sharks, ice cream, methane and hot water bottles

Analogy of the week has to go to Gary Younge in his piece about immigration and job losses.

Because two things are correlated does not mean one causes the other. Shark attacks and ice-cream sales both rise in the summer. They're linked by the season. But that doesn't mean ice-cream attracts sharks or people react to fear about shark attacks by eating more ice-cream.

This image outstrips another analogy that I found in the new issue of The Land. It's an obscure yet vital magazine. Produced by The Land Is Ours crew, it always gets into the fundamental cogs and gears of land ownership and use. Intelligent, thoughtful and informative, every issue has a number of things that make you want to read them out loud to people. I lifted their article Can Britain Feed Itself? for U-Know.

In the run-up to the Copenhagen Climate Blahblahblah, I pointed out that the Chinese and Indian use of measuring 'carbon intensity' rather than carbon emissions was a way of wriggling out of reducing emissions. The current issue of The Land has chewed the pencil and crunched the numbers. Check out these graphs.



Elsewhere there's a discussion about the climate impact of methane. It's a far more potent greenhouse gas than CO2, but it breaks down quicker. The convention is to measure a gas' potency over 100 years. At that level, methane is about 25 times stronger than CO2 [IPCC Fourth Assessment Report, Chap 2, table 2.14]. Some people are arguing that we should pick a shorter term (over 20 years, it's 72 times stronger), as cuts in methane mean greater cuts in the immediate greenhouse effect.

Anyway, the silver medal analogy of the week comes in a piece about this. The Land's Simon Fairlie argues that the longer-term impact of CO2 is what actually makes it more important than methane, not less. He quotes a piece by Geoff Russell:

a tonne of methane contributes 100 times more warming during the first five years of its lifetime as a tonne of CO2, yet 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 100 years, regardless of their atmospheric lifetimes.

This is like applying a blow torch to your leg for 10 seconds but calculating its average temperature 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 when measuring heat sources applied to legs. The implication being, of course, that a blow torch for 10 seconds and a 48 degree hot water bottle for 20 minutes have the same effect.

Fairlie then runs with it.

The analogy is potentially illuminating, but it is misleading because the methane blowtorches and the CO2 hot water bottles aren't being applied to anything as sensitive as a leg, but are heating up the atmosphere, as in a room.

Also, it is 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 blowtorches are individually intensely hot, they go out within a matter of seconds, whereas the hot water bottles keep piling up until their collective 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 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 blowtorches won't prevent the hot water bottles continuing to pile up until the heat becomes unbearable again; that will eventually happen even if the flow of blowtorches is completely stopped, and when it does happen it will be much harder to lower the temperature again.

In fact, the shorter lifetime of methane also speaks in its defence. In order to maintain the blowtorch heat, the blowtorches have to come into the room thick and fast. In other words, in order to maintain a given level of methane in the atmosphere we have to keep pumping out regularly otherwise the number of parts per million will fall away rapidly...

On the other hand, if humans stopped burning fossil fuels tomorrow, the burden of CO2 emitted in the 20th century would linger on for several generations.

This means that if the world decided to stabilise greenhouse gases at their current level, we would only need to reduce global methane output by 6.1 percent, but CO2 emissions by anything from 50 to 85 percent.

Any 'targeting' of methane to compensate for the manifest failure to reduce CO2 emissions... would be scapegoating methane to bale out CO2; or put another way, it would be extracting a subsidy from methane emitters for the benefit of fossil fuel users...

Whereas UK and US methane emissions comprise 8 and 9 percent of the greenhouse gas emissions respectively, India's methane emissions, two-thirds of which come from cows and rice, are reported to comprise 35 percent of her total. India, like most poor countries, burns far less fossil fuels per head than the USA or UK, and for many of her poor, a goat or a cow may represent almost the entirety of their greenhouse gas emissions.

Targeting methane emissions such as these to compensate for a failure to reduce CO2 emissions is another facet of the neo-colonialism that has pervaded international climate negotiations.

The Land. Go buy it.