Professor Peter Thorne:

As my colleague, Dr. Rogelj, said, most of that methane, because of its half life being 12 years, has been emitted in the past 20 to 30 years. It will be from those principal sources. There was a figure in the submission I made that arose from the Intergovernmental Panel on Climate Change. Fossil fuels are contributing approximately 114 Tg annually, landfills and waste contribute approximately 55 Tg, biomass burning contributes 20 Tg to 40 Tg, rice cultivation contributes 25 Tg to 37 Tg and livestock contributes 106 Tg to 113 Tg. The two principal sources globally, and I stress this is globally, are fossil fuels and livestock. They are approximately equal. They are probably about one third each with all other human sources accounting for the remaining third.