|
|
Background Information |
|
|
|
|
|
|
|
What is global warming?
Global warming is a term that has been used to describe a period in
recent history when the earth’s surface temperature warmed. There
have been three periods of global warming since 1850; from 1860 to
1880, 1915 to 1945, 1975 to 1998 (see graph). The most recent
warming was originally thought to be caused by the emissions by man
of carbon dioxide, commonly called by its scientific name CO2. Each
period of warming was separated by a period of global cooling. The
warming/cooling cycles, and their associated change in precipitation
patterns are called climate change. Climate change has been
occurring for the past 11,000 years since the last ice age. Recent
research has shown that this steep curve is probably a product of
what is known as the heat island
effect rather than global warming.
|
|
 |
| |
| |
Global mean
surface temperature anomaly 1861-2004. Anomaly means the
departure from a fixed starting point.
(Source: Wikipedia) |
|
|
| |
| |
|
 |
| |
An illustration showing the exchanges of energy between
outer space, the earth’s atmosphere, and the earth’s
surface. The greenhouse effect results from the ability of
greenhouse gases in the atmosphere to capture and recycle
energy emitted by the earth’s surface.
(Source: Wikipedia) |
|
|
|
What are
greenhouse gases?
Greenhouse gases are those gases that allow most solar radiation
(mainly visible light) to penetrate to the earth’s surface, but
absorb thermal infrared radiation emitted by the earth’s surface. As
solar energy reaches the earth’s surface some of it is reflected
back out into space, some is absorbed by the atmosphere, and the
rest is absorbed by the earth and warms it. The warm earth then
emits infrared radiation which we cannot see. Most of this infrared
radiation is absorbed by the various greenhouse gases, much of which
is emitted back down to the surface of the earth where it starts the
cycle again. This cycle is called the greenhouse effect
because it acts somewhat like a greenhouse in that it allows the
sunlight to penetrate the greenhouse, but as the greenhouse warms,
the glass ceiling and walls prevent most of the heat from escaping.
The most powerful greenhouse gas is water vapor, not carbon dioxide.
|
|
What gases
have a greenhouse affect?
Most
gases in the atmosphere do not have greenhouse gas properties. Of
the various gases that have greenhouse properties, water vapor,
clouds, carbon dioxide, methane, nitrous oxides are the most
important. Carbon dioxide is not the most powerful greenhouse gas.
This fact is rarely mentioned. In fact, it is a distant second.
Water vapor and clouds are the most powerful by far. The greenhouse
potential of each gas is difficult to measure because the earth’s
atmosphere is constantly in a state of flux due to constantly
changing weather patterns and seasons. Furthermore, some greenhouse
gases are more effective in trapping heat than others. For instance,
methane is about 20 times more effective as a greenhouse gas than
carbon dioxide. So even though there is far less methane in the
atmosphere than carbon dioxide, methane is still a very important
greenhouse gas. When all of these factors are considered, the
potential effectiveness of a greenhouse gas can be estimated. Water
vapor accounts for 31 to 70 percent of all the greenhouse gas
potential in the atmosphere at any one time. When clouds are added,
this increases to 65 to 85 percent. Carbon dioxide, on the other
hand, only accounts for 9 to 27 percent. Since most carbon dioxide
in the atmosphere is produced naturally from plant decay, exhaling
from animal life, soil microbiotic activity and other sources, only
3 percent of the maximum 27 percent is from burning fossil fuel and
other human activity. Methane and other greenhouse gases make up the
balance of greenhouse gases. Of all greenhouse gases, water vapor
and clouds are by far the most powerful greenhouse gases.
|
|
 |
| |
Of the
most important greenhouse gases, water vapor and clouds are
by far the most important. Carbon dioxide comes in a distant
second and man-caused carbon dioxide is hardly a blip on the
scale. |
|
|
|
|
|
|
|
The
molecular structure of CO2 |
 |
|
|
|
The
atmospheric concentrations of CO2 has increased from
about 315 ppm in the late 1950s to 380 ppm in 1998 |
|
|
|
What is
carbon dioxide?
Carbon
dioxide (CO2 = 1 carbon, 2 oxygen atoms) is a colorless,
odorless, tasteless gas which is about 1.5 times as heavy as air.
Under normal atmospheric conditions it is stable, inert (does not
react with other substances or gases), and nontoxic. In solid form
it is known as dry ice. The atmosphere contains approximately 0.033
percent carbon dioxide by volume. Nearly all animal life produces
carbon dioxide during respiration which is exhaled (breathed out).
Nearly all plant life absorbs CO2 as the building block
for food production in a process called photosynthesis. When animal
and plants decompose, carbon dioxide is released as a by-product.
Carbon dioxide is also a byproduct of burning plant material and
fossil fuels. Since it is also a greenhouse gas, many consider
human-emitted carbon dioxide to be the major source of global
warming in the twentieth century. The atmospheric concentrations of
CO2 has increased from about 270 ppm (parts per million)
in the early 20th century to 380 ppm in 1998. Most of
this increase has come from the burning of fossil fuels, but could
also come from volcanoes and a warming ocean. As the ocean warms, it
cannot hold as much carbon dioxide and billions of tons of CO2
is released into the atmosphere.
|
|
|
The
effectiveness of carbon dioxide as a greenhouse gas decreases with
increasing CO2 concentrations
As carbon
dioxide concentrations increase it becomes increasingly difficult
for additional CO2 molecules to further increase the
greenhouse effect. The first 20 ppm (parts per million) of
atmospheric carbon dioxide has a huge effect. The second 20 ppm is
much less. By the time atmospheric carbon dioxide reaches the modern
day level of 380 ppm, additional increases have an extremely small
affect. The carbon dioxide caused global warming theory is not based
on a direct cause and effect relationship, but an indirect
relationship based on the belief that carbon dioxide will increase
high elevation cirrus cloud formation. Cirrus clouds trap heat in
the upper troposphere
(layer of atmosphere directly
above the earth's surface), around 5 to 8 miles in altitude, causing it
to warm faster than the troposphere at the earth’s surface. This is
called "positive feedback." Every climate model has this assumption
built into it.
Actual
measurements are showing this warming is not occurring. Instead
of a positive feedback, it is now proven there is a "negative
feedback." This means the maximum the earth will warm with a
doubling of atmospheric CO2 is about 0.5oC, not 2-3o
claimed by warming alarmists, including the IPCC.
|
|
 |
| |
The
effectiveness of carbon dioxide as a greenhouse gas
dramatically diminishes with increasing carbon dioxide
concentration. At modern day concentrations, CO2
will not directly cause much warming. Instead, the global
warming theory says that CO2 increases high
elevation cirrus clouds
which then increase the temperature.
(Source:
Climate Outlook to 2030) |
|
|
|
|
|
- When the trade winds shift and
push warm water from the western pacific to the eastern Pacific,
the jet streams change, changing the weather patterns and climate.
When the trade winds change back the ocean cools and it is called
La Nina.
See a NASA animation.
|
El Nino
A
change in the Pacific Ocean’s surface temperature by a few degrees
Celsius when wind pushes warm water from the western Pacific to the
eastern Pacific Ocean. These changes cause atmospheric conditions
often resulting in rain, thunderstorms or drought around the world.
When the wind no longer pushes the warm water east, cool water
returns and is called La Nina. A corresponding, but less pronounced
cycle occurs in the Atlantic Ocean. El Nino's are thought to be
caused by
solar activity working
through the Pacific Decadal Oscillation. Image showing
when a very strong El Nino strikes surface waters in the Central
equatorial Pacific Ocean warmed
- Links:
- See a NASA
visualization:
http://www.globalwarmingclassroom.info/el_nino.htm
-
http://meteora.ucsd.edu/~pierce/elnino/whatis.html
-
http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html
|
| |
| |
| |
|
|
|
