Air pollution question.?

Question

I've just watched a programme about the invention and developement of the jet engine. Here's a scientific fact I didn't know and would never have guessed.

After 9/11 all civil aviation in the USA was stopped for three days, AND THE WEATHER CHANGED.The daytime temperature went up by one degree, and the nightime came down by one. (Really, they measured it.)

Environmental scientists established that this temporary effect was caused by the vapour trails being gone. Vapour trails create cloud cover, causing cooling by day and holding in heat by night. After civil aviation resumed things went back to normal.

So my question is, if something as simple as aircraft generated water vapour can effect the climate, how much damage is the engine exhaust doing.

Answer 1

Yes, you are right, I also read the same thing.

When you ask about 'engine exhaust' damage, you mean: car engine, right?

Well, there is a difference. You see, in order to form clouds, the moisture in the air has to go from gas to liquid (droplets), and to do that, water vapour has to give away energy in form of heat. But it has nearly no mass and in order to form a droplet, it has to condensate on something; just anything. So, when the air high up is 'polluted' by the particles from the jet engine combustion, it creates clouds that are called contrails.

But the CO2 released by our cars is only at the surface of the earth and CO2 is heavier than air. Of course, at the end, air mixes, rises in convective low pressures, fronts, etc. But I don't think it works as a jet aircraft engine on the formation of clouds.

By the way, did you know that when burning fossil fuel, an engine releases more CO2 than it burns fuel? That's because the carbon content of the fuel mixes with oxygen of the air and what is released by the exhaust is more than what is burnt as liquid fuel in weight. If I remember correctly, a liter of gas (about 0.7 kg) releases a bit more than 2 kg CO2. :-(

Answer 2

Probably a lot (if global warming is true), but from what you said it would take more pollution to affect the climate then it would water vapor.