Geoscience Reference
In-Depth Information
“greenhouse effect,” and the gases responsible for it are thus termed “greenhouse gases.” The
greenhouse effect is hardly controversial. Indeed, without a natural greenhouse effect, Earth would be
a frozen planet lacking life as we know it. By increasing the concentrations of these gases in the
atmosphere, it was only logical that we should be further warming Earth's surface.
Figure 2.2: The Atmospheric Greenhouse Effect
Earth is warmed by the incoming radiation from the Sun, and its temperature can stabilize only by producing its own invisible outgoing
(infrared) radiation. The greenhouse effect involves the absorption of some of that outgoing radiation by greenhouse gases in our
atmosphere. The greenhouse effect warms the surface by sending some of this radiation back toward Earth rather than allowing it to
escape to space.
(3) Indeed, as mentioned earlier, thermometer measurements told us that by the mid-1990s Earth
had already warmed a little more than a degree Fahrenheit (roughly 0.6°C) since the dawn of
industrialization. The globe was in fact warming. This observation alone may not seem that decisive;
after all, the warming might have been at least partly natural in origin. However, the observation did
not exist in isolation. There was now evidence as to the probable cause.
(4) By the mid-1990s, it was possible to investigate the causal mechanisms behind changes in
Earth's climate using relatively sophisticated mathematical models of Earth's climate. These models
solved the same complex equations of atmospheric physics that numerical weather prediction models
did. But they also took into account components of the climate system other than the atmosphere,
including the oceans, the continental ice sheets, and even life on Earth (collectively known as the
“biosphere”), and they attempted to account for the physical, chemical, and biological interactions
