While waiting to speak to Pastural Farming’s submission to the Finance & Expenditure Committee I listened to a submission by a scientist Rob Caithness on methane. He was submitting as a private individual. The basis of his submission is that methane is not a problem. Good on him for caring enough to take time off work and appear before the Committee.
Little by little the argument that enteric methane is causing global warming is eroding away. There was never much of an argument there in the first place. Tim Groser in his correspondence has indicated that he acknowledges the mounting uncertainty; Simon Upton who was the clown who signed Kyoto for Jenny Shipley’s government has admitted that including methane was a mistake.
If the uncertainty over whether methane is a problem isn’t enough, the use of Global Warming Potentials (GWP) to quantify emissions of greenhouse gases like methane is itself being questioned. And now with all this uncertainty the Government is proposing to increase the GWP of methane from 21 to 25. This will lift NZ’s emissions by 8% at the stroke of Minister Groser’s pen. Any work he does on free trade agreements will be instantly undone with his insistence on changing the GWP which, if future governments commit to an international agreement, will cost us billions.
The GWP has been 21 while Kyoto is in force because Kyoto agreed to use that value. The IPCC in its 4th assessment report of 2007 assigned a GWP of 25 to methane. With Kyoto all but over the Minister believes we should adopt the IPCC value. However since the IPCC’s 4th assessment report volumes have been written about the huge uncertainties of this GWP of 25. It uses the wrong timing, it is wrongly based on weight rather than volume and incorrectly assumes hydroxyl ions are scarce and ozone is increasing, among other concerns. The big problem with GWP’s is that the value depends on the time horizon and if that is short it is biased against a short lived gas like methane. The IPCC 5th assessment report will be released in 2014, there will be big changes to the GWP metric and the Government could have quite legitimately kept the GWP at 21 until the next review in 2015.
Prior to the signing of Kyoto a work by Daniel Lashof & Dilip Ahuja called Relative Contributions of Greenhouse Gas Emissions to Global Warming was the basis on which the idea of a single metric to measure different greenhouse gases progressed. They calculated that the GWP of a molecule of Methane was 3.7, which is 10.1 on a weight basis per tonne. This is a lot lower than 25 and the reason is that GWP’s are hugely complex, they attempt to compare the different effects of different gases. But gases have different effects depending on the concentration of that gas already in the atmosphere, and the concentration of other gases which interact with it. There are so many variables to factor in that it is impossible. The UNFCC acknowledges that GWP’s don’t work and if it could find a replacement metric it would use it and one of the reasons they don’t work is their complexity and variability. To nail down a metric and a number that equates the effect of one gas with another in every case is as easy as nailing jelly to the wall.
So to solve that problem the variables which are factored into Lashof and Ahuja’s work for accuracy were factored out and arbitrary figures used which were negotiated by the politicians and a GWP of 10 became 21 and now 25. Accuracy was sacrificed for convenience.
Not only is it overly simplistic and naïve to say that a tonne of methane has 25 times the same effect as a tonne of CO2, it is simplistic to assume that it has any impact on global warming at all. And this is backed up by Rob Caithness B Sc Chem
Iam off to Australia for a few days, I could not get the link to Rob’s submission to work and the plane won’t wait, so when I get back I will post the link to his submission on te website, it is worth the read.