An image showing sunlight vs infrared from earth's surface
The top image shows in red, the radiant energy hitting the surface. The bottom image shows in red the infrared energy emitted by the warm surface.
In the Wikipedia image, the yellow is what does not reach the surface. (what happens to it?)
But you can see a lot of infrared does make it through the atmosphere. (what happens to it?) Where you see yellow but no read, the atmosphere has somehow absorbed or reflected the energy, before it reaches sea level. (what happens to it?) Note that water vapor (H2O) is the reason for most of the blocking of infrared reaching sea level. Water vapor keeps the earth cooler, by blocking the infrared from reaching us, down here at sea level. As well as keeping us warm.
Let's look at another view of the situation. From an astronomy site (infrared is used to look at the Universe)
(as always, click to enlarge)
Most of the infrared light coming to us from the Universe is absorbed by water vapor and carbon dioxide in the Earth's atmosphere. Only in a few narrow wavelength ranges, can infrared light make it through (at least partially) to a ground based infrared telescope.
So there you have it, most of the infrared can't reach us from the sun. These same windows (where infrared can freely go) let infrared in and out. The same blocking by greenhouse gases that keeps us warmer (by stopping heat from just radiating away), also protects us from the intense heat from the sun. The window goes both ways.
The Straighter Dope, answering questions nobody has asked.
here is a good NASA image of the water vapor window.
Why even post about this? Oh right, because I just read this.
What’s great about the graph is you can see clearly how the radiation from the sun can be easily discriminated from the radiation from the earth. There’s no complicated deductive work, if you measure radiation below 4μm, you know it came from the sun, no matter how many things it bounced off in the meantime. If you measure radiation above 4μm, you know it’s generated by the terrestrial system. - Science of Doom blog
Here's the graphic from the blog post.
He is saying any radiation (light energy) "above 4μm" comes from the Earth, not the sun, " If you measure radiation above 4μm, you know it’s generated by the terrestrial system", which as we see in our first graphics, is hard to believe. We can see the sun radiates plenty of energy, and that it even reaches the surface.
So what's going on here? That graphics shows no sunlight "above 4μm", but we see in the other graphics plenty of radiation.
Somebody is wrong on the internet. And I don't want it to be me.
So let's look at a few more images. This one is concerned with what wavelengths are blocked by the atmosphere, at least at ground level.
So the "windows" where water vapor doesn't effect infrared is easy to see, but lets look at another astronomy based image, showing the difference altitude makes.
And a Spectroscopy of Rocks and Minerals web page. Note the calculated changes from CO2
We can see the greenhouse effect, and that it is different at altitudes, due to low or no water vapor.
One more image, from a blog that took it from another blog that no longer is to be found.
We see a different view of the solar coming in. Recall that incoming solar looks like this, compared to outgoing earth infrared.
What is going on with these graphics?
