Extratropical Climate Change in the Upper Troposphere and the Routing of Aircraft (EXTRA)

Lead Research Organisation: University of Reading
Department Name: Meteorology

Abstract

The upper troposphere in mid-latitudes is the region encompassing altitudes of around 8-12 km, which includes the jet streams, regions of very strong winds, which are closely related to strengths and paths of the mid-latitude depressions. Climate change is expected to change the nature of the upper troposphere at mid-latitudes - climate models indicate that over coming decades, it will warm, the relative humidity will increase and the strength and orientation of the jet stream might change, and the boundary between the troposphere and the overlying stratosphere (the tropopause) will increase in altitude. However, when different climate models are used to predict future climate change, there is a significant spread in the results they produce; the reasons for this spread are not fully understood.

Understanding climate change in the mid-latitude upper troposphere is of importance in its own right, but it has a wider economic significance. The cruise altititude of commercial aircraft is in the upper troposphere and flight times can be strongly affected by the wind conditions. Most obviously, the duration of flights between (as an example) London and New York are normally more than an hour faster when going eastbound, as the aircraft attempt to fly in the jet stream and receive an extra "push" - by contrast, westbound flights normally try to avoid the jet stream as this would impede progress. However, day-to-day variations in weather conditions in the north Atlantic mean that flight durations of both eastbound and westbound flights can vary by up to 100 minutes, depending largely on the strength and position of the jet stream. Since fuel use, and hence carbon dioxide emissions, are closely related to the flight duration, there are both economic and climate consequences for this variation. In our recent research we have shown that the weather in the upper troposphere in the North Atlantic can be split into characeristic patterns (5 in winter and 3 in summer) for which the aircraft routes are distinct. In addition we have shown that other climate effects of aircraft emissions (for example, contrails and ozone change resulting from emissions of oxides of nitrogen) very likely vary between these weather patterns.

Since aircraft routing is dependent on the weather situation in the upper troposphere, it is natural to ask whether climate change could impact on aircraft routing. There has been much research on the effect of aviation on climate change, but surprisingly little that asks the reverse question: what is the effect of climate change on aviation? Our proposal aims to answer this question, while at the same time improving understanding of upper tropospheric climate change. Since the aviation industry aims to put constraints on its carbon dioxide emissions, the effect of climate change on aviation routing could either assist or work against these aims.

We will consider how the routes of individual aircraft may be affected by the changes in the frequency of different weather patterns in the North Atlantic, predicted by a number of different climate models. We will exploit a recent, large and easily available set of simulations of possible future climate change from a range of world-leading climate models that have been produced for the fifth assessment report of the Intergovernmental Panel on Climate Change, which is currently being written. We will assess how well the climate models reproduce the present-day weather patterns in the North Atlantic and then look at how these patterns change for various possible future climates. We will then see how aircraft routing is affected by these weather patterns and compute the impact of this carbon dioxide emissions. We will also investigate the impact of both the climate change and re-routing on the other climate impacts of aviation.

We will extend this work to cover the North Pacific, which is expected to show a significant increase in air traffic over coming decades.

Planned Impact

There are a very wide range of users associated with the aviation industry that will benefit directly from EXTRA. Possible changes in aircraft routing and associated changes in the climate impact of aviation will be of importance to airlines, air traffic control, aircraft manufacturers, airport operators and non-governmental organisations interested in the environmental impact of aircraft. There are industry-wide efforts (for example under the "Sustainable Aviation" initiative (www.sustainableaviation.co.uk/) to control the growth in aircraft emissions of carbon dioxide, and associated climate effects). Our work will add a new dimension to their considerations. Our work may also have implications for the management of air space, with consequent impacts on airlines, air traffic control, aircraft manufacturers and airport operators. Finally, there is an important economic aspect, if routing, and hence fuel use, is impacted by climate change.The airline industry is extremely competitive, often working on quite tight margins, and fuel use is one of their major operational costs.

With the likely imminent inclusion of international aviation CO2 emissions within the EU Emissions Trading System, our work will be of direct interest to national Government departments (particularly DECC and DfT), the European Union and to bodies that advise Government (such as the Committee on Climate Change (CCC)), as well as the aviation industry itself.

Other atmospheric science researchers outside of academia, either specifically engaged in aviation and climate research, or more generally in climate change research, such as the Met Office (and particularly the Hadley Centre) will find this work of importance, and indeed it will contribute to generic understanding of atmospheric processes beyond its specific aviation focus.

Publications

10 25 50
 
Description Our research examined the impact of changes in climate on aviation and the way these changes in climate themselves impact on the climate change due to aviation.

We have published a paper which examines how future predicted changes in winds over the North Atlantic may alter the routing of aircraft - the impacts appear quite modest, and seem unlikely to have a strong impact on air traffic control and flight planning, which is of reassurance to the industry. However, we have consulted with NATS, the UK national air traffic provider, as to what impacts they regard as significant and the ideas from one of our meetings stimulated a focus of the final part of the research. This particularly concerns the advantages and disadvantages of aircraft flying at different altitudes than the most common cruise altitude. We quantified the time penalty (which equates to fuel use and hence CO2 emissions) for flights across the north Atlantic at different altitudes, and did this separately for westbound and eastbound flights. We showed that impacts on flight times were modest (a few minutes in a few hour flight times). Nevertheless, given current targets for climate-neutral growth of the aviation industry, our work will be of benefit in achieving these goals. After presenting our results to NATS, they indicated that one possible way of exploiting any time saving was to allow aircraft to cruise at lower speeds, as this too has a fuel saving benefit. The work was published in the journal Meteorological Applications in 2018.

We have also published a paper which examines the changes in the potential for contrail formation in a warming world, which shows that in polar regions contrails will become more common, while in the tropics they will become less common. This is important for quantifying the future impact of aviation on climate. This work was followed up by a more focused study examining the UK and East Atlantic sector. This was because some available climate model output (from the international archive of climate model output CMIP5, which is designed to inform the assessment reports of the Intergovernmental Panel on Climate Change) indicated large changes in contrail occurrence in the UK in coming decades, while other models did not. We examined the characteristics of the models that had large changes.
Exploitation Route Forward planning by aviation stakeholders, especially air traffic control, and the wider international industry, to help meet agreed goals for carbon-neutral growth of aviation.
Sectors Aerospace, Defence and Marine,Environment

 
Description We were in regular contact with NATS (the UK's national air traffic management organisation) who are a project partner and shared our research papers with them, and received input, and also discussed them at two meetings with staff at the aircraft engine manufacturers, Rolls Royce, coupled to discussions about possible further funding. The co-I (now employed in a different part of the University of Reading, was requested to write a update report for NATS, summarising the work in EXTRA, and other recent research, during 2019. This is all part of the overall aim for climate-neutral growth by the aviation industry. The findings were also presented to a major conference in Germany in 2015 (Transport, Atmosphere and Climate) that included many stakeholders from the aviation industry.
First Year Of Impact 2018
Sector Aerospace, Defence and Marine,Environment
Impact Types Economic,Policy & public services

 
Description Collaboration with NATS, the UK's national air traffic management organisation 
Organisation National Air Traffic Services Limited
Country United Kingdom 
Sector Private 
PI Contribution Consultation of the relevance of our research to air traffic management, and in particular to environmental targets, and how air traffic management may be impacted by climate change
Collaborator Contribution Discussions with several members of NATS staff engaged either in environmental issues of air traffic management, or the operation of the air traffic management system
Impact This has enabled further targetted research which is of interest to the stakeholder
Start Year 2015
 
Description Contrail Avoidance Group, Greener by Design group of RAeS 
Organisation Royal Aeronautical Society (RaES)
Country United Kingdom 
Sector Learned Society 
PI Contribution Presentation of ongoing work, and participation to ideas about whether aircraft can be re-routed to avoid contrail formation and reduce their overall climate impact
Collaborator Contribution All members of the group (with representatives from the Royal Aeronauatical Society, NATS (national air traffic managements), the German Aerospace Centre, and at some meetings, British Airways) presented ideas on the science and air traffic aspects of contrail avoidance.
Impact Ideas for undergraduate research project, linked to our NERC EXTRA grant - this work was subsequently presented at a meeting of this group in 2017
Start Year 2016
 
Description Meeting with Rolls Royce 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Set of talks to representatives from Rolls Royce, concerning meteorological issues linked to engine performance. This was part of a wider set of presentations from our Department on aviation-related research. It led to proposals to follow-on funded activity to our NERC EXTRA grant, with discussions on these ongoing.
Year(s) Of Engagement Activity 2016
 
Description Presentation to Greener By Design group of the Royal Aeronautical Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Greener-by-Design group of the Royal Aeronautical Society organised a meeting Delivering Sustainable Growth in Aviation in October 2016. Shine spoke at this, and reached a broad cross-section of the aviation stakeholder community in industry and NGO's. Led to further requests to talk to similar groups
Year(s) Of Engagement Activity 2012,2016
 
Description Presentations at NATS, the UK's main air traffic management organisation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Two presentations to a group involved in the efficiency (from a climate change perspective) air traffic management operations, especially in the North Atlantic sector. The presentations both alerted NATS to the current understanding in the field, and alerted us to the main issues facing the industry. Specific issues raised during the discussions led to a change in some of the emphasis in the final period of the project and has led to a paper being submitted to the journal Meteorological Applications, which is currently undergoing assessment after revisions.
Year(s) Of Engagement Activity 2016
 
Description Rolls Royce Environmental Advisory Board 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Discussion with aircraft manufacturer about wider climate change issues and specific ones of interest to the aviation industry

Request for more advice on climate change issues
Year(s) Of Engagement Activity 2014
 
Description Rolls Royce Water in Atmosphere workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact extensive discussion of relevance to aircraft maunfacturers

further discussions
Year(s) Of Engagement Activity 2014
 
Description Stakeholder Event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact This event was aimed at stakeholders in the aviation industry (including air traffic management, airlines, the Met Office and consultancies linked with the aviation industry) and showcased work performed within the project Extratropical Climate Change in the Upper Troposphere and the Routing of Aircraft (EXTRA), funded by the Natural Environment Research Council, and closely-related aviation work at the Department of Meteorology. Three speakers associated with the EXTRA project gave talks highlighting our results. This was followed by a lecture from a renowned guest speaker from the German Aerospace Centre, Professor Ulrich Schumann. The talks were followed by a reception which included posters presented by other members of the Department of Meteorology involved in NERC and other funded projects relevant to aviation.
Year(s) Of Engagement Activity 2017
 
Description University of Reading Aviation Event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Increased interaction with aviation stakeholders

Request to organise bespoke workshop for Rolls Royce plc on water in the atmosphere
Year(s) Of Engagement Activity 2013
URL http://www.met.reading.ac.uk/Aviation_workshop/