The Greenhouse Effect
"Greenhouses are used to grow plants, especially in the winter.
Greenhouses work by trapping heat from the sun. The glass panels of the
greenhouse let in light but keep heat from escaping. This causes the greenhouse
to heat up, much like the inside of a car parked in sunlight, and keeps
the plants warm enough to live in the winter."
Greenhouse gases in the atmosphere behave much like the glass panes in a
greenhouse. Sunlight enters the Earth's atmosphere, passing through the
blanket of greenhouse gases. As it reaches the Earth's surface, land, water,
and biosphere absorb the sunlight's energy. Once absorbed, this energy is
sent back into the atmosphere. Some of the energy passes back into space,
but much of it remains trapped in the atmosphere by the greenhouse gases,
causing our world to heat up.
The greenhouse effect is the rise in temperature that the Earth experiences
because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous
oxide, and methane, for example) trap energy from the sun. Without
these gases, heat would escape back into space and Earth's average temperature
would be about 60ºF colder."
from: EPA Global Warming site - http://www.epa.gov/globalwarming/kids/greenhouse.html
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The role of Carbon
Greenhouse gasses - the most important element in most of these gasses is CARBON
carbon dioxide - CO2 - the most important greenhouse gas, it is released to the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned.
carbon monoxide - CO - a toxic component of automobile exhaust.
methane - CH4 - is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock.(largely produced by cows and termites.)
Chlorofluorocarbons - CFCs - by weight, much more than potent CO2 at trapping heat, also destroys ozone. CFCs are byproducts of foam production, refrigeration, and air conditioning, and are generated by industrial processes (also hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) - some have an atmospheric lifetime of more than 2000 years).
water vapor - H2O - may trap heat, but it depends on where and what form.
nitrous oxide - N2O - is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels.
from: EPA GLOBAL WARMING/Climate
http://www.epa.gov/globalwarming/climate/index.html
CO2 - The most important greenhouse gas.
Before the Industrial Revolution, human activity released very few gases
into the atmosphere, but now through population growth, fossil fuel
burning, and deforestation, we are affecting the mixture of gases in the
atmosphere.
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Climate Change
Average global temperature has increased by almost 1ºF over the
past century; scientists expect the average global temperature to
increase an additional 2 to 6ºF over the next one hundred
years. This may not sound like much, but it could change the Earth's
climate as never before. At the peak of the last ice age (18,000 years ago),
the temperature was only 7ºF colder than it is today, and glaciers
covered much of North America!
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Here are some of the ways that scientists gather evidence about climate,
both past and present:
(http://www.epa.gov/globalwarming/kids/detectives.html)
![]() Global Surface Air Temperature is based on surface air measurements at meteorological stations. Click for temperature maps and more detailed data. Since corresponding data are unavailable over the ocean, surface air temperature anomalies are combined with ocean temperature anomalies to obtain a 'Land-Ocean Temperature Index'. |
![]() Common Sense Climate Index is based on quantities noticed by people such as extremely hot and cold days. Click for maps leading to climate indices of individual cities. |
Global Satellite Montage of Sea and Land Temperatures
http://www.ssec.wisc.edu/data/comp/latest_cmoll.gif
Prior to the mid-1800's, there are not enough instrumental measurements
to determine
global trends. Paleoclimatologists instead use proxy records, such
as the Vostok temperature
record below, to interpret the climate of the pre-historic past. Understanding
past climate is the key
to determining if the observed warming of the past century is natural,
or the result of human
activities.
![]() Ice Core sample taken from drill. Photo by Lonnie Thompson, Byrd Polar Research Center, Ohio State University. |
![]() Scientists extrude the core from its barrel with the utmost care. Photo by Kendrick Taylor, DRI, University of Nevada-Reno. |
![]() Temperature Anomaly, Vostok Antarctica. Change vs. today in degrees C., in thousands of years before present, derived from deuterium. Source: J. Jouzel, et al. http://www.ngdc.noaa.gov:8800/paleo/globalwarm.html |
![]() Scientists take samples from the center of the coral. Clipperton Atoll, 10°N, 109°W. Photo by Maris Kazmers. |
![]() ![]() Tree rings in Mexican Cypress (Cupressus lusitanica). Photo by Peter Brown. Diagram of rings in a young conifer. From Fritts, H.C. 1976. Tree Rings and Climate. Academic Press, New York, NY. |
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"Once, all climate changes occurred naturally. However, during the
Industrial Revolution, we began altering our climate and environment through
agricultural and industrial practices.
from: EPA Global Warming site - http://www.epa.gov/globalwarming/kids/greenhouse.html