Analysis by Carbon Brief: Aviation to consume half of UK’s 1.5C carbon budget by 2050
The UK aviation’s greenhouse gas emissions could consume around half the carbon budget available to the UK in 2050, even if the sector’s emissions growth is constrained. An assessment by Carbon Brief shows that even with no new runway, the anticipated demand for air travel – from DfT forecasts – could mean UK aviation (flights taking off from UK airports) could be 47 MtCO2e by 2050. With a new runway, the emissions could be as much as 51 MtCO2e in 2050. The Paris climate agreement means the UK must raise its existing climate ambition. The UK’s current legislated target, to limit global temperature rise to below 2 degrees C, is to cut CO2 emissions 80% below 1990 levels by 2050. ie. from 800 MtCO2 per year to 160 MtCO2 per year. To keep below 1.5 degrees C the reduction in CO2 would be around 91% (86 – 96%) below the 1990 level, ie. 72 MtCO2 per year for the UK. Therefore if UK aviation emitted 37.5 MtCO2 per year by 2050 would be about 52% of the UK’s carbon limit of 72 MtCO2 for a 1.5C global target, or about 23.4% of the UK’s carbon limit of about 160 MtCO2 for a 2C global target. And if instead of sticking to the 37.5 MtCO2 limit (which the DfT now says is “unrealistic”)* UK aviation emitted 51 MtCO2 by 2050 that would be about 71% of the UK’s carbon limit of 72 MtCO2 for a 1.5C global target, or about 32% of the UK’s carbon limit of about 160 MtCO2 by 2050 for a 2C global target.
Analysis: Aviation to consume half of UK’s 1.5C carbon budget by 2050
By Simon Evans (Carbon Brief)
Aviation’s greenhouse gas emissions could consume around half the carbon budget available to the UK in 2050, even if the sector’s emissions growth is constrained.
The numbers make for awkward reading as the government approves a new runway at Heathrow, which it says is needed to meet ever-rising demand for air travel.
In order to meet this aim, countries must make careful use of the very limited remaining carbon budget. That budget could be used up within five years, leaving the world reliant on unproven negative emissions technologies in order to draw CO2 out of the atmosphere.
Paris means the UK must raise its existing climate ambition: it will have to reach net-zero emissions, whereas its current legislated target is to cut emissions 80% below 1990 levels by 2050. [ie. from 800 MtCO2 per year to 160 MtCO2 per year. AW note]
The Committee on Climate Change (CCC), the government’s official advisers, says it is too early to set a date for reaching net zero. However, the CCC notes that the 1.5C goal of Paris implies UK reductions of “at least 90% below 1990 levels by 2050”.
It gives a range of 86-96% for cutting emissions by 2050, if the UK takes an equal per capita share and if the world aims for at least a 50% chance that 1.5C will be avoided. Note that other ways to divide the burden of cutting emissions would probably entail more drastic cuts for the UK, while, arguably, a 50% chance of exceeding the 1.5C limit is risky.
Setting aside these questions, the middle of the CCC’s range – a 91% cut – [from around 800 MtCO2 in 1990 link p 21 ] would give the UK a carbon budget of 72 million tonnes of CO2 equivalent (MtCO2e) in 2050. This is close to the limit of what the CCC believes to be possible using currently known technologies and options. [The target for aviation the CCC suggests is 37.5MtCO2 by 2050. AW note ]
It thinks the maximum plausible cuts to UK emissions in 2050 would reach 92% below 1990 levels, or 64MtCO2e. It’s worth adding that this builds in significant use of negative emissions, including biomass with carbon capture and storage (BECCS), as well as afforestation.
Where do aviation emissions fit into this? In its most recent forecasts [DfT 2013] of demand for air travel, the government said that even without a new runway at Heathrow, UK airports would serve 445 million passengers per annum (mppa) in 2050. This is more than twice the 211 mppa served in 2010.
The Department for Transport (DfT) said UK aviation emissions, including international flights departing from UK airports, would reach 47MtCO2e by 2050 without airport expansion. With new runways, passenger numbers could rise to 480mppa, the DfT says. Carbon Brief estimates this would translate into emissions of 51MtCO2e in 2050.
This figure is more than two-thirds (71%) of the 72MtCO2e mid-range carbon budget for 2050 implied by the CCC, if the UK is to play its part in meeting the ambition of the Paris Agreement. [Of a 1.5 degree C global warming target]
It is also nearly a third (32%) of the budget for 2C, assuming the UK sticks with its 80% by 2050 target.
[So, UK aviation if up to 51 MtCO2 by 2050 would perhaps emit up to about 70% of the UK’s carbon limit of 72 MtCO2 for a 1.5C global target, or about 32% of the UK’s carbon limit of about 160 MtCO2 by 2050 for a 2C global target. AW note]
However, the CCC has said that UK aviation emissions should be limited to no more than 2005 levels, if the UK is to meet its 2050 carbon targets as cheaply as possible. This would mean a cap of 37.5MtCO2e for UK-based air travel.
That 37.5MtCO2e cap would be equivalent to more than half (52%) of the allowable 1.5C-compatible carbon budget in 2050.
[[So, UK aviation if up to 37.5 MtCO2 by 2050 would perhaps emit up to about 52% of the UK’s carbon limit of 72 MtCO2 for a 1.5C global target, or about 23.4% of the UK’s carbon limit of about 160 MtCO2 for a 2C global target. AW note]
UK greenhouse gas emissions including the UK share of international aviation. Historic data runs through to 2014, the latest year for which aviation figures are available. The shaded area shows projected linear progress towards an overall 91% cut in 2050, with aviation capped to 2005 emissions.
The CCC says the 37.5MtCO2e cap can be met if plausible increases in aircraft efficiency and use of lower carbon fuels is accompanied by demand growth of no more than 60% above 2005 levels.
Note that this cap includes additional room to grow compared to today’s levels because emissions fell from 37.5MtCO2e in 2005 to 31.9Mt in 2010, partly as a result of the financial crisis. They had reached only 32.9MtCO2e in 2014, still more than 10% below the 2005 cap.
For its part, the Airports Commission led by Sir Howard Davies, said that demand for air travel would grow by closer to 100% to 2050. This would breach the CO2 cap for aviation and would entail the UK buying overseas carbon offsets to balance the books.
(The UK will participate in an international carbon trading scheme [through ICAO] to limit aviation emissions at 2020 levels, agreed by 191 countries in Montreal on 6 October. This will cover between 75-80% of air traffic – nowhere near all of it. The coverage of emissions growth may total between 75-80% eventually, but only 20% of total aircraft CO2 emissions between 2021 and 2035 will be offset. Link )
However, the CCC continues to oppose the use of international offsets, saying that “UK targets should focus on domestic effort”.
Writing in the Telegraph this week, Davies says that climate goals mean it would be a mistake to allow both Heathrow and Gatwick to expand. He writes:
It’s worth adding that Davies suggests Birmingham airport might be expanded in future. His comments also relate to the UK’s existing climate targets, rather than the tougher goals likely to result from Paris.
The UK is already responsible for an above-average share of international air travel, a position it presumably wishes to retain as it goes out into the world without EU membership.
Aviation emissions are among the most difficult to tackle, along with those from farms and factories. That’s why the new aviation climate deal is based around emissions offsets.
At a global scale, aviation could consume a quarter of the global carbon budget for 1.5C, recent Carbon Brief analysis showed. If the UK wants new runways, it must also take responsibility for the emissions those flights generate.
Page 15 of the DfT document (25.10.2016)
Further Review and Sensitivities Report
Airport Capacity in the South East
“1.12 The AC’s approach to modelling the carbon-capped scenario uses carbon price assumptions that are higher than the central values published by the Department of Energy and Climate Change (DECC) for appraisal. The carbon-capped scenario is helpful for understanding the varying effects of constraining aviation CO2 emissions on aviation demand and the impact on the case for airport expansion, but was described by the AC as “unrealistic in future policy terms”. ”
In other words it can’t be done..