The results of Foote’s simple experiments were confirmed through hundreds of tests by scientists in the US and Europe. It happened more than a century ago.
If carbon dioxide (CO2) simply absorbed energy, including sunlight, without re-emitting it, it could lead to cooling at the Earth’s surface. This is because the absorbed energy would not be radiated back to the surface, resulting in a net loss of energy from the Earth-atmosphere system.
Hmm, I don’t follow the argument. If the CO2 and other atmospheric molecules were unable to re-emit the light, they would need to dissipate the excess energy via non-radiative processes. So the main transfer of energy to the surroundings would be via collisions with other molecules. The density of molecules is greater as you approach the surface, and the density in space is very very low. So there are many more molecules to collide with that move the energy in the direction of the surface, and there is no easy pathway to get the heat out of the earth, other than hot molecules diffusing into space.
So, unless there is an important hole in my reasoning, removing the radiative pathway would ultimately result in a hotter earth because a larger percentage of the energy of light is trapped.
I think that the main problem in your comment is that it does not account for what happens to the energy that is absorbed. This energy does not disappear - you need to account for it.
However, the greenhouse effect is supposed to work by absorbing outgoing infrared, not sunlight which the experiment measured. The absorption of sunlight is not much compared to the absorption of outgoing infrared. Therefore I still believe the experiment is irrelevant to the greenhouse effect, while the part of my comment you quoted might be wrong.
The experiment showed that the CO2 gas was an efficient absorber of some form of radiant energy that came from the sun. We now know that this energy is infrared radiation. This radiation is emitted by hot bodies, and the sun emits a lot of it.
But yes, you are correct in that her experiment was not about the greenhouse effect itself - which includes more complicated interactions such as the reflection and emission of IR from the earth’s surface. But, still, the absorption of IR by CO2 is a very important component. And her observations - using the sun as the source of the infrared - is also a very relevant observation. This is because:
Infrared light can carry heat energy from one hot body to another
A large amount of the heat transfer from the sun to the earth comes in the form of infrared light
CO2, which is present in the atmosphere in a significant amount, is a strong absorber of infrared light
So I don’t think her work is irrelevant. It is very relevant. But I do think that the title “Scientists understood physics of climate change” is stretched because this experiment by itself is not enough to describe all of the complexity of the green house effect and climate change.
Hmm, I don’t follow the argument. If the CO2 and other atmospheric molecules were unable to re-emit the light, they would need to dissipate the excess energy via non-radiative processes. So the main transfer of energy to the surroundings would be via collisions with other molecules. The density of molecules is greater as you approach the surface, and the density in space is very very low. So there are many more molecules to collide with that move the energy in the direction of the surface, and there is no easy pathway to get the heat out of the earth, other than hot molecules diffusing into space.
So, unless there is an important hole in my reasoning, removing the radiative pathway would ultimately result in a hotter earth because a larger percentage of the energy of light is trapped.
I think that the main problem in your comment is that it does not account for what happens to the energy that is absorbed. This energy does not disappear - you need to account for it.
Thanks for the criticism.
However, the greenhouse effect is supposed to work by absorbing outgoing infrared, not sunlight which the experiment measured. The absorption of sunlight is not much compared to the absorption of outgoing infrared. Therefore I still believe the experiment is irrelevant to the greenhouse effect, while the part of my comment you quoted might be wrong.
Ah, I see what you mean.
The experiment showed that the CO2 gas was an efficient absorber of some form of radiant energy that came from the sun. We now know that this energy is infrared radiation. This radiation is emitted by hot bodies, and the sun emits a lot of it.
But yes, you are correct in that her experiment was not about the greenhouse effect itself - which includes more complicated interactions such as the reflection and emission of IR from the earth’s surface. But, still, the absorption of IR by CO2 is a very important component. And her observations - using the sun as the source of the infrared - is also a very relevant observation. This is because:
So I don’t think her work is irrelevant. It is very relevant. But I do think that the title “Scientists understood physics of climate change” is stretched because this experiment by itself is not enough to describe all of the complexity of the green house effect and climate change.