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In the end of glacial periods there seems to be an increasing release of carbon dioxide as the global warming increase and at the end of these global warming periods the content of carbon dioxide in the lower atmosphere seems to decrease in correlation to the temperature. Except from the obvious that carbon dioxide is more soluble in cold water and perhaps that some carbon dioxide is trapped in glacial ices, which are the known mechanisms?

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  • $\begingroup$ What are you really asking here? You appear to admit that carbon dioxide is a greenhouse gas by your use of the words "except from the obvious". Are you asking about the mechanisms that make polyatomic molecular gases such as water vapor, carbon dioxide, methane greenhouse gases while diatomic molecular gases and monoatomic gases are not? If that's the case, ask that directly. The body of your question asks something very different. $\endgroup$ – David Hammen May 4 at 17:33
  • $\begingroup$ @DavidHammen: I'm trying to understand what's is happening to the world in our time. I want to know what is secure about the correlation. $\endgroup$ – Lehs May 4 at 17:37
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Except from the obvious that carbon dioxide is more soluble in cold water and perhaps that some carbon dioxide is trapped in glacial ices, which are the known mechanisms?

Those obvious mechanisms, particularly the first, are the primary mechanisms. Atmosphere carbon dioxide content gradually drops to very low levels during a glaciation precisely because cold water can dissolve much more carbon dioxide than can warm water.

When the Milankovitch cycles reaches a stage where the Earth starts warming up at the end of a glaciation, the Earth's waters start warming up, too. The warmer waters cannot hold as much CO2 as they held during the glaciation. The CO2 comes out of solution, adding to the Milankovitch-driven warming. This is one of the key reasons why the exit from a glaciation is much more abrupt than is the entry into one.


Based on comments by the OP, the OP appears to doubt that carbon dioxide and other polyatomic gases are greenhouse gases. The three principal components of the dry atmosphere, nitrogen (N2), oxygen (O2), and argon, are not greenhouse gases. Electronically neutral monatomic gases and diatomic gases comprising two atoms the same substance have zero dipole moment. These gases have essential zero cross section to low energy (e.g., thermal infrared) photons.

On the other hand, polyatomic molecules have many more degrees of freedom than do the homogeneous diatomic molecules and monoatomic gases that comprise the bulk of our atmosphere. Some such as water vapor have a marked permanent dipole moment. Others such as carbon dioxide nominally have a zero dipole moment, but transients due to thermal vibrations can temporarily given them a non-zero dipole moment. The combination of increased degrees of freedom and a non-zero dipole moment make these polyatomic gases very good at absorbing some parts of the thermal infrared spectrum.

All other things being equal, adding greenhouse gases to the Earth's atmosphere increases the Earth's equilibrium temperature. It's important to note that this greenhouse effect is essential for life. Without it, the Earth would be a frozen icefall, from pole to pole. In fact, during the Cryogenian (850-635 million years ago) the Earth apparently was covered or nearly covered with ice from pole to pole.

The end of a glaciation adds significant portions of the two most important greenhouse gases to the Earth's atmosphere. Water vapor increases because a warmer atmosphere can hold more water vapor than can a cold one. Carbon dioxide increases because a warmer ocean can hold less carbon dioxide than can a cold one.

While the OP asked about the end of a glaciation, the real question being asked was about what is happening now. What happened at the end of glaciations and what is happening now are one and the same thing. Adding greenhouse gases to the Earth's atmosphere increases the Earth's equilibrium temperature. The end of a glaciation added greenhouse gases to the Earth's atmosphere, making the subsequent warming very rapid. Humanity is adding greenhouse gases to the atmosphere, carbon dioxide in particular, resulting in an even more rapid warming than that that occurred at the end of a glaciation.

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  • $\begingroup$ How to explain the abnorm global warming since 1970 (0,8 degree Celsius)? There is a hypothesizes of Green house effect, do you deny that totally? $\endgroup$ – Lehs May 4 at 17:00
  • $\begingroup$ @Lehs - Of course not. I answered the question you raised in the body of your opening post where you specifically asked about what happens at the end of a glaciation. The question in the title is a bit orthogonal to the body, and is rather broad. Overly broad questions are not a good match for stackexchange network sites; broad questions are typically closed as such. The body of your opening post asks a good specific question, so that is what I answered. $\endgroup$ – David Hammen May 4 at 17:07
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    $\begingroup$ At this point it is completely unclear to me what you are asking, @Lehs. See the comment I left under your question. $\endgroup$ – David Hammen May 4 at 17:36
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    $\begingroup$ @Lehs - Re your penultimate comment, "The fact that the oceans absorb CO2 from the atmosphere now also weakens your answer". No, it does not. By way of analogy, water temperature does not have to get to boiling for water to evaporate. Even ice evaporates (but that's called sublimation). It's all about equilibrium. If air isn't saturated in water vapor, water vapor has a tendency to evaporate. And if the oceans aren't saturated in CO2, the oceans have a tendency to absorb CO2. That tendency increases if the amount of CO2 in the atmosphere suddenly increases -- like it has in the last century. $\endgroup$ – David Hammen May 5 at 23:11
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    $\begingroup$ @Lehs - Re your last comment, "I'm especially interested in why CO2 decreases rapidly as some as the global temperature starts to decrease". Look at the graph you yourself posted. The temperature decrease and CO2 decrease are rather gradual when a glaciation starts. On the other hand, the temperature increase and CO2 increase are nearly discontinuous when a glaciation ends, at least on the time scale used in that graph. That near discontinuity at the end of a glaciation is the more challenging of the two issues for climatologists. $\endgroup$ – David Hammen May 5 at 23:15

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