The Runaway Greenhouse Effect and Ice Ages

Some planets behave like they have some sort of geological bipolar disorder.  If you look at long-term climate changes and the potential of a runaway greenhouse effect, you may see what I mean.  If a planet like Earth were to heat up in some random, isolated incident, more evaporation would occur, the atmosphere would expand, and since water is a greenhouse gas, the planet would heat up, more evaporation would occur, and since water is a greenhouse gas, the planet would heat up, more evaporation would occur…you get the point.  Eventually most water in the atmosphere would achieve escape velocity and leave us.  This is referred to as the runaway greenhouse effect.  There is very little chance this would occur on Earth any time soon because we have our own negative feedback system in the carbon dioxide cycle.  However, Earth does experience its own significant climate swings.

In case you didn’t know, Ice Age isn’t just a fantastic movie.  Since the CO2 cycle works very slowly, a decrease in volcanic activity can lead to less CO2 in the atmosphere and less of a greenhouse effect.  When you combine this effect with changes in Earth’s axial tilt, you just might end up with a period of pretty cold temperatures.  If these temperatures were cold enough to cause oceanic freezing, you might end up with an Earth similar to the image above.  The resulting increase in reflectivity would have further reduced Earth’s temperature through reducing the amount of visible light absorbed by the Earth’s surface.  Evidence suggests that this actually happened around 750 million years ago.

So why didn’t Earth continue to experience decreasing temperatures, a sort of negative runaway effect?  Luckily, this snowball effect was only skin-deep, and Earth’s interior never cooled off, so there was all this CO2 inside the Earth ready to be released.  Once there was a sufficient increase in volcanic activity, the greenhouse effect became stronger and stronger until the Earth’s surface melted.  Earth’s temperature began to increase drastically with the resulting decrease in its surface’s reflectivity, leading to an Earth that was even hotter than it is today.  Hot to cold, cold to hot?  Geological bipolar disorder.

I had a good laugh at this person below…


One response to “The Runaway Greenhouse Effect and Ice Ages

  1. Your perspective about the greenhouse effect on Earth causing it to be bipolar is really interesting. You definitely did a better job explaining it than the girl in that video, and what you said made a lot of sense. The cycle of Earth going from cold in ice ages to warm in between is an interesting thing, and the fact that we haven’t been totally frozen yet is all due to the greenhouse effect, so that’s an interesting application of the topic.

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