Can cutting methane emissions be effective in helping slow global warming?

Yes.  In fact, reducing methane emissions from large sources like the fossil fuel industry, agriculture, and others is mission-critical for slowing warming. But to get atmospheric methane levels to fall by cutting emissions alone, we would have to fast-track it far beyond what has been done to date. We need to do everything possible to cut manmade methane emissions.  But if emissions don’t fall far enough or fast enough to bring atmospheric methane down to safe levels, we will need to couple methane emissions reduction with additional strategies.

The UN Environment Program and the Climate and Clean Air Coalition recently released a Global Methane Assessment which addresses how reducing methane emissions would impact climate change.  It found that full deployment of available emissions reductions measures by 2030 could slow the rate of global mean warming over the next few decades by more than 25%, while preventing around a 0.25oC of additional global mean warming in 2050 and 0.5 oC in 2100.  On the other hand, slow or delayed methane action leads to a 5% increase in global mean warming from 2030 to 2050.

If current trends continue unabated, anthropogenic methane emissions would continue rising.  UNEP reports some estimates suggesting they could reach 800 million metric tons (MMt) per year by 2100 compared to less than 400 MMt per year today.

That would have a big impact on warming.  Historical methane emissions contributed to around 0.5 C (±0.1 C) of present-day global mean warming above pre-industrial levels (1850–1900), which is around half of carbon dioxide’s contribution (0.9 ± 0.2 C).  But if methane rises as expected in a business-as-usual scenario, it could contribute another 0.6 C (±0.1 C) of warming by 2050, or around 0.9 C(±0.2 C) by 2100.  Overall, unchecked methane emissions could contribute between 0.75 C and 1.5 C of warming by the end of this century.

According to the Global Methane Assessment, available mitigation measures could potentially cut anthropogenic methane emissions by as much as 45% by 2030.  Taking economically feasible steps to lower methane emissions from the fossil fuel sector, such as detecting and stopping leaks, could avoid around 0.1 C of global warming by 2050, or 0.2 C by the end of century.  Addressing landfill emissions, for example with source separation, could avoid another 0.16 C by 2100.  Abating emissions from livestock, for example through selective breeding and better grass and manure management, might avoid another 0.46 Cby 2100.

Such reductions could avoid nearly 0.3 C of methane-induced warming by the 2040s.  That would complement other climate mitigation efforts and help keep the goal of limiting warming to 1.5 C within reach.

It’s important to achieve this.  And it won’t be easy.  Some sources of methane emissions are more susceptible to mitigation than others.  For example, methane from some agricultural sources (e.g. rice paddies) are considered so-called “survival” emissions – emissions necessary for human survival – which make them difficult to cut deeply or rapidly.

Assuming we could cut anthropogenic methane emissions 45% by 2030, this would only return atmospheric methane levels to where they were in 2020, after an especially rapid rise in emissions since 2007.  Cutting anthropogenic methane emissions in half by 2030 wouldn’t prevent methane from contributing as much as an additional 1C of warming by 2100. 

We can’t eliminate 100% of anthropogenic methane emissions. Some are unavoidable. And as the planet warms, methane emissions from all sources – manmade and natural — will intensify, contributing further to global warming. 

Combining robust methane emissions abatement with other strategies will give us the best chance to bring atmospheric methane down to safe levels.

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