The European project REACT4C (FP7) investigated the
potential of climate-optimised flight routing as a
measure to reduce the atmospheric impact of aviation. The four year research project
started in January 2010 and has successfully completed its implementation in
The project was coordinated
by the DLR-Institute of Atmospheric Physics and was funded by the European
Commission within the 7th Framework Programme (grant number
ACP8-GA-2009-233772). The REACT4C Consortium is
composed of a total of eight partners.
The collaborative project REACT4C
(Reducing Emissions from Aviation by Changing Trajectories for the benefit of
Climate) had the objectives:
explore the feasibility of adopting flight altitudes and flight routes
that lead to reduced fuel consumption and emissions, and lessen the
- to estimate the overall global
effect of such ATM measures in terms of climate change.
The novelty in REACT4C is a modelling chain for optimisation of aircraft trajectories with respect to their
climate impact, which is depending on actual weather situation, taking into
account the weather-dependent climate impact of aviation emissions (CO2 and
non-CO2, such as NOx, H2O and contrail cirrus) released during individual
Description of work
We have performed a weather classification for the
North-Atlantic region, computed 4- dimensional climate cost functions for various species and using different metrics, combined them with the
traditional operational cost functions airlines use to optimise
their routing. Most efficient reduction of climate impacts is calculated for
given changes in operating costs (socalled Pareto
fronts). This novel methodology turns out to more effectively reduce the air
traffic's climate impact than simply flying higher or lower, as we showed using
results from a variety of participating chemistry-transport models.
Key findings of the
can be performed using weather classes. The weather situations over the North
Atlantic at cruise altitudes were categorised into a
small set of distinct frequently-occurring patterns. Strength and orientation
of the jet stream; the flight routing and durations, for both eastbound and
westbound flights, depend on these patterns.
These weather patterns were
used to estimate the CO2 and non-CO2 climate impacts of aviation, and formed
the basis of for calculating the routes that had minimal climate impact, i.e.
climate-optimised trajectories that depend on the
actual weather. Climate cost functions are the basis of this optimisation which describe the
atmospheric sensitivity to aviation emissions with respect to climate,
depending on the geographic position, the flight altitude and time.
By this weather dependent
flight trajectory optimisation it is possible to
significantly reduce the overall climate impact of aviation considering CO2 and
non-CO2 impacts at only moderate cost increases. It is even possible to convert
costs into gains for airlines by combining our method with an emission trading
system and turning the these climate optimised trajectories into non-regret measures.
A novel analysis of
airflows in North-Atlantic weather systems examined the typical duration of
regions of ice supersaturated air, when following a parcel of air along these
air flows. It was shown that individual parcels normally remain supersaturated
for less than 6 hours. The weather conditions in which longer-lived areas of
super-saturation can occur were identified, which is crucial for contrail formation
by air traffic.
A higher temporal and
spatial resolution of meteorological fields is needed in order to sufficiently
resolve contrail cirrus. It is still AIC (aviation induced cloudiness),
followed by sulphur aerosols whose climate cost
functions have the largest uncertainties. One needs to use the full set of
climate cost functions (all effects) in order to minimise
the total climate impact of aviation.
Uncertainty studies have
been performed and it was shown that while absolute values may change when
uncertain parameters are varied, the overall results of the study were robust.
Simplified mitigation procedures (flying higher and flying lower) are less cost
effective than weather dependent routing.
Our method is flexible such
that new results and findings on species' impacts on climate can easily be
incorporated, resulting in additional components of the climate cost functions.
This conceptual approach can be used for further mitigation assessment studies.
A road map for implementation of our method was assessed for moving towards
conceptual use in any flight planning system on a long-term time horizon.
This project has received funding from the
European Union’s Seventh Framework Programme
for research, technological development and demonstration under grant agreement