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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theDOCK aims to innovate the Israeli maritime sector. Pexels<p>The UN hopes that new investments in ocean science and technology will help turn the tide for the oceans. As such, this year kicked off the <a href="https://www.oceandecade.org/" target="_blank" rel="noopener noreferrer">United Nations Decade of Ocean Science for Sustainable Development (2021-2030)</a> to galvanize massive support for the blue economy.</p><p>According to the World Bank, the blue economy is the "sustainable use of ocean resources for economic growth, improved livelihoods, and jobs while preserving the health of ocean ecosystem," <a href="https://www.sciencedirect.com/science/article/pii/S0160412019338255#b0245" target="_blank" rel="noopener noreferrer">Science Direct</a> reported. It represents this new sector for investments and innovations that work in tandem with the oceans rather than in exploitation of them.</p><p>As recently as Aug. 2020, <a href="https://www.reutersevents.com/sustainability/esg-investors-slow-make-waves-25tn-ocean-economy" target="_blank" rel="noopener noreferrer">Reuters</a> noted that ESG Investors, those looking to invest in opportunities that have a positive impact in environmental, social and governance (ESG) issues, have been interested in "blue finance" but slow to invest.</p><p>"It is a hugely under-invested economic opportunity that is crucial to the way we have to address living on one planet," Simon Dent, director of blue investments at Mirova Natural Capital, told Reuters.</p><p>Even with slow investment, the blue economy is still expected to expand at twice the rate of the mainstream economy by 2030, Reuters reported. It already contributes $2.5tn a year in economic output, the report noted.</p><p>Current, upward <a href="https://www.ecowatch.com/-innovation-blue-economy-2646147405.html" target="_self">shifts in blue economy investments are being driven by innovation</a>, a trend the UN hopes will continue globally for the benefit of all oceans and people.</p><p>In Israel, this push has successfully translated into investment in and innovation of global ports, shipping, logistics and offshore sectors. The "Startup Nation," as Israel is often called, has seen its maritime tech ecosystem grow "significantly" in recent years and expects that growth to "accelerate dramatically," <a href="https://itrade.gov.il/belgium-english/how-israel-is-becoming-a-port-of-call-for-maritime-innovation/" target="_blank" rel="noopener noreferrer">iTrade</a> reported.</p><p>Driving this wave of momentum has been rising Israeli venture capital hub <a href="https://www.thedockinnovation.com/" target="_blank" rel="noopener noreferrer">theDOCK</a>. Founded by Israeli Navy veterans in 2017, theDOCK works with early-stage companies in the maritime space to bring their solutions to market. The hub's pioneering efforts ignited Israel's maritime technology sector, and now, with their new fund, theDOCK is motivating these high-tech solutions to also address ESG criteria.</p><p>"While ESG has always been on theDOCK's agenda, this theme has become even more of a priority," Nir Gartzman, theDOCK's managing partner, told EcoWatch. "80 percent of the startups in our portfolio (for theDOCK's Navigator II fund) will have a primary or secondary contribution to environmental, social and governance (ESG) criteria."</p><p>In a company presentation, theDOCK called contribution to the ESG agenda a "hot discussion topic" for traditional players in the space and their boards, many of whom are looking to adopt new technologies with a positive impact on the planet. The focus is on reducing carbon emissions and protecting the environment, the presentation outlines. As such, theDOCK also explicitly screens candidate investments by ESG criteria as well.</p><p>Within the maritime space, environmental innovations could include measures like increased fuel and energy efficiency, better monitoring of potential pollution sources, improved waste and air emissions management and processing of marine debris/trash into reusable materials, theDOCK's presentation noted.</p>
theDOCK team includes (left to right) Michal Hendel-Sufa, Head of Alliances, Noa Schuman, CMO, Nir Gartzman, Co-Founder & Managing Partner, and Hannan Carmeli, Co-Founder & Managing Partner. Dudu Koren<p>theDOCK's own portfolio includes companies like Orca AI, which uses an intelligent collision avoidance system to reduce the probability of oil or fuel spills, AiDock, which eliminates the use of paper by automating the customs clearance process, and DockTech, which uses depth "crowdsourcing" data to map riverbeds in real-time and optimize cargo loading, thereby reducing trips and fuel usage while also avoiding groundings.</p><p>"Oceans are a big opportunity primarily because they are just that – big!" theDOCK's Chief Marketing Officer Noa Schuman summarized. "As such, the magnitude of their criticality to the global ecosystem, the magnitude of pollution risk and the steps needed to overcome those challenges – are all huge."</p><p>There is hope that this wave of interest and investment in environmentally-positive maritime technologies will accelerate the blue economy and ESG investing even further, in Israel and beyond.</p>
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