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 April 2014.
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
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 flights.
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.
- to explore the feasibility of adopting flight altitudes and flight
routes that lead to reduced fuel consumption
and emissions, and lessen the environmental impact;
- to estimate the overall global effect of such ATM measures in terms of
Key findings of the project are:
Climate-friendly routing 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.