Geography Reference
In-Depth Information
A typical monsoon cycle occurs in India. There, from April to June, the weather gets hotter and hotter,
and the air is very dry. Winds blow outward from the land. Then in June or July, the wind reverses direc-
tion and the monsoon bursts. The day when the rain will begin can often be forecast. Then winds begin to
blow from the sea, bringing with them rain.
What's More Likely, Another Ice Age or a Glacial Meltdown?
Geologists are just beginning to scratch the surface of the ice when it comes to understanding long-
range historical climate changes. Deep-drilling research currently going on in Greenland, for instance, will
provide more evidence about the earth's historical temperature changes than any past research has offered
to date. We do know that there have been regular warm periods between the extensive glacial eras or ice
ages. During the colder ice-age periods, glaciers and vast snow sheets extended over large areas of the
earth, changing sea levels and affecting the patterns of ocean and air currents.
Currently, the earth is enjoying a sort of “tropical vacation,” a warm interglacial period. Historically,
these warm periods have lasted about ten thousand years. But our current warm phase is about that old,
and there are researchers who believe conditions are now similar to those of about ninety thousand years
ago when a sudden period of cooling took place. Some climatologists even suggest that there is evidence
of glacial advance during the past thirty years. Of course, the difference between past and present—and
it is a big one—is the human factor. The human impact on the earth's long-term climate is a bit of a coin
toss. Some scientists suggest that the dust and fumes we have been adding to the air since the beginning of
the Industrial Revolution may create a “sun screen” or umbrella, that will reduce the sun's heat, lowering
the earth's temperature and hastening the next ice age.
On the other side—which is probably more crowded—are the scientists who argue that just the opposite
is happening. As human activities throw increasing amounts of certain gases into the atmosphere, a “green-
house” effect is created that will effectively
raise
world temperatures, referred to as
global warming
. A lot
of people don't take the greenhouse effect very seriously. Other skeptics are people who have heard sci-
entists cry “The sky is falling!” one too many times. Maybe the problem is with the name “greenhouse.” It
sounds a little too attractive, too positive. After all, greenhouses are places where flowers and vegetables
grow all the time. That doesn't seem so terrible.
Maybe it should be called the car-with-the-windows-closed-on-a-hot-day-at-the-beach effect. Maybe
then people would take the threat of global warming seriously. After all, not many people have been inside
greenhouses. But a great many more understand what it means to leave the car locked up tight in the sun-
shine on a hot day. Open the car doors and you get a furnacelike blast of superheated air in the face, the
steering wheel is too hot to touch, and the upholstery practically sears your flesh.
Carbon dioxide is what makes seltzer and soda fizzy. Sounds pretty benign. It is also one of the most
important gases in the atmosphere, even though it amounts to a mere .03 percent of it. When the sun's en-
ergy strikes the earth's atmosphere, much of it bounces back into space. But some is absorbed by carbon
dioxide, warming the surface of our globe through what is commonly referred to as a greenhouse effect.
Carbon dioxide and other gases in the atmosphere act like the glass in a greenhouse—or your car win-
dows—letting the sun's rays through but trapping some of the heat that would otherwise be radiated back
into space. Humanity needs a certain level of carbon dioxide to make life possible. The average temperat-
ure of the planet might be 30˚C colder if not for the carbon dioxide factor.
This is not a new idea. In 1896, a Swedish chemist named Svante Arrhenius coined the term “green-
house effect” and predicted that the burning of fossil fuels would increase the amount of carbon dioxide
