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Extracting samples from 450 year old Mongolian trees allows scientists to look at the growth rings of trees, the shape of which indicates a relative warming of the world over the last 100 years.

Also on the programme: Cleaning up the environment with genetically modified E-coli bacteria which filter out metals like cadmium and nickel from water; and could concerns about wildlife prevent the world's largest offshore wind farm being built 3km off the coast of Great Yarmouth, UK.