From Dr. Roger Pielke, Sr. at Climate Science:
Recommended Reading Of An Article By Joe D’Aleo On The Lack Of Quality Of The Long Term Surface Temperature Trend Data Set Over Land
There is an excellent article by Joseph D’Aleo at Pajamas Media titled
It very effectively summarizes a number of major issues with the quality of the land portion of the long-term surface temperature trend record that was used in the 2007 IPCC report, and is being assumed as robust at the current Copenhagen meeting.
I recommend this article for anyone who wants to see how really bad this temperature data is with respect to its application to the quantitative assessment of long-term surface temperature trends.