Veronica Chapman

By e-mail

Roger W Worth

Team Leader

Aviation Emissions Division

Department for Transport

Zone 1/22

Great Minster House

76 Marsham Street

London

SW1P 4DR

Direct Line: 020 7944 8387

Web Site: www.dft.gov.uk

Ref: E0004412

19August2008

Dear Veronica,

FOI request for information on contrails

Thank you for your e-mail to DEFRA,requesting the above information, which has been passed to this department which has the policy lead on this issue. I am writing to confirm that the Departmenthas now completed its search for the information which you requested.I have identified a number of pieces of information which fall within the scope of what you request and include it below. None is being withheld.

The vast majority of information held on vapour or condensation trails relates to their potential contribution to climate change with only very minor references to their chemical composition. The reports consistently indicate that they are composed of ice particles forming on small particles and water vapour emitted by aircraft. A number of documents comment briefly on the composition of the particles using the following or very similar text:‘such particles are formed as a result of any combustion process using hydrocarbon fuels and are composed of soot and sulphate particles. The latter from the very small amounts of sulphur in aviation kerosene.‘

The aircraft creating contrails are predominantly civil airliners flying at high altitudes, 30-40,000 feet and authorised under a range of international agreements and regulations. The remainder being military aircraft such as fuel tankers, freighters and airborne surveillance aircraft whose airframe or engines are often based on civil airliners so will produce similar contrails.

We are not aware of any concerns raised by the scientific community about the potential health effects of contrails from aircraft. There is no credible evidence that they are contaminated other than by the exhaust gases and particulates. We have an interest in characterising any ultrafine particulates and determining if aircraft engine technology can be developed to reduce the frequency, size and persistence of contrails.

Currently, it is too early to say whether contrails are worth avoiding because of the uncertainties in the warming effect, and the potential costs of the air traffic management system to avoid them. Moreover, avoidance of contrails may incur a penalty of higher fuel usage such that CO2 warming may be increased. Thus, more study is required. The Department sponsored a major international scientific meeting in 2006 (see which presented significant new research on the subject.

If you are unhappy with the way the Department has handled your request or with the decisions made in relation to your request you may complain within two calendar months of the date of this letterby writing to me at the above address. Please see attached details of the Department for Transport’s complaints procedure and your right to complain to the Information Commissioner.from [department] you may ask for an internal review. You should contact [name of official and address] if you wish to complain

If you have any queries about this letter, please contact me. Please remember to quote the reference number above in any future communications.

Yours sincerely,

Roger W Worth

Your right to complain to DfTand the Information Commissioner

You have the right to complain within two calendar months of the date of this letterabout the way in which your request for information was handled and/or about the decision not to disclose all or part of the information requested. In addition a complaint can be made that DfT has not complied with its FOI publication scheme.

Your complaint will be acknowledged and you will be advised of a target date by which to expect a response. Initially your complaint will be re-considered by the official who dealt with your request for information. If, after careful consideration, that official decides that his/her decision was correct, your complaint will automatically be referred to a senior independent official who will conduct a further review. You will be advised of the outcome of your complaint and if a decision is taken to disclose information originally withheld this will be done as soon as possible.

If you are not content with the outcome of the internal review, you have the right to apply directly to the Information Commissioner for a decision. The Information Commissioner can be contacted at:

Information Commissioner’s Office
Wycliffe House
Water Lane
Wilmslow
Cheshire
SK9 5AF

080804 FOI 4412 Chapman Contrails