# Global Warming/Earth Size

If one considers that all materials have some thermal cefficient of expansion, will the earth expand significantly as a result?

For example the cefficient of linear expansion of iron is 12.1 x 10^6 for 1 degree centigrade. I’ve heard reports of up to 5 degrees increase in global temperature over the next century. If the diameter of the earth is 1.2756 x 10^7 meters,and the coefficient for iron is similar the the average coefficient of total earth (WAG), then a 5 degree increase will result in a diameter increase of 771 meters or and increase in circumference of 2.4 kilometers or 1.5 miles.

1. Will the GPS have to be reprogrammed ?

2. Could this cause stresses under the surface of the earth resulting in earthquakes?

The 5 degree increase is an increase in air temperature. It does not apply to the Earth as a whole. The amount of heat involved is not remotely enough to increase the temperature of the planet to any significant degree.

The oceans are warming, however, and their themal expansion, along with the melting of ice caps and glaciers, is contributing to rising sea levels.

If the temperature of the air envelope increases doesn’t that result in a temperature increase of an interior object. I mean the forced air heating in my home warms up ther toilet seat.

Sure, but the amount of heat exchanged depends on the relative masses of the two objects involved. The mass of the atmosphere is trivial compared to the mass of the Earth as a whole.

If you heat a ball bearing red-hot and put it on a marble slab, the marble slab isn’t going to heat up significantly. Although heat will be transferred to the slab, the ball bearing doesn’t contain enough to make a difference.

I got news for you, we have had global warming since the end of the last ice age.

And it was not caused by hair spray, or freon, or cars, etc. either.

The temperature difference wouldn’t penetrate more than a few meters (tens? hundreds? probably not thousands. . .) into the crust because, as Colibri says, it would take a termendous amount of heat to significantly change the temperature of more than just the skin of the planet.

Another thing to think about is that the coefficient of thermal expansion you looked up there is probably for solid iron at standard pressures. The conditions on the Earth’s interior are quite different. You’re in an entirely different part of the phase diagram. (Sorry, don’t know the details.)

The consensus of the world’s climate scientists is that the current warming is much faster than can be accounted by natural climate cycles, and is caused at least in part by human activities. This has been acknowledged even by George W. Bush.

I suggest you do some searches and some reading on the subject before making further statements.

Your trusting Bush’s knowledge of geography and climates? What is this world coming to?

Regardless, you are correct. The Earth is warming naturally, however the use of CFCs and increased CO2 in the air has sped the heating process to a point where it is quickly becoming a problem.

I understand that, but aren’t we talking about a matter of time here. Heat is absorbed by the earth from the atmosphere, but the atmosphere’s heat energy is continually replenished by the sun. My understanding of green house gases is that they limit the reflectivity of electromagnetic energy from the sun, hence the earth must be absorbing more energy. The only way I can underdstand the earth not heating up and observing the “conservation of energy” principle is if heat energy is being converted to some other form of energy.

My mention of Bush, of course, is because he can hardly be described as a rabid environmentalist and has previously expressed skepticism about global warming. But the evidence is now so strong - as documented by Bush’s own committee of climate scientists - that even he doesn’t deny its reality.

To some extent. Some heat is being transmitted from the atmosphere to the Earth’s surface, as evidenced by the increased melting of permafrost in polar regions. And some is being transmitted to the oceans, although because of the ocean’s large mass and the high heat capacity of water the temperature lags well behing that of the atmosphere.

But the most important thing you are ignoring is that the Earth’s temperature increases with depth due to pressure. The Earth’s average surface temperature is about 15﻿° C. The base of the lithosphere, at 120 km depth, is at about 1000﻿° C, for a temperature gradient of about 8﻿° C in this area. (The core is at more than 4000﻿° C.) Since heat won’t flow from an area of lower temperature to a higher one, an increase of 2.7﻿° C (= the 5﻿° F increase you cite in the OP) won’t affect more than about the top 300 m of the Earth even given infinite time.

The effects are complex. Greenhouse gasses trap solar radiation in the atmosphere, and prevent it from being re-radiate. However, increased temperatures cause increased evaporation from the ocean surface, resulting in increased cloud cover, which in turn reflects some of the incoming solar radiation. This negative feedback loop somewhat ameliorates the effect of increased greenhouse gasses, and makes outcome difficult to model.

Thankyou Colibri, I shouldn’t have concerned myself with looking at effects below the mantle, but now I have an even greater concern. Since the radius of the earth isn’t appreciably affected by global warming, the surface will be, will it not? And the total increase in length due to thermal expansion for a great circle, should remain as I first postulated, should it not? I see earth quakes and mountain building here.

No. Your calculations are based on the coefficient of expansion of iron. (And note that you use the coefficient of expansion expressed in ﻿C﻿°, while the 5﻿° increase you cite is F﻿°) Most of the lithosphere is not iron, but silicates, oxides, carbonates, and other minerals, and will have a quite different (I suspect lower) coefficient of expansion. Bear in mind also that the lithosphere is not homogenous. Much of it is porous to some degree, so you would have to calculate the thermal expansion of the rock strata as a whole, rather than that of the individual minerals as if they composed a solid mass.

The overall effect will be difficult to calculate; for a mere 2.7﻿° rise in temperature, I suspect it is also trivial.

Just to elaborate a little more, expansion coefficients for many materials tend to be around 10 x 10[sup]-6[/sup]. This is going to amount to about 1 cm per km. This could perhaps cause stress problems if the material is homogeneous, non-porous, and rigid. But I suspect that many formations strata near the surface have sufficient ‘give’ or compressibility in them so that excessive stress will not build up.