Yet another sky is falling report is out. I'm sure you'll hear all about it on the news. Below is a summary of an interesting PhD Thesis by an Australian who carefully reviewed the landbased temperature sensors. Could it be a just a few people changed the temp readings over the years to compensate for urban heat island and either intentionally or unintentionally, mislead the scientific community?

"HadCRUT4 is the primary global temperature dataset used by the Intergovernmental Panel on Climate Change (IPCC) to make its dramatic claims about “man-made global warming”.  It’s also the dataset at the center of “ClimateGate” from 2009, managed by the Climate Research Unit (CRU) at East Anglia University.

The audit finds more than 70 areas of concern about data quality and accuracy.

But according to an analysis by Australian researcher John McLean it’s far too sloppy to be taken seriously even by climate scientists, let alone a body as influential as the IPCC or by the governments of the world.

Main points:

The Hadley data is one of the most cited, most important databases for climate modeling, and thus for policies involving billions of dollars.
McLean found freakishly improbable data, and systematic adjustment errors , large gaps where there is no data, location errors, Fahrenheit temperatures reported as Celsius, and spelling errors.
Almost no quality control checks have been done: outliers that are obvious mistakes have not been corrected – one town in Columbia spent three months in 1978 at an average daily temperature of over 80 degrees C.  One town in Romania stepped out from summer in 1953 straight into a month of Spring at minus 46°C. These are supposedly “average” temperatures for a full month at a time. St Kitts, a Caribbean island, was recorded at 0°C for a whole month, and twice!
Temperatures for the entire Southern Hemisphere in 1850 and for the next three years are calculated from just one site in Indonesia and some random ships.
Sea surface temperatures represent 70% of the Earth’s surface, but some measurements come from ships which are logged at locations 100km inland. Others are in harbors which are hardly representative of the open ocean.
When a thermometer is relocated to a new site, the adjustment assumes that the old site was always built up and “heated” by concrete and buildings. In reality, the artificial warming probably crept in slowly. By correcting for buildings that likely didn’t exist in 1880, old records are artificially cooled. Adjustments for a few site changes can create a whole century of artificial warming trends.
Details of the worst outliers
For April, June and July of 1978 Apto Uto (Colombia, ID:800890)  had an average monthly temperature of  81.5°C, 83.4°C and 83.4°C respectively.
The monthly mean temperature in September 1953 at Paltinis, Romania is reported as -46.4 °C (in other years the September average was about 11.5°C).
At Golden Rock Airport, on the island of St Kitts in the Caribbean, mean monthly temperatures for December in 1981 and 1984 are reported as 0.0°C. But from 1971 to 1990 the average in all the other years was 26.0°C."