Probability of severe winter weather and its statistical independence

M. Ackroyd made this Freedom of Information request to Meteorological Office

This request has been closed to new correspondence from the public body. Contact us if you think it ought be re-opened.

The request was partially successful.

Dear Met Office,

Dr David Quarmby CBE, in his audit "The Resilience of England's Transport Systems in December 2010" December 2010 said "The Met Office advice to our main Review earlier this year was that severe winters have only a 1 in 20 chance, that the weather in any one winter is virtually independent (statistically speaking) of weather in preceding winters,..."

Please supply a copy of the communication to Dr Quarmby or to his colleagues in which this information (probability = 1-in-20, statistical independence) was provided.

Please also supply a copy of the Met Office internal report stating how this probability estimate was derived and giving an assessment of the evidence for statistical independence.

Finally, please supply a copy of the Met Office document in which this information was approved for release.

Yours sincerely,

M. Ackroyd

Naomi Lawrence, Meteorological Office

Dear Sir/Madam

Thank you for your enquiry.
We have forwarded this on to our FOI team. Your reference number for this
enquiry is WD0000938.

If you have any further questions or need additional information please
contact the Weather Desk on 0870 9000 100 where one of our advisors will
be happy to help you. The number is open 24 hours a day, seven days a
week.
Kind regards

Naomi
Weather Desk Advisor
Met Office, FitzRoy Road, Exeter, Devon, EX1 3PB, United Kingdom.
Tel: 0870 900 0100 or +44 (0)1392 88 5680 Fax: 0870 900 5050
Email: [1][Met Office request email] [2]http://www.metoffice.gov.uk

Please see a Christmas message from everyone at the Met Office at
[3]http://www.metoffice.gov.uk/christmas2010/
Your personal details will be stored in our database. The information will
not be passed to any third parties. Please advise us if you do not wish
your details to be stored. The Met Office is an Executive Agency of the UK
Ministry of Defence and is registered under the Data Protection Act 1998.

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FOImanager, Meteorological Office

Dear M. Ackroyd,

Please accept this as acknowledgement of your enquiry dated 23 December
2010.

Under the requirements of the Freedom of Information Act
2000/Environmental Information Regulations 2004, you will receive our
response within a period of 20 working days from the date it was received
within the Ministry of Defence.

You should therefore expect to receive our response by the 25 January
2011.

Yours sincerely,
FOI Manager

Met Office FitzRoy Road Exeter EX1 3PB United Kingdom
Tel: +44 (0)1392 884081 Fax: +44 (0)1392 88 5681
Email: [email address]
[1]http://www.metoffice.gov.uk

Confidentiality Notice
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Dear FOImanager,

Thank you for your acknowledgment of my enquiry dated 23 December 2010.

Please note that the information I requested is environmental information and so my request should be handled under EIR rather than FOI.

Also, I want the information referred to by Dr Quarmby, irrespective of whether or not it was supplied to him by the Met Office.

Yours sincerely,

M. Ackroyd

Dear Naomi Lawrence,

Many thanks for your acknowledgement of my enquiry, which you gave the reference number WD0000938.

I sent a brief follow-up but I am not sure if it got through. Please would you forward the following additional notes to your colleagues who are dealing with my request.

* Please note that the information I requested is environmental information and so my request should be handled under EIR rather than FOI.

* Also, I want the information referred to by Dr Quarmby, irrespective of whether or not it was supplied to him by the Met Office.

Yours sincerely,

M. Ackroyd

Sandy Berridge, Meteorological Office

Dear M Ackroyd,

Thank you for your enquiry.
We have forwarded this on to our FOI team and they will get back to you as
soon as possible.
If you have any further questions or need additional information please
contact the Weather Desk on 0870 9000 100 where one of our advisors will
be happy to help you. The number is open 24 hours a day, seven days a
week.
Kind regards,

Sandy.
Weather Desk Advisor
Met Office, FitzRoy Road, Exeter, Devon, EX1 3PB, United Kingdom.
Tel: 0870 900 0100 or +44 (0)1392 88 5680 Fax: 0870 900 5050
Email: [1][Met Office request email] [2]http://www.metoffice.gov.uk
Please see a Christmas message from everyone at the Met Office at
[3]http://www.metoffice.gov.uk/christmas2010/
Your personal details will be stored in our database. The information will
not be passed to any third parties. Please advise us if you do not wish
your details to be stored. The Met Office is an Executive Agency of the UK
Ministry of Defence and is registered under the Data Protection Act 1998.

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FOImanager, Meteorological Office

3 Attachments

Dear M. Ackroyd,

Please find attached a letter in response to your recent Freedom of
Information request
<<0000938 Ackroyd.PDF>>

<<Ackroyd attachment 1.PDF>> <<Ackroyd attachment 2.PDF>>

Kind regards

FOI Manager
Met Office FitzRoy Road Exeter EX1 3PB United Kingdom
Tel: +44 (0)1392 884081 Fax: +44 (0)1392 88 5681
Email: [email address]
[1]http://www.metoffice.gov.uk

Confidentiality Notice
This e-mail is intended for the addressee only. Its contents are provided
"in confidence" and may be covered by contractual, legal or other
privilege. If you are not the addressee, you may not use or copy it to any
other person. If you receive this e-mail in error, then please contact the
sender as detailed above.

References

Visible links
1. http://www.metoffice.gov.uk/

Dear FOI Manager,

Thank you for your reply to my enquiry. However, I am disappointed to find that my requests have not been complied with.

(1) I asked for a copy of the communication to Dr Quarmby or to his colleagues in which the probability of severe winters being 1-in-20 and their statistical independence was provided.
*This communication has not been provided.*

You said "(...) I attach a copy of the correspondence between Met Office staff and Dr Quarmby's colleague listing the Met Office amendments to an extract of the final draft of the report which refers to the 1 in 20 statistic and statistical independence".

It is obvious that the Quarmby Review had *already* received guidance from the Met Office that the probability was 1 in 20 and that statistical independence could be assumed. This is obvious because they had, by then, already included this information in their draft.

The Quarmby Review is in the public domain. Providing a copy of part of the Quarmby Review final draft containing the information previously provided by the Met Office, annotated with some improvements to wording suggested by Met Office staff,
*absolutely does not comply with my request.*

(2) I asked for a copy of the Met Office internal report stating how the probability estimate of 1 in 20 was derived and giving an assessment of the evidence for statistical independence. This report has not been provided.

You said "I attach an email between Met Office staff explaining how the 1 in 20 calculation was estimated using the HdGEM1 model and the climate mean CET."

The email you attached (dated 26 November 2010) *does not* say how the 1 in 20 probability was estimated. It starts "The calculation of the changing odds was done as follows."

The 1 in 20 probability used by the Quarmby review has nothing to do with "changing odds". It is the probability that a winter in the current time frame is severe. Thus it is clear that the sender of the email is talking about something quite different, even though they use the phrase "1 in 20 odds".

In any case, it says merely: "(...) For the 1 in 20 odds I needed to estimate how different current mean climate is from the pre-industrial era of CET as a result of global warming. This calculation is a rather crude calculation compared to the more sophisticated types of calculation we are planning to do in future (...)"

To précis, the writer is saying two things:
- what they thought they needed to do (*but not how they actually did it*).
- that the calculation was rather crude (*but not how it was done*).

But even if it were dealing with the 1 in 20 probability provided to the Quarmby Review, the provisions of an informal email containing a few lines that merely mention a calculation *absolutely would not comply with my request*.

Finally, there is no discussion whatever of how the conclusion of statistical independence was derived.
*This part of my request has been ignored completely.*

(3) I asked for a copy of the Met Office document in which this information was approved for release. I note that you said that this information was approved for release verbally during meetings and teleconferences. I find it astonishing that approval for release of important quantitative information would not be documented but I have to accept that this is how the Met Office works.

Please now, as quickly as possible, provide what I actually asked for:

1. A copy of the communication to the Quarmby Review in which the 1 in 20 probability of severe winter weather and the validity of statistical independence was provided.

2. A copy of the internal Met Office report detailing the calculation of the 1 in 20 figure and showing the analysis that enabled the statistical independence conclusion to be drawn.

Yours sincerely,

M. Ackroyd

Dear Met Office FOI Manager,

On 25 January 2011, I sent a reply to your communication "Attachment 0000938 Ackroyd.PDF.pdf" ("Your reference number for this enquiry is WD0000938").

Are we in communication?

Yours sincerely,

M. Ackroyd

FOImanager, Meteorological Office

Dear M. Ackroyd,

Thank you for your correspondence on the 25th and 26th January. We are
currently looking into your questions and will respond as soon as possible

Kind regards

FOI Manager
Met Office FitzRoy Road Exeter EX1 3PB United Kingdom
Tel: +44 (0)1392 884081 Fax: +44 (0)1392 88 5681
Email: [email address]
[1]http://www.metoffice.gov.uk

Confidentiality Notice
This e-mail is intended for the addressee only. Its contents are provided
"in confidence" and may be covered by contractual, legal or other
privilege. If you are not the addressee, you may not use or copy it to any
other person. If you receive this e-mail in error, then please contact the
sender as detailed above.

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FOImanager, Meteorological Office

Dear M. Ackroyd,

Thank you for your email.

The Met Office does not hold any information in addition to our previous response, however, I will address your questions below.

1. We have asked the people concerned to search and we conclude that the Met Office does not hold any further information in addition to our previous response.

2. As previously advised, the Met Office does not hold this information. There were verbal discussions concerning the 1 in 20 statistic and the statistical independence issue, the 1 in 20 statistic is the approximate current frequency of cold winters (as measured by the HadCET Central England temperature record being colder than the 2009-2010 winter). In the HadCET record, generally the odds of a cold winter following a cold winter are generally the same as the odds of a cold winter following a warm winter.

I hope this answers your enquiry

Kind regards

FOI Manager
Met Office FitzRoy Road Exeter EX1 3PB United Kingdom
Tel: +44 (0)1392 884081 Fax: +44 (0)1392 88 5681
Email: [email address]
http://www.metoffice.gov.uk

Confidentiality Notice
This e-mail is intended for the addressee only. Its contents are provided "in confidence" and may be covered by contractual, legal or other privilege. If you are not the addressee, you may not use or copy it to any other person. If you receive this e-mail in error, then please contact the sender as detailed above.

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