Professor Myles Allen:

I will speak directly on that point. Our long-term legacy on geological timescales is undoubtedly our fossil CO2. In that respect, biological cycles are not effecting the release of fossil CO2 whereas methane from mining is. On multi-century timescales, it is the fossil carbon that matters. That is why I said in my little briefing note that I know that we are talking about methane. I get that we have to stay on topic this afternoon, but I know that the committee is going on to talk about sectoral budgets so please do not forget about fossil CO2 because that is what our great grandchildren will actually care about.

We are focused on methane here. There is no question that increasing a herd size has a warming impact on the planet because it increases the amount of methane in the atmosphere. It stirs up the methane cycle. It may be a natural cycle but if you increase the number of cattle, you are revving it up and increasing the amount of methane in the air at any one time. All I have been arguing for is that it should be reflected in the accounting and that the impact on these different gases on global temperatures.

On Dr. Mitloehner's point on fracking, it is important to get this right and dangerous to get wrong. In my briefing note, I quoted a sentence from the recent Intergovernmental Panel on Climate Change report, which states, "Expressing methane emissions as CO2-equivalent using GWP100 (the standard method) overstates the effect of constant methane emissions on global temperature by a factor of 3 to 4, while understating the effect of any new methane emission source by a factor of 4 to 5". This means that those frackers got away with the impact of their activities on global temperature in the past 20 years being understated by our conventional accounting systems by a factor of four to five, while at the same time we have an accounting system that overstates the impact of a herd that has been around for more than 20 years by a factor of three to four. We do not need to have this problem. We can do this right. We do not need to misrepresent the impact of these gases on global temperature. All I am calling for is that we get it right. Methane is important. That is why it is so important to get its impact on global temperature right in formulating policy.