Thread: If Earth Lost its Atmosphere, No Temperature Change?

What would happen to the surface temperature of the Earth if Earth had the Moon's lack of an atmosphere? My initial knee-jerk response was as follows:
the Earth would have drastic temperature swings like the Moon.

According to the Artemis Project data, the moon and earth's temperatures compare as follows:

Minimum surface temperature of Earth: -89 degrees C.
Maximum surface temperature of Earth: 58 degrees C.
Temperature spread of Earth: 147 degrees C.

Minimum surface temperature of the Moon: -147 degrees C.
Maximum surface temperature of the Moon: 100 degrees C.
Temperature spread of the Moon: 247 degrees C.

As you can see, the Moon has a much greater spread between high and low temperatures. The ratio of the Earth's temperature spread to the Moon's is .595, rounded off to .60.

But then it occurred to me that the Earth's surface area is mostly water and the Moon's surface area is mostly basalt. Question: How much does the presence of water verses basalt affect the surface temperature of the Earth?

Time to do some math:

Water has a specific heat capacity of 4.1813 J/g*deg. C and its mass is 18 g per mole. Basalt's specific heat capacity is .84 J/g*deg. C and its mass is 54 grams per mole.

Q = cm(T)

c is the specific heat coefficient, m is mass, T is the change in temperature, Q is the amount of energy needed to affect the temperature change.

Assuming that the Earth and Moon receive about the same amount of solar energy, it makes sense to use the same value for Q when comparing basalt and water.

Water: 100J = (4.1813)(18g)( T)
T(water) = 1.33 deg. C.

Basalt: 100J = (.84)(54g)(T)
T(basalt) = 2.2 deg. C.

Conversely, if the water and basalt were allowed to cool, and lost 100 J, their temperatures would decrease -1.33 deg. C and -2.2 deg., respectively.

Now, what do you suppose happens when I divide 1.32 deg. C by 2.2 deg. C?
I get .60--the same ratio as the Earth/Moon temperature spreads. Now that's interesting!

When solar energy is added or removed, water increases and decreases nearly the same rate as the Earth, and basalt's temperature increases and decreases at nearly the same rate as the Moon.

The implication here is that if the Earth lost its atmosphere, its surface temperature would not change much. It appears to be the oceans, not the atmosphere which have the greatest impact on the Earth's surface temperatures.

Your thoughts?

If the Earth lost its atmosphere the pressure at the surface of the oceans would be zero. If the temperature didn't change, say 15 C, the vapor pressure of water is around 0.02 bar. The oceans would evaporate. As they did so the latent heat would cool the oceans until they froze for some depth. The planet would be cold.

Thanks for your reply. I don't don't presume to know what would really happen if the earth lost its atmosphere. I have never conducted that experiment. What I find interesting, however, is the correlation between the temperature changes when comparing water/basalt, Earth/Moon temperature changes.

Let's assume Earth keeps its atmosphere. The oceans appear to impact temperature change more than the atmosphere according to the math. The atmosphere's influence or value, if I understand you correctly, is that it holds the oceans in place. The bottom line then is if the oceans remain in place, Earth's temperatures won't change much. Feel free to post your math or empriracal data that contradicts this claim.

I also find the theory that the earth would be cold if the oceans evaporated interesting. Water vapor is a greenhouse gas, and you would think it would warm the planet. What you seem to be suggesting is that water vapor won't warm the planet or keep temperatures stable. If that is true, then it would be foolhardy to assume that greenhouse gases must necessarily warm the planet.

If the temperatures did cool, I would imagine that the vapor would condense and warm the planet. On the one hand you have less pressure due to a lack of atmosphere, but on the other you have the high specific heat capacity of water vapor. Additionally, more solar energy would make it to the surface initially if the atmosphere was removed. That should have a warming effect countering the cooling effect.

But again, I welcome your math and emprical data.

Where I am, the ocean changes just a few degrees seasonally. Because my climate rolls over that ocean, summer high does not require air-conditioning, and winter low some years can't even stop roses from blooming.

There is also an organic blanket effect, on the ground. Go a few feet down, we find constant temperature. This is where tree roots are, plus layers of moldering sodden soil and deadwood. In winter it just doesn't freeze. Most of Canada's west coast is covered in that, and under canopy.

I also find the theory that the earth would be cold if the oceans evaporated interesting. Water vapor is a greenhouse gas, and you would think it would warm the planet. What you seem to be suggesting is that water vapor won't warm the planet or keep temperatures stable. If that is true, then it would be foolhardy to assume that greenhouse gases must necessarily warm the planet.

Your scenario had no atmosphere. Hence, playing your totally unrealisitc game, the water vapor goes off to wherever the rest of the atmosphere went, to maintain the no atmopshere scenario.

For thought experiments to have any value they must have some grounding in reality.

Originally Posted by Bunbury

I also find the theory that the earth would be cold if the oceans evaporated interesting. Water vapor is a greenhouse gas, and you would think it would warm the planet. What you seem to be suggesting is that water vapor won't warm the planet or keep temperatures stable. If that is true, then it would be foolhardy to assume that greenhouse gases must necessarily warm the planet.

Your scenario had no atmosphere. Hence, playing your totally unrealisitc game, the water vapor goes off to wherever the rest of the atmosphere went, to maintain the no atmopshere scenario.

For thought experiments to have any value they must have some grounding in reality.

Well Einstein suggested that reality is relative. LOL! For that reason, I can appreaciate your relative point of view. However, in my reality, additional solar radiation and water's high specific heat capacity would offset your cooling reality. Further, when Einstein did his thought experiments, he wasn't a dull boy. He had fun! "What would happen if you traveled the speed of light?" How real is that assumption? Or how about M theory? Or the greenhouse gas theory? How real are those? LOL! Again I welcome your math or emprirical data. Crunch some numbers for me, please? Common, I did it for you.

Originally Posted by Pong

Where I am, the ocean changes just a few degrees seasonally. Because my climate rolls over that ocean, summer high does not require air-conditioning, and winter low some years can't even stop roses from blooming.

There is also an organic blanket effect, on the ground. Go a few feet down, we find constant temperature. This is where tree roots are, plus layers of moldering sodden soil and deadwood. In winter it just doesn't freeze. Most of Canada's west coast is covered in that, and under canopy.

Thanks for that empirical data. Yep, my math confirms your observations. Water is king. The .0384% of CO2 in the atmosphere just is not enough to make my boots shake.