Environmental Audit Cttee says government should take account of aviation non-CO2 impacts on climate
The Environmental Audit Committee report is highly critical of the government’s handling of the issue of carbon emissions created by a 3rd Heathrow runway. The EAC raises the issue of non-CO2 impacts, which is something this government (and the Airports Commission) tries to totally ignore. Atmospheric science is complicated, and the exact extent that non-CO2 impacts from emissions by aircraft high in the atmosphere contribute to warming effects is uncertain. It is estimated to be up to twice the impact of the CO2 alone. The government used to use a multiplier of x1.9, but this was quietly dropped after 2011.The EAC have asked the Secretary of State whether “the DfT’s upcoming aviation strategy would examine greenhouse gas emissions other than CO2. He said that non-CO2 emissions would be reduced alongside CO2, but “there is no clear scientific basis to look at other emissions and put those at the heart of our strategy”. The Appraisal of Sustainability says that non-CO2 emissions “are likely to be up to two times the magnitude of the CO2 emissions themselves, but […] cannot be readily quantified due to the level of scientific uncertainty and therefore have not been assessed”. The EAC says the government should take account of the likely additional climate change impact of some non-CO2. Read the briefing on non-CO2 impacts.
An AirportWatch member has written to the Environmental Audit Committee, on the subject of non-CO2 impacts of aviation.
These impacts arise from atmospheric effects, largely from water vapour – that causes contrails and the formation of cirrus cloud – and effects from NOx.
The letter to the EAC states:
Thank you for your excellent (and well-publicised) report ‘The Airports Commission Report Follow-up: Carbon Emissions, Air Quality and Noise’.
I was particularly interested in the following (para 58): “We asked the Secretary of State whether its upcoming aviation strategy would examine greenhouse gas emissions other than CO2. He said that non-CO2 emissions would be reduced alongside CO2, but “there is no clear scientific basis to look at other emissions and put those at the heart of our strategy”. The Assessment of Sustainability says that non-CO2 emissions “are likely to be up to two times the magnitude of the CO2 emissions themselves, but […] cannot be readily quantified due to the level of scientific uncertainty and therefore have not been assessed”.
Although the science for non-CO2 greenhouse gas emissions is less certain than for CO2, work on the subject has been done by climate scientists. However, none of scientists seem to be prepared to put their ‘head above the parapet’ insofar as trying to inform public policy.
You may therefore like to see a report which shows how, as a result, the government has systematically downplayed non-CO2 emissions. [This is copied below].
While the estimates are acknowledged to be provisional and very approximate, we conclude that an addition of 60% should be made (factor of 1.6 applied) to the CO2 emissions to allow for the effect of non-CO2 emissions. This is a very conservative figure because, in particular, the effects of cirrus cloud are not included.
Given the scale of the impacts, I think it unacceptable to simply ignore non-CO2 emissions on the grounds of scientific uncertainty. I hope you agree.
I wonder, therefore, if you might be able to promote or encourage some research that would inform public policy on this important matter.
Name and address supplied.
Non-CO2 impacts Briefing in June 2015
“Government airbrushes aviation’s non-CO2 greenhouse gas emissions”
While it been recognised for many years that the climate change impacts of aviation extend well beyond those of carbon dioxide (CO2), this fact is largely ignored by the government and its agencies. Our report examines the reasons for this and proposes an ‘index’ which will help to ensure that the issue of non-CO2 gases is properly accounted for.
2. Executive summary
In recent years there has been systematic downplaying of the issue of non-CO2 gases by the UK government and its associates. This report provides the evidence for that claim.
While ‘scientific uncertainty’ is claimed as the reason to ignore non-CO2, the real reason is that aviation emissions are an embarrassment to government and others who want to expand airports and air travel.
In earlier governmental and academic studies a ‘Radiative Forcing Index’ (RFI) has been used in order to capture non-CO2 impacts. However, RFI is a ‘backward looking metric’ and is therefore considered unsuitable for informing aviation policy.
This report argues that instead of just dropping the previously used RFI, it should be replaced by a ‘Global Warming Potential’ (GWP) index for estimating impacts and developing policy responses.
A rough value for the index of 1.6 is estimated. CO2 emissions should be multiplied by 1.6 in order to allow for the impact on non-CO2 GHGs. This is a very conservative figure – the true figure could be much higher, due mainly to cirrus.
The estimate and calculations around it are very approximate. The factor of 1.6 should therefore be regarded very much as an interim, pending a thorough and independent review of the issue of aviation’s non-CO2 emissions.
Although the proposed index is approximate and interim, it should be used forthwith in order to demonstrate impacts and inform policy. Citing scientific uncertainly as a justification for ignoring an issue would not be acceptable in other fields of public policy and should not be accepted when it comes to aviation emissions.
The full report with much more detail is at
See the Environmental Audit Committee (EAC) report
- Read the report summary
- Read the report conclusions and recommendations
- Read the full report: The Airports Commission Report Follow-up: Carbon Emissions, Air Quality and Noise
The EAC report states:
We asked the Secretary of State whether its upcoming aviation strategy would examine greenhouse gas emissions other than CO2. He said that non-CO2 emissions would be reduced alongside CO2,* but “there is no clear scientific basis to look at other emissions and put those at the heart of our strategy”. [ Link is from Oral Evidence, 30 November, 2016 Q74 ] The Assessment* of Sustainability says that non-CO2 emissions “are likely to be up to two times the magnitude of the CO2 emissions themselves, but […] cannot be readily quantified due to the level of scientific uncertainty and therefore have not been assessed”.
[ * This is an nonsense statement, if the CO2 reductions the aviation sector hopes to make are only from offsetting, rather than actually emitting less from planes into the atmosphere. AW comment]
[ **misprint. Should say Appraisal of Sustainability ]
17. The Government’s aviation strategy should be integrated with the cross-Government emissions reduction plan. It should set out costed policies to either meet the Committee on Climate Change’s planning assumption or to make up the shortfall from other sectors. This decision will have to take account of the limited progress towards decarbonisation outside the energy sector and the likely additional climate change impact of some non-CO2 emissions. Where the Government makes assumptions that are more optimistic than the Committee on Climate Change’s advice it should subject those assumptions to independent scrutiny from industry and the CCC and, if necessary, revise its plans accordingly. This strategy should be available well before the end of the scrutiny period for the draft National Policy Statement and consultation on it should be completed before the National Policy Statement is finalised. (Paragraph 63)
New EAC report says government must provide clarity about its intentions on Heathrow CO2 emissions
The EAC has now published a follow up report to its November 2015 report, after the oral evidence given by Chris Grayling on 30th November. It is highly critical of the government on its assurances that the runway will meet carbon limits. The EAC says: “The Government claims that Heathrow expansion can be delivered within “the UK’s climate change obligations”. The Government has not set out what it means by “obligations”, let alone how it will meet them. It has not decided whether to accept the Committee on Climate Change’s recommendation on limiting emissions from international aviation. It has not decided on whether to follow the CCC’s advice on offsetting. The Airports Commission told us the appropriate body to make recommendations on managing aviation emissions is the CCC. It would not be a credible position for the Government to claim that it can deliver Heathrow expansion within emissions limits whilst rejecting independent advice as to what those limits should be and how they should be met.” … The EAC says though Chris Grayling said told them the Government had not decided whether it intended to work towards the planning assumption [of limiting UK aviation to 37.5MtCO2 by 2050], when asked if he “had consulted other Ministers or sectors over the higher emissions reductions that they might be required to make if the planning assumption was not met. He said he had not yet done so.” And much more ….