Guest post: The Global Methane Pledge must be expanded to limit global warming to 1.5C.

Today’s COP26 summit in Glasgow saw the official launch of the Global Methane Pledge by Joe Biden, US president, and Ursula von der Leyen president of European Commission. 

Announced in SeptemberThe pledge asks countries for a reduction in their emissions. methane emissionsby 30% over 2020-30, and agree to stricter reporting standards. In his speech, Biden said “nine countries had signed on” in September, but “today, it’s over 80 and approaching 100 countries”. (US climate envoy John Kerry later clarified that “we’re up to 105”.)

These countries include the US and EU countries, as well as Canada, Brazil, Indonesia, and the UK. In total, the number of countries signed up represents “nearly half the global methane emissions” and “70% of global GDP”, Biden noted.

According to the EU and US, delivering on the pledge “would reduce warming by at least 0.2C by 2050”. But can it keep this promise?

Global mitigation efforts have been rightly focused on CO2 (carbon dioxide) emissions. To stop further warming, global CO2 emission must reach net-zero as soon as possible. But, we will continue to experience warming until net zero CO2 is achieved. increasingly devastating extreme weather. 

As global warming becomes more alarming, lived reality for the global populationThe world’s attention should be on what it can do to quickly change the direction of travel and limit global warming to 1.5C.

Using simple climate models known as “emulators”, we show that cutting methane can have a huge impact on limiting near-term warming, but global methane reductions of around 50% will likely be needed to realise the 0.2C saving.

Emissions cuts

Methane is an organic compound. potent greenhouse gasThe second largest contributor to human-caused global heating after CO2 is methane. Methane emissions from agriculture, fossil fuel leaks and waste have contributed 0.5C of global warming to date, compared to CO2’s contribution of 0.8C. 

Methane emissions have been addressed for a long time. low-hanging fruit for climate policy. 

Methane’s short atmospheric lifetime of around 10 years means that cutting emissions can reduce its temperature contribution almost immediately. This contrasts with CO2, which has zero emissions only result in no further warming – underpinning the scientific basis of net-zero targets – but not in a reduction of it. 

How effective are methane cuts for combating climate change?

We ran simulations of different levels and compared them with the actual results. SSP2-4.5 pathwayWith a slight modification to ensure that baseline methane emissions remain constant into the future, As methane emissions remain within 3% of today’s levels until 2040 in SSP2-4.5, this forms an appropriate baseline assumption for the medium term. Additionally, SSP2-4.5 is chosen as it is the scenario that is closest to the combined impact of current emissions pledges by individual countries – known as Nationally Determined Contributions (NDCs) – according to a recent UNFCCC report.

In our methane mitigation scenario, we applied global methane cuts of 30%, 40%, 50% and 50% in 2030. These reductions were relative to 2020. We will keep them at that level for the future. To transition to the 2030 scenarios, we applied straight-line methane cuts between 2020 and 2030. 

For comparison, we also simulated the impact of another COP26 priority – phasing out coal power. The coal phaseout scenario calculates the current-day global emissions for coal (including air pollutants) and quantifies global emissions from coal in 2040. It does this by analysing primary electricity supply from coal projections for SSP2-4.5. IIASA SSP Scenario Database. These values were subtracted from global emissions for all future years. We also implemented a linear decrease in emissions starting at 2020 and ending at 2040. In addition to the 30% reduction in methane, the coal phase out scenario was used.

These emissions scenarios were all run using “FaIR”, a climate model emulatorThis report estimates the impact on the global average temperature surface.

The output is shown below. It includes the different levels methane emission cuts (red line) and the additional cooling benefits of phasing away coal on top a 30% reduction in methane (black line). This figure will be up until 2100.

Below are three charts that show the impact of these emissions cuts on temperatures in 2030, 2050, and 2100. The black bar shows the temperature decreases if both a 30% reduction in methane and a coal phase out are enacted.

Society reaps the benefits

It is evident from the figures that methane cut have the greatest impact on near-term temperatures. They should be an integral part of efforts towards limiting global warming to as low a level as possible. 

The figures also indicate that methane reductions of around 50% – rather than 30% – will likely be needed to realise the 0.2C of avoided warming aimed for in the pledge. (In addition, the scenarios are based upon global emissions and therefore are more ambitious that the pledge as it stands.

It is important to note that methane mitigation benefits can be shown by themselves. Low-cost methane mitigation options could also reduce CO2 emissions. This will further increase the impact.

These figures demonstrate that methane cut have immediate benefits, but they diminish over time. When combined with a coal-phase-out, long-term climate benefits and improved air quality can be achieved. A rapid coal phase-out is essential for meeting long-term temperature targets. However, it has a limited impact on the environment. short-term warming effect from less air pollution. This effect is limited when combined with agricultural and fossil methane reductions. 

These results are very supportive of the headline assessment(pdf) The first part of the Intergovernmental Panel on Climate Change’s (IPCC) sixth assessment report (AR6) – published in August this year – which concluded that “strong, rapid and sustained reductions in [methane] emissions would…limit the warming effect resulting from declining aerosol pollution and would improve air quality”.

The coal phase out pledge is the most significant of all the COP aims for the benefit to the surface temperature in the long-term. Both measures bring enormous benefits to society and the environment. They would lead to less pollution and better health. 

It is important to prevent leaks from fossil fuel infrastructure. Healthier dietsBetter animal husbandry and better farming practices are more difficult issues, but they are still essential for methane reductions at a sufficient scale to keep 1.5C on the table.  

This analysis uses data and code that is freely available here.