Climate Explained: Methane Is Short-Lived in the Atmosphere but Leaves Long-Term Damage
Алексей Филатов / Getty Images
By Zebedee Nicholls and Tim Baxter
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Methane is a shorter-lived greenhouse gas - why do we average it out over 100 years? By doing so, do we risk emitting so much in the upcoming decades that we reach climate tipping points?
The climate conversation is often dominated by talk of carbon dioxide, and rightly so. Carbon dioxide is the climate warming agent with the biggest overall impact on the heating of the planet.
But it is not the only greenhouse gas driving climate change.
Comparing Apples and Oranges
For the benefit of policy makers, the climate science community set up several ways to compare gases to aid with implementing, monitoring and verifying emissions reduction policies.
In almost all cases, these rely on a calculated common currency - a carbon dioxide-equivalent (CO₂-e). The most common way to determine this is by assessing the global warming potential (GWP) of the gas over time.
The simple intent of GWP calculations is to compare the climate heating effect of each greenhouse gas to that created by an equivalent amount (by mass) of carbon dioxide.
In this way, emissions of one gas - like methane - can be compared with emissions of any other - like carbon dioxide, nitrous dioxide or any of the myriad other greenhouse gases.
These comparisons are imperfect but the point of GWP is to provide a defensible way to compare apples and oranges.
Limits of Metrics
Unlike carbon dioxide, which is relatively stable and by definition has a GWP value of one, methane is a live-fast, die-young greenhouse gas.
Methane traps very large quantities of heat in the first decade after it is released in to the atmosphere, but quickly breaks down.
After a decade, most emitted methane has reacted with ozone to form carbon dioxide and water. This carbon dioxide continues to heat the climate for hundreds or even thousands of years.
Emitting methane will always be worse than emitting the same quantity of carbon dioxide, no matter the time scale.
How much worse depends on the time period used to average out its effects. The most commonly used averaging period is 100 years, but this is not the only choice, and it is not wrong to choose another.
As a starting point, the Intergovernmental Panel on Climate Change's (IPCC) Fifth Assessment Report from 2013 says methane heats the climate by 28 times more than carbon dioxide when averaged over 100 years and 84 times more when averaged over 20 years.
Many Sources of Methane
On top of these base rates of warming, there are other important considerations.
Fully considered using the 100-year GWP and including natural feedbacks, the IPCC's report says fossil sources of methane - most of the gas burned for electricity or heat for industry and houses - can be up to 36 times worse than carbon dioxide. Methane from other sources - such as livestock and waste - can be up to 34 times worse.
While some uncertainty remains, a well-regarded recent assessment suggested an upwards revision of fossil and other methane sources, that would increase their GWP values to around 40 and 38 times worse than carbon dioxide respectively.
These works will be assessed in the IPCC's upcoming Sixth Assessment Report, with the physical science contribution due in 2021.
While we should prefer the most up to date science at any given time, the choice to consider - or not - the full impact of methane and the choice to consider its impact over 20, 100 or 500 years is ultimately political, not scientific.
Undervaluing or misrepresenting the impact of methane presents a clear risk for policy makers. It is vital they pay attention to the advice of scientists and bodies such as the IPCC.
Undervaluing methane's impact in this way is not a risk for climate modellers because they rely on more direct assessments of the impact of gases than GWP.
The idea of climate tipping points is that, at some point, we may change the climate so much that it crosses an irreversible threshold.
At such a tipping point, the world would continue to heat well beyond our capability to limit the harm.
There are many tipping points we should be aware of. But exactly where these are - and precisely what the implications of crossing one would be - is uncertain.
Unfortunately, the only way we can be sure of where these tipping points are is to cross them. The only thing we know for sure about them is that the impact on lives, livelihoods and the places we love would be beyond catastrophic if we did.
But we cannot ignore disturbing impacts of climate change that are already here.
The scientific understanding of climate change goes well beyond simple metrics like GWP. Shuffling between metrics - such as 20-year or 100-year GWP - cannot avoid the fact our very best chance of avoiding ever-worsening climate harm is to massively reduce our reliance on coal, oil and gas, along with reducing our emissions from all other sources of greenhouse gas.
If we do this, we offer ourselves the best chance of avoiding crossing thresholds we can never return from.
Zebedee Nicholls is a PhD Researcher at the Climate & Energy College, University of Melbourne.
Tim Baxter is a Fellow - Melbourne Law School; Senior Researcher - Climate Council; Associate - Australian-German Climate and Energy College, University of Melbourne.
Disclosure statement: Zebedee Nicholls is affiliated with The University of Melbourne's Climate & Energy College. He is funded by the Australian Government via the Australian Government Research Training Program (RTP). Tim Baxter is employed by the Climate Council, a non-profit organisation providing independent, authoritative information on climate change and its solutions to the Australian public and has previously been employed under various Australia Research Council grants.
Reposted with permission from The Conversation.
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Jean-Marc Neveu and Olivier Civil never expected to find themselves battling against disposable mask pollution.
When they founded their recycling start-up Plaxtil in 2017, it was textile waste they set their sights on. The project developed a process that turned fabrics into a new recyclable material they describe as "ecological plastic."
Mounting Piles of Waste<p>It is not only the streets of Chatellerault where pandemic pollution is piling-up, but also the world's beaches and oceans. Once there, they can take up to 450 years to degrade and disappear.</p><p>Esther Röling, co-organizer of the annual Adventure Clean Up Challenge held on Hong Kong Island, has seen this waste firsthand. In October the sports challenge pitted teams against one another in a competition to remove trash from 13 hard-to-reach coastal areas around the city.</p><p>They find tons of both disposable and reusable masks, said Röling. "You wonder how it ended up there. Was it just thrown on the ground? Or was it in a garbage bag that broke open?"</p><p>Almost 10,000 kilometers away in Antibes on the sunny French Riviera, it's a similar picture. For the past few months, divers and clean-up volunteers working with an ocean clean-up non-profit called Operation Mer Propre have been collecting an increasing number of masks found on land and in the sea.</p><p>"Since the beginning of the lockdown when we started to count, we've reached 800, 900, [and now in total] 1000 masks," said co-founder Joko Peltier. </p><p>According to <a href="https://unctad.org/news/growing-plastic-pollution-wake-covid-19-how-trade-policy-can-help" target="_blank">UN estimates</a>, up to 75% of all coronavirus-related plastic could end up as waste in oceans and landfills.</p>
The Limits of Recycling<p>Yet not all are convinced the recycling of this waste is possible on a global scale. </p><p>"What those citizen groups are doing is really beneficial but once they collect it, it should just go to a landfill or an incinerator. They shouldn't necessarily expect it to get recycled," said Jonathan Krones, an industrial ecologist and visiting assistant professor of environmental studies at Boston College.</p><p>That's because mask recycling programs like Plaxtil are few and far between and most don't have the benefit of a readily adaptable production process. </p><p>Even in countries with solid recycling infrastructure, he says, the system is designed to separate out specific types of waste like bottles or cardboard.</p><p>"I imagine that it would be technically feasible to develop a separation process to filter out masks, but there simply aren't enough of them to make that economical," he said.</p><p>Collection is a big hurdle, he adds. Since each mask only weighs a fraction of a gram and they're scattered on roads or mixed with other trash, it is difficult and costly. </p><p>"You need a lot of raw material of the right quality to make investing in the recycling technology and the recycling system worthwhile," he said.<span></span><br></p>
Hemp, Sugar Cane and Sustainable Alternatives<p>Some projects are instead addressing the material used to make masks.</p><p>French company Geochanvre have created a mask made primarily from hemp, while in Australia, researchers at the Queensland University of Technology are experimenting with a disposable product made from agricultural waste. </p><p>Biodegradable options are exciting alternatives to reduce the fossil fuels needed for the creation of plastic-based masks, said Krones, but they don't absolve the wearer from the responsibility of what happens afterwards. </p><p>Bio-based masks often need their own composing solutions, he explains, because in landfill they can produce high amounts of the greenhouse gas methane when anaerobic bacteria feeds on the organic material. Methane is known to be significantly more potent than carbon dioxide.</p><p>"I think as long as we have in our mind that we want to have disposability, we're going to have to wrestle with a variety of different sorts of environmental tradeoffs," he said, adding that reusable, fabric masks are the best option available to most people.</p><p>Precimask is developing a clear face covering with an optional visor made from hard plastic, designed to be long-lasting.<br></p><p>Air enters either side of the cheeks through a technology normally found in pool filters and car exhaust systems, said company spokeswoman Juliette Chambet.</p><p>"We wanted to make ceramic-based filters that would be washable and cleanable, which would allow them to be reused as many times as desired without having to buy a new consumable or produce waste," she said. </p><p>Ultimately, encouraging mask wearers to think about the entire lifecycle of a mask is key, explains Neveu. </p><p>"We want people who put on the masks to realize that they are also responsible for the waste, he said. "It's not inevitable that this [pandemic] will become an environmental catastrophe.</p><p><em>Reposted with permission from </em><em><a href="https://www.dw.com/en/covid-19-recycling-pollution-trash-pandemic/a-55707817" target="_blank">Deutsche Welle</a>.</em><a href="https://www.ecowatch.com/r/entryeditor/2649032193#/" target="_self"></a></p>
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