EDGAR32FT2000 was used for anthropogenic
emissions, with the transport sectors’ emissions
replaced by improved estimates for the present
and for the IPCC A1 and B1 scenarios (2025,
2050) from the new QUANTIFY inventory. The
A1 scenario represents a world of very rapid economic growth, especially in developing countries,
and rapid introduction of new and more efficient
technologies. The B1 scenario assumes rapid
introduction of clean and resource-efficient technologies, and is considered to be far more optimistic with respect to environmental policy
making than the A1 scenario. The results from
the scenario calculations for the impact of shipping on ozone in the lower troposphere (surface to
800 hPa) point to a significantly increasing impact
on ozone from the shipping sector, if emissions
evolve according to the A1 scenario, while the B1
scenario leads to a much smaller increase. The
results obtained for shipping are particularly interesting in the sense that the impacts on the
hydroxyl radical (OH) and thus on methane
(CH4) were larger than anticipated. The reduction
of the global atmospheric lifetime of methane due
to ship emissions was about a factor of 2–3 larger
than that due to road emissions, and about a factor
of 4 larger than that due to air traffic emissions
[15]. This is a consequence of the more pristine
chemical conditions over the oceans and the
slightly different mix of emissions from ships.
As a result, the net impact on radiative forcing of
ozone and methane perturbations from shipping is
negative, corresponding to a more or less globally
uniform cooling. This adds up to the cooling via
widespread cloud modifications caused by ship
emissions of sulfate aerosols [27]. In contrast,
the atmospheric chemistry influence on radiative
forcing by aviation remains strongly positive.
The radiative forcing of aviation in the year
2000 in relation to all other transport sectors is
given in Table 1 (QUANTIFY [30]. Peculiarities
in comparison to other modes of transport emerge:
First, the radiative forcing is nearly doubled by
inclusion of the effect of ozone formation due to
the emission of nitrogen oxides at cruising altitudes. Second, aviation-induced cloudiness in
form of contrails and contrail cirrus adds substantially to the positive radiative forcing, however, is
rather uncertain. Overall, aviation remains the
sector with strongest additional effects besides
the basic CO 2 -related radiative forcing. The line
named indirect aerosol effect in Table 2 needs a
special remark. It is to a large extent due to model
calculations using comparably crude parameterizations for the aerosol influence on cloud droplet
number and on absorption of solar radiation by
soot. This research is still in its infancy as shown
by the huge error bars, and one should not argue
like very often lobbies would do that any climate
policy measure concerning aviation has to be
postponed until small error bars are reached for
all entries. What is needed is a flexible reaction
should major changes become evident.
Transport Sector’s Contribution to
Future Climate Change
Using a coupled atmosphere/ocean/land-model
and the A1B scenario of IPCC as well as accounting for six different forcings (CO 2 , CH 4 , O 3 , and
aerosols for all sectors, CFCs and HCFCs for road
traffic, and contrail formation for aircraft) Olivie
et al. [28] found: In the year 2100, the warming
from all transport sectors due to the CO 2 increase
reaches about 0.5 Kwith the largest contribution
from road traffic (0.3 K). The non-CO 2 impact
from air traffic is larger than its CO 2 impact, the
latter amounting to 0.15 K at 2100. It is caused by
an enhanced O 3 production (compared to road and
ship traffic) due to the altitude of the NOx emissions, and by the positive direct radiative forcing
from linear contrails and contrail-induced cirrus.
Because the total anthropogenic global temperature increase is about 3 K in 2100 with a contribution of about 0.65 K from the transport sector,
with 0.5 K due to CO 2 impact and 0.15 K due to
non-CO 2 impact dominated by aircraft traffic, the
transport sector contributes slightly less than its
share in total energy use. This reduced impact is
caused by both the reduction in methane lifetime
and comparably low N 2 O and CH 4 emissions. The
warming is in general more pronounced at high
latitudes, but the signal there is strongly
influenced by the timing of the Arctic sea-ice
melting, which is quite uncertain.
Aviation and Atmosphere
339
emissions, with the transport sectors’ emissions
replaced by improved estimates for the present
and for the IPCC A1 and B1 scenarios (2025,
2050) from the new QUANTIFY inventory. The
A1 scenario represents a world of very rapid economic growth, especially in developing countries,
and rapid introduction of new and more efficient
technologies. The B1 scenario assumes rapid
introduction of clean and resource-efficient technologies, and is considered to be far more optimistic with respect to environmental policy
making than the A1 scenario. The results from
the scenario calculations for the impact of shipping on ozone in the lower troposphere (surface to
800 hPa) point to a significantly increasing impact
on ozone from the shipping sector, if emissions
evolve according to the A1 scenario, while the B1
scenario leads to a much smaller increase. The
results obtained for shipping are particularly interesting in the sense that the impacts on the
hydroxyl radical (OH) and thus on methane
(CH4) were larger than anticipated. The reduction
of the global atmospheric lifetime of methane due
to ship emissions was about a factor of 2–3 larger
than that due to road emissions, and about a factor
of 4 larger than that due to air traffic emissions
[15]. This is a consequence of the more pristine
chemical conditions over the oceans and the
slightly different mix of emissions from ships.
As a result, the net impact on radiative forcing of
ozone and methane perturbations from shipping is
negative, corresponding to a more or less globally
uniform cooling. This adds up to the cooling via
widespread cloud modifications caused by ship
emissions of sulfate aerosols [27]. In contrast,
the atmospheric chemistry influence on radiative
forcing by aviation remains strongly positive.
The radiative forcing of aviation in the year
2000 in relation to all other transport sectors is
given in Table 1 (QUANTIFY [30]. Peculiarities
in comparison to other modes of transport emerge:
First, the radiative forcing is nearly doubled by
inclusion of the effect of ozone formation due to
the emission of nitrogen oxides at cruising altitudes. Second, aviation-induced cloudiness in
form of contrails and contrail cirrus adds substantially to the positive radiative forcing, however, is
rather uncertain. Overall, aviation remains the
sector with strongest additional effects besides
the basic CO 2 -related radiative forcing. The line
named indirect aerosol effect in Table 2 needs a
special remark. It is to a large extent due to model
calculations using comparably crude parameterizations for the aerosol influence on cloud droplet
number and on absorption of solar radiation by
soot. This research is still in its infancy as shown
by the huge error bars, and one should not argue
like very often lobbies would do that any climate
policy measure concerning aviation has to be
postponed until small error bars are reached for
all entries. What is needed is a flexible reaction
should major changes become evident.
Transport Sector’s Contribution to
Future Climate Change
Using a coupled atmosphere/ocean/land-model
and the A1B scenario of IPCC as well as accounting for six different forcings (CO 2 , CH 4 , O 3 , and
aerosols for all sectors, CFCs and HCFCs for road
traffic, and contrail formation for aircraft) Olivie
et al. [28] found: In the year 2100, the warming
from all transport sectors due to the CO 2 increase
reaches about 0.5 Kwith the largest contribution
from road traffic (0.3 K). The non-CO 2 impact
from air traffic is larger than its CO 2 impact, the
latter amounting to 0.15 K at 2100. It is caused by
an enhanced O 3 production (compared to road and
ship traffic) due to the altitude of the NOx emissions, and by the positive direct radiative forcing
from linear contrails and contrail-induced cirrus.
Because the total anthropogenic global temperature increase is about 3 K in 2100 with a contribution of about 0.65 K from the transport sector,
with 0.5 K due to CO 2 impact and 0.15 K due to
non-CO 2 impact dominated by aircraft traffic, the
transport sector contributes slightly less than its
share in total energy use. This reduced impact is
caused by both the reduction in methane lifetime
and comparably low N 2 O and CH 4 emissions. The
warming is in general more pronounced at high
latitudes, but the signal there is strongly
influenced by the timing of the Arctic sea-ice
melting, which is quite uncertain.
Aviation and Atmosphere
339