Athmosphere question

General Questions
#1

Ok… Let me see if I can explain my question all in one post and not have to clarify it later:

The Earth is covered with air. This air is either warm or cold depending on where it is, although if you were to take all the air and mix it together, you’d eventually get one average temperature.

Because there were times when large sections of the Earth were frozen solid, and I’m assuming that at the same time the warm regions didn’t jump up thirty degrees, I am guessing that the Earth’s average temperature can change.

Remembering grade school experiments done with a balloon and a radiator, not to mention checking the air pressure in my tires before and after driving 20 miles, I feel safe to say that warm air expands and cold air contracts.

Sooooo…

How much does the athmosphere on the planet contract or expand? I remember creationists saying that if the athmosphere was -nth bits thicker or thinner it would not protect us from the sun (or else block out too much of the sun as the case may be) and this number is usually something like 1/10th to 1/4 of an inch. Granted, they might be full of BS, but that’s not the issue. The question is, does the athmosphere expand like that? And once the temperature has risen or dropped in a global level (naturally, not via ozone depleteing what’s-its) what was changing it back anyway? I can buy the “meteor hits earth, dust blocks sun, Earth cools” theory once, but hasn’t the Earth had many an Ice Age? Is there an average temp the Earth just tries to maintain, meteors be damned?

“I guess one person can make a difference, although most of the time they probably shouldn’t.”

#2

Wasn’t Athmos the fifth musketeer? (sorry)

#3

Hmm… I did spell that wrong didn’t I?
A-T-M-O-S-P-H-E-R-E

Ok… I feel atoned…

“I guess one person can make a difference, although most of the time they probably shouldn’t.”

#4

Must be all those situps.

#5

ok. this is me totally guessing

the upper reaches of the atmosphere is cold, that’s a given. thinner air/atmosphere, the less it’s able to hold heat.

the lower reaches of the atmosphere has fatter (ok i know that doesn’t work…maybe thicker?) air, which is able to hold air. during the day the sun heats the air, and in varying degrees depending on where the air is (over water, on a mountain, etc). the warmer air expands, and creates wind where the warmer (and expanded) air rushes in to fill the voids left by shrinking colder air.

maybe it’s right, maybe not. but that’s how i explain it in my head

#6

Dear me, yes, the atmosphere changes its effective thickness by many miles at a time, daily. It’s also quite a bit expanded at the equator relative to the pole for the reason you cite (it’s warmer). Sometimes satellites get dragged down earlier if the Sun is acting up and the atmosphere expands more than expected. Remember Skylab?

No one knows what causes an Ice Age. Whatever your favorite theory is, it’s hard to test, hmmm? Part of the problem is that it is clear there are feedback cycles, complicated ones, but no one is fully sure what they do. For example, when the Earth gets warmer, as it is doing, the cloud cover increases (because more water evaporates from the oceans). But the extra clouds reflect more sunlight, which tends to bring the temp back down.

And let’s not forget the effect of living things. Trees produce CO_2, and the greenhouse effect from this and other gases keeps the average temp of the Earth about 20 degrees higher than it should be at this distance from the Sun. So the response of the biosphere to changes in Solar radiation, concentraton of greenhouse gases, etc., is very important. And, of course, largely unknown.

#7

I thought trees produce oxygen.

“It is lucky for rulers that men do not think.” — Adolf Hitler

#8

Libertarian: Trees do make CO2, it’s the animal life that makes CO2 (and methane, etc).

#9

Aiyaaa! Slams head against desk

I meant: trees do make oxygen.

#10

You’re both right.

The process of photosynthesis uses CO2 and releases oxygen as a by-product.

However, trees (and other plants) don’t do this out of the goodness of their hearts. They do it to store energy (among other reasons). When they USE that energy, they consume oxygen and release CO2, just like animals do all the time.

The net daily effect is that they produce more oxygen than they use, but it’s not a one-way street.

Also, when trees decay (or are eaten, or burn, or…) some of that CO2 goes back into the atmosphere.

But we digress: Yes, the atmosphere expands and contracts with temperature by a considerable amount. The “1/4 inch” stuff sounds like complete BS to me, even if you assume they mean average thickness.

#11

I’m gonna agree with torq that it is ludicrous to measure anything about the atmosphere in inches. Of course, it’s done all the time, as alluded to in the OP. Another example is a college professor I had who insisted that the ozone layers was three millimeters thick (it’s actually about 60 kilometers thick, IIRC, but what’s a half dozen orders of magnitude between friends?).

And cgrayce is right that there are a huge number of feedback cycles regulating global temperature. An example of one cycle which might (help to) create an ice age is this:
Let’s say a bunch of trees die off, say because a bunch of ungulates have eaten all there leaves. Then the methane-belching ungulates die because they have no leaves left to eat. This means there is less of a greenhouse gas, which causes the earth to cool slightly. This means trees living at the low-temperature end of their tolerance will die, reducing the amount of trees left for our remaining hungry leaf-eaters. They die too, and the cycle starts anew.

This cycle is of course counterbalanced by a kazillion other feedback cycles, some positive, some negative. So it’s a necessarily simplistic answer. It’s just intended to show that while atmospheric conditions affect life forms, life forms affect atmospheric conditions. I speculate idly that some form of evolution created new species, which exerted new biogeochemical pressures, which created the Ice Age.

#12

In fact, both three millimeters and 60 km are right. The ozone is spread out through a 60 km layer of the atmosphere, but in very low concentration. If it was collected into a pure layer at sea-level pressure, its thickness would be about three mm.

First up on a Google search:
http://www.gcrio.org/CONSEQUENCES/summer95/impacts.html

Bob the Random Expert
“If we don’t have the answer, we’ll make one up.”