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The carbon gap in the Airports Commission’s new runway analysis

A key issue in the airport expansion debate is whether or not a new runway would be compatible with national climate change commitments. The Airports Commission gives the impression that the issue has been fully considered, but in fact a number of questions remain to be answered.

We have three major concerns about the Commission’s approach to analysing the climate change implications of airport expansion. Below each issue we have given our recommendations of what the Airports Commission needs to do before publishing its final report. We would urge everybody responding to the Airports Commission’s consultation, which closes on the 3rd February, to include our three recommendations in their response to questions 4, 5 or 6.

Issue one: Forecasts

The Airports Commission has produced its own forecasts of carbon dioxide emissions from aviation that are lower than official forecasts from the Department for Transport.

No explanation has been provided for the discrepancy, which applies both to national level forecasts of aviation and to the anticipated (no new runway) ‘baseline’ emissions for Heathrow and Gatwick. As a result, we are concerned about the reliability of the Commission’s forecasts of emissions from a new runway.

What the Airports Commission should do: Explain why its CO2 emissions forecasts are lower than the Government’s latest forecasts, what assumptions have been made and how sensitive the results are to them.

Issue two: policies to reduce emissions

Even with lower emissions forecasts, the Airports Commission’s own work has shown that building a new runway would be inconsistent with UK climate change commitments unless new, unspecified action was taken by Government to cap aviation emissions.

The sustainability assessment for each short-listed scheme predicts that national aviation emissions would be higher than the level consistent with the Climate Change Act if the runway scheme proceeds, even if aviation is included in a carbon trading scheme.

The Commission has claimed that working out what additional policy action would be needed to limit emissions (new taxes or planning restrictions on other airports, for example) is outside its remit, as is, indeed, assessing the likelihood that even carbon trading policies will be successfully extended to cover aviation.

What the Airports Commission should do: Set out in meaningful detail what policy developments would be required in order to limit emissions to the aviation cap while building new capacity.

Issue three: Economic analysis

The economic analysis of the shortlisted expansion options does not include the economic costs of restraining greenhouse gas emissions from UK aviation to a level compatible with the Climate Change Act.

The Committee on Climate Change, the Government’s official climate advisers, told the Airports Commission in an open letter in 2013:

Given the need to limit aviation demand growth in a carbon constrained world, we recommend that this should be reflected in your economic analysis of alternative investments. For example, for each investment, you should assess whether this would make sense if demand growth were to be limited to 60% by 2050.

The Commission has not completed this analysis, citing technical difficulties and the fact that the carbon component (costs associated with restraining emissions) “would dominate the capacity appraisals”. The Airports Commission’s estimates of the economic benefits that would arise from each its shortlisted schemes are therefore misleadingly high. The admittance by the Airports Commission that it has not included the ‘carbon costs’ in its economic analysis is hidden on page 25 of the consultation document.

What the Airports Commission should do: Fully include the economy-wide cost of keeping national aviation emissions to within 37.5 Mt in its cost benefit analyses, in line with the recommendations of the Committee on Climate Change. This analysis should be presented prominently in the final report.


Background information on the importance of climate change in the airport expansion debate is available to download here.

Image Credit: Jez via Flickr

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