shite.

[Donaldson Tan]

Hence the weather in England is f&#^$*@ Shite.

It is cloudy sky + very strong wind with cold front

[Yafmot]

    Ah, excuse me, but has anyone taken into account the fact that this incident occurred in September? It was just ten days fron the autumnal equinox, so naturally the days could've been getting shorter/cooler regardless of aviation activities (or lack thereof). At least in the Northern Hemisphere.

    Also, the lack of ability to fly resulted in much higher use of automobiles, buses, and trucks to move people and goods around. In terms of seat-miles/gallon airplanes are far more efficient than cars so, if this greenhouse baloney had any validity at all. it should've warmed up!

[Borek]

Ah, excuse me, but has anyone taken into account the fact that this incident occurred in September?

You have to ask those that took the measurements and did the analysis. Could be they knew what they were doing. You may assume everyone else is a complete idiot, but you will be occasionally wrong.

Also, the lack of ability to fly resulted in much higher use of automobiles, buses, and trucks to move people and goods around. In terms of seat-miles/gallon airplanes are far more efficient than cars so, if this greenhouse baloney had any validity at all. it should've warmed up!

Not necesarilly. These are not instant effects. Besides, assuming that there are about 3.81 x 10⁸ gallons of gasoline burnt each day in US, that solar constant is 2 cal cm^-2s^-1, assuming then 12 hours of sun, 125 kbtu/gal and 9.8 x 10⁶ km² of US land, amount of heat from the gasoline source is well below 10^-5 of the amount of energy US get from the Sun at the same time. Sure this should be corrected for weather, sun height over the horizon, filtering by atmosphere and so on, make it ten times less of sun - still we are talking about below 10^-4. Hardly noticeable.

[constant thinker]

To control for temps do to season, you probably can look at where the jet stream was and the average temps at the time N to S and E to W, and then compare with past averages. This could give you some general conclusion. I don't know if enough data would even exist to do that though...