The cycle, whereby more carbon dioxide in the atmosphere reduces the absorptive power of the ocean, thus increasing the amount of carbon dioxide in the atmosphere, is an example of a feedback loop. In general, a feedback loop is a situation in which one condition creates other conditions that reinforce the first.
For example, imagine a student is late and hurrying to get out of the house, so he accidentally drops his keys in the toilet. Panicked, he stumbles and hits the handle, flushing the keys away. Even more panicked, he races around looking for the spare keys, trips, and twists his ankle. More panicked than ever, he stumbles about . . . and so forth. The fact of being late creates other conditions (loss of keys) that make the student fall even further behind.
Scientists believe that numerous feedback loops exist that may result from the interaction of global warming and water.
One of the most powerful involves water vapor. Water vapor is the gaseous form of water. It is also what physicist John Cook calls "the most dominant greenhouse gas."7 Water vapor is a significant component of the atmosphere, and it is much more effective at trapping the sun's rays than is carbon dioxide. Whereas carbon dioxide levels can rise more or less indefinitely, however, there is a limit to how much water vapor the atmosphere can hold before releasing it through precipitation.
Nonetheless, water vapor can have a significant effect on climate change. As temperatures go up, more water evaporates from the surface of the ocean. That means more water vapor is in the atmosphere, which traps more of the sun's rays, and thus increases global warming. This is, then, a classic feedback loop: Warming produces water vapor, which adds to the warming.
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