Methane Emissions Can’t Be Overlooked, Researchers Say – Expert Reaction

Evidence indicates that methane emissions were responsible for about half of global warming between the preindustrial period and the 2010s—but compared to carbon dioxide, methane has received little attention. A team of researchers highlights 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 team lays out three steps they say we must take and proposes a tool to help countries take action.

The Science Media Centre asked third-party experts to comment.

Robert McLachlan, Distinguished Professor in Applied Mathematics, Massey University, comments:

“The article by Drew Shindell and fourteen other international climate scientists arrives at a timely moment for New Zealand, as our second emissions reduction plan covering emissions to 2030 and the pathway to 2050 and beyond is in preparation. Two reviews of our methane target are in preparation, one by the Climate Change Commission and one by a separate, newly appointed panel as part of the Government’s Coalition Agreement.

“Atmospheric methane levels have accelerated recently and are increasing at twice the forecast rate. Therefore, emissions must decrease faster than anticipated. For a 1.5 ºC future, global methane emissions must fall 35% by 2030 and 53% by 2050. The article supports the split gas approach in which agricultural methane emissions do not need to reach net zero; nevertheless, they should fall 20% by 2030 and 30% by 2050.

“However, in a separate commentary, Andy Reisinger (not an author of the study) notes that these projections relied on immediate and deep cuts to all emissions from 2020. As this did not take place, ambition should be raised to include faster cuts in CO2 and/or methane, possibly leading to net zero emissions of all gases.

“Shindell et al. suggest that the alternative climate metric, GWP* has been misused to argue that current levels of methane emissions cause ‘no additional warming’, and that this ‘ignores emissions responsible for roughly half the warming to date and appears to exempt current high methane emitters from mitigation. This is neither equitable nor consistent with keeping carbon budgets within reach.’ Two of the five members of the new methane review panel were authors of the original GWP* study.

“New Zealand can be proud of our political commitment under the Global Methane Pledge and its opportunity to contribute to this global target.”

No conflict of interest.

Professor Mark Howden, Director, Institute for Climate, Energy & Disaster Solutions, Australian National University, comments:

“This paper is a comprehensive and balanced assessment of the science and policy issues around methane emissions, their consequences and reduction.

“Keeping global temperatures to between well-below 2.0°C and as close to 1.5°C as possible requires both CO2 emissions to quickly go to net zero but also for substantial reductions in methane emissions. Not reducing methane emissions reduces the remaining CO2 budget bringing forward the likely date when we will exceed any give temperature goal. Hence methane and CO2 reductions need to be considered together to find the best pathway forward for any given country.

“The paper outlines the substantial number of options to reduce methane emissions, many of which are low cost compared with the damage that would arise from their emission. They are also low cost compared with the costs of reducing other GHG emissions. There are many low-cost options available in the fossil-fuel extraction industries as well as some in agriculture and the food system. Many of the options have co-benefits that make them additionally desirable. However, these options need policy frameworks that would accelerate their adoption.”

Conflict of interest statement: No conflicts of interest with any of the authors of Shindell et al. For one of the commentaries, Dr Andy Reisinger is a honorary member of my Institute at ANU.

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