Some answers
<font color=blue>Which gases are known as the "greenhouse gases"?</font>
All gases in the atmosphere have "heat retention capability", what makes them "greenhouse gases". What we must take into account is: 1) degree of heat retention, 2) concentration in the atmosphere. From there we could make a table of "importance" of the gases. (Although the gases with the highest heat retention are CFCs, they are present in the stratosphere and troposphere at concentrations ranging from 100 ppb (parts per bilion) to 0,1 ppt (parts per trillion), making them worthless as greenhouse gases.
In such <b>Greenhouse Gases Table</b> we would see the most important one is <b>"water vapor"</B> (better known as "relative humidity), because of its huge concentration in the atmosphere. Then comes, lagging far behind, CO2, then Methane, NOx (nitrous oxides), Argon, and other gases whose importance is near zero (as CFCs and ozone, whose concentration is 0,000003 percent, or three millionths percent).
Water vapor accounts for about 95% of the "heat retention" capability of the atmosphere. Humidity comes from the evaporation of water in the oceans (75% of Eart's surface), rivers, lakes, evapoperspiration from forests, jungles, grass lawns, prairies, crops, etc... anything with leaves. CO2 is provided in its 97% by nature (volcanoes, forests and savanas fires, rotting of wood and organic matter in forests and jungles, etc). Man made CO2 amounts to about 3,5%. Methane is mostly provided by nature, (rice paddies, forests, zillion of ants, termites and other insects, and some comes from cattle belching and other bodily functions).
<font color=blue>What percentage of Earth's atmosphere do they currently represent? </font>
Water vapor = 95% - CO2 = 3,5% - Methane = 1%. Other gases = 0,5%
<font color=blue>Has the percentage trended up or down or stayed steady lately?</font>
CO2 has increased from 312 ppm in the 19th century to 365 ppm today. Not much, considering that when CO2 went down from 6,000 ppm to 2,600 ppm during the Cretaceus period (90-60 millions years ago), the temperature remained quite the same (1° C higher than now). But CO2 concentrations, as determined by proxy studies, did not go up when the temperature increased during the Climatic Optimum between 800-1250 AD, when temperatures reached 2°C higher than now. Nor did the concentrations go down when the Little Ice Age came about 1300 AD. This show there is no correllation between <b>CO2 increase</b> and <b>then</b>, temperature increase, (or viceversa). Many studies have shown, though, that some correllation exists: the CO2 increase <b>comes after</B> temperature increase, lagging about 100-300 years. But there is strong and direct positive correllation between sun's activity (sunspots) and climatic change. See:
<A href="http://solar-center.stanford.edu/sun-on-earth/glob-warm.html"><B>Global Warming: Does it Exist? </B></A>
<font color=blue>Do we know how many years back that trend goes? (>100, I hope?) </font>
See above.
<font color=blue>Of that percentage, how much is attributable to man? </font>
Increase of CO2 can be attributed to mankind in about 3%.
<font color=blue>Has that percentage trended up or down lately? </font>
The trend is upwards since beginning of the 20th century.
<font color=blue>Of those percentages, what has their rate of change been? </font>
CO2: From 312 ppm to 360 ppm in about 150 years.
<font color=blue>Do we have figures on how fast the Earth converts "greenhouse gases" into something less problematic? (say, CO2 -> O2) </font>
For example, measurements from Mount Mauna Loa (Hawaii), showed an accumulation of CO2 aproximately equivalent to a liberation of 3 Gt (giga tons , or million tons) of carbon every year, However, in 1978 and 1979, fossil fuels burned amounted to 5,1 and 5,4 Gt of carbon. More than 2 Gt of carbon (some years more than 2,5 Gt) is absorbed by the oceans and other natural processes perhaps transforming it into limestone (calcium carbonate). Oceanologists and chemists said the oceans cannot absorb such amount, until George Woodwell (Marine Biological Laboratory, Woods Hole, Mass.) and Bert Bolin, in Stockholm, proved that the old notion claiming that most CO2 was absorbed by biomass, stimulating growth of forests and jungles in viewe of the more availability of CO2 for photosynthesis was wrong. They proved (independently) that forests and biomass actually can produce more CO2 than they remove from the atmosphere.
Measurements of ice cores from polar samples, showed that during the most recent glaciation (from 11,000 years ago to 100,000 years ago), CO2 concentrations could have been half of today's, probably because cold oceans absorb more CO2, or perhaps there was less green areas producing CO2 (most of the Northern Hemisphere was covered with a 3,000 meters high ice layer).
<font color=blue>What are the major mechanisms that the Earth uses for this conversion? </font>
As stated above, oceans absorb CO2, depositing it in the ocean floor. There is small conversion being performed when cement and lime mortars absorb CO2 to be tranformed into calcium carbonate. But this process just reverses the original release of CO2 occurred when cement and lime was manufactured: calcium carbonate transformed into calcium oxide (quick lime), or limestone burned to make cement "clincker".
<font color=blue>If "greenhouse gases" are growing, are they growing faster than Earth's ability to convert them? </font>
CO2 is growing at a rate of 2 ppm per year. Scientists are divided into two groups, those who say CO2 increase is "man-made" (fossil fuels) and hence the warming produced by CO2, and those claiming that CO2 increase is mostly produced by the increased temperatures that produce increased growth of vegetation, and a silght increase in volcanic activity during the 20th century.
--- BTW, hydrocarbons, or oil, <b>are NOT FOSSILS</b>. Fossils are only carbon layers coming from ancient jungles and forests, quite superficial layers, of course. According to the theory of Dr. Thomas Gold, Stanford Univ. Oil is being produced constantly by helium and methane, deep in the Earth's crust (8,000 meters deep and more). This seems plausible, as if oil was produced by ancient forests and jungles, where did those 8,000 -16,000 meters of thick covering came from? That's a lot of sediment necessary for covering the whole Earth. Carbon deposits can be explained this way, but not oil. Just see: <A HREF=http://mitosyfraudes.8k.com/INGLES/FossilFuels.html"><B> "Fossil Fuels are not Fossil"</B></A>.
<font color=blue>Are there any "sudden" changes climatologists are hoping for to affect the conversion? (volcanoes, sea salt, iceberg melt, ocean methane, etc.) </font>
There are not sudden changes in paleoclimatic history. Leave out asteroid impacts. Earth processes are measured in a geological scale, that means, hundred of thousands, or millions of years.
Before you start thinking in more questions, it would be useful if you paid a visit to this link:, where you can get the scientific facts and necessary data: <A HREF="http://www.john-daly.com/"><B>"Still Waiting for the Greenhouse"</B></A>. There you can find links to other sources and institutions involved in the Global Warming issue. You could also go to: <A HREF="http://www.nationalcenter.org/KyotoQuestionsAnswers.html"><b>Kyoto Questions and Answers"</B></A>
Other interesting site that covers most environmental issues (Myths and Frauds) is located at: <A HREF="http://mitosyfraudes.8k.com/ENGLISH.html"><B>"Ecology: Myths and Frauds"</B></A> where you can satisfy your thirst for knowledge. Have a nice trip in the web!
