Hi Claudia,
It is depends on the GCM.
Monthly means HadAM3P data is here
[url]http://www.precisrcm.com/HadAM3P/
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Various fields for HadCM3Q0/3/16 are here
[url]http://www.precisrcm.com/HadCM3/
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More HadCM3Q can be found at BADC, see instructions here:
http://www.metoffice.gov.uk/research/applied/applied-climate/precis/qump/badcWe don't have any data for Era-40 or Era-Interim -- I suspect ECMWF has them somewhere.
HadGEM2-ES would be (I think) at a CMIP5 archive
http://cmip-pcmdi.llnl.gov/cmip5/availability.htmlHope this helps
David