10525Re: Transit pass - Best Weapon Against Climate Change?
- Oct 17, 2007Jym Dyer <jym@...> wrote:
> No, the transport sector is responsible for more emissions thanMethane has a greater impact, but this impact declines over time;
> that, any way you slice it. The question would actually seem
> to be which type of emission has more impact.
however this may not matter if we're at a "tipping point."
Methane from animals has a 23 times stronger global warming potential
than does Carbon dioxide, but the difference is that methane breaks
down in the atmosphere into carbon dioxide and water, with a half-life
of 7 years. That is, if you put 100 units of methane into the
atmosphere today, they contribute to global warming like 2,300 units
of carbon dioxide, but after 7 years there are 50 units of methane and
50 of CO2, with an effect of 50x23 + 50 = 1,200; after 14 years, it's
25x23 + 75 = 750, and so on.
So if we stopped all CO2 emissions today, that stuff would still be
there forever, but if we stopped all methane emissions today, its
effect would decline over time.
Now, that decline may or may not matter, in that if we're at some
"tipping point" where the human-added effects lead to a feedback loop,
then that methane will be less tomorrow doesn't help us today - if the
climate's on the edge of a cliff, that what gives it the final shove
over to fall under its own weight will later decline doesn't matter.
Good farming practices mean a small level of meat consumption, and
would lead to much less methane emissions.
Absent fossil fuels to make fertiliser, etc, we'll need animals on the
land. And that sort of mixed farm, the "traditional" one with family
cow, a pig or two, a chicken coop, a vegetable garden, few acres of
grain and pasture, works very well. Those animals will breed (you have
to breed cows if you want their milk), and that'll be more than the
land can support, so you have to kill them; you may as well eat them.
This however leads to a much lower meat consumption than we see today
in the West; in the USA and Australia it's something like 110kg
(240lbs) annually per person. In an economy of mixed farms it'd be
more like 10kg.
Animals on mixed farms produce far less methane than animals in
feedlots being fed corn. Combine that with less livestock overall, and
you'll get considerably smaller methane emissions.
I think that carfree cities would inevitably mean less meat in any
case, as with trade reducing in range, and less volume of trade
overall, the large factory farms producing it all would become
financially unviable. About ten years back it was seriously proposed
that all of the EU's pig-farming could be done in a large central
facility in Poland. That sort of One Big Facility, whether for pigs or
electricity or t-shirts, is not really practical in terms of the
carfree cities concept, as I understand it.
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