The Climate Change Benefits of Reducing Methane Emissions

The PAGE95 integrated assessment model is used to calculate the marginal benefit of immediate cutbacks in methane emissions, and compare them with the benefits of carbon dioxide reductions and the costs of methane reduction measures. The main result is that immediate cutbacks of methane bring a marginal benefit of between $30 and $260 per tonne, with a mean value of $110 per tonne. This compares to a benefit of between $10 and $50 per tonne of carbon, with a mean value of $20, for immediate cutbacks of carbon dioxide (all values in 1990 dollars). A sectoral and regional breakdown finds that two-thirds of the benefit is non-economic and only about 5% of the benefit occurs in the European Union (EU) and 8% in the USA; the vast majority of the benefit is felt in other regions, particularly in the developing world. Analysis up to 2200 shows the benefit continuing throughout the next century, peaking after 2050, even though methane stays in the atmosphere for only about a decade. This is because the surface-troposphere system typically takes decades to regain equilibrium, owing principally to the thermal inertia of the oceans. Exploring a range of alternative assumptions shows that the benefit from methane reduction is most sensitive to the discount rate. Using a pure time preference rate of 2% per yr instead of 3% per yr, almost doubles the mean benefit to $190 per tonne; a rate of 1% per yr doubles the mean benefit again to $380 per tonne.