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This section describes the albedo effect, and the effect of natural
aerosols, and greenhouse gases.
Albedo | Aerosols:
Volcanoes | Greenhouse Gases
Albedo: Ice, Water, Land, and Plant Surfaces
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| Ice and clean show surfaces have
high albedos Figure 1. Sea Ice in Lancaster Sound in the Canadian
Arctic. |
Ice and clean show surfaces have high albedos Sea Ice in Lancaster
Sound - Canadian Arctic.
Solar energy is reflected from the earth back into the atmosphere.
Differences in surface characteristics of the planet affect the
amount of radiation reflected from Earth's surface back through
the atmosphere into space. This reflectivity is called albedo.
If there is a high albedo, there is high reflectivity of light
and only a small amount is absorbed, therefore there is less energy
available for conversion to heat.
Light, shiny and smooth surfaces have a higher albedo than dark,
dull and rough surfaces. For example, snow covered fields reflect
more light (absorb less) than a deciduous forest.
Ice and clean show surfaces have high albedos as most solar radiation
(light and heat) is reflected. The greater the area covered by
continental ice sheets the cooler the planet.
Oceans, and plants have low albedo and absorb most of radiation
striking them. Increases in areas of ocean and vegetation cause
a decrease in planetary albedo and a warmer Earth. Land use changes,
such as ploughing the soil, asphalt paving and removing tree canopy,
change the Earth's albedo.
Albedo is the proportion of the Sun's energy reflected by a surface.
Here are the albedo values for:
Snow = 0.9 Bare land = 0.3 Sea water = 0.1
ACTIVITY 1:
- Design an experiment to determine the albedo
effect ie solar energy is absorbed by differnent surfaces. Choose
materials such as different paving materials or house paints,
different coloured automobiles or roofing materials as well as
lawns, gardens, snow and ice when appropriate!!
- Calculate the savings in air conditioning
for a manufactured material above with a higher albedo. Compare
equal areas after temperature measurements for any calculations.
Research: odd thoughts!
- Check out the science of coloured filters
used in lighting stage productions and also how the stage lighting
equipment is designed to handle excessive heat.
- What connection do volcanoes have with the
earth's temperature? Why?
AEROSOLS: Volcanoes
Aerosols generally cause a cooling effect.
Volcanoes complicate the climate. The world map above is after
the explosion of Mount Pinatubo in the Phillipines. In June 1991
the ERS-1 satellite charted the spread of airborne dust. The data
for October 1992 shows the dust at its most widespread.
Greenhouse Gases (Global Warming
Potential)
Plate tectonics is a slow process. It influences the atmospheric
greenhouse effect. Over the last 300 million years, back to the
last known Great Ice Age (the Gondwanaland) the continental plates
have moved greatly. Temperatures dropped because of the changes
in the natural production rate of carbon dioxide (CO2), the number
one greenhouse gas. CO2 is produced in volcanoes and in the mid-ocean
trenches. It is lost by being slowly absorbed in the oceans. Both
of these processes are slow - about the right time scales to explain
the great Ice Ages.
CO2 is produced at a faster rate of sea-floor spreading
and there is a subsequent increase in volcanism during these times.
The higher the volcanic activity and higher ocean levels reduce
the chemical weathering of rocks. This promotes global warming
by enriching the CO2 content of the atmosphere. Similarly,
global cooling may result from stalled or slowed spreading.
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