Talk:Airborne fraction

Surely airborne fraction is what it's name suggests.....simply the Airborne fraction of a gas, and not limited simply to human GHG emissions. Restepc (talk) 20:50, 15 March 2008 (UTC)
 * I've never heard it used that way. Have you? William M. Connolley (talk) 21:08, 15 March 2008 (UTC)

I've never heard it used before today at all, it does not appear to be a well known scientific term, so I was interpreting it as if it were straight forward English....which I imagine is how the term originated. I see the term used as 'the airborne fraction of CO2', which I imagine means it could be used for other gases as well....I can't see any reason why it wouldn't be, although obviously it's used most about CO2 because of the sheer amount of attention paid to it recently...Restepc (talk) 21:27, 15 March 2008 (UTC)
 * How would you know if it were a commonly used term in climatology? Like most technical terms, it has a technical meaning. Its derivation is obvious: its the fraction of human-emitted CO2 that remains airborne. The concept is needed because CO2 in the atmos is going up by less than we emit; because its being absorbed by the oceans and land. AFAIK, other gases (e.g. methane) don't have natural sinks-by-absoption in the same way (methane sink is by being destroyed) so the concept isn't so interesting there. You can use the methane lifetime instead, since it has one. CO2 has many William M. Connolley (talk) 22:35, 15 March 2008 (UTC)

I am still not convinced, but as the article is so new I'll leave it for a few weeks in the hope that it gathers appropriate sources

Restepc (talk) 22:47, 15 March 2008 (UTC)

Knorr paper
Just scanning a few of the news reports mentioning the Knorr paper, it is abundantly clear that many, at the very least, most of the headline writers, do not have a clue as to what this article is about. I read one article claiming that this was a death knell for the global warming crowd. Sad, really.-- SPhilbrick  T  00:44, 2 January 2010 (UTC)
 * Surprise! That's why we prefer to avoid the popular press for scientific topics as far as possible. --Stephan Schulz (talk) 00:47, 2 January 2010 (UTC)

Unclear

 * The airborne fraction is a scaling factor defined as the ratio of the annual increase in atmospheric CO2 to the CO2 emissions from anthropogenic sources. 
 * It represents the proportion of human emitted CO2 that remains in the atmosphere. 

These statements can't both be true, can they? (Unless the airbourne fraction never ever changes.)

One refers to annual absorption, the other refers to the long term absorption. If the sinks became differently effective, then the annual increase would change, and so would the percentage of total emissions still airborne, but not equally so.

For eg, suppose the sinks suddenly became much more effective, so much so that the annual increase dropped to zero, or went negative. After one year, there would still be man made carbon in the air, so while the percentage of total emissions still airborne would have dropped, it would certainly not have dropped to zero.

Alternately, if the sinks failed completely, the ratio of the annual increase to emissions would actually exceed 100% (because of the natural sources of carbon), but the percentage of total human emissions still airborne would be less than 100% because of past absorption of past emissions.

The amount absorbed in a given year should be related to the amount in the atmosphere, not the amount added to the atmosphere.

Regards, Ben Aveling 06:53, 8 January 2010 (UTC)

Wiki Education assignment: Biogeochemical Cycles
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