Why so secretive?

Steve McIntyre of Climate Audit has been having problems getting data out of the met Office. The Met Office seem to think that weather records are in some way sensitive. Oddly it now seems that the Climatic Research Unit (CRU) at The University of East Anglia (UEA) has just started deleting data. Steve McIntyre points out, quite correctly:

"Under U.K. Freedom of Information Act, once FOI requests have been made for information, public authorities are not permitted to "alter, deface, block, erase, destroy or conceal any record held by the public authority, with the intention of preventing the disclosure by that authority of all, or any part, of the information to the communication of which the applicant would have been entitled." As fordprefect observed the other day, the Computer Misuse Act also prescribes various offences, one of which is the unauthorized modification of the contents of a computer with the intent "to prevent or hinder access to any program or data held in any computer"."

Anyone might think they had something to hide...