Agriculture Reference
In-Depth Information
Reducing emissions of short-lifetime potent gases such as methane is therefore a
valuable means of rapidly slowing global temperature rise. This gives reduction of
methane emissions a high economic value (perhaps even greater than that reflected in
the GWP of 23) as they are effective at slowing the rate of global warming. They are
also likely to be even more important at some point in the future should the effects of
climate change become critical and fast-acting measures need to be adopted.
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In other words, if pressure from climate change becomes more intense we are likely to
see the GWP of methane jacked up even further with the result that methane will occupy
a more imposing proportion of the global carbon budget. In the language of economists,
the higher the discount rate, the more commanding a position methane takes in the glob-
al carbon budget. There are increasing calls from vegan and anti-livestock commentators
such as Peter Singer and Robert Goodland for the GWP of methane to be raised from 25 to
72. Singer, together with two colleagues Geoff Russell and Barry Brooks, has employed a
useful analogy to explain the effect of GWP ratings:
A tonne of methane has 100 times the warming during the first five years of its
lifetime as a tonne of CO
2
, but under current Kyoto rules, its comparative potency is
set at 21. This is because the relative impacts of ALL greenhouse gases are averaged
over the same period of 100 years, regardless of their atmospheric lifetime. This is like
applying a blow torch to your leg for ten seconds but calculating its average temper-
ature as just 48 degrees because that's what it is when averaged over 20 minutes, with
20 minutes being used because that happens to be some agreed international standard.
The implication of course being that a blow torch for ten seconds and a 48 degree hot
water bottle have the same effect.
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The analogy is potentially illuminating, but it is misleading because the methane blow-
torches and the CO
2
hot water bottles aren't being applied to anything as sensitive as a leg,
but are heating up the atmosphere in a room; and it is also incomplete, because there isn't
just one blowtorch and one hot water bottle, there are hundreds of them being brought into
the room continuously. Although the blow torches are individually intensely hot, they go
out within a matter of seconds, whereas the hot water bottles keep piling up until their col-
lective heat far outstrips that of the relatively few blowtorches that remain ignited at any
one time.
At the point where the heat becomes unbearable, the obvious first course of action is to
reduce the flow of blowtorches into the room. That will be the quickest way of reducing the
temperature back to the level it was just before it became unbearable. Reducing the flow of
hot water bottles will have comparatively little immediate effect. But removing the blow-
torches won't prevent the hot water bottles continuing to pile up until the heat becomes
