Aviation Industry Set to Triple Its Global Greenhouse Gas Emissions by 2050
If commercial aviation were a country, it would rank seventh in global greenhouse gas emissions according to a recent report by the International Council on Clean Transportation (ICCT).
The aviation industry is growing so quickly that its greenhouse gas (GHG) emissions are expected on present trends to triple globally by 2050. The industry itself is committed to reducing its emissions, but technological and political constraints are hindering rapid progress.
Technologically, the fate of aviation GHGs depends on how much more fuel-efficient airplanes can become, and how soon lower-carbon fuels can be made available at a palatable cost.
Politically, it depends on whether the United Nations International Civil Aviation Organisation (ICAO) can establish agreement among member states on a regulatory mechanism, which in turn may depend largely on whether—and when—the U.S. Environmental Protection Agency (EPA) chooses to regulate aviation emissions.
A final unknown is whether the sector’s efforts can produce results in time to avoid climate catastrophe.
By 2050, the aviation industry aims to halve its CO2 emissions compared with 2005 levels, says Steve Csonka, executive director of the Commercial Aviation Alternative Fuels Initiative, a U.S. public-private partnership.
The group is exploring “biomass-derived synthetic jet fuel,” which includes oils from plants and algae, crop and forest product residues, fermented sugars and municipal solid waste.
While this type of fuel can, in principle, be used in jet engines today, Csonka says the most important goal in the near term is to develop alternatives to petroleum-based fuel “at a reasonable price point.” A few airlines are buying alternative fuels at a higher price to encourage the market, Csonka adds, but widespread adoption awaits competitive pricing.
Aviation fuel efficiency has been increasing, but it is not keeping pace with the sector’s growth. The ICCT report finds there was no improvement between 2012 and 2013, and that the gap between the most and least efficient airlines widened—with American Airlines burning 27 percent more fuel than Alaska Airlines for the same level of service.
This gap suggests the industry could reduce GHG emissions significantly if the least efficient airlines would emulate the most efficient, says Daniel Rutherford, the ICCT’s programme director for aviation and a co-author of its report. Most of the reductions so far have come from carrying more passengers per flight, replacing old engines and buying new, more efficient planes.
Like most businesses, airlines don’t want to replace equipment until it makes economic sense. Nor does the industry want to be pinned to standards like those in the U.S. auto industry, which would force “airplanes to improve to a certain degree every year or x number of years.” Csonka says.
Such standards “completely overlook the capital ramifications” for the airlines, he adds, and companies’ profitability is a major factor in the pace at which they can replace old equipment. But the ICCT report suggests that airlines that have spent the most on new, efficient planes are also the most profitable.
Airplanes are at a disadvantage compared with vehicles and power stations. At present there are no low-carbon or no-carbon technologies—such as solar, fuel cells, nuclear reactors, electricity or hydrogen combustion—that will work for aviation. Nor are there market-ready radically different airframe or engine designs.
Fuels derived from plants such as switchgrass, corn and algae can be used in existing engines, but to provide the same energy they need to be “essentially identical” to petroleum-derived kerosene, Csonka says. And if their hydrocarbon structure is the same, burning them will emit the same GHGs.
The advantage of synthetics, Csonka adds, is that “we are pulling recycled carbon out of the biosphere and not out of the ground,” which reduces the net carbon footprint—provided the fuels’ production does not generate too many GHGs itself.
For the foreseeable future, this is the best that can be expected from alternative fuels. This means there is a limit on how much aviation’s net GHG emissions can be reduced, even with alternative fuels, as long as the commercial airline fleet changes only incrementally and no major technological breakthroughs reach the market.
However, there are new engines, materials and aircraft designs now available that can make a big difference, Rutherford says: “We project that the fuel burn for new aircraft can be reduced by as much as 45 percent in 2030 through pretty aggressive technology and development, better engines, improved aerodynamics and lighter materials.”
Campaigners would like to see regulation obliging the industry to increase efficiency by improving faster.
Aviation needs a global policy and enforcement structure; all major airlines’ aircraft emit GHGs globally. This problem brought the European Union’s Emissions Trading Scheme (ETS) to its knees in 2014.
The ETS, which came into effect in 2012, charges airlines for their emissions in European Economic Area airspace. When non-EU airlines protested, the European Commission temporarily exempted flights to or from non-EU airports but still charged for emissions within EU airspace.
Washington, one of the most energetic lobbyists against the charges, forbade its airlines by law from paying the EU fees. The U.S. also threatened trade sanctions, and China suspended its orders from European airplane manufacturer Airbus. There is now a moratorium on extra-EU carbon charges, pending the results of the next ICAO meeting in 2016.
But despite the EU’s surrender to foreign pressure, many observers think the dispute has increased pressure on the ICAO to devise a meaningful emissions reduction programme.
The ICAO’s actions are expected to be closely co-ordinated with those of the U.S. Environmental Protection Agency. Within the U.S., GHGs are regulated by the EPA under the Clean Air Act, which requires action if an air pollutant is found to endanger the public. The U.S. Supreme Court ruled in 2007 that GHGs are pollutants.
Several U.S. environmental NGOs say the EPA is dragging its feet on deciding “whether emissions cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare”.
It has refused repeated requests for an interview with an expert source and says it does not see the need for an interview. The agency expects to issue any regulations in 2016—presumably in time for the ICAO meeting.
But there is no doubt that the EPA will have to produce an endangerment finding and eventually issue a regulation, says Vera Pardee, an attorney for the Center for Biological Diversity who worked on the NGOs’ notice to the EPA.
Politics Versus Science?
In 2013 the ICAO committed to what the Center for Climate and Energy Solutions calls “an aspirational mid-term goal of zero carbon emissions growth for the aviation industry beginning in 2020.” In addition, Csonka says, the aviation industry has accepted the notion of “a market-based mechanism to offset if we miss that goal in an international environment. Our industry will have carbon monetised from 2020 onward to some degree.”
Yet time is vital, and there is a risk that action taken by governments and industry may be politically feasible but scientifically ineffectual. There is no guarantee that the 2016 ICAO meeting will result in binding obligations.
In the meantime, the Intergovernmental Panel on Climate Change currently aims at a 40 percent - 70 percent drop in total global GHG emissions by 2050 to avoid a greater than 2˚C rise in global temperature. In January 2013, climate scientist Thomas Stocker warned in the journal Science that delayed action results in the “fast and irreversible shrinking, and eventual disappearance, of the mitigation options with every year of increasing greenhouse gas emissions.”
But the next two years are likely to see a firming up of the aviation industry’s commitment to GHG reductions and some sort of international mechanism to charge for emissions.
There are signs that industry experts and green advocates are cautiously optimistic. “I see the EPA’s domestic regulation of the airlines as a real catalyst for global action,” says Pardee. “If the EPA acts, the rest of the world will have to follow.” And Csonka adds: “The future is somewhat bright.”
Valerie Brown, based in Oregon, U.S., is a freelance science writer focusing on climate change and environmental health. She is a member of the National Association of Science Writers and Society of Environmental Journalists.
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Two decades ago scientists and volunteers along the Virginia coast started tossing seagrass seeds into barren seaside lagoons. Disease and an intense hurricane had wiped out the plants in the 1930s, and no nearby meadows could serve as a naturally dispersing source of seeds to bring them back.
Restored seagrass beds in Virginia now provide habitat for hundreds of thousands of scallops. Bob Orth, Virginia Institute of Marine Science / CC BY 2.0<p>The paper is part of a growing trend of evidence suggesting seagrass meadows can be easier to restore than other coastal habitats.</p><p>Successful seagrass-restoration methods include <a href="https://www.sciencedirect.com/science/article/abs/pii/S0304377099000078?via%3Dihub" target="_blank">transplanting shoots</a>, <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1061-2971.2004.00314.x" target="_blank" rel="noopener noreferrer">mechanized planting</a> and, more recently, <a href="https://www.nature.com/articles/s41467-020-17438-4" target="_blank" rel="noopener noreferrer">biodegradable mats</a>. Removing threats, proximity to donor seagrass beds, planting techniques, project size and site selection all play roles in a restoration effort's success.</p><p>Human assistance isn't always necessary, though. In areas where some beds remain, seagrass can even recover on its own when stressors are reduced or removed. For example, seagrass began to recover when Tampa Bay improved its water quality by reducing nitrogen loads from runoff by roughly 90%.</p><p>But more and more, seagrass meadows struggle to hang on.</p><p>The marine flowering plants have declined globally since the 1930s and currently disappear at a rate equivalent to a football field every 30 minutes, according to the <a href="https://www.unep.org/resources/report/out-blue-value-seagrasses-environment-and-people" target="_blank" rel="noopener noreferrer">United Nations Environment Programme</a>. And research published in 2018 found the rate of decline is <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GB005941" target="_blank" rel="noopener noreferrer">accelerating</a> in many regions.</p><p>The causes of decline vary and overlap, depending on the region. They include thermal stress from climate change; human activities such as dredging, anchoring and coastal infrastructure; and intentional removal in tourist areas. In addition, increased runoff from land carries sediment that clouds the water, blocking sunlight the plants need for photosynthesis. Runoff can also carry contaminants and nutrients from fertilizer that disrupt habitats and cause algal blooms.</p><p>All that damage comes with a cost.</p>
The Value of Seagrass<p>As with ecosystems like rainforests and <a href="https://therevelator.org/mangroves-climate-change/" target="_blank">mangroves</a>, loss of seagrass increases carbon dioxide emissions. And that spells trouble not just for certain habitats but for the whole planet.</p><p>Although seagrass covers at most 0.2% of the seabed, it <a href="https://www.unenvironment.org/news-and-stories/story/seagrass-secret-weapon-fight-against-global-heating" target="_blank">accounts for 10%</a> of the ocean's capacity to store carbon and soils, and these meadows store carbon dioxide an estimated 30 times faster than most terrestrial forests. Slow decomposition rates in seagrass sediments contribute to their <a href="https://www.researchgate.net/publication/238506081_Assessing_the_capacity_of_seagrass_meadows_for_carbon_burial_Current_limitations_and_future_strategies" target="_blank" rel="noopener noreferrer">high carbon burial rates</a>. In Australia, according to <a href="https://onlinelibrary.wiley.com/doi/10.1111/gcb.15204" target="_blank" rel="noopener noreferrer">research</a> by scientists at Edith Cowan University, loss of seagrass meadows since the 1950s has increased carbon dioxide emissions by an amount equivalent to 5 million cars a year. The United Nations Environment Programme reports that a 29% decline in seagrass in Chesapeake Bay between 1991 and 2006 resulted in an estimated loss of up to 1.8 million tons of carbon.</p>
Eelgrass in the river delta at Prince William Sound, Alaska. Alaska ShoreZone Program NOAA / NMFS / AKFSC; Courtesy of Mandy Lindeberg / NOAA / NMFS / AKFSC<p>Seagrasses also protect costal habitats. A healthy meadow slows wave energy, reduces erosion and lowers the risk of flooding. In Morro Bay, California, a 90% decline in the seagrass species known as eelgrass caused extensive erosion, according to a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0272771420303528?via%3Dihub" target="_blank" rel="noopener noreferrer">paper</a> from researchers at California Polytechnic State University.</p><p>"Right away, we noticed big patterns in sediment loss or erosion," said lead author Ryan Walter. "Many studies have shown this on individual eelgrass beds, but very few studies looked at it on a systemwide scale."</p><p>In the tropics, seagrass's natural protection can reduce the need for expensive and often-environmentally unfriendly <a href="https://www.nioz.nl/en/news/zeegras-spaart-stranden-en-geld" target="_blank" rel="noopener noreferrer">beach nourishments</a> regularly conducted in tourism areas.</p><p>Seagrass ecosystems improve water quality and clarity, filtering particles out of the water column and preventing resuspension of sediment. This role could be even more important in the future. By producing oxygen through photosynthesis, meadows could help offset decreased oxygen levels caused by warmer water temperatures (oxygen is less soluble in warm than in cold water).</p><p>The meadows also provide vital habitat for a wide variety of marine life, including fish, sea turtles, birds, marine mammals such as manatees, invertebrates and algae. They provide nursery habitat for <a href="https://wedocs.unep.org/bitstream/handle/20.500.11822/32636/seagrass.pdf?sequence=1&isAllowed=y" target="_blank" rel="noopener noreferrer">roughly 20%</a> of the world's largest fisheries — an <a href="https://www.floridamuseum.ufl.edu/science/seagrass-meadows-harbor-wildlife-for-centuries/" target="_blank" rel="noopener noreferrer">estimated 70%</a> of fish habitats in Florida alone.</p><p>Conversely, their disappearance can contribute to die-offs of marine life. The loss of more than 20 square miles of seagrass in Florida's Biscayne Bay may have helped set the stage for a widespread <a href="https://www.wlrn.org/2020-08-14/the-seagrass-died-that-may-have-triggered-a-widespread-fish-kill-in-biscayne-bay" target="_blank">fish kill</a> in summer 2020. Lack of grasses to produce oxygen left the basin more vulnerable when temperatures rose and oxygen levels dropped as a result, says Florida International University professor Piero Gardinali.</p>
Damaged Systems, a Changing Climate<p>Governments and conservationists around the world have already put a lot of effort into coastal restoration efforts. And that's helped some seagrass populations.</p><p>Where stressors remain, though, restoration grows more complicated. <a href="https://www.rug.nl/research/portal/en/publications/the-future-of-seagrass-ecosystem-services-in-a-changing-world(3a8c56db-7bed-4c9e-ac7f-c72453e2a102).html" target="_blank">Research</a> published this September found that only 37% of seagrass restorations have survived. Newly restored meadows remain vulnerable to the original stressors that depleted them, as well as to storms — and <a href="https://www.ecowatch.com/tag/climate-crisis">climate change</a>.</p>
Seagrass in Dry Tortugas National Park, Florida. Alicia Wellman / Florida Fish and Wildlife / CC BY-NC-ND 2.0<p>In Chesapeake Bay a cold-water species of seagrass is currently hitting its heat limit, especially in summer, according to Alexander Challen Hyman of University of Florida's School of Natural Resources and Environment. As waters continue to warm due to climate change, the species likely will disappear there.</p><p>Climate-driven sea-level rise complicates the problem as well. Seagrasses thrive at specific depths — too shallow and they dry out or are eaten, too deep and there isn't enough light for photosynthesis.</p>
But There’s Good News, Too<p>Luckily, left to its own devices, a seagrass meadow can flourish for hundreds of years, according to a <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2019.1861" target="_blank" rel="noopener noreferrer">paper</a> published last year by Hyman and other researchers from the University of Florida. The researchers arrived at their conclusion by looking at shells of living mollusks and fossil shells to estimate the ages of meadows in Florida's Big Bend region on the Gulf Coast.</p><p>That area has extensive, relatively pristine seagrass meadows. "Our motivation was to understand the past history of these systems, and shells store a lot of history," said co-author Michal Kowalewski.</p><p>A high degree of similarity between living and dead shells indicates a stable area, while a mismatch suggests an area shifted from seagrass to barren sand. The researchers found that long-term accumulations of shells resembled living ones, suggesting that the seagrass habitats have been stable over time.</p><p>That stability allows biodiversity to thrive, creating conditions where specialist species can survive and flourish, according to Hyman.</p><p>Discovering the long-term stability of seagrass meadows has implications for choosing restoration sites, Kowalewski notes.</p><p>"There must be reasons they thrive in one place, while a mile away they don't and fossil data says they probably never did," he said. "If we remove a seagrass patch, we cannot hope to plant it somewhere else. It's not just the seagrass that is special. The location at which it's found is special, too."</p><p>A better approach is conserving these habitats in the first place, but we're not doing enough of that right now. The UN reports that marine protected areas safeguard just 26% of recorded seagrass meadows, compared with 40% of coral reefs and 43% of mangroves.</p>
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