Does anyone have the breakdown of how these figures are calculated? I've yet to see anything that quashes my natural scepticism.
To take the simplest example, if you have a lone atom of carbon it has a mass of 12. If you fully combust it in air you end up with carbon dioxide, which has mass 12+16*2 - this is likely to be the essence of the apparent magnification.
There's no net change in mass, the air got 'lighter' when its oxygen was stolen. Jet A1 will be a mix of hydrocarbons so they will have taken a representative mix and performed a similar calculation.
On the quantitative side, one needs to be careful with the the metrics, carbon vs carbon dioxide, and as all aviators know mass vs volume. (There is another factor that i forgot; other gases with a greenhouse effect. I cannot recollect an example, but it's possible that for convenience of a single metric, these gases may be converted into an equivalent CO2 amount.)
Newsnight on BBC2 had a good running report on lower carbon lifestyles in the form of Justin Rowlatt and his family's investigation into reducing their environmental impact.
http://news.bbc.co.uk/1/hi/programme...ht/4741392.stm
Here's his blog, generally very interesting reading and he has some genuine experts go through some of the thornier issues (if you feel the need to comment on the first issue, i'd suggest confining it to his blog comments not here):
http://www.bbc.co.uk/blogs/newsnight...ustin_rowlatt/