Select Committee on Environmental Audit Ninth Report


Growth estimates

8. The Department for Transport 2002 airports consultation is based on predictions that passenger numbers will increase from 180 million passengers per annum (mppa) to 501 mppa by 2030.[8] This increase is based upon 'unconstrained demand'—it assumes that there is no restriction on the amount of additional airport and airspace capacity necessary to meet any level of future demand. The figure of 501 mppa represents a mid-point forecast, and the DfT states that in the past outturns have exceeded even their upper estimates.[9] We also note that, while this report focuses on passenger growth, air freight is forecast to increase at an even greater rate.[10]

9. In response to such forecasts, the DfT has examined proposals for runway expansion in various parts of the country, and the extent to which these would satisfy the likely growth in demand. To do so, it commissioned two major studies to examine options in the south-east of England (SERAS) and in other regions (RASCO). Indeed, the DfT consultation was launched on a similar basis, with one consultation document for the south-east and other consultation documents for other regions. There is no document which brings these together at a strategic level, though some of the material in the consultation documents is common.

10. We reproduce below a table showing the overall results of the DfT's analysis.[11] This shows that—even on the basis of no new runways—the DfT expects that passenger traffic will increase to 428 mppa—some 2.4 times the present baseline of 180 mppa. The rate of growth would increase to a factor of 2.6 with the addition of 3 or 4 new runways.

Passenger traffic in 2030 (mppa)
Scale of development at South East airports
South East airports
Other airports
Maximum use (no new runways)
1 new runway
2 new runways
3/4 new runways

Source: Department of Transport

The impact on emissions

11. The impact of such an increase in air travel on global warming would be immense. Emissions from aircraft contribute far more to global warming than the same level of emissions from surface-based sources. This concept is known as radiative forcing. It is due to the fact that aircraft emit not only carbon dioxide, but water vapour and nitrogen oxides (NOx)—both of which can lead to global warming effects when emitted in the stratosphere at the altitude at which passenger aircraft normally fly.

12. On the basis of available scientific evidence, the IPPC suggested in 1999 that aviation emissions might have 2.7 times the effect on global warming when compared to a similar weight of carbon dioxide emitted on the ground. This figure represents a best estimate: the scientific uncertainties involved mean that the effect could be substantially larger or smaller.[12] The Treasury have based their calculations for 2030 on a factor of 2.5.[13] We have done the same.

13. The Department for Transport forecasts that aviation emissions will rise from their present value of 30 million tonnes of CO2 to at least 70 million tonnes by 2030—even if no new runways are built anywhere in the UK. On the basis of a 'high capacity' scenario where 3 or 4 new runways are provided, emissions might rise to 80 million tonnes CO2.[14] If account is taken of radiative forcing, this would be equivalent to 200 million tonnes of CO2—about a third of the UK's total ground-based CO2 emissions at the moment.

14. The Government has recently committed itself to a 60% cut in CO2 by 2050, in line with the target proposed by the Royal Commission on Environmental Pollution (RCEP).[15] In this context, the impact of the growth of aviation is even more startling, as demonstrated by the following table.

Forecast growth in Aviation Emissions
TOTAL UK EMISSIONS (excluding aviation)
Million tonnes CO2
Million tonnes CO2
Million Tonnes CO2
2000 / 2001
2050 60% target

Source: Environmental Audit Committee

15. By 2030, aviation could account for nearly 90% of the Government's 2050 CO2 target of 229 million tonnes. If growth were to continue after that date, it would in practice wipe out the entire savings the UK would make in achieving the 60% target. Even by 2010, if international flights are included, the increase in aviation emissions would entirely negate the reductions achieved by the Government under the Kyoto Protocol and its domestic CO2 programme.

16. Greener by Design suggested to us that technological improvements and the use of larger aircraft could make some impact on curbing emissions.[16] While we accept that useful progress can be made here, there is substantial evidence that the scale of future improvements will be small. Indeed, it has been suggested that we are now in a position where some environmental impacts such as noise may have to be traded against others such as emissions, or that—within emissions—one might have to trade CO2 off against water vapour and NOx.[17] We see no sign of any breakthrough which will lead to radical improvements: future concepts such as the 'flying wing' design might offer such a promise but are at least 50 years off.

17. We regard the proposed growth in emissions into the atmosphere by the aviation industry as unsustainable and unacceptable. Were such growth to occur, it could totally destroy the Government's recent commitment to a 60% cut in carbon dioxide emissions by 2050. In Aviation and the Environment, the Government is accepting responsibility for the UK share of international emissions. It would therefore be particularly inappropriate if the Government response to our report argued otherwise.

8   DfT, South-East consultation, page 41. Back

9   Ibid. page 40, paragraph 5.22. Back

10   Ibid, paragraph page 115ff. Back

11   Ibid, page 24. Back

12   Aviation and the Global Atmosphere, Special Report of the Intergovernmental Panel on Climate Change (IPCC), 1999. Back

13   See Aviation and the Environment, HM Treasury, page 21 table C1.  Back

14   DfT South-East consultation, page 184. Back

15   The Energy White Paper, Our energy future - creating a low carbon economy, March 2003, DTI, Cm 5761, paragraph 1.10. Back

16   Ev16ff. Back

17   Ev22, Q87. Back

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