The HadCRUT4 dataset is a joint production of the UK Met Office’s Hadley Centre and the Climatic Research Unit of the University of East Anglia. One of the most cited, most important databases for ‘climate modeling’, it informs all climate policies.
Dr McLean audited the HadCrut4 data from 1850 onwards for his PhD thesis, then continued til it was complete. His supervisor was Peter Ridd, famously sacked for saying that “the science was not being checked, tested or replicated” and for suggesting we might not be able to trust the institutions.
The climate modeling algorithms along with much of the data is being withheld, and is not available even to other climate scientists… meaning it’s impossible to know which sites are included in the final temperature analysis, and whether a site’s records have been adjusted or not.
McLean found freakishly improbable data, systematic adjustment ‘errors’ , large gaps of no data, along with simple geography, location and spelling errors.
In the data, Fahrenheit temperatures have been mistaken for Celsius and no one noticed, for seventy years.
There have been almost no quality control checks: data point outliers that are obvious mistakes have not been corrected – one town in Colombia spent three months in 1978 at an average daily temperature of over 80 degrees C. 
Another town, in Romania spent a whole month at minus 46°C. 
In the early 1980’s, St Kitts, a Caribbean island, was recorded at 0°C for a whole month, twice! 
Temperatures for the entire Southern Hemisphere in 1850-1854 are calculated from just one site in Indonesia and some hand written ships logs, but are still include.
In some cases boats on dry land seemingly recorded ocean temperatures from as far as 100km inland.
When a thermometer is relocated to a new site, ‘adjustments’ assume the old site to be “heated” by concrete and buildings. By correcting for buildings that likely didn’t exist in 1880, old records are artificially cooled.
These ‘adjustments’, even applied to just a few sites, can be used to effectively create a whole century of artificial warming trends.
 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.
For more information, see: https://joannenova.com.au/2018/10/first-audit-of-global-temperature-data-finds-freezing-tropical-islands-boiling-towns-boats-on-land/