Aviation and Climate Science

To get the answers you want, you simply ask the right question, and no industry is better at asking the right question than the aviation industry. Almost all air passengers will have been consoled at one stage or another by answering the aviation industry’s rhetorical question about why they should be targeted for criticism when they only account for 2% of anthropogenic CO2 emissions, and many environmentalists will have been pushed onto their back feet wondering how to counter this seemingly invincible argument.

In this essay we are going to unpick the 2% argument and put it into perspective. We will explain that the 2% is both out of date and it fails to tell the whole story as it does not take into account the growth in aviation that has been experienced since 1990, or the future growth that the aviation industry is trying to create. We will demonstrate that once the wider impacts of aviation are taken into account then its contribution to greenhouse gases rises further and we will further demonstrate that there are no technological solutions or alternative energy sources that will allow aviation to meet the massive cuts needed in CO₂ emissions that are necessary to avoid runaway climate change.  Fundamentally, the only way we can avoid runaway climate change is for a massive reduction in excess consumption and excess travel.  

As stated above the 2% relates to 1990 IPCC figures and so is hopelessly outdated. Since 1990, the aviation industry has been growing between 5% and 9% per annum which is far higher than world economic growth. Applying this rate of growth to the aviations 2% contribution to anthropogenic emissions, it can be conservatively calculated that as of 2010 aviation’s contribution to total greenhouse gas emissions will have risen to approximately 4%.

Bringing these numbers closer to home and considering the proportion of aviation emissions within the UK total CO₂ budget, Gillian Merron (Secretary of State for Transport) confirmed in 2007 that aviation accounted for 6.3% of total UK emissions. However this was with the incredible caveat that international emissions were limited to only outgoing journeys, as it is deemed too difficult to reconcile the full impact of international emissions. As international travelers outnumber domestic travelers by about 8 to 1, then the true figure of emissions to and from UK airports would be 11.9%. What has been done amounts to a cynical way of avoiding the most contentious issue of the day.

But even if we were to give the aviation industry the benefit of the doubt and assume that they kept their emissions at just 2% of total anthropogenic gases, then it would still be unacceptable as total manmade anthropogenic emissions are increasing at the alarming rate of 3.4% per annum. This is despite the much hyped low carbon technologies, carbon trading agreements and environmental campaigns.  When we apply a little bit of mathematics to a 3.4% compound growth rate, we see that the annual emissions double in approximately 20 years (see note 1) placing the planet’s CO₂ growth projections well beyond the worse case scenario of the IPCC reports which has a doubling period of 30 years. So using the airlines own argument, that they remain at only 2% of total CO₂ emissions, we would also be expecting their annual emissions to double in the next 20 years. This is bang inline with the predictions of emissions growth that environmentalists claims, but which the aviation industry claims are far too pessimistic.

The credibility of the claim that aviation’s emissions will double in just 20 years can be tested by looking at emerging events around the world. Just as the developing countries such as China want to eat more meat, then they also want more aviation. With predicted sales in China of 2,800 passenger planes in the next 20 years, China, along with India, are primary markets for Boeing and Airbus.  Recently, David Cameron was extolling the virtues of Britain as a long haul and thus high carbon holiday destination for the Chinese. In the UK, and elsewhere in Europe, all the main regional airports are pushing expansion plans with the expectation that they will be able to open up additional long range routes using the new Boeing 787. Meanwhile the EU has liberalised access to airport hubs with the open skies policy which has the express purpose of developing aviation further.

Now for a bit more simple but scary maths; because manmade emissions are growing at 3.4% per annum the total CO₂ that we will emit in the next 20 years will be the same as all the emissions since the beginning of the industrial revolution (see note 2). This is absolutely terrifying as our climate is already unravelling with the current levels of CO₂, and we have absolutely no way of knowing how it will behave when we double the CO₂ loading.  To add to the terror level, this doubling will happen on a 20 year timescale, rather than the 250 year timescale since the start of the industrial revolution; so our planet will have virtually no time to absorb the surge in greenhouse gases that we are about to inflict on it.  This surge will occur when the scientific evidence is telling us that we must reduce our atmospheric CO₂ to 350ppm to have a reasonable chance of avoiding runaway climate change. Today our CO₂ emissions are at 390ppm and rising steadily. When we include all the other greenhouse gases such as methane and fluoride gases we are at 455ppm. We are already deeply into the danger zone, and worse, the rate of increase is increasing. If the rise of CO₂ emissions continues on its current track, then by 2032 we will have exceeded 450 ppm of atmospheric CO₂, which is considered the trigger point beyond which irreversible and catastrophic climate change is unavoidable.

The current situation is so desperate it is difficult to imagine a worse case. In these circumstances, it does not matter if an industry’s emissions are 2% or 20% of the total anthropogenic CO₂ as everyone’s moral obligation must be to massively reduce greenhouse gas emissions over and above everything else. So the aviation industry’s argument that they should be allowed to continue business as usual because their 1990 emissions were only 2% of total anthropogenic emissions is a hollow claim and a cruel distortion of the facts

They also can not claim that they are being unfairly targeted, or that cuts can be made in other industries to offset their emissions.  While it is true that other manufacturing industries such as paper, steel and cement account for similar slices of the total greenhouse gas emissions pie, these industries are finding it equally as difficult as the aviation industry in cutting their emissions as they are as wedded to fossil fuel as the aviation industry. Lakshmi Mittal’s successful lobbying for extra carbon credits for his steel businesses, along with threats to relocate his steel manufacturing to China if not provided, shows they will fight just as hard and dirty as the aviation industry to maintain their right to pollute.

The fundamental fact is that the significant emissions cuts that we need can only be achieved by reducing output, and this is the crux of the problem. Which outputs do we target first and by how much - the manufacture of essential materials or the right to luxury travel for the rich?    

If we had an ideal world where new low carbon technologies came on line, such as renewables and safe nuclear to power our cars and houses, we would see the proportion of the total emissions from the high carbon industries increasing over time.  The aviation industry and its supporters are of course saying that they will also reduce their emissions by finding new technologies, alternative new fuels such as hydrogen and alternative energy sources such as biofuels, all of which will make the future a nirvana of green aviation and so they should be allowed to continue with business as usual today because tomorrow all will be well. This is a fantasy world fit only for dreamers.

Technology will never deliver planes that are so fuel efficient as to be considered “green.” To do this we would need fuel reductions in the order of 90%. This is impossible. The newest planes coming onto the market such as the Boeing 787 are only 10% more fuel efficient per passenger kilometre and there is nothing significantly better on the drawing board. Worse, this improvement is not used to environmental benefit; it is used for commercial benefit to fly more often and to further destinations. This will maintain the upward trend in total aviation emissions that has existed since the Wright Brothers flew their first plane and despite the continuous improvements in technology. We would be hopelessly naïve to believe that this relationship is suddenly going to change with the introduction of the next fleet of planes, especially when the Boeing 787 is the most successful plane at launch ever with over 800 orders confirmed and that Airbus’s flagship A380 super jumbo is being sold as a private jet to Middle Eastern billionaires.

As for hydrogen as an alternative energy source, it simply does not have the energy density necessary to power a plane and the energy needed to compress the massive volume of hydrogen would defeat the logic of the idea. Then, try explaining to the local residents of an airport that their houses are still safe when planes are taking off with massive fuel tanks of hydrogen pressurised to tens of thousands of pounds per square inch whilst aeronautical engineers are simultaneously challenged with hydrogen embitterment of key safety critical components such as the engines and fuels tanks on the planes.  An accident on a hydrogen powered plane would instantly transform it into a bomb so massive it would make the Hindenburg disaster seem like watching candles burning on a birthday cake.

The other dream world is that biofuels can be used to replace existing fossil fuels and airlines such as Air New Zealand have been pushing forward on this front.  Air New Zealand has pursued the idea of using the Jatropha plant, which is a weed deemed to be so poisonous and invasive that it is not allowed into New Zealand and instead has to be grown in developing countries that have little or no environmental legislation.

Despite Jatropha’s status as a poisonous weed, it is still quoted by the industry as being the knight in shining white armour; its supporters claim it can be grown in semi-arid regions of the world and without fertilizer, and because it is poisonous it does not compete with food supplies. How much longer does the industry expect us to believe that the laws of science can continue to be broken and that basic human rights can also be ignored?  Field experience supports common sense, and shows that if the Jatropha crop is not irrigated and fertilised, it will not produce fruit. The stupidity of the logic only increases when the end result is a large scale replacement of food crops and other ecosystems with a poisonous weed so in any future famine, neither the produce nor the land can not be transferred back to the food market.  Then there is the slight problem of being able to find all these semi arid unused parts of the world that the industry implies are so abundant. It is being achieved today by the appalling land grabs which are so prevalent in Africa. Calculations show an area well over twice the size of France would be needed to fuel just half the aviation industry at today’s levels of consumption – but we know from our basic maths that the demand will double, so in only 20 years we will need four times the area of France. This will happen when agricultural land is coming under increasing stress as climate change impacts are starting to hit much harder and quicker than predicted. At best, for all this damage we would only be cutting aviation’s emissions by half and with the current industry growth rates we would then be back at today’s totally unsustainable levels well within 20 years.

Having failed with Jatropha, the industry is pushing the idea of using genetically modified algae, but still there is no large scale proven production process and many of the ideas propose using the CO₂ from the flue gases from power stations as a feedstock. This is not carbon neutral, as we simply use aviation to delay by a couple of weeks the time it takes for dirty power stations gases to be released into the atmosphere. Our objective with fossil fuel power stations must be to either close them or to use carbon capture – using the exhausts for biofuels is counter to all these efforts.

In additional to the CO₂ emissions from planes, there are other greenhouse forcing gases that significantly increase aviation’s impacts on the environment. When these are taken into consideration, aviation’s contribution rises considerably above their 2% claim.  The two main factors are the impact of NO_x gasses which have a warming effect of 400 times that of CO2 and the high altitude water vapour. 

With the NO_x gases there is an essential compromise. To make a plane’s engine efficient and so reduce, its CO₂ emissions, the engine must run as hot as possible and with as high a compression as possible.  But running an engine at very hot temperatures and high pressures causes the nitrogen in the air to burn with oxygen, and so there is always a compromise. You can either reduce NO_x gases but increase CO₂ or visa versa. To put it in perspective, while the total quantity of NO_x gases is very much smaller than CO2, the warming impact is almost as great.  

Also coming out the aircraft engines exhaust is water. At high altitude, this causes the formation of circus clouds. While these to a certain extent reflect some of the sun’s energy, this is countered by the warming effect that they cause by preventing heat from the earths surface being radiated back to space. The total warming effect is highly positive, and again is estimated to be at least equivalent to the actual CO₂. So in total, the combination of the NO_x gases and high altitude vapour results in the uplift factor which is currently assessed as being between 2 and 4 of the actual CO₂ impact, and is known as radiative forcing. The warming effect of cirrus clouds also destroys the rational of the hydrogen powered planes, as they produce even more water than conventional fuel and maximum efficiency a hydrogen powered plane has to fly higher, further accentuating this effect.

From the UK perspective, the result of the radiative forcing is that aviation’s impact on the environment rises from 6.3% to approximately 20% of our total greenhouse effect. When this is placed in context with our ambitions to create 20% of just our electrical power from renewables, it is clear that emissions from aviation will negate all the efforts from building wind farms and other renewable energy projects around the country.

The ongoing compound growth in aviation emissions, and the inability to create an environmentally acceptable alternative, will on its own prevent the UK from meeting its own targets as set out in the Climate  Change Act, even if every other sector in the economy went down to zero carbon. Try explaining to people who are loosing their jobs in the steel industry, or the old people that are living in the cold that their hardship is so the aviation industry can continue to send the richest in our society to holiday in the Caribbean and you will see the social fabric of the country almost immediately break down.

To finally complete the picture of the damage that aviation does, one has to look beyond the exhaust gases from the engines, and consider how aviation facilitates many other unsustainable industries.  To understand this, consider how the industry delights in explaining how important it is to the world economy and the things that it has enabled. The flip side of this claim is that without the aviation industry, we would not have obscenities such as Dubai on the edge of the desert complete with both indoor ski centres and the world’s highest per capita CO₂ footprint or flowers being grown in Kenya which is one of the most food insecure countries in the world.

As well as enabling some of the most unsustainable industries and countries, the aviation industry requires its own industrial complex of fuel supplies, airports, factories and mines  to keep it going. This complex can only be managed with huge greenhouse gas emissions, none of which the aviation industry claims, instead these will be accounted to other industries such as manufacturing, oil industry, mining and the military. As we are going to increasing lengths to secure oil, such as developing the Canadian Tar sands, pursuing in Iraq the most energy intensive resource war ever and burning down the tropics for biofuels, enormous secondary emissions are created which will by far exceed the emissions directly from the planes.  Absolutely none of this is accounted for in the 1990 estimate of 2% of total emissions that the industry uses, but without this invisible greenhouse gas overhead being paid the planes will not fly.  

So as for the 2% claim –it has been prepared by those whose interest is to be economical with the truth; it is for dreamers and for those that are easily fooled; it is for the comfort of the passengers who read about it in the in-flight magazines as they fly over the millions of poverty stricken climate refuges; it is for governments to justify their support of one of the most environmentally damaging industries the planet has ever seen, and it is for the powerful elite on our planet who want to maintain their right to hypermobility.

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Note 1 - Doubling time = log(2)/log(1.034)= 20.7 years

Note 2- Analysis of areas under a exponential growth curve: