Not sure if this has been remarked upon before, but the Met Office now
have in an easily accessed form, the climatological averages for
1971-2000, alongside those for 1961-1990 at the following page:-
http://www.metoffice.com/climate/uk/averages/index.html
the two datasets enable changes over the two 30-year periods to be
assessed.
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FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm