Under the 2015 Paris Agreement, governments worldwide agreed to limit global warming to less than 2°C with an aspirational target of 1.5°C using nationally determined contributions (NDCs) to cut greenhouse gas (GHG) emissions. A rise of more than 1.5°C above pre-industrial temperatures is the gateway to dangerous levels of warming. In its report, the IPCC has stated that climate change is now widespread, rapid and intensifying, and the world has already warmed by 1.1°C since the mid-19th century.

NDCs are not on track to meet the Paris Agreement, where the current emission trajectory places the world on the road to a disastrous 3.2°C of warming by 2100. The 1.5°C target is likely to be breached by the early 2030s and this comes with an increased risk of more extreme weather events such as droughts, floods, heatwaves and wildfires.

GHG emissions are dominated by the release of CO₂, but other gases also add to the warming. Methane (CH₄) is second only to CO₂ in driving global warming and accounts for 30–40% of observed global warming to date. Methane emissions come from human activities as well as natural ecosystems which are integral to the global climate system. Overall, nature accounts for around 40% of methane emissions, where agriculture, livestock and waste deposits account for another 30% (think rice-paddy farming, flatulating cattle and landfills).

The global energy sector accounts for the rest, through emissions from coal mining and natural gas extraction (including fracking), as well as fugitive emissions from pipelines and end-users. The International Energy Agency (IEA) estimates that fossil fuel operations generate about 120mn t/y of methane emissions (2020).

Although present at much lower atmospheric concentrations than CO₂, methane is an extremely potent GHG, responsible for about 84 times more warming than CO₂ over a 20-year time period (and up to 34 times more over 100 years). Think of methane as a blowtorch to the climate compared to a gradual boil from CO₂. One positive feature of methane is that it has a relatively short lifetime of only 9–12 years in the atmosphere compared to decades, or even centuries, for CO₂, meaning that control of methane emissions can help to put the brakes on global warming in the short term.

If we are to prevent dangerous warming above 1.5°C then we urgently need to rapidly cap GHG emissions. The IPCC has stated that for a 50% chance of avoiding global warming above 1.5°C then no more than another 500 Gt of CO₂ can be emitted to the atmosphere (as of January 2020). With global CO₂ emissions now at around 45 Gt/y (and growing), the remaining carbon budget, as of June 2022, is about 385 Gt. This budget equates to less than all of the GHGs emitted in the last decade (2010–2019) and, at current emission rates, will be exhausted in about 8.5 years.

Disturbingly, if emissions of non-CO₂ GHG emissions (including methane) are not rapidly reduced, then the carbon budget shrinks to 300 Gt. When you do the maths on the time left before we blow this budget cap at the current emission rate, then you will understand why Professor Jim Skea, Co-Chair of the IPCC and former President of the Energy Institute, says that: ‘It’s now or never if we want to limit global warming to 1.5°C. Without immediate and deep emissions reductions across all sectors it will not be possible.’

The IPCC has stipulated date targets for reducing GHG emissions and staying within the carbon budget. For CO₂, a 43% reduction (based on 2019 levels) is needed by 2030, with a 34% reduction for methane. By 2050, total carbon emissions must reach net zero, meaning that for each tonne of CO₂ emitted then another tonne must be removed from the atmosphere. So-called negative emission technologies, or NETs, are needed to achieve this net zero goal, but such technologies are nascent and doubts remain over their feasibility and scalability. This places an absolute priority on quickly reducing carbon emissions and is why the IEA stipulated in its May 2021 report Net zero by 2050: A roadmap for the global energy sector that there should be no new oil, coal or gas development post-2021.

‘It’s now or never if we want to limit global warming to 1.5oC. Without immediate and deep emissions reductions across all sectors it will not be possible.’ – Professor Jim Skea, Co-Chair of the IPCC and former President of the Energy Institute

Methane emissions 
Methane is emitted during the production and transport of coal, natural gas and oil. Emissions also result from livestock and other agricultural practices and from the decay of organic waste in municipal solid waste landfills. They can be classified as coming from either natural sources or anthropogenic sources.

Natural sources 
Natural sources of methane include gas hydrates, freshwater bodies, oceans, termites and wetlands as well as other sources such as wildfires. Wetlands are defined as ecosystems in which soils or peats are water saturated or where surface inundation, whether permanent or not, dominates the soil biogeochemistry and determines the ecosystem species composition. Examples of wetlands are bogs, fens, marshes, muskegs, peatlands and swamps.

Anthropogenic sources 
So far, human activities have increased the concentration of CO₂ in the atmosphere to about 418 ppm, an increase of about 50% compared to pre-industrial levels. The build-up of methane in the atmosphere is also of concern, where emissions have accelerated in the last decade to a high of 1,860 ppb, with a record jump of 17 ppb in 2021 alone. With GHG levels moving in the wrong direction, the atmospheric level of CO₂ is now at its highest in at least the last 2mn years. Levels of methane are at their highest in the last 800,000 years, having risen by over 250% since pre-industrial times.

Approximately 60% of total global methane emissions come from anthropogenic sources. Of these, more than 90% originate from three sectors: agriculture, ~40%; fossil fuels, ~35%; and waste, ~20%.

Agriculture: Emissions from enteric fermentation and manure management represent roughly 32% of global anthropogenic emissions. Rice cultivation adds another 8% to anthropogenic emissions. Agricultural waste burning contributes about 1% or less. Biomass burning, which has a mixture of anthropogenic and natural causes, and biofuels are relatively minor sources of methane emissions, as are industry and transport.

Fossil fuels: Release during oil and gas extraction, pumping and transport of fossil fuels accounts for roughly 23% of all anthropogenic emissions, making up roughly two-thirds of the sector’s total emissions, with emissions from coal mining contributing 12%. Within the fossil fuel sector, the oil and gas subsector is the largest emitter, accounting for roughly two-thirds of the sector’s total emissions, with emissions from coal mining making up most of the remainder.

A continued build-up of fossil-fuel infrastructure (FFI) presents on-going challenges to timely GHG emission reductions. The IEA says there should be no further development of fossil fuels post-2021, as GHG emissions associated with the remaining lifespan of existing infrastructure already exceeds the carbon budget and 'locks-in' a temperature overshoot above 1.5°C. Indeed, recent analyses shows that current, committed and planned FFI amounts to over 1,500 Gt of CO₂ emissions – more than eight times the remaining carbon budget without limiting non-CO₂ emissions (including methane). This is a key reason why the IEA called for more specific methane emission cuts of 75% from the oil and gas industry by 2030, as detailed in its May 2021 report.

Waste: Landfills and waste management make up about 20% of global anthropogenic emissions.

While all sources of methane emissions are important in every region, there are some significant regional differences. Emissions from the coal and rice subsectors are particularly important in Asia. Fossil fuel-related emissions are generally a large share of regional emissions throughout the northern hemisphere, in particular the Middle East, Russia and North America. 

 
Fig 1: Estimated annual sectoral methane emissions by region and global sector totals, excluding Oceania, in 2017 (in mn tonnes) 
Source: UNEP Global Methane Assessment 2021

Scientists are not exactly sure why levels of methane are climbing so quickly in our atmosphere. It may be because of fugitive emissions associated with natural gas fracking, or due to increased emissions associated with land clearance for agriculture – or even emissions from natural ecosystems. As the world warms, natural carbon sinks like peatlands, wetlands and permafrost release planet-warming GHGs to the atmosphere. The extra warmth then speeds-up further the emission of methane in a destabilising positive feedback loop.

In ASEAN, two sectors stand out: agriculture, and the oil and gas sector. The former is the largest methane contributor while the latter is considered a ‘low-hanging fruit’.

In Indonesia, the Philippines, Vietnam and Thailand, rice cultivation and livestock farming produce much more methane than the whole oil and gas industries of these countries.

The forest fires in Indonesia, together with livestock farming, account for more than half of its methane emissions, which is greater than the total methane emissions of any other south-east Asian country.

The good news is that the potential to reduce methane emissions ranks highly amongst available and low-cost mitigation options specified by the IPCC, where costs range from net positive (ie less than $0/t) up to a modest cost of $20/t of methane. The IEA says that it is possible to avoid more than 70% of current methane emissions using existing technologies, with around 45% of the cuts possible at no net cost to the global energy sector.

Mitigation measures include methane leak detection and repairs, and bans on non-emergency gas flaring and venting. Further reductions are possible with the advent of more accurate data on methane emissions and the ability to detect site-specific sources of methane using advanced satellite technology. In the short term, it is estimated that if methane emissions were cut by 40–45% before 2030, then 0.3°C of warming could be avoided by 2040. Such action provides precious time to develop NET technologies to achieve a low carbon economy and net zero GHG emissions.

Singapore, Vietnam, the Philippines, Malaysia and, critically, Indonesia (one of the largest methane emitters in the world), have committed to the Global Methane Pledge under which participants have pledged to take voluntary actions to contribute to a collective effort to reduce global methane emissions by 30% from 2020 levels by 2030.

Given that methane is responsible for 30–40% of the global rise in temperatures then the deployment of cost-effective, readily available technologies to cut methane emissions is the most plausible contribution that the global energy sector can make to quickly bend the GHG emission curve downward and avoid catastrophic climate change in what the IPCC has described as a ‘brief and rapidly closing window to secure a liveable and sustainable future for all.’