These developments should make a real difference. But even with a greater focus on emissions reductions, some methane emissions, particularly in food production, will be difficult to eliminate. Natural sources of methane could even increase in the coming decades as wetlands warm and Arctic permafrost thaws. So in addition to cutting methane emissions, we need ways to remove methane from the atmosphere, too.
Methane levels today are about 2.6 times higher than in preindustrial times — higher, in fact, than at any time in the last 800,000 years. Those record-high levels are accelerating climate change. Over a 20-year period, methane is at least 80 times more potent as a warming agent than carbon dioxide. Although it has a shorter life span in the atmosphere, methane has a much higher capacity than carbon dioxide to absorb energy and block heat from escaping, which accounts for its outsized impact on warming. Reducing existing atmospheric methane could slow warming down, shaving peak global temperatures and extending the time it takes to reach even more dangerous climate thresholds.
According to the U.N. Global Methane Assessment, we would need to cut methane emissions 45 percent by 2030 — 50 percent more than the U.S.-E.U.-led Methane Pledge goal of 30 percent — just to stay on track to meet the Paris agreement goal of keeping warming within 1.5 degrees Celsius. (For comparison, the planet has already warmed more than 1 degree Celsius globally.) And after 2030, we’ll probably need to cut methane emissions even more to keep below a 1.5 degrees Celsius rise in temperatures.
But there are practical and intrinsic limits to how much methane emissions we can cut, and how fast we can cut them. That’s why methane removal is an important topic in Glasgow, where scientists and policy experts are discussing it in multiple COP26 sessions and side events. There’s even an effort to create governance for it through a draft declaration.
Methane removal is the science of removing or destroying methane that is already in the atmosphere, for example by speeding up natural methane oxidation, which breaks it down into carbon dioxide and water vapor. Researchers are testing methods to accelerate methane removal, because current emissions levels are overwhelming the atmosphere. Our recent modeling shows that if we successfully deploy methane removal technologies at scale, it could prevent 0.4 degrees of warming by 2050.
Doing this wouldn’t put any additional carbon dioxide into the atmosphere than would otherwise be there, because all methane in the atmosphere turns into CO2 and water eventually anyway. But enhancing methane oxidation could speed up the conversion process and greatly reduce methane’s contribution to global warming, ideally in time to help tamp down temperature increases. Methane removal is analogous in some ways to carbon dioxide removal (CDR), but with key differences: There’s no need to sequester methane after it has been oxidized, and many methane removal methods require much less energy than CDR methods.
Of the various methane removal methods, one promising approach is now being tested at the University of Copenhagen: iron salt aerosols. In nature, when sunlight hits sea spray, it releases chlorine atoms into the air that oxidize methane, a natural cleansing mechanism. Adding iron salt to this process could increase it by orders of magnitude locally, oxidizing much more methane. Many ships already emit iron in their exhaust when they burn iron-rich fuel, so the first step in field testing iron salt aerosols is for researchers to search for enhanced methane oxidation downwind of such ships.
Other methane removal technologies use catalysts to break down methane. These include photocatalysts, such as titanium dioxide, which can be mixed in paints, and which oxidize methane in the presence of sunlight. Metal catalysts such as iron or copper also show promise, especially when embedded in high surface area minerals, such as zeolites. One opportunity would be to combine direct air capture plants that are being developed for carbon dioxide removal with methane removal. That way we’d be paying the energy and financial costs of moving the air through the system to remove carbon dioxide, but multiplying the benefits by removing methane and other greenhouse gases at the same time.
Mitigating emissions (that is, cutting the amount of carbon dioxide and methane we put into the atmosphere) is still the most important weapon to fight climate change. That’s why the recent Global Methane Pledge and action by the U.S. Congress and EPA are so important. But if we can scale them up fast, methane removal technologies offer a path to restore the atmosphere, lowering methane to preindustrial methane levels, shaving peak temperatures and delaying temperature rises. That would allow time for us to scale up other climate actions and keep us below critical thresholds.
There are tens of billions of dollars, including in U.S. and E.U. public funding, for carbon dioxide removal. There is no reason we shouldn’t invest in methane removal, too. Methane action is the most powerful lever we have for reducing temperatures over the next few decades. If we are going to avoid dangerous tipping points, we need to act now by both dramatically reducing methane emissions and funding, developing and scaling up methane removal. The future of our climate and our planet could depend on it.