Annex B
Extract from:
Aviation and the Environment: Using Economic
Instruments, Department for Transport, March 2003
AVIATION'S
SHARE OF
CO2 EMISSIONS
3.9 For 2000, estimates[8]
show that UK civil passenger aviation produced 30 million tonnes
of CO2, which corresponds to 18% of all UK transport
CO2 emissions and 5% of UK CO2 emissions
from all sectors.
3.10 Estimates reported in The Future
Development of Air Transport in the United Kingdom: South East
(ANNEX E, Table E.2) suggest that passenger aviation will be responsible
for c.70 million tonnes of CO2 in 2030 in a scenario
with high growth of airport capacity.
3.11 The 2030 carbon dioxide forecast implies
an increase of 2.3 times the year 2000 total of 30 million tonnes
of CO2. On the basis of current policies, including
the full impact of the Climate change programme, overall UK carbon
dioxide emissions might amount to some 135 million tonnes of carbon
in 2020. While there is no specific aviation forecast for the
same year, interpolation suggests that aviation might produce
some 14-16 million tonnes of carbon in 2020[9],
about 10-12% of total UK CO2 emissions from all sectors.
For the reasons given in the section on radiative forcing (see
below), aviation's share of total climate change effects is higher
than its share of CO2 alone.
| Year | Aviation (MtCO2)
| Total UK emissions (MtCO2)
| Share of total UK CO2 emissions
|
| 2000 | 30 |
600 | 5%
|
| 2020 | 55 |
495 | 10-12%
|
RADIATIVE FORCING
B.1 Aircraft emit gases and particles directly into the
atmosphere altering its composition. These gases and particles
alter the concentrations of atmospheric greenhouse gases, including
carbon dioxide (CO2), ozone (O3), and methane
(CH4); trigger formation of condensation trails (contrails)
and may increase cirrus cloudiness, all of which contribute to
climate change. When a particular human activity alters greenhouse
gases, particles or land status, such activity results in radiative
imbalance. Such an imbalance cannot be maintained for long, and
the climate system—primarily the temperature and clouds
of the lower atmosphere—adjusts to restore the radiative
balance. The IPCC uses a single measure of climate change: radiative
forcing (RF), which is calculated directly from changes in greenhouse
gases, aerosols, and clouds.
B.2 The radiative forcing index (RFI) is defined as the
ratio of total radiative forcing to that from CO2 emissions
alone. For CO2 radiative forcing, it makes no difference
whether the fossil fuel is burned by aircraft or by other transportation/energy
sectors. Total radiative forcing induced by aircraft is the sum
of all forcings, including direct emissions (e.g. CO2,
soot) and indirect atmospheric responses (e.g. CH4,
O3, sulphate, contrails). RFI is a measure of the importance
of aircraft-induced climate change caused by all emissions, not
just the contribution from the release of fossil carbon alone.
According to the 1999 IPCC report, Aviation and the Global
Atmosphere, in 1992, the RFI for aircraft is 2.7, within an
uncertainty range as described on page 211 of that report.
B.3 The cost of carbon values therefore needs to be scaled
up to reflect the impact of radiative forcing from emissions at
altitude. Professor David Lee of Manchester Metropolitan University
and QinetiQ (the consultants who produced the CO2 estimates
in SERAS) says that:
"Excluding the landing and take-off (LTO) cycle,
the average Radiative Forcing of aviation is 2.7 times that of
CO2 alone. Radiative forcing effects arise from CO2
plus other emissions that result in ozone (arising from NOx emissions)
and contrail formation. 2.7 times is, of course, the reciprocal
of 37%, which is CO2's share of total radiative forcing
from aviation at altitude."
B.4 Therefore, the original cost of carbon estimated in
the Eyre et al study, and subsequently adopted by DEFRA, has been
scaled up by 2.7.
8
National Environmental Technology Centre (NETCEN). Back
9
See page 72 of Our Energy Future-creating a low carbon economy,
February 2003, DTI. Back
|
