From: kym@kymhorsell.com   
      
   Peter Percival  wrote:   
   > R Kym Horsell wrote:   
   >> Peter Percival  wrote:   
   >>> One hears about the degree to which airlines, shipping, cattle   
   >>> farming,... are contributing to greenhouse gases and thus to global   
   >>> warming.  How much do humans contribute by exhaling?   
   >>   
   >> Carbon comes in several forms call "isotopes".   
   >> Some isotopes indicate the carbon has come from underground and   
   >> out of contact with the environment for millions of years.   
   >> Some isotopes indicate they have come from a biological source   
   >> recently.   
   >>   
   >> Scientists can look at the carbon in CO2 and determine that the   
   >> extra carbon dioxide in the atmosphere that has accumulated significantly   
   >> since the 1850s (roughly 1600 Gt) is almost all from a source that was   
   >> biological yet out of contact with the enviornment for millions of years.   
   >>   
   >> Moreover the amount of extra CO2 in the atm roughly corresponds   
   >> with about 1/2 the total coal and oil burned in the past 150 years.   
   >> The other 1/2 has apparently ended up in the oceans where it has   
   >> decreased the pH by around .3 points.   
   >>   
   >> Google and highschool science is your friend.   
   >   
   > It maybe that my question was not clearly worded.  My apologies if   
   > that's so.  I'll try again.  One hears that cattle farming, for example,   
   > puts so many tonnes of CO_2 into the atmosphere annually.  Or it may be   
   > that cattle contribute such-and-such a percentage of all emissions.   
   > What I'm asking for is the numbers for humans: so many tonnes per annum   
   > or such such-and-such a percentage of all emissions.  Get it?   
   ...   
      
   The wording was as clear as the underlying assumptions.   
      
   But as indicated breath is not a human emission. Emissions accumulate   
   in the atm and it seems human-breathed-out-CO2 does not.   
      
   Calculating a percentage then makes as much sense as what   
   is the fraction of 5 apples from 10 oranges.   
      
   If you want to calculate the number of Gt then take the amount of   
   CO2 breathed out by a single human in 1 year, multiply by 7 billion   
   and divide by around 2 to allow for the range in sizes.   
      
   Google and a calculator are your friends.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)