This video segment continues our examination of climate forcing factors.
Here we focus on internal forcing factors: processes on Earth that influence climate.
The major points of the segment are number one, certain internal forcing factors, progeny,
epeirogeny and volcanism depends on tectonic movements of Earth's crust.
Number two, albedo, the percentage of solar energy reflected varies widely on different
natural materials.
Number three, Earth exchanges energy with its surroundings in the form of electromagnetic
radiation.
Number four, electromagnetic radiation can be characterized by its wavelength.
Five, One-half of the electromagnetic radiation from the Sun has wavelengths in the visible
spectrum.
Six, Greenhouse gases in the Earth's atmosphere are transparent to visible light, but absorb
in the infrared.
Internal forcing factors include orogeny, epeirogeny, volcanism, albedo and atmospheric
composition.
Often these factors operate in conjunction with one another.
For example, volcanic activity may affect both Earth's albedo and atmospheric composition.
The following introduces each type of internal forcing factor and evaluates their current
influence.
Orogeny, Greek for mountain building, is a process in which tectonic movements of Earth's
crust or volcanic activities from mountains.
Mountains particularly with a north-south orientation, for example, the Sierra Nevada,
Rocky Mountains, Appalachian Mountains, Andes, and Euros disrupt global atmospheric circulation
patterns, that generally move east-west because of Earth's rotation.
Uplifting of mountains also moves and exposes rock that undergoes chemical weathering and
absorbs carbon dioxide.
Moreover, higher elevations accumulate ice and snow that increases Earth's albedo, the
reflections of solar energy.
For these reasons times of relatively rapid mountain building, say 40 million years ago
when the Himalayas and Sierra Nevadas first arose are usually cooler periods.
Epeirogeny is the formation of continents and ocean basins through tectonic deprivations
of earth's crust.
As discussed previously, global distributions of land masses determines the amplitude of
glacial/interglacial cycles, and at the extreme may foster a snowball earth.
In addition, mid ocean ridges where most of the new clay material is produced release
large amounts of energy and greenhouse gasses.
Moreover, sea levels rise and fall as new plate materials modify the shape of ocean
basins.
Orogeny and epeirogeny proceed slowly over many millions of years.
In contrast, volcanism can have an explosive effect on climate.
For example, when Mt.
Pinatubo in the Philippines erupted in June of 1991 after 460 years of inactivity, it
spewed vast amounts of sulfur dioxide and fine particles into the upper atmosphere.
These materials quickly spread over most of the world and formed a haze of aerosols in
the stratosphere that reflected enough sunlight to lower global temperatures by as much as
a half a degree Celsius for nearly two years.
Volcanic eruptions as large as Pinatubo, occur only every century or so.
But the smaller, yet significant eruptions, such as Mount Saint Helens and El Chichon
occur every decade.
All of these eruptions release carbon dioxide a greenhouse gas that contributes to global
warming, as well as sulfur dioxide and fine particles that reflect some light and contribute
to global cooling.
The amount of CO2 released from volcanoes however averages about 10,000 fold less than
from the burning of fossil fuels.
Therefore on balance volcanic eruptions cool rather than warm the planet.