The following is an explainer provided by Frontiers in Science. The introduction has been lightly edited.
Methane is the second-most important greenhouse gas driving climate change – and levels are rising fast, especially since 2020. Despite this, little action has been taken to reduce methane emissions.
In a new paper published in Frontiers in Science, a team of researchers - including Zhen Qu, assistant professor of marine, earth and atmospheric sciences at NC State - examine the faster-than-predicted rise in methane emissions, the reasons for it, and how this threatens our ability to limit global warming to 1.5°C or 2°C. The article also outlines three methane "imperatives" for reducing emissions – and provides analyses and a new online tool to help countries optimize cost-effective strategies for reducing methane emissions. The article's main points are summarized below.
Why do methane emissions matter?
Methane is a potent greenhouse gas, responsible for about half of global warming since preindustrial times. Alarmingly, methane emissions have risen rapidly since 2006, with 2021 and 2022 recording the largest emissions on record. This rise is much faster than projected by models and, if not addressed, puts our ability to meet climate targets at risk. On the flip side, reducing methane is a cost-effective way to rapidly slow warming.
Methane impacts human health and agriculture too, by contributing to the formation of ground-level ozone. This harmful air pollutant causes premature deaths in adults through respiratory illness and cardiovascular disease and in children under five years old, especially in low- and middle-income countries. Ozone is also harmful to many plants and reduces crop yields.
Why are methane emissions growing?
Previous studies identify three main sources of rising methane emissions since 2006:
• fossil fuels, through leaks and incomplete flaring of gas during the extraction, processing, and transport of oil, natural gas, and coal
• agriculture, mainly through increased numbers of livestock and, to a smaller extent, expanding rice production in Africa
• natural wetlands, where global warming is causing faster decomposition of organic matter by methane-producing microbes.
The researchers conclude the 2020-2023 spike is driven mainly by the fossil fuel sector, especially oil and gas operations, and surging emissions from wetlands due to La Niña conditions.
While landfill is another major source of anthropogenic emissions, these are unlikely to have increased recently. Other natural sources, such as thawing permafrost, currently make only a small contribution to total methane emissions.
What can we do to reduce methane emissions?
The authors call for three actions, or imperatives, for reducing methane emissions.
- Reverse the growth in methane emissions across all major anthropogenic sources: fossil fuels (coal, oil, and gas), agriculture (livestock and rice), and landfill.
- Align methane and carbon dioxide (CO₂) mitigation to reduce atmospheric levels of both gases simultaneously, instead of the current focus on CO₂.
- Optimize technologies and policies for methane abatement at a global, national, and sector level.
Reducing methane emissions requires a mix of technological solutions and systemic changes to practices and behaviors. The authors show the majority of these are cost-effective – but need strong policy measures to support their broad adoption.
Technological solutions include capturing methane and using it for energy generation; minimizing leaks from fossil fuel operations by repairing infrastructure; improving the efficiency of gas flaring and eventually phasing it out; and inhibiting methane-producing microbes in cattle, through vaccines and feed supplements, as well as in treatment facilities for manure and other organic waste.
Systemic changes include reducing livestock numbers through improved productivity and dietary shifts towards plant-based foods; reducing emissions from livestock; using rice cultivars with lower methane emissions; improving water and fertilizer management in rice cultivation; and diverting organic waste from landfills through recycling, composting, and reducing food loss and waste.
Policy measures for methane abatement include emission reduction targets, enforceable regulations, and financial incentives such as subsidies and methane pricing.
Why do we need to reduce CO₂ and methane emissions at the same time?
Methane and CO₂ are the largest contributors to global warming-so we need to cut both to meet climate goals. Their different properties mean we can maximize climate benefits by reducing each at the same time.
CO₂ remains in the atmosphere for centuries, leading to long-term warming. Methane, on the other hand, is a much more potent greenhouse gas, but has a much shorter atmospheric lifespan of about a decade. By limiting short-term warming through cuts to methane emissions, we can more easily achieve long-term CO₂ reduction goals and minimize reliance on carbon removal technologies. This integrated approach ensures we can keep the 1.5°C global warming target within reach, reduce overall climate impacts, and avoid the worst effects of climate change.
How can countries optimize methane reduction strategies?
Countries need to prioritize investments in the sectors, technologies, and practices that can reduce the most methane emissions within their national context. To guide this, the authors mapped the sector per country with the largest and most feasible potential for methane mitigation. They then analyzed the cost-effectiveness of options in different sectors, in the 50 countries with the largest potential for reducing methane emissions in the next decade.
The authors created a new online tool that allows countries to explore these options and generate an optimized, economically viable national methane reduction strategy. The tool also incorporates some data from satellite observations, with more planned. These data enhance the accuracy of emission estimates and allow identification of methane super-emitters-helping countries to target their efforts to the most significant emission sources. Real-time satellite data can also ensure accountability and track progress towards methane reduction targets.
