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.
The Treasury have based their calculations for 2030 on a factor
of 2.5. 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 2030even
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.
If account is taken of radiative forcing, this would be equivalent
to 200 million tonnes of CO2about 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).
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
|AVIATION EMISSIONS PLUS |
Million Tonnes CO2
|2000 / 2001||572
|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
16. Greener by Design suggested to us that technological
improvements and the use of larger aircraft could make some impact
on curbing emissions.
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 thatwithin
emissionsone might have to trade CO2 off against
water vapour and NOx.
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.