Which of the following climate variables is most significant to Earth's temperature?

Question

Please rank in order of significance:

A. Carbon dioxide
B. Clouds
C. Water vapor

I would rank them B, C, A

Bob, I don't think any of the variables can change temerature by its self.

I will offer the following link to support my ranking (page marked 33):

http://www.pr.caltech.edu/periodicals/EandS/articles/LXIX3/fetzer.pdf

I see it this way, greenhouse gases scatter IR (infrared or heat) frequencies, effectively acting like a mirror to part of the energy and allowing part of the energy to pass. This works for IR radiating away from the Earth and for IR coming from the sun. So, greenhouse gases also prevent IR, originating from the sun, from reaching the surface of the planet. Greenhouse gases are virtually transparent to energy in the visible spectrum, nearly all of that energy reaches the surface, if not for clouds, especially low dark clouds. Energy in the visible spectrum heats the surface of the planet and is radiated back towards space in the IR spectrum and greenhouse gases will reflect some of the IR back towards the surface. If an increase in low cloud cover prevents visible energy from reaching the surface, less IR is in the atmosphere and at the surface.

Just an interesting side note, the link I provided was written by a man that got a BS in Physics from Berkeley, same as Dana1981, as well as a PhD in atmospheric science from the University of Colorado.

Answer 1

B
C
A

It's a tricky question because B & C are co-dependant. Water vapor accounts for 95% of the greenhouse process, but a 1% increase in cloud cover can negate all of the the added forcing caused by the 100 ppm increase of CO2 that everyone is up in arms about. A 1% decrease in atmospheric water vapor would have neglible impact on climate forcing.

.
.

Answer 2

The SUN.

Which affects B (cloud formation is enhanced by Cosmic Rays - the intensity of which are affected by the sun's magnetic field) and C (water vapor).

If A actually were driving temperature the way all the GCMs (Global Climate Models) claim it does, there would be a "hot spot" fingerprint in the Troposphere over the Tropics. Of course, no such hotspot exists, so we are pretty sure that Carbon Dioxide is only a minor player, whatever A and C do.

DATA - the preferred Kool-Aid of Global Warming Skeptics everywhere.

Answer 3

I'll answer your question first, but there's a "but".

C. first, then
B., then
A.

The order is scientifically clear, ie it's not a close call.

Now, a slightly different question (but very important) .

Which of the variables is most significant to CHANGES in the Earth's temperature?

A. first then
B. (clouds can warm things or cool them, depending, it's probably close to a wash) then
C.

Water vapor cannot change the temperature by itself because excess water vapor falls out as precipitation very rapidly. In scientific terms its' "residence time" is too short. Details here:

http://environment.newscientist.com/channel/earth/climate-change/dn11652

And that order is equally clear. It's not a close call.

LARRY - You're right. CO2 can only change temperatures by leveraging solar radiation. But solar radiation's been pretty constant (actually decreasing a bit) lately. In any event, your question asked for comparisons between the three, which is all my answer addressed.

Water vapor is actually quite a bit more powerful than clouds. Clouds make a difference of just a few degrees, since they can both block the Sun (just a little), AND hold heat down low. Water vapor warms the Earth by tens of degrees. The greenhouse effect, while invisible, is a really powerful thing, and it only goes one way.

PIP - Thank you.

RAINBOW WARRIOR - Thanks too, but save that energy for more important stuff :-).

Answer 4

B - is hundreds or thousands times more important than the next most important 'gas'.

What everyone overlooks is heat from within our planet:
http://volcano.und.edu/vwdocs/vwlessons/lessons/Earths_layers/Earths_layers4.html
We are sitting on a VERY THIN CRUST! with a 1600 degree mantel just 3-50 miles under us.
Quote:
"The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust."

Answer 5

Agree with Bob and Dana
C
B
A

Climate change
A
B
C

Answer 6

C - Water Vapor

Answer 7

I was going to explain it.. but Bob did a wonderful job.

Answer 8

Temperature:

C
B
A

Climate change:

A
B
C

Answer 9

Bob's on a roll today !!!

You rule Dude !!!

No mercy.