Cloud cover

Scientists have known for a long time that climate affects rainfall. NASA (the National Aeronautics and Space Administration in the U.S.) has shown that the relationship may work in reverse, however — that the changing rain patterns might, in turn, indirectly affect global warming. Rainfall patterns correspond to cloud cover. Depending on their thickness and shape, clouds can reflect light during the day and hold in surface heat overnight. (See Figure 3-1.) The amount of water vapor in the air has recently increased (which we talk about in Chapter 2), which means more clouds, which means more rainfall. This increase in cloud cover might help explain why nighttime temperatures are rising more than daytime temperatures in global warming trends. It gives a whole new meaning to having a hot night!

Figure 3-1:

Clouds reflect light during the day and hold in surface heat overnight.

Sun's energy passes through most atmospheric gases and water vapor

Sun's energy passes through most atmospheric gases and water vapor

Sun's energy warms the soil surface

Heat energy radiated from soil surface is absorbed by water vapor and other greenhouse gases

Ultimately, however, increased cloud cover seems to be a result, not a cause, of climate change. But, like the increased water vapor, it may further aggravate global warming.

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