[Stoves] New article on effects of traditional cooking methods

[Tami Bond]

Hi all,

Anyone who asked for a copy of the paper will get it on Nov 1. That is 
when the study is published officially. I don't mind sending it out 
before that, but the pdf does not have real page numbers in it, so it 
would be difficult to reference.

> 1: Is there the equivalent to a "half life", for these particles? For 
> example, if 1 tonne of such particles were distributed in the atmosphere 
> today, how much time would have to elapse before the particle content would 
> be 1/2 tonne?
>   
I prefer to think in terms of "e-folding time" (time to decay to 1/e 
tonnes) but it is not too far different. Models indicate that this 
lifetime is in the range of 5 to 9 days. We don't know all the processes 
that remove the particles, so one could say that this lifetime is uncertain.
> 2: Is there an "equivalent to CO2", in terms of the warming effect of such 
> particles? For example, if one tonne of such particles were added to the 
> atmosphere, what would be the tonnage of CO2 that would have to be added to 
> the atmosphere to get the same effect?
>   
Yes, although not everyone agrees that you can make such an equivalence. 
I did, anyway. (I think the first public estimate of this--ever-- was in 
my post to this list in 2001!) One also has to consider the lifetimes of 
the two species. The standard approach for trading in the climate 
business is to add up total warming over 100 years. One would think that 
this would make sooty particles negligible contributors, since they are 
gone within a few days. But in fact, they are very good absorbers, and 
do a lot of warming in their short lives. Integrated over 100 years, the 
warming by 1 tonne of black particles is about equivalent to the warming 
of 680 tonnes of CO2. That's in another ES&T article which we published 
last year.
> 3: Is there a difference in the warming effect of such particles depending 
> on their location within the biosphere?  For example, I would guess that a 
> particle on the ground, or near ground level, would have a greater warming 
> effect than would a particle at high elevation where half of the absorbed 
> radiation could be re-radiated back into space.
>   
Actually, the really high black particles warm more-- because they are 
over bright clouds which would otherwise reflect the radiation back to 
space. Yes, the warming depends on location. I can't think of a simple 
way to account for that, though. Will my stove emissions get 
convectively lofted and warm a lot, while your stove emissions are 
trapped under an inversion, and therefore my emissions are more 
'special' than yours? One could make such arguments, but I think one can 
gain a decent understanding from the average picture, too.

cheers,

Tami