When I've seen that argument being made before, carbon dioxide is usually the major gas of interest. Obviously, there are a lot of sources of CO2 out there.
On that page you linked to... there's some interesting information there, but certain aspects of the presentation worry me.
Here's a couple of quotes:
web.archive.org/web/20020...l/gwp.html says the GWP of methane is 21 for a 100 year time horizion, but that page is a few years old. The wikipedia article on GWP has 23 for this number.
Now, there isn't an indication of the time horizon in use on the methan sources page. If they're using a 100 year horizon, and the use of Tg in the section on natural sources isn't just a persistent accidental omission of something that is included in the numbers, those 145 Tg of methane per year correspond to...
3045 to 3335 TgCO2 Equivalents. (Depending on which GWP number you use; the higher number from wikipedia is likely the more current one.)
It makes those totals from the U.S. seem less impressive.
Of course, there's some caveats here.
One, of course, is that those numbers *are* just for the U.S. To make useful comparisons to the numbers for global natural methane production, numbers for the entire world on human-caused methan production would be required.
Two, they could be using a longer time horizon than 100 years. In which case things become quite a bit less dramatic.
I haven't seen (and lack the time to continue looking for) anything to indicate that the "60% of global methane emissions are related to human-related activities (IPCC, 2001c)" estimate is wrong. But the way this particular page is constructed makes me highly suspicious, because I see two possibilities which both bother me.
1. The numbers in the natural methane sources section are in TgCO2 Equivalents, but the notation is wrong by accident. This requires no malicious intent on anyone's part, but casts certain doubts on their professionalism. The page says it was last updated in October; if it was an error, I can't believe I'd be the first to notice it.
2. The numbers in the natural methane sources section are in Tg, with the proper notation used. In this case, I have a hard time believing that deception isn't intended. TgCO2 Equivalents and Tg cannot be directly compared, yet the design of the page sets you up to compare the numbers. I once had a class which covered ways various statistics could be used to deceive, and one of the major ones was inviting a comparision between two things that are in different measurements or on different scales. It's a great technique, because you can do it without technically lying. But that doesn't make it less a deception.
Now, could they have decided to use these different types of numbers without any deceptive intent? Yes. But it would be a pretty damn stupid thing to do. The point of GWP and TgCO2 Equivalents is to make reasonable comparisons between the effects of different gases. That's why it's used in places like the document on methane emissions from landfills - because that document also discusses N2O emissions. Reasonable comparisons are useful.
Given the commonality of use of TgCO2 equivalents, I have a much easier time believing malice in this case than I do stupidity. In either scenario, it makes me doubt the reliability of this page, and by extension the reliability of the organization that produced it.
-Morgan.
"Oh poor Lyner... you go out with so many underage girls you can't remember them all."
-Krusche
On that page you linked to... there's some interesting information there, but certain aspects of the presentation worry me.
Here's a couple of quotes:
Quote:
Table 1 U.S. Methane Emissions by Source (TgCO2 Equivalents)
Quote:Natural methane is being measured in teragrams in all cases in that section. The section on human-related sources and pages with further details that I've looked at use TgCO2 Equivalents, which includes another factor - the GWP (Global Warming Potential) of the gas in question.
Although much uncertainty remains as to the actual contributions of these natural sources, available information indicates that global methane emissions from natural sources are around 190 Tg per year.
web.archive.org/web/20020...l/gwp.html says the GWP of methane is 21 for a 100 year time horizion, but that page is a few years old. The wikipedia article on GWP has 23 for this number.
Now, there isn't an indication of the time horizon in use on the methan sources page. If they're using a 100 year horizon, and the use of Tg in the section on natural sources isn't just a persistent accidental omission of something that is included in the numbers, those 145 Tg of methane per year correspond to...
3045 to 3335 TgCO2 Equivalents. (Depending on which GWP number you use; the higher number from wikipedia is likely the more current one.)
It makes those totals from the U.S. seem less impressive.
Of course, there's some caveats here.
One, of course, is that those numbers *are* just for the U.S. To make useful comparisons to the numbers for global natural methane production, numbers for the entire world on human-caused methan production would be required.
Two, they could be using a longer time horizon than 100 years. In which case things become quite a bit less dramatic.
I haven't seen (and lack the time to continue looking for) anything to indicate that the "60% of global methane emissions are related to human-related activities (IPCC, 2001c)" estimate is wrong. But the way this particular page is constructed makes me highly suspicious, because I see two possibilities which both bother me.
1. The numbers in the natural methane sources section are in TgCO2 Equivalents, but the notation is wrong by accident. This requires no malicious intent on anyone's part, but casts certain doubts on their professionalism. The page says it was last updated in October; if it was an error, I can't believe I'd be the first to notice it.
2. The numbers in the natural methane sources section are in Tg, with the proper notation used. In this case, I have a hard time believing that deception isn't intended. TgCO2 Equivalents and Tg cannot be directly compared, yet the design of the page sets you up to compare the numbers. I once had a class which covered ways various statistics could be used to deceive, and one of the major ones was inviting a comparision between two things that are in different measurements or on different scales. It's a great technique, because you can do it without technically lying. But that doesn't make it less a deception.
Now, could they have decided to use these different types of numbers without any deceptive intent? Yes. But it would be a pretty damn stupid thing to do. The point of GWP and TgCO2 Equivalents is to make reasonable comparisons between the effects of different gases. That's why it's used in places like the document on methane emissions from landfills - because that document also discusses N2O emissions. Reasonable comparisons are useful.
Given the commonality of use of TgCO2 equivalents, I have a much easier time believing malice in this case than I do stupidity. In either scenario, it makes me doubt the reliability of this page, and by extension the reliability of the organization that produced it.
-Morgan.
"Oh poor Lyner... you go out with so many underage girls you can't remember them all."
-Krusche