A perspective paper on methane mitigation as a response to climate change.

preFAce COPENHAGEN CONSENSUS ON CLIMATE copenhAgen consensus on climAte The Copenhagen Consensus Center has commissioned 21 papers to examine the costs and benefits of different solutions to global warming. The project’s goal is to answer the question: “If the global community wants to spend up to, say $250 billion per year over the next 10 years to diminish the adverse effects of climate changes, and to do most good for the world, which solutions would yield the greatest net benefits? ” The series of papers is divided into Assessment Papers and Perspective Papers. Each Assessment Paper outlines the costs and benefits of one way to respond to global warming. Each Perspective Paper reviews the assumptions and analyses made within an Assessment Paper. It is hoped that, as a body of work, this research will provide a foundation for an informed debate about the best way to respond to this threat. Given the large uncertainties in the climate science and in assessments of climate change impacts, the estimated expected economic benefits of emissions reductions are very uncertain. A relevant alternative to benefit estimates is to base policies on acceptable levels of climate change such as the widely supported 2 K target. Methane is the second most important anthropogenic greenhouse gas only preceded by carbon dioxide. Methane has a relatively short atmospheric short-life time and therefore it has other economic characteristics than carbon dioxide. For example, if the ultimate aim of international climate policy is to stabilise the global average surface temperature to 2 K above the pre-industrial level at lowest possible cost, the current relative value of reducing methane as compared to carbon dioxide should be lower than its Global Warming Potential (GWP) value used in the Kyoto Protocol. However, this result is changed to the opposite if one adopts a cost-benefit approach. Methane is also an important precursor to tropospheric ozone. Tropospheric ozone has in turn serious consequences on human health, agricultural production and ecosystems. Taking into account this in social cost/shadow price estimates of methane can increase the value considerably, in the order of 100 %. Consequently, the benefit cost ratios of methane mitigation are strongly dependent on which approach is adopted when valuing methane’s economic impacts and if the tropospheric ozone co-benefit of methane mitigation is considered or not. Many sources of methane are non-point emission sources. This makes it harder to regulate and control methane emissions than most carbon dioxide emissions. The most important single sector emitting methane is livestock production. The technical measures available to reduce emissions from livestock are small. The combination of being a non-point emission source and having few technical abatement measures implies that output based policies may be appropriate policies for reducing these emissions. Our back of the envelope estimates point to a benefit-cost ratio of about 2 of having a beef meet tax on US$ 1 in OECD countries. This would reduce global emissions by 30 to 70 M ton CO2 equivalents per year using GWP calculated over 100 years.