Transport & Planes

When was the last time you traveled by plane? As little as 3 percent of the global population flew in 2017, and at most, only about 18 percent have ever done so. But things are changing.

According to International Civil Aviation Organization (ICAO) estimates, there were 3.7 billion global air passengers in 2016 — and every year since 2009 has been a new record-breaker.

Although aviation is a relatively small industry, it has a disproportionately large impact on the climate system. Direct emissions from aviation account for about 3% of the EU’s total greenhouse gas emissions and more than 2% of global emissions. If global aviation was a country, it would rank in the top 10 emitters.

With an estimated 4 billion airline passengers expected by the end of 2017, Insight examines the environmental cost of keeping so many planes flying in the sky. With no viable options for long haul travel, just how long will the world be able to sustain the burden, and what if anything can be done to clean up the planet’s air.

Airplane pollution, which has risen by about two-thirds since 2005, is forecast to jump as much as sevenfold by 2050 as incomes in developing economies advance, making flying more affordable for hundreds of millions if not billions of people, according to some estimates. The International Air Transport Association, the industry’s biggest trade group, expects the number of airline passengers to double by 2037, to more than 8 billion a year.

But at a time when we urgently need to reduce our impact, greenhouse gas emissions from aviation continue to grow. For example, since 1990, CO2 emissions from international aviation have increased 83 per cent. The aviation industry is expanding rapidly in part due to regulatory and taxing policies that do not reflect the true environmental costs of flying. “Cheap” fares may turn out to be costly in terms of climate change.

Greenhouse Gasses from Aviation

Carbon Dioxide
Carbon dioxide (CO2) is emitted during the combustion of aviation fuel (kerosene) in direct proportion to the kerosene consumed: 3.16 kilograms CO2 are produced per kilogram of kerosene burned. Given the current condition of the carbon cycle, natural CO2 sinks (e.g. oceans and vegetation) absorb CO2 from the atmosphere at approximately half the rate that anthropogenic atmospheric CO2 emissions are produced, leading to a net accumulation. The resultant long-lived CO2 spreads globally and affects climate independent of where the emissions originated. CO2 is the leading anthropogenic (human-induced) GHG and its warming effects are well understood; it is therefore often used as the basis for comparison of all other emission effects (see Radiative Forcing Index and Global Warming Potential). The climate response to CO2 emissions is independent of where emissions occur; CO2 from aircraft has the same effect as CO2 from other ground level sources.

NOx
In addition to CO2, aircraft emit nitrogen oxides, known as NOx, which contribute to the formation of ozone, another greenhouse gas. The impact of NOx emissions from aircraft, which, although representing only 1–2% of the total emissions of NOx from man-made and natural my have a pronounced impact on the chemical composition of the atmosphere. During the last three decades numerous studies have focused on the different implications of NOx emissions from aircraft.

NOX emissions have followed a steeper upwards trend than CO2 in recent years. They increased from 313 to 700 thousand tonnes between 1990 and 2016 according to the Convention on Long-Range Transboundary Air Pollution data from the UN Economic Commission for Europe, and by 25% between 2005 and 2017 according to estimates from the IMPACT model. Most importantly, NOx emissions from aircraft are expected to increase ozone in the upper troposphere and lower stratosphere region (UTLS).

In contrast to all other major anthropogenic emission sources, aircraft emit their exhaust products directly into the UTLS, where pollutants have a much longer lifetime than at Earth’s surface, allowing excess nitric oxide and ozone to accumulate to larger and more persistent perturbations than at Earth’s surface.

EU study predicts 43% rise in NOx emissions from planes within two decades, due to increased air traffic

Water Vapor
Water vapor (H2O) is another Greenhouse Gas (GHG) that is emitted during air travel. Most subsonic aircraft water vapor emissions are removed from the atmosphere through precipitation within one to two weeks and therefore cause short-lived, regional effects. These effects are greater at high altitudes (i.e. a stronger climate response occurs when water vapor is emitted in the upper stratosphere than in the lower stratosphere ) where water vapor stays longer and can accumulate. This would have climate implications if air travel was expanded into these higher altitudes, but this is currently not common with commercial aircraft. Current science indicates that the warming effect of water vapor from air travel emissions is small. (For information on the effects of condensed and frozen water, see contrails and cirrus clouds.)

The atmosphere is thin and cold the higher up a plane goes. The exhaust from a plane's engine is much hotter than the atmosphere. The water vapor from the hot plane engine turns to ice mid-air which we see as white lines in the sky called contrails.

Effects on the Environment

Climate change
Aircrafts emit a range of greenhouse gases throughout the different stages of flight. Aircrafts are unique in that they emit gases directly into the higher levels of the atmosphere. Research suggests that gases can have different effects when emitted at this altitude relative to emission at ground level.

Scientific evidence strongly indicates that greenhouse gases contribute to climate change. CO2 is generally viewed as the most problematic greenhouse gas. While many factors contribute to emissions in aviation, CO2 is primarily generated by burning carbon-rich 'fossil fuels' in engines. It has a long life cycle and plays a key role in climate change. Some factors are under the control of airlines, airports or regulators, but even the weather plays a part.

If the annual aviation industry emissions were to reach the said 2.7 billion tonnes of carbon dioxide by 2050, it would mean that at that point flying would be an alarmingly significant source of CO2 emissions: the Intergovernmental Panel on Climate Change (IPCC) and climate scientists have calculated that in 2050 the human-induced CO2 emissions should not amount to more than six billion tonnes in total if we realistically want to keep the warming of our climate under the 1.5 °C level. Any warming above this limit is already generally considered to be very dangerous.

Environmental Impact Of Aviation Emissions & CO2 On Climate Change

Noise pollution
Aircraft engines are the major source of noise and can exceed 140 decibels (dB) during takeoff. There are health consequences of elevated sound levels. It can cause community annoyance, disrupt sleep, adversely affect academic performance of children, and could increase the risk for cardiovascular disease of people living in the vicinity of airports.

Air pollution
Airplane exhaust, like car exhaust, contains a variety of air pollutants, including sulfur dioxide and nitrogen oxides. Many of these particles of pollution are tiny, about a hundred millionths of an inch wide, or smaller than the width of a human hair.

So-called particulate matter that's especially small is the main culprit in human health effects, especially since the particulates can become wedged deep in the lung and possibly enter the bloodstream, scientists say

Globally, the team estimated that about 8,000 deaths a year result from pollution from planes at cruising altitude (about 10,668 meters), whereas about 2,000 deaths result from pollution emitted during takeoffs and landings.

The most common causes of death due to air pollution are cardiovascular and respiratory diseases, including lung cancer, according to the UN's World Health Organization.

Solutions

Airplanes are becoming more and more efficient, so what does the future of air travel look like?

The third problem is that unlike other sectors where there might be a greener alternative (solar not coal, LEDs not lightbulbs etc), there is currently no way to fly 8m people every day without burning lots of dirty kerosene. Aircraft are becoming more fuel-efficient, but not quickly enough to offset the huge demand in growth. Electric planes remain decades away, weighed down by batteries that can’t deliver nearly as much power per kilo as jet fuel.

Electric power will soon disrupt the general aviation industry. This could forever change not just the design of aircraft, but the design of our cities and the way we live. In this talk, aviation engineer and entrepreneur Joshua Portlock shows why electric aviation is inevitable - and imminent.

But here’s the peculiar thing: although no other human activity pushes individual emission levels as fast and as high as air travel, most of us don’t stop to think about its carbon impact.

While in many countries new cars, domestic appliances, and even houses now have mandatory energy efficiency disclosures, air travel’s carbon footprint is largely invisible, despite it being relatively much bigger. For instance, a return trip from Europe to Australia creates about 4.5 tonnes of carbon. You could drive a car for 2,000 kilometers and still emit less than that. And the average per capita emissions globally is around 1 tonne.

Several studies have found people to be quite ignorant of how their own flying behaviour contributes to climate change.

Carbon Neutral: what does it mean? Carbon offsetting can make a difference but it won't solve the climate problem

Legislative action
From a legislation standpoint, there have been significant developments – for example, in October 2016, 191 nations signed a landmark UN accord agreeing to achieve a 50 per cent reduction in aviation-related carbon dioxide emissions by 2050.

Combating noise pollution
Airports are able to tackle this problem by setting up sound walls or noise barriers designed to protect against noise pollution. Similarly, aircraft engine manufacturers are continuously making progress in the reduction of noise emitted from engines. This is achieved by increasing the noise-containing airstream around the actual hot and noisy explosive exhausts of each engine.

Technology in the 21st century is developing with exponential speed, but aviation has fallen behind. In fact, commercial flight today is slower than it was fifty years ago. How can this be? Join entrepreneur Blake Scholl for an awe-inspiring look at the future of aviation where the cheapest flight is also the fastest one. Blake Scholl is the Founder and CEO of Boom Supersonic, a Denver startup that is building supersonic passenger aircraft capable of flying from San Francisco to Tokyo in under six hours

What do you do regarding making more sustainable transportation choices? By tagging us with #theconsciouschallenge you can share your ideas!

Want to contribute to our Ecological Footprint Bible? Submit us your scientific articles! Mail us at info@theconsciouschallenge.org

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