The science behind global warming and its impacts
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A compilation of questions and answers by Sanjeev Sabhlok
Note from compiler: The subject of global warming has become sufficiently important that each of us fully understand its science so that we can promote the appropriate solutions. This website is my attempt to understand this science. Started 9 January 2008. This document will keep changing potentially from day to day until I am able to make a final conclusion. In the meanwhile, an article which highlights the need to keep one’s mind open. |
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Initial thoughts: climate change and accountability
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Question: What is the temperature of the world?
Details: The temperature of the world is recorded and reported at the following websites. 1) Climatic Research Unit (CRU) of the University of East Anglia at Norwich in the UK – measures the global air temperatures. 2) NASA’s Goddard Institute of Space Studies (GISS) 3) National Climatic Data Center (NCDC)
What is measured? (a) surface temperature (b) lower troposphere (measured by radiosondes and satellites), (c) ocean temperature – of two types: sea surface temperature (SST) and marine air temperature ( MAT)
While scientists use standard weather station instruments to detect warming on land, they have been forced to rely on the crews of ships to make measurements over the vast ocean regions. Crews have taken the temperature by dipping buckets into the sea or using water flowing into the engine intakes.
It is crucial to note that surface temperature records have been mainted for 150 years but are questionable on many counts. The main argument for greenhouse effect is that the upper layers of the atmosphere are warmed first. So satellite data is likely to be more appropriate for measuring greenhouse effect.
The Urban Heat Island effect (UHI) is very important in surface measurements. The same raw data can give rise to two different sets of time series, eg. see here.
The 1880-2004 average combined land and ocean annual temperature is 13.9°C (56.9°F), the annually averaged land temperature for the same period is 8.5°C (47.3°F), and the long-term annually averaged sea surface temperature is 16.1°C (60.9°F). (source)
Conclusion:
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Question: Is the globe warming?
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Conclusion: The fact of warming is more likely than the fact of not warming. Conclusive proof probalbly comes from the melting of ice sheets. This doesn’t imply that CO2 is the cause of this warming. That is a separate question.
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Question: Does the greenhouse gas effect really exist?
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Conclusion:
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Question: Is CO2 a greenhouse gas?
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Conclusion:
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Question: How much does CO2 affect temperatures?
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Conclusion:
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Question: How much has CO2 increased in the atmosphere?
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Conclusion: ?? CO2 has gone up by 30% but temperature has gone up by 0.15% This is a very strange relationship, to say the least.
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Question: What are the positive feedback and negative feedbacks at work in climate change?
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Conclusion: ?? CO2 has gone up by 30% but temperature has gone up by 0.15% This is a very strange relationship, to say the least.
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UNSORTED MATERIAL
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Basic chart
In other words, CO2 has gone up by 30% but temperature has gone up by 0.15% This is a very strange relationship, to say the least. (source of data: http://www.giss.nasa.gov/research/briefs/ma_01/)
Most likely explanation – I probably agree http://members.shaw.ca/sch25/FOS/CO2_Versus_Water.html The range of infrared radiation from Earth is 6 to 22 microns. Each greenhouse gas and water vapor absorbs radiation from different areas of the electromagnetic spectrum. Carbon dioxide and water absorb long wave radiation from 12 to 19 microns. Methane absorbs wavelengths 6 to 8 microns. Water blocks radiation below 7 microns from being reflected out to space. What is the window of possible infrared radiation back out to space and how do these gases contribute to closing the window? (see: http://www.enviroliteracy.org/pdf/labge1.pdf)
The Greenhouse Effect is logarithmic. It increases rapidly to saturation, then levels off. Any further increase in concentration has no further effect. The CO2 spectrum is near saturation already. Though CO2 increase to infinity, it will have minimal additional greenhouse effect. (source: http://forums.wnd.com/index.php?fa=PAGE.view&pageId=22&forumPage=21)
The official Department of Energy chart says 99.438% of greenhouse gas is carbon dioxide. Footnote: excludes water vapor. Water vapor is 95%; CO2 is 99.438% of the remaining 5%. Because of relative heat absorption coefficients, CO2 only accounts for 72.369% of the actual greenhouse effect from that 5%. Human activity produces only 3.22% of CO2. So the fraction of the total greenhouse effect caused by human-produced carbon dioxide is 3.22% times 72.369% times 5% equals 0.0011, effectively zero. Whatever is happening with the climate, it is not caused by any greenhouse effect from human-produced CO2.
The heat radiated into space is a factor of the temperature (degrees Kelvin) to the FOURTH POWER. (http://www.engineeringtoolbox.com/radiation-heat-transfer-d_431.html) So, if the earths temperature gradually rises the thermal radiation from the hemisphere in darkness will increase expotentially, self limiting global warming.
Multivariate Analysis Causes of global temperatures: We need longitudinal studies, not cross-sectional multivariate studies
The Swedish Nobel laureate Svante Arrhenius built a greenhouse in 1896 to predict future ice ages. He proposed that the heat buildup in a greenhouse was based on the concentration of CO2, which he believed enveloped heat. Almost all scientists, particularly leading German scientists from the Kaiser Wilhelm-Max Planck Institute, as late as 1970, considered this random speculation. Using Arrhenius' model, all greenhouse operators could merely add additional CO2 to their greenhouses and they could turn off or use smaller space heaters during the cold seasons! (SOURCE: http://en.epochtimes.com/news/7-6-6/55985.html)
CO2 is found near the ground: CO2 which has a molecular weight of 44, while air is only 29. That means CO2 naturally concentrates near the ground, where plants can derive nourishment.
A hypothesis: an initial temperature trigger (for example, changes in the earth's orbit), result in release of CO2 and other greenhouse gases to the atmosphere (for example, release of CO2 from the ocean as it warms). As the greenhouse gas concentration in the atmosphere builds up, it results in more warming and further release of greenhouse gases (i.e. a feedback cycle).
Questions to address: Why ice age when CO2 levels were 12 times the levels today? Tim Patterson[34], paleoclimatologist and Professor of Geology at Carleton University in Canada: "There is no meaningful correlation between CO2 levels and Earth's temperature over this [geologic] time frame. In fact, when CO2 levels were over ten times higher than they are now, about 450 million years ago, the planet was in the depths of the absolute coldest period in the last half billion years. On the basis of this evidence, how could anyone still believe that the recent relatively small increase in CO2 levels would be the major cause of the past century's modest warming?"[35][36] We are coming out of an ice age – hence temperature is rising.
Global warming is a real phenomenon: Earth's temperature is increasing.
Global warming is something that has been happening for a long time. The temperature of the Earth has been increasing more or less continuously since the time of the cave man.
Approximately 18,000 years ago the Earth began a gradual process of warming up after more than 100,000 years of Ice Ages. Much of North America, Europe, and Asia lay buried beneath great sheets of glacial ice.
By about 15,000 years ago the Earth had warmed sufficiently to halt the advance of glaciers, and sea levels worldwide began to rise.
By 8,000 years ago the land bridge across the Bering Strait was drowned, cutting off the migration of men and animals to North America.
Since the end of the Ice Age, Earth's temperature has risen approximately 16 degrees F and sea levels have risen a total of 300 feet! Forests have returned where once there was only ice.
From a geological perspective, global warming is the normal state of our accustomed natural world. Technically, we are in an "interglacial phase," or between ice ages. The question is not really if an ice age will return, but when.
Don't panic when you hear global alarmists warning the Earth may have warmed almost 1 degree in the last 200 years. Although this still hasn't yet been proven, it is in fact exactly what should be happening if everything is normal.
If global warming stops, then you can start worrying! It means our warm interglacial phase is over and we may be heading into another Ice Age!
The Greenhouse Effect is real and contributes to global warming. The Greenhouse Effect helps to moderate temperatures -- especially nighttime temperatures. Without the greenhouse effect, the average temperature of the Earth would be -18 degrees C. Greenhouse gases allow sunlight to pass through Earth's atmosphere, but as sunlight strikes the Earth it is partially changed to radiant heat. Greenhouse gases like carbon dioxide, water vapor, and methane help inhibit the escape of radiant heat back into space. That is why the danger of nighttime frost is greater when the skies are clear than when skies are cloudy.
The main cause of the modern warming trend is most likely to be:
Global warming occurs in cycles caused mainly by changes in the sun's energy output and the sun's relative position to the Earth.
Major Causes of Global Temperature Shifts
(1) Astronomical Causes
11 year and 206 year cycles: Cycles of solar variability ( sunspot activity ) 21,000 year cycle: Earth's combined tilt and elliptical orbit around the Sun ( precession of the equinoxes ) 41,000 year cycle: Cycle of the +/- 1.5° wobble in Earth's orbit ( tilt) 100,000 year cycle: Variations in the shape of Earth's elliptical orbit ( cycle of eccentricity)
(2) Atmospheric Causes
Heat retention: Due to atmospheric gases, mostly gaseous water vapor (not droplets), also carbon dioxide, methane, and a few other miscellaneous gases -- the "greenhouse effect" Solar reflectivity: Due to white clouds, volcanic dust, polar ice caps
(3) Tectonic Causes
Landmass distribution: Shifting continents (continental drift) causing changes in circulatory patterns of ocean currents. It seems that whenever there is a large land mass at one of the Earth's poles, either the north pole or south pole, there are ice ages. Undersea ridge activity: "Sea floor spreading" (associated with continental drift) causing variations in ocean displacement.
The Greenhouse Effect is caused primarily by: Over 95 percent of the Greenhouse Effect is the result of atmospheric water vapor in Earth's atmosphere. But because water droplets held in suspension (clouds) make almost as good a reflector as they do a thermal insulator, there is little rise in daytime temperatures due to the Greenhouse Effect. Any greenhouse warming, if it does occur, is limited to primarily increasing nighttime temperatures, which provides beneficial moderation of nighttime low temperatures, but no increase in daytime high temperatures. Dr. Patrick Michaels, professor of environmental sciences, University of Virginia, has demonstrated this phenomenon very effectively.
Did you know... The world's natural wetlands produce more greenhouse gas contributions annually than all human sources combined.
Which most accurately describes the effects of Global Warming in the United States over the last 100 years?
Temperatures have gone through nearly two complete cycles of warming and cooling over the last 100 years. During the period 1900 to 1940 temperatures were increasing. Then from 1940 to 1975 temperatures were decreasing. Currently, temperatures are increasing back to about where they were in the 1930's.
Overall, the total average annual temperature increase in the last century is so slight the actual amount is uncertain -- maybe 1/3° C.
CO2 levels in the atmosphere today are at record high levels. - FALSE Carbon Dioxide is such a small component of Earth's atmosphere (380 ppmv) that the "slice" it represents in this chart is really only a "line" about 1/2 as thick as the line shown. Compared to former geologic times, Earth's atmosphere is "CO2 impoverished."
In the last 600 million years of Earth's history only the Carboniferous Period and our present age, the Quaternary Period, have witnessed CO2 levels less than 400 ppm, except during periods of glacial expansion during ice ages.
Late Carboniferous to Early Permian time (315 mya -- 270 mya) is the only time period in the last 600 million years when both atmospheric CO2 and temperatures were as low as they are today (Quaternary Period).
Temperature after C.R. Scotese http://www.scotese.com/climate.htm CO2 after R.A. Berner, 2001 (GEOCARB III)
There has historically been much more CO2 in our atmosphere than exists today. For example:
During the Jurassic Period (200 mya), average CO2 concentrations were about 1800 ppm or about 4.7 times higher than today.
The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Cambrian Period, nearly 7000 ppm -- about 18 times higher than today.
The Carboniferous Period and the Ordovician Period were the only geological periods during the Paleozoic Era when global temperatures were as low as they are today. To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age while at the same time CO2 concentrations then were nearly 12 times higher than today -- 4400 ppm.
According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence Earth temperatures and global warming.
Carbon dioxide from coal-fired power plants damages forests. Carbon dioxide (CO2) is the principal gas that trees and other plants need to survive, just like oxygen (O2) is the principal gas that humans and other animals require. Trees absorb CO2 and release O2 -- animals inhale O2 and exhale CO2. See how nice this all works!
Earth's first, primitive forests made their prolific debut 300 million years ago during the Carboniferous Period. Before then, the atmosphere held far more CO2 but concentrations declined throughout the Carboniferous Period as plants flourished.
During the Carboniferous Period the atmosphere became greatly depleted of CO2 (declining from about 2500 ppm to 350 ppm) so that by the end of the Carboniferous the CO2-impoverished atmosphere was less favorable to plant life and plant growth slowed dramatically. Today, CO2 concentrations are barely at 380 ppm -- still CO2-impoverished.
Carbon dioxide (CO2) is not to be confused with its poisonous evil cousin carbon monoxide (CO), which can kill humans and animals in just a few minutes. Life as we know it could not exist without carbon dioxide in our atmosphere.
Did you know ...
Carbon dioxide is invisible. The puffs of clouds you see from coal-fired power plants are just that -- clouds. Power plants use steam to drive the turbines which generate electricity. Steam must be cooled and condensed to water to reuse it to make more steam.
The fat, curvy towers that look like they are belching white smoke are really only emitting pure water vapor. They are in effect making clouds.
The actual exhaust emissions come from the smokestack, which is the tall skinny tower. Because modern technology makes it possible to remove much of the fly ash and sulfur before releasing smokestack gases to the air, smokestack emissons today are often almost invisible.
Is there a consensus? No.
In 1989 as the Cold War and the threat of nuclear war were winding down, the Union of Concerned Scientists began to circulate a petition urging recognition of global warming as potentially the great danger to mankind. The petition was eventually signed by 700 scientists. Only three or four of the signers, however, had any involvement in climatology. Richard S. Lindzen, MIT
"When a bureaucracy's reason for existence is threatened, it typically generates new missions." Desperately Seeking Mission: Why the State Department's Gone Green --- Peter VanDoren
President Clinton and others cite a letter signed by 2600 scientists that global warming will have catastrophic effects on humanity. Thanks to Citizens for a Sound Economy, we know now that fewer than 10 percent of these "scientists" know anything about climate. Among the signers: a plastic surgeon, two landscape architects, a hotel administrator, a gynecologist, seven sociologists, a linguist, and a practitioner of traditional Chinese medicine. Global Warming Treaty is All Pain, No Gain --- Malcom Wallop
"It's unfortunate that many people read the media hype before they read the (IPCC) chapter on the detection of greenhouse warming. I think the caveats are there. We say quite clearly that few scientists would say the attribution issue [the argument that global warming is caused by human industrial activity] was a done deal."
Which temperature measuring method most accurately measures global warming? Orbiting satellites provide the most accurate global temperature readings -- accurate to 0.1 degree C. Interestingly, in the 18 years that satellites have been recording temperature they have actually showed a slight decrease in average global temperatures. Ground-based thermometers that were originally in rural areas have been reading increasingly hotter temperatures with time due to urban encroachment. The asphalt and concrete structures replacing green leafy plants makes for hotter local ground temperatures. This phenomenon is known as the "urban heat-island effect" and has been well-documented by climatologist Dr. Patrick Michaels, professor of environmental sciences, University of Virginia. In a November 1997 press release Vice President Al Gore proclaimed that 1997 was the hottest year on record. Ground-based temperature readings were the basis for this announcement. Had the data from orbiting satellites been cited the report would have been much different: no net increase in global temperatures in 1997.
Question: Which answer below provides the best explanation for the following temperature record?
The primary cause of variations in global temperature is the cycles of the sun and Earth's orbit about the sun. In addition to 40-year cycles and 500-year cycles, other temperature cycles include: · 21,000 - year cycle: Elliptical orbit of the Earth around the Sun (precession of the equinoxes) · 41,000 - year cycle: Cycle of the +/- 1.5 degree wobble in Earth's orbit · 100,000 - year cycle: Variations in the shape of Earth's elliptical orbit (cycle of eccentricity) http://www.nineplanets.org/earth.html The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks and to a lesser extent dissolved into the oceans and consumed by living plants. Plate tectonics and biological processes now maintain a continual flow of carbon dioxide from the atmosphere to these various "sinks" and back again. The tiny amount of carbon dioxide resident in the atmosphere at any time is extremely important to the maintenance of the Earth's surface temperature via the greenhouse effect. The greenhouse effect raises the average surface temperature about 35 degrees C above what it would otherwise be (from a frigid -21 C to a comfortable +14 C); without it the oceans would freeze and life as we know it would be impossible. (Water vapor is also an important greenhouse gas.)
http://www.scotese.com/climate.htm
==== Carbon dioxide takes heat for global warmingMore than 99 percent of Earth's atmosphere is nitrogen and oxygen, while carbon dioxide constitutes just 370 molecules of air for every 200,000 molecules of oxygen. Yet it is an important substance that is taking the heat for causing global warming.
Although photosynthesis and respiration are often thought of as the balancing factors between carbon dioxide and oxygen in the atmosphere, the geological record says otherwise, and there are other factors such as deforestation, and wildfires that contribute to the balance.
Five hundred million years ago, carbon dioxide levels were nearly 20 times greater than today and Earth's temperature was about 20 degrees Fahrenheit higher.
Shortly after a rapid increase in carbon dioxide, following the "Cambrian Explosion" around 500 million years ago, there was a slow decline in atmospheric carbon dioxide, punctuated by a few peaks and valleys for 100 million years. Then something happened and the levels began a sharp decline, reaching a minimum and leveling off near present day levels around 340 million years ago just after the beginning of the Carboniferous Period, a division of the geologic time named for the large amounts of coal that were deposited in stagnant swamps during the period. The carbon dioxide level remained low for 60 million years throughout the Carboniferous and on into the Permian Period, which ended 245 million years ago. Oxygen levels in the atmosphere varied only slightly from the time of the Cambrian explosion, but at about the same time that the carbon dioxide level began its sharp decline, the oxygen level began to rise sharply, reaching a peak just when the carbon dioxide level was at its lowest.
But at the beginning of the Carboniferous period, Earth was impacted by three large extraterrestrial objects that left craters, two of them 30 miles across, a third one twice that size. These all occurred within an 8-million-year period, a long time in human years, but the blink of an eye in geologic time.
The beginning of the Carboniferous period was also marked by a mass extinction that wiped out 75 percent of all species on Earth at the time, as is verified in the rock record worldwide, everywhere these fossils have been found, below the Carboniferous layers, but never within or above them.
Mass extinctions are not uncommon in the fossil record. Throughout Earth's history there have been quite a few of varying degrees of grievousness.
Many are associated in time with, and appear to have been caused by, impacts of extraterrestrial objects such as asteroids or comets.
The greatest extinction of all was the at the end of the Permian Period when 95 percent of all species went extinct. At the time of the Permian extinction the oxygen level had fallen back to a normal level of between 15 and 20 percent. After the Permian extinction the carbon dioxide level rose again rapidly, reaching a peak of 2,500 parts per million in the middle of the Jurassic period 175 million years ago. Since then it has declined steadily with only a slight upward peak at the K-T mass extinction, which included the demise of the dinosaurs 65 million years ago.
The geological record shows that throughout most of Earth's history its temperature has been around 70 degrees Fahrenheit. There have been only four brief intervals where it deviated from this.
We are in one such interval now. Earth's temperature now is about 55 degrees. It has been only 10,000 to 15,000 years since the most recent retreat of the Pleistocene glaciers, which began their advance 1.6 million years ago, and at the height of their most recent advance 18,000 years ago covered much of the northern hemisphere with a 2-mile-thick sheet of ice. During the Ice Age, as it is commonly called, glaciers advanced and retreated across North America, Europe, and South America at least four times, averaging about 75,000 years per advance. Between advances, interglacial periods averaged about 50,000 years. Two of the other periods of prolonged cold also coincided with glacial periods. One of these was during an ancient ice age at the boundary between the Silurian and Ordivician Period about 440 million years ago. The other was a lesser ice age during the Carboniferous, which is the only other time in Earth's history that both temperature and carbon dioxide levels were similar to current conditions. Our data tell us that the amount of carbon dioxide has increased by about 30 percent since the middle of the 19th century, with nearly half of it since 1970. Our data tell us that in the same time period the average global temperature has risen likewise over the past two decades, with three of the four warmest years on record occurring 2002, 2003 and 2004. On the other hand, geologic record for the past 600 million years does not show that there is a connection between carbon dioxide and global temperature. We know that Earth's temperature has fluctuated only briefly in the past, and we know that throughout most of Earth's history the planet's temperature has been much warmer than it is today. What we do not know is whether we are in an interglacial period or coming out of a glacial age. We don't know what will happen in the future. All we really know is that the world is getting warmer and that we are changing the composition of the atmosphere by adding carbon dioxide. Michael Crichton's new book, "State of Fear" has already caused quite a bit of controversy, and it should, but it should also stimulate serious thought about our assumptions. As sophisticated as we may be scientifically, and as successful as science has been in understanding, describing, and explaining natural phenomena, it appears that we may be in danger of becoming a society that relies on mysticism rather than on science. Any statistician knows and so should any scientist, that correlation does not imply causation. The ancient Egyptians attributed the annual flooding of the Nile to the rising of the star, Sirius at sunset, assigning a causality to the correlation and evolving a society that worshiped of the star. Let us hope that we do not fall prey to the same kind of misconceptions and take the wrong action, whatever it might be. Richard Brill picks up where your high school science teacher left off. He is a professor of science at Honolulu Community College, where he teaches earth and physical science and investigates life and the universe. He can be contacted by e-mail at rickb@hcc.hawaii.edu
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http://mysite.verizon.net/mhieb/WVFossils/global_warming.html
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Carbon Dioxide
from all 
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Temperature |
Density |
Specific Heat Capacity |
Thermal Conductivity |
Kinematic Viscosity |
Prandtl Number |
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-50 |
1156 |
1.84 |
0.086 |
0.119 |
2.96 |
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-40 |
1118 |
1.88 |
0.101 |
0.118 |
2.46 |
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-30 |
1077 |
1.97 |
0.112 |
0.117 |
2.22 |
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-20 |
1032 |
2.05 |
0.115 |
0.115 |
2.12 |
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-10 |
983 |
2.18 |
0.110 |
0.113 |
2.20 |
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0 |
927 |
2.47 |
0.105 |
0.108 |
2.38 |
|
10 |
860 |
3.14 |
0.097 |
0.101 |
2.80 |
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20 |
773 |
5.0 |
0.087 |
0.091 |
4.10 |
|
30 |
598 |
36.4 |
0.070 |
0.080 |
28.7 |
Carbon dioxide gas is produced from the combustion of coal or hydrocarbons or by fermentation of liquids and the breathing of humans and animals.
Carbon dioxide is at a low concentration in the atmosphere and acts as a greenhouse gas. Carbon dioxide is assimilated by plants and used to produce oxygen.
Carbon dioxide gas is colorless and heavier than air and has a slightly irritating odor.
Freezing point is -78.5oC where it forms carbon dioxide snow or dry ice.
Greenhouse Gases: Refining the Role of Carbon Dioxide
There has been growing interest in the global temperature of Earth. Recent headlines such as "1997 Hottest Year on Record" have generated a greater awareness that the global climate may be changing. Global warming is attributed to the steady increase of atmospheric trace gases produced largely by human activities, such as carbon dioxide, methane, nitrous oxides, and chlorofluorocarbons (CFC or "Freon"). These gases are commonly referred to as "greenhouse gases" because they let in most of the incoming solar radiation that heats Earth's surface, yet prevent part of the outgoing thermal radiation from escaping to space, thus trapping some of the surface heat energy. Water vapor is also a major natural greenhouse gas, but its volatility, i.e., readily evaporating and condensing in response to temperature changes, complicates its role. Increases in the amount of atmospheric water vapor, under warmer conditions, reinforces the heat absorption by the other greenhouse gases. On the other hand, more clouds may form, as a consequence of increasing amount of atmospheric water vapor. Clouds can provide either a positive or a negative feedback by trapping outgoing thermal radiation or increasing the amount of solar radiation reflected back to space, respectively. At present, roughly 30% of the incoming solar radiation is reflected back to space by the clouds, aerosols, and the surface of Earth. Without naturally occurring greenhouse gases, Earth's average temperature would be near 0°F (or -18°C) instead of the much warmer 59°F (15°C).
The concentration of greenhouse gases, especially carbon dioxide and methane, has fluctuated naturally over geological time scales. While the mechanisms responsible for these fluctuations are unclear, the temperature of Earth has responded to them by switching between ice age and interglacial conditions, i.e., periods of reduced and increased greenhouse warming. In addition to these slow natural variations, the atmospheric concentrations of these gases are being changed rapidly (on a geological time scale) by human activity as we burn fossil fuels, clear forests, and use gasoline-dependent transportation. In particular, the amount of carbon dioxide (CO2) has increased by 30% since pre-industrial times (from about 270 molecules of CO2 per million molecules of air in 1850 to the present 360 parts per million), and continues to rise over time, due primarily to the burning of fossil fuel.
Because carbon dioxide
can drive climate change, it is important to be able to accurately determine
its heat absorption characteristics. The spectrum of heat absorption by
Earth's atmosphere contains hundreds of thousands of absorption
"lines". For carbon dioxide alone there are over sixty thousand
lines. In order to model the absorption spectrum of CO2, we need
to know the spectral location (wavelength), the strength, and also the shape
of each line. If we visualize the absorption line as an inverted bell-shaped
curve, the depth 
(amplitude) of the
curve is determined by the strength of the line and the amount of the
absorbing gas present in the atmosphere, whereas the width of the line is
determined by pressure and temperature. Near the center of the line, the
"Lorentz profile", based on a simple assumption that collisions
between molecules take place instantaneously, works well. However, as we move
away from the center toward the wings of the line, this is no longer true.
Here the details of collision processes play their roles in altering the line
shape. Understanding this collision-broadened absorption and determining more
accurate far-wing line shapes has been the focus of research conducted by
Drs. Ma and Tipping.
The figure at right shows the amount of absorption (y-axis) beyond one of the CO2 bands as a function of spectral location (x-axis) calculated assuming a Lorentz line profile (dashed curve) compared to laboratory measurements (shown by +). This clearly shows that away from the band the Lorentz profile greatly overestimates the amount of absorption. Thus, this line shape is not applicable here. Meanwhile, the calculated absorption based on Ma and Tipping's line profile (solid curve) agrees well with the measurements. As a result of this study, a more accurate calculation of CO2 absorption can be made, permitting a more precise determination of greenhouse warming due to CO2.
References
Ma, Q.
and R. H. Tipping 1998. The
distribution of density matrices over potential-energy surfaces: Application
to the calculation of the far-wing line shapes for CO2. J. Chem. Phys. 108, 3386.
Climate Change - A quick rebuttal to Augie Auer's opinion in the NZ Herald.
In the first week of May 2006, former NZ MetService chief meteorologist Augie Auer said global warming was a myth. He blamed journalists and bad science.
The article quoting Augie Auer is here: Auer in the NZ Herald
And a repeat of his personal views on the matter in May 2007 here: Augie Auer 'debunks' global warming...
In a nutshell, his main argument against anthropogenic (human made) climate change, and an argument made by many other climate sceptics is, that water vapour in the atmosphere is a much more potent 'greenhouse' gas than CO2 and that due to the vast abundance of water vapour the relatively small (380 parts per billion) CO2 content in the atmosphere would not contribute much to global warming, let alone the small contribution that humans were making to that CO2 content. And as most water vapour is naturally generated due to evaporation of the oceans, there was nothing that humanity would be able to do about it.
Let us look at the situation a bit more carefully:
It is true that by comparison of quantity there is a hell of a lot more water vapour in the atmosphere than CO2. Water vapour is a perfect absorber of infrared radiation and thus the main contributor to the so called 'greenhouse' effect. So far Augie is right.
And he is also right, that the Earth would be covered in ice, if it was not for the warming blanket of that water vapour.
However Augie omits to say this: Water vapour is not absorbing (shielding against radiation heat loss) in the entire infrared spectrum. In fact there are, thankfully, a few relatively clear 'open windows' in the absorption spectrum of water vapour because of the physical properties of the water molecule. If it was not for these 'windows' in the absorption spectrum of water vapour, our earth would find it more difficult to radiate heat away to space. And radiating in the infrared spectrum, a bit like the glow from your hot potbelly stove in winter, is the only way that Earth can loose thermal energy to space! If these remaining open windows in the infrared spectrum between the various bands in which water vapour absorbs were not there, then Earth would a much warmer place, and probably not very conducive to the current forms of life.
Water is so abundant in the atmosphere that in those areas where it absorbs heat radiation, the atmosphere is practically impermeable or 'black'. In other words in these areas the absorption spectrum is completely saturated. And no matter how much more water vapour there would be, it can't get 'blacker than black'. It’s a bit like putting a black tarp over your window at home. After the first one it dose not matter how many more you add, it won't get any darker - at least through that window!
But here is the catch: CO2 and also Methane have absorption areas of infrared radiation in some of the few remaining 'windows' in which the earth can 'shine out' so to speak and loose heat, because these windows in the spectrum are not already closed by water vapour's thick blanket. And it does not take much of a CO2 concentration at all, to lead to a strong absorption in these areas. In fact CO2 is so good at absorbing heat radiation in its bands that even at the natural background concentration of 280 parts per billion of CO2, the atmosphere is practically already almost 'black' in the centre of the CO2 absorption bands!
The anthropogenic additions of CO2 - in fact we will be practically doubling it by the mid of the century - will have a very measurable effect to the ability of Earth to radiate out of this 'window' precisely because the natural CO2 concentration is so low (compared to water) and the absorption is not yet saturated in these frequency bands so that any additional CO2 we bring to release is directly contributing to the darkening around the CO2 window in the absorption spectrum.
Thus Augies argument of the low concentration of CO2 relative to Water is actually coming home to roost!
Infrared Absorption Spectrum for CO2 and other greenhouse gases:
Absorption spectra of Water (H2O) - blue, Carbon Dioxide (CO2) - green, Oxygen and Ozone (O2 and O3) - red and the total (added) absorption spectrum - top.
The black line marked 5780K is the incoming solar spectrum, the 255K is the spectrum of the earth radiating out.
It is clear that the green CO2 absorption lines are blocking an important part of the 'water window' (blue line) in which Earth can radiate in the infrared out of the atmosphere.
To come back to the example of the house: Imagine that you have 6 windows through which you can see out. 4 are covered by a stack of black blankets (water vapour). Now somebody darkens one of the last two open windows with a thin sheet of dark fabric. How would that affect your house?
Augie says: How come you argue about one little thin sheet of fabric when I can see that stack of thick blankets…. Well, it all matters where you put it as it seems….
And so it goes that these few hundred parts per billion of CO2 will have a very dramatic effect on life on Earth.
All this is not to say, that there is nothing left to discover about the mechanisms of climate change and the regulatory system of our Earth atmosphere, far from it. And water plays a vital role in transporting heat around the Earth, especially in though processes of evaporation and condensation and the fact that these two processes happen often in different places.
But the basic science behind the effects of CO2 and Methane on the ability of Earth to radiate heat away to space is pretty sound. And once you calculate this, then it is obvious that Earth must warm measurably in response to our human made doubling of CO2. Everything else is almost an afterthought, i.e. what happens to the trapped heat, where will it go and how will it affect us.
Augie Auer also made a colossal mistake in the NZ Herald interview
inferring that only 3.2% of the CO2 in the athmosphere was human made. Far
from it. Since the the beginning of the Industrial Revolution the CO2 content
has risen from 280ppb to 380ppb, an increase of over 35%! And in short order
we will have doubled the CO2 content to levels double of anything the Earth
atmosphere has seen for hundreds of thousands if not millions of years
For further reading I recommend the following articles from the
Wikipedia:
Global
Warming
CO2, properties
CO2
in the atmosphere
Greenhouse
Gases
Radiative
Forcing
And from RealClimate:
Water
vapour: feedback or forcing?
How do we
know that recent CO2 increases are due to human activities?
And an excellent summary of answeres to many questions
raised by so called global warming skeptics:
Answers to
Global Warming Skeptics Questions
and from New Scientist:
Climate
change: A guide for the perplexed