Methane from farms, waste and fossil fuels rising
An international effort to get a handle on methane emissions has revealed the potent gas is rising in the atmosphere faster than it has for 20 years. Long-running measurements of the air at Wellingtons windy Baring Head contributed to the French-led study , which involves researchers from Australia, the United States, Japan, the Netherlands, New Zealands Niwa and elsewhere, all working under the umbrella of the Global Carbon Project . The goal is pinning down how much methane is being released to the air, and where from. The study found current rates of methane emissions are at the highest, hottest end of the range of scenarios put out by the Intergovernmental Panel on Climate Change (IPCC) though the authors say that trend needs confirming in the next few years. Methanes current trajectory is in between the two worst IPCC emissions scenarios a trajectory putting the world on track for more than 3 degrees Celsius of warming by the end of this century, said the authors. This trajectory implies that large reductions of methane emissions are needed to meet the 1.5 to 2C target of the Paris Agreement, they said. The researchers found peoples activities not natural sources seemed to be behind most of the increase, with equal shares coming from the fossil fuel sector, agriculture and the waste sector. Globally, livestock are the biggest source of methane from human activities, the research shows, closely followed by oil and gas drilling, then waste and landfills, then coal mining. Next comes rice-growing. If oil, gas and coal extraction and use are added together, fossil fuels rival animal farming as a methane source, even leaving aside the climate impact of carbon dioxide from burning oil, gas and coal. READ MORE: * Seen from space, US gas well blowout created a methane 'super-emitter' * Greenhouse gas levels broke records in 2018 * The power of a poem: Kiwi scientist boils down IPCC climate change report in haiku Rice paddies, cows and sheeps guts and landfills all produce methane by creating an oxygen-free environment where methane-making microbes thrive. Natural sources are also a large contributor, making an estimated 40 per cent of the output, compared with 60 per cent from peoples activities. Natural methane emissions are dominated by wetlands, with much smaller contributions from other sources, such as wild animals. Even wild termites are a non-trivial source of the greenhouse gas, the study shows. Like cows, termites produce methane when they digest plants. But it is human-created sources that are rising quickly and causing concern among researchers. Niwa principal scientist Mike Harvey said the analysis showed methane in the atmosphere was increasing faster than any time in the past 20 years. There has been a 9 per cent global increase in annual emissions, or 50 million tonnes a year, between the beginning of the 21st Century (when methane in the atmosphere was stable) and 2017, he said. Methane concentrations are now at the highest levels we have recorded at Baring Head since the start of the 21st Century. This trend is a significant cause for concern in tackling global warming. There remains uncertainty about some estimates of methane sources. Despite improvements in understanding since the last tally, the studys authors ended up with a large gap about 30 per cent between the estimates of how much methane was coming from sources on the ground, versus how much was actually found in the atmosphere. The study drew together two different techniques: records monitoring methane levels in the air, from different parts of the globe, and ground-up estimates of what human and natural activities are making (for example, by adding up the output of all the individual cows). The authors acknowledged the uncertainties, especially in the tallies of natural sources, particularly wetlands, geological leaks and inland water bodies, suggesting there might be some double-counting. New Zealand researchers who were not directly involved in the study said it was a shame the findings didnt incorporate isotope data. Victoria University Adjunct Professor Martin Manning, a methane specialist, said although the isotope data has limits, proceeding without it made the claim of best estimates optimistic. Isotopes can be used to fingerprint methane molecules and tag them as coming from either hundreds-of-millions-of-year-old fossil fuel sources or fresher sources, such as agriculture. GNS Sciences Jocelyn Turnbull said isotope information was likely to be added to the next iteration of the methane budget. The MethaneSAT project to track methane by satellite which has $26m New Zealand government funding could also help fill in some unknowns, said Turnbull. Satellite data was not used this time, because the work is still fairly new. This latest effort shows that, although there is now a good general understanding of methane emissions, the devil is in the details, and there is still a lot left to understand, particularly at the national and regional scales, Turnbull said. Globally, methane is the second major climate-heating gas after carbon dioxide. New Zealand is unusual in that methane makes up a large portion of its climate impact , with livestocks methane output dwarfing that of landfills or fossil fuel industries. (Carbon dioxide from transport is rising fast, but thats a separate category). Researchers have debated how much methane needs to fall to keep New Zealands contribution to warming within responsible limits. But scientists working in the field agree our output must drop, with the Government setting an interim target of 10 percent from 2017 levels by 2030. Work has been underway for years to find a vaccine or a food supplement that could help shrink cattles output, however none is yet on the market. Breeding for lower-methane output is another possibility . Lord Deben, chair of British Climate Change Commission , told a New Zealand Agricultural Greenhouse Gas Research Centre seminar this week that meat consumption in countries such as New Zealand needed to drop to avert worsening climate change. But, he added, New Zealand farms were in a good position to supply the remaining demand.