II.
Mechanics of Global Warming
"With
the possible exception of another world war, a giant asteroid,
or an incurable plague, global warming may be the single largest
threat to our planet. For
decades human factories and cars have spewed billions of tons
of greenhouse gases into the atmosphere, and the climate has
begun to show some signs of warming.If we don't curb our greenhouse
gas emissions, then low-lying nations could be awash in seawater,
rain and drought patterns across the world could change, hurricanes
could become more frequent, and El Ninos could become more
intense" says John Weier writing in EarthObservatory.nasa.gov. Then some scientists (I believe in the minority)
believe global warming will result merely in "warmer winters
and increased plant growth."
John Weier states, "In truth, the future
probably fits somewhere between these two scenarios."
i.e. What he's saying is the future lies somewhere
between totally disastrous global warming side effects (i.e.
The Day After Tomorrow scenario) and little more than warmer winters-which
is what?-a good amount of disastrous global warming side effects
in the middle of this PS (Pooch Screw) scale.
[sorry, I couldn't help myself.]
He states, "To understand global warming we must understand
the science behind it." I've
given you a lot of the side effects and what's going on right
up front. Now let's take a look at the science of global
warming and simply how the earth is a stable and warm enough
environment to support life.
Got to know how a well functioning system works, before
we can really understand how it can get messed up.
Right? So let's go.
[ http://earthobservatory.nasa.gov/Library/GlobalWarming/
]
- The sun warms the Earth with a constant
amount of radiant energy which reaches the Earth at all
times. The sun's output has remained relatively
constant over millennia of time.
- About 30 percent of the sun's total energy
striking the Earth reflects back into outer-space, and 70
percent is absorbed in the form of UV, visible light and
near infrared solar radiation. I say it is held, but this is only for
a period of time.
- The energy which is held doesn't stay bound
up on Earth forever, but ends up being radiated back off
into outer-space at a near constant rate that leaves the
Earth at a mean constant of around 59 degrees Fahrenheit.
As the sun heats the Earth's surface, land and oceans,
it heats them, and they in turn emit thermal radiation in
the form of long-wave infrared back into outer-space.
So
what holds the Earth at 59 degrees F?
Some of this long-wave infrared radiation being radiated
back upwards from the earth's surface is re-absorbed by water
vapor, C02 and methane and re-radiated back toward Earth's
surface-trapped at the top of the troposphere.
Without the greenhouse gases, Earth's average surface
temperature would be a nice cold -18 degrees C (-0.4F), and
life as we know it would be impossible, the Earth would be
essentially frozen.
But over the past 250 years, from 1750 to the present,
human activity has been raising greenhouse gas concentrations
in the atmosphere by our factories, power plants and vehicles,
all burning coal, gasoline and diesel fuel, and pouring C02
into the atmosphere in increasing amounts. Once carbon-based greenhouse gases (C02 &
CH4) get into the atmosphere beyond the levels that maintain
global temperatures at a steady, even level, they stay there
for decades, or for C02, even longer, up to 100 years.
The IPCC says since the start of the Industrial Revolution
carbon dioxide (C02) is up 31 percent, and methane (CH4) is
up 151 percent. Paleoclimate
readings from ice cores and fossil records show these two
gases are at their highest levels in the past 420,000 years
(i.e. one half million years).
These increased levels of greenhouse gases are preventing
additional thermal radiation from leaving Earth, trapping
excess heat in Earth's atmosphere, causing a steady rise in
the average mean temperature of the Earth.
Here are the facts: Most leading
researchers and scientific organizations project that the
average mean surface temperature of the Earth will increase
along with emissions, according to the IPCC, with surface
temperatures (mean) raising anywhere between 1.4 C and 5.8
C by the end of the 21st century. It only rose by 0.5 C, a lot in and by itself,
over the past 100 years. Now
in the next 100 years it is projected to rise 1.4 C (3 times
as much in the same time span) to 5.8 C (a whopping 11 times
as much in100 years!). This is an exponential rise in global mean surface
temperature-from 56 F in 1900 to 59 F in 2000, to anywhere
from 63 F to 67 F by the end of the 21st century.
Normal average mean temperatures over extended periods
of time, geologically speaking, are very stable.
i.e. During the last ice age Earth was 5 C cooler.
It has gradually increased to present levels, at a
very slow rise rate (1 C between every 1,000 to 4,000 years
depending on when you date the last major Ice Age-i.e. whether
you view C-14 as an accurate dating method or not). We've just experienced a rise of 0.5 C in a
very short 100 year time-span, and now the projected rise
in average mean surface temperature is between 1.4 C and 5.8
C within the next 100 years. The mid-range between 1.4 C and 5.8 C is a projected
3.6 C rise in 100 years or less.
That's close to 68 F average mean surface temperature! [ http://earthobservatory.nasa.gov/Library/GlobalWarming/warming2.html
]
So,
in review greenhouse gases are gaseous components of the atmosphere
that contribute to the "greenhouse effect".
i.e. those are the gases that help contribute to the
trapping of solar energy in the form of heat-the trapping
of the suns infrared spectrum.
With insufficient "greenhouse gases" the sun's radiant
energy would escape back into outer-space, and earth would
be a giant deep-freeze. Too much, and the climate warms, with all the
resultant side-effects we've been reading about. Now let's learn about those gases.
Greenhouse Gases 101: The major green-house gases are
1)
Water vapor. Yes, amazingly water vapor is a green-house
gas. Water vapor represents
anywhere from 36 percent to 70 percent of the greenhouse effect
on earth.
2)
Carbon dioxide, which
represents anywhere from 9 to 26 percent of the greenhouse
effect (G.H.E).
3)
Ozone, 3 to 7 percent
of the G.H.E.
Other gases:
4)
Methane
5)
Nitrous Oxide
6)
Sulfur Hexaflouride
7)
The Fluorocarbon's (Freon:
RF-12 & RF-22 from refrig and
ac units)
Water Vapor: Water vapor is a natural greenhouse gas and it accounts
for the largest percentage of the greenhouse effect. In climate models an increase in temperature
caused by the greenhouse effect do to a rise in C02 and methane
levels will in turn lead to an increase in evaporation and
thus water vapor content in the troposphere.
This in turn leads to a further increase in the greenhouse
effect, and thus a further increase in temperature, and thus
a further increase in water vapor until some equilibrium is
reached (i.e. the atmosphere at the higher temp becomes saturated
with the amount of water vapor it will hold (it's dew point)).
So we see that water vapor acts as a positive feedback
to the forcing provided by human released greenhouse gases
such as C02. Water vapor provides a powerful positive feedback
in the global warming sequence of events.
Carbon Dioxide: The C02 level
just as the industrial revolution began in 1750 was 280 ppm
(parts per million). It
has steadily increased without any real drop in ppm to 365
in the year 2000, a 31 percent increase.
The problem with C02 is that although an actual molecule
of C02, if followed in its life-cycle, would remain in the
atmosphere for only a few years-before the ocean with its
phytoplankton and zooplankton absorbed it permanently from
the atmosphere-the calculation of the dissipation of a large
increase in C02 levels would be measured in 100's of years.
Methane: Methane in 1750 was
700 ppb (parts per billion).
In the year 2000 it has risen to 1745 ppb, a 150 percent
increase. What happens to Methane in the air? Lightning and high intensity rays from the sun
"burn" it with the 02 in the atmosphere so it becomes water
vapor and C02, both greenhouse gases.
So the half-life on methane isn't the true half-life
of the greenhouse effect it has, because it's degrading down
to water vapor and C02 continues it's effect.
Nitrous oxide in 1750 was 270 ppb, and in the year
2000 has risen to 314 ppb.
Aside from water vapor near the earth's ocean surface-which
has a residence time of a few days-most greenhouse gases take
a very long time to dissipate from the atmosphere [see http://www.sciencedaily.com/encyclopedia/Greenhouse_gas
. Look up NOAA Paleoclimatology
Program-Vostok Ice Core, go ahead, do a Google search on your
own.]
A
must see, with good explanations and clear charts, log onto
NOAA CMDL CCGG Interactive Atmospheric Data Visualization,
NOAA C02 Data at: http://www.cmdl.noaa.gov/aggi/ .
"NOAA
issued the Annual Greenhouse Gas Index (AGGI) today, its benchmark
measurement of gases in the atmosphere that affect the Earth's
climate. This year's
AGGI reflects an increase in carbon dioxide (C02) and nitrous
oxide (N20) but a leveling off of methane (CH4), and a decline
in two chlorofluorocarbons (CFCs), gases that contribute to
the cause of the Antarctic ozone hole.
Overall, the AGGI shows a continuing, steady rise in
the amount of heat-trapping gases in the atmosphere.The AGGI
is referenced to a baseline value of 1.00 for the greenhouse
gas levels that were present in the atmosphere in 1990. The
value of the AGGI for 2005 is 1.215.
This reflects a continuing upward trend in the accumulation
of greenhouse gases, as well as the change in the amount of
radiative forcing. Radiative forcing indicates the balance between
radiation coming into the atmosphere and radiation going out. Positive radiative forcing tends on average
to warm the surface of the Earth, and negative forcing tends
on average to cool the surface.
Radiative forcing, as measured by the index, is calculated
from the atmospheric concentration of each contributing gas
and the per-molecule climate forcing of each gas.Most of the
increase in radiative forcing [positive] since 1990 is due
to C02, which now accounts for approximately 62 percent of
the radiative forcing by all long-lived greenhouse gases.
Global C02 increased from an average of 376.8 parts
per million (ppm) in 2004 to 378.9 ppm in 2005.
This increase 0f 2.1 ppm means that for every one million
air molecules there were slightly more than two new C02 molecules
in the atmosphere. The
pre-industrial C02 level was approximately 278 ppm. [Probably determined from ice-core samples,
fairly accurate.] [taken
from http://www.publicaffairs.noaa.gov/releases2006/may06/noaa06-050.html
] 
As
we have just seen, the National Oceanic and Atmospheric Administration,
NOAA, has said that for this year of 2006, in May, there was
a continuing rise in carbon dioxide and nitrous oxide, though
methane leveled off. There
was also a decline in chlorofluorocarbons, gases that contribute
to the ozone hole over the Antarctic.
Currently the concentration of carbon dioxide in the
atmosphere has climbed to a record 381 parts per million last
year.the reading up 2.68 ppm according to NOAA's David J.
Hofmann. In addition
to C02, the 2004 data from WMO calculated nitrous oxide,
which has been steadily rising since 1988, totaled 318.6 ppb. Methane has risen the most dramatically over
the past two centuries, with the total amount in 2004 at 1,783
ppb, but its growth has been slowing down, according to the
World Meteorological Organization.
Said Leonard Barrie of WMO, "If
you have that much more energy being trapped, where does it
go? [keep that question in the back of your mind,
it's important]...Given the lifetime of carbon dioxide in
the atmosphere is 50 to 200 years depending on how you calculate
it.it doesn't take a nuclear scientist to state that we're
going to have this problem for a long time.If we stop now
C02 emissions to the atmosphere, it would take 50 to 100 years
before we were starting to see approaches to pre-industrial
levels." Scientists worry that overall warming will melt glaciers
and the polar ice caps, raising sea levels enough to damage
many low-lying islands and cities around the world. In addition,
warmer climate could lead to changes in weather patterns,
agriculture and even allow some diseases to expand into new
areas. [March 15, 2006, Associated Press]
[
http://www.cmdl.noaa.gov/ccgg/trends/co2_data_mlo.php
]
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