March 14, 2024

The Atmospheric Methane Challenge

There’s a concerning mystery in climate science: the amount of methane in the atmosphere is now more than 2.5 times higher than pre-industrial levels and rising fast, yet scientists don’t yet agree on why it’s grown so much recently. Methane emissions are already causing 0.5oC of warming and growing, right when we’re depending on sharp decreases in methane to help stabilize the climate. Critical methane emissions mitigation work is underway and needs to accelerate, but rising natural sources of methane may increasingly impact our ability to reverse the trend of growing concentrations. In parallel with work to advance methane emission mitigation, Spark is currently supporting scientific research on atmospheric methane removal approaches to explore what, if any, additional tools might be made available in the future to help address atmospheric methane levels should more methane be emitted from climate feedbacks outside of our direct control.

We must urgently and aggressively mitigate human methane emissions to help slow global heating; the impact of this critical work will be felt quickly since methane is relatively short-lived. While in the atmosphere, methane is a potent greenhouse gas, 43x stronger than carbon dioxide “molecule for molecule” (IPCC Chapter 7 pg 204, Table 7.15). Ultimately the amount of methane in the atmosphere is driven by the difference in methane emissions and methane breakdown. Methane is broken down—or “removed”—by natural “sinks” via oxidation, the chemical or biological conversion to carbon dioxide and water. The current sinks give methane a lifetime of roughly a decade; about 95% of atmospheric methane is converted by atmospheric processes (mainly through reactions with hydroxyl radicals, with a minor contribution from chlorine radicals), while about 5% is converted by methane-consuming soil microbes. 

Up until about 2000, the growth of methane was clearly driven by growing human-caused emissions from fossil fuels, agriculture, and waste. But starting in the mid-2000s, after a brief pause where global emissions were balanced by sinks, the level of methane in the atmosphere started growing again. At the same time, atmospheric measurements detected an isotopic signal that the new growth in methane may be from recent biological—as opposed to older fossil—origin. Multiple hypotheses exist for what the drivers might be, though the answer is almost certainly some combination of these. Hypotheses include changes in global food systems, growth of wetlands emissions as a result of the changing climate, a reduction in the rate of methane breakdown and/or the growth of fracking

None of these possibilities are good news — some are particularly concerning since they suggest sources and dynamics, such as natural systems emissions changes driven by climate change, that could be outside of our direct control if we don’t manage to rapidly stop climate change overall. Indeed, on our current climate trajectory, even if we’re only seeing the beginnings of it today, we expect to see higher natural system methane emissions from wetlands and permafrost that risk only further accelerating this dangerous trend.

The first and best response we have is to aggressively reduce human-caused methane emissions. There is critical work underway to scale up existing methane mitigation strategies led by our colleagues at the Global Methane Hub and supported by many non-profit organizations; crucially this fast mitigation work could address over 50% of projected human-caused methane emissions. Addressing the other 50% of human-caused methane emissions requires developing new mitigation approaches, especially in livestock emissions, where Spark has an active program. Further investment in solution development across emissions sources is critical to further expand addressable methane emissions.

Even as ambitious methane mitigation efforts scale up, recent research has highlighted the risk of rising methane emissions from wetlands as a result of climate change; these emissions could add tenths of a degree of additional warming in some scenarios. In addition, as global temperatures approach 1.5oC, the likelihood of triggering tipping elements increases, including permafrost thaw, which could emit still more methane. We currently don’t have good monitoring of wetlands in particular, so there is substantial uncertainty in the scale and dynamics of the emissions. Not only that, there aren’t any known approaches to safely mitigate these emissions beyond halting warming overall. Meanwhile, these potential wetland emissions are not accounted for in the latest IPCC models. Spark is actively exploring the state of the science around natural methane sources to determine what can be done to better elevate awareness, characterize, and address these risks. In tandem, we are also helping support the new field of atmospheric methane removal, which could provide an additional set of approaches to help address these rising natural emissions.

Atmospheric methane removal approaches are all in early research phases, with a small research community, and little funding availability. None of these approaches are ready for field testing, much less deployment. Furthermore, appropriate governance and transparent stakeholder engagement will be a critical part of potential atmospheric methane removal approach deployment. 

As we’ve worked to advance this field of study — through research workshops, presentations, information sharing, collaborative roadmaps, and targeted research funding — it’s become increasingly clear that the lack of research funding in these areas must be addressed. While we await the output of the NASEM report developing an Atmospheric Methane Removal Research Agenda, we’re continuing to support fundamental research to learn more about current natural sinks, measurement approaches, and new potential atmospheric methane removal approaches.

We need to do it all; cut CO2 emissions, remove CO2, cut methane and other greenhouse gas emissions, explore the possibility of removing methane and other greenhouse gases, and explore additional climate responses beyond those. The scientific community doesn’t yet know if any of these methane removal approaches will ultimately prove safe, effective or scalable, which is why we believe this foundational research is so critical. What we do know is that progress towards a stable climate requires atmospheric methane concentrations to drop. We must expand our portfolio of potential strategies to reduce risk over the short, medium and long-term.

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