In 2015 the industry generated 781 megatons of CO2, more than the total emissions of the state of Germany. The total equaled 2% of global CO2 emissions from anthropogenic sources.
Why would the agreement only target CO2?
Largely because the industry and science have yet to agree upon a hard-and-fast number for aerosol and soot, unburned hydrocarbons, NO2, SO2, and water vapour impacts from aircraft and the contribution to global warming. For example, there appears to be a strong correlation between contrails formed behind aircraft flying at high altitudes and the formation of cirrus clouds in the upper troposphere. The research on the heat-trapping impact of these aircraft-induced cloud formations, however, has yet to be fully understood.
Scientists suspect, however, that these additional emissions could increase the industry’s impact up to four times more than its current CO2 contribution to global warming. For example, there appears to be a strong correlation between contrails formed behind aircraft flying at high altitudes and the formation of heat-trapping cirrus clouds in the upper troposphere. The contrails, although transient in nature (one of the reasons science struggles to measure their impact) contain aerosols, soot, unburned hydrocarbons, SO2, NO2 and water vapour. And contrail formation varies by location. For example, winter and overnight flights produce more of them, and altitude contributes as well. High flying aircraft generate more contrails than those flying at lower elevations. In a study published in 2014, it recommended that cruising altitudes 610 meters (2,000 feet) lower could reduce NO2 emissions by 40%. A paper released last month suggests restricted aircraft routes and flight trajectories, in other words, no fly zones, could further reduce harmful emissions.
The infographic appearing below describes what scientists suspect is happening and how aircraft contribute to climate change.
Of course, the most significant contribution the industry can make is through technological innovation, creating new aircraft and engines that contribute fewer greenhouse gas and aerosol emissions while removing older airplanes that are high emitters. A paper published this week in Nature Letters presents findings from sampling exhaust plumes of jet aircraft and shows that adding biofuels to conventional jet fuel in a 50/50 mix can reduce aerosols by 50 to 70%.
NASA is studying hybrid battery-powered electric and gas combined engines with lighter airframe structures and new aerodynamic shapes to reduce emissions. It is also studying a design concept it calls distributed propulsion, taking the engines from beneath the wings and putting them up front on the wing edge, increasing the number of engines while reducing their size, narrowing the wing and running single motors on wingtips at cruising altitudes. All these changes will contribute to better lift at low speeds, greater fuel efficiency, and a significant drop in greenhouse gas emissions.
Much of the research into reduced greenhouse gas emissions and aviation innovation related to reducing greenhouse gas emissions may grind to a halt under the current United States administration. One can only hope that is not the case.
]]>In 2010 global aviation consumed 142 million metric tons of fossil fuel which produced 448 million tons of CO2 emissions. By 2040, fuel consumption is expected to grow by as much as 2.8 to 3.9 times which means, if the fuels remain the same, the industry would be contributing well over 1 billion tons of CO2 to the atmosphere.
Those are the numbers today.
But yesterday marked the day when governments and the industry agreed collectively to reduce emissions from air traffic. At the 39th Session of the International Civil Aviation Organization (ICAO) in Montreal, the 190 countries signed on to a measure to address global emissions from air traffic.
Here are some of the details.
Through these measures the member nations of the ICAO hope to reduce the rate of growth in CO2 emissions expected as the industry expands. In the graph appearing below from the most recent ICAO Environmental Report it illustrates the expected gap reductions that the industry will gain from improvements to infrastructure and technological innovation. The remaining gap to achieve carbon neutral growth amounts to 1,039 Megatons.
So how does the industry intend to address the gap? The ICAO Carbon Offsetting and Reduction Scheme for International Aviation or CORSIA describes its strategies as MBM. It stands for market-based measures. The industry intends in the interim to use cap-and-trade (MBM) to buy credits to fill the emissions gap until innovation and alternative low-carbon fuels get developed. The goal would conceivably achieve carbon neutrality beginning as early as 2020.
Alternative low-carbon fuels replacing petroleum-based products would yield a net CO2 emission reduction of 63% as depicted in the graph below.
The agreement is expected to cost airlines about $5.3 billion U.S. at the onset, and by 2035 $23.5 billion annually. The projected cost to travelers is expected to amount to a fare increase from 50 cents on short routes to $7 on intercontinental and transcontinental flights.
Why is curtailing airplane emissions so important?
Because of where the emissions occur. A significant portion of the airplane emissions happen at high altitude. These emissions include more than CO2 including nitric oxide (NO), nitrogen dioxide (NO2), sulfur oxides, water and soot. The NO and NO2 emissions impact ozone both positively and negatively. At lower altitudes ozone levels increase and at higher elevations they decline. Soot destroys ozone as well. There also appears to be a correlation between flight density and condensation trails (contrails) and upper atmosphere cloud formation. The association of cirrus clouds and airplanes is said to contribute to 3.5% of another measure of climate change, the radiative forcing (RF) or climate forcing brought on by human activity. Positive RF is a contributor to global warming as greenhouse gases like water vapour and CO2 absorb infrared radiation and emit it into the atmosphere. And then there is CO2 emissions, which have been steadily increasing since the first comprehensive analysis done back in the 1990s. At that time aviation was estimated to produce 1% of all anthropogenic carbon emissions. But increases in air traffic since the 1990s has increased CO2 emissions by 3 to 4% per year with an estimated growth of 400% by 2040. That’s why an agreement was very much needed.
Olumuyiwa Benard Aliu, President of the ICAO Council, described the environmental measure unanimously recommended by 170 international experts convened by the United Nations 36-state Governing Council, stating, “the goal of this process is ultimately to ensure that when the next generation of aircraft types enter service, there will be guaranteed reductions in international CO2 emissions.” He further stated that by enacting such measures, “the projected doubling of global passengers and flights by 2030” can “be managed responsibly and sustainably.”
