Several studies have looked in depth at possible heat island contamination of land temperature records. (skepticalscience.com)
One of the records is a completely random signal (white noise) on top of a rising trend and the other is the real hadcrut land temperature record. (judithcurry.com)
It's also worth noting that Muller himself has been careful not to pronounce on AGW, only the validity of the global land temperature record. (tamino.wordpress.com)