THE THIRD PLANET
Eric R. Swanson – spring 2009
Weather and Climate
“It is hot and sunny again today in San Antonio”, says the weather reporter.
as you know, was the weather report and not the climate report.
Weather is defined as
the state of the atmosphere at a particular place and time.
“It is hot and sunny today
in San Antonio”.
Climate involves a longer period of time and
climate is defined as the
weather conditions over a long period of time
San Antonio, for example, has a
Semi-tropical suggests that San Antonio experiences hot summers
and relatively mild winters, the result of San Antonio being just a little north of the
tropics and far south of the Arctic Circle.
We might also add semi-arid to San Antonio’s
climatic description to describe the amount of precipitation received.
In May of 2006, at the conclusion of graduation ceremonies at Harvard University,
24 students who had just been formally inducted, as they say in those parts, into the
company of educated men and women, were asked the following simple question: What
causes the seasons?
20 out of 23 newly minted Harvard graduates failed to answer the
question correctly, as did a Harvard history professor who was there as the proud parent of
one of the graduating seniors.
Perhaps Harvard can take some consolation in the fact that
the incorrect answers were given eloquently, grammatically correct and with complete
The fact still remains, however, that these “educated men and woman” did not
understand why it was warmer in Cambridge, Massachusetts in the July than it was in
Most of the respondents understood that Earth’s orbit is elliptical, meaning that
Earth’s distance from the Sun varied with the seasons, but they incorrectly concluded that
summer was caused by the Earth being closer to the Sun in July.
While their grasp of the
situation might explain why there is snow in Boston in January, they seemed to have never
wondered why we are able to import fresh grapes from Chili that very same month or why
Australians spend Christmas at the beach.
In other words, their explanation did not explain
why the Southern Hemisphere is having summer while it is winter across the northern half
of the Earth.
As for being farther from the Earth, Earth actually comes 3 million miles
closer to the Sun during winter in the Northern Hemisphere, making winter a little warm but
winter still the same.
Northern Hemisphere winters and summers are slightly milder than
they might otherwise be, but the heat effect of the change in distance from the Sun is too
slight to be the cause for the seasons.
More importantly, it offers no explanation for why the
Northern and Southern Hemispheres don’t experience summer or winter temperatures and
the same time.
Seasons are the delightful result of the Earth’s axis making a 23.5 degree angle to