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!
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.
The dataset starts in 1850 but for just over two years at the start of the record the only land-based data for the entire Southern Hemisphere came from a single observation station in Indonesia. At the end of five years just three stations reported data in that hemisphere. Global averages are calculated from the averages for each of the two hemispheres, so these few stations have a large influence on what's supposedly "global".
According to the method of calculating coverage for the dataset, 50% global coverage wasn't reached until 1906 and 50% of the Southern Hemisphere wasn't reached until about 1950.
In May 1861 global coverage was a mere 12% - that's less than one-eighth. In much of the 1860s and 1870s most of the supposedly global coverage was from Europe and its trade sea routes and ports, covering only about 13% of the Earth's surface. To calculate averages from this data and refer to them as "global averages" is stretching credulity.
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.
Data prior to 1950 suffers from poor coverage and very likely multiple incorrect adjustments of station data. Data since that year has better coverage but still has the problem of data adjustments and a host of other issues mentioned in the audit.
Another implication is that the proposal that the Paris Climate Agreement adopt 1850-1899 averages as "indicative" of pre-industrial temperatures is fatally flawed. During that period global coverage is low - it averages 30% across that time - and many land-based temperatures are very likely to be excessively adjusted and therefore incorrect.
A participant in the IPCC, who resigned, atmospheric physicist Richard Lindzen was Alfred P. Sloan Professor of Meteorology at MIT. He is noted for his work in dynamic meteorology, atmospheric tides, ozone photochemistry, quasi-biennial oscillation, and the Iris hypothesis. Lindzen is certainly qualified to talk about the physics of the atmosphere, where the greenhouse effect occurs. Several key points of the talk are summarized below.
"Nature has numerous examples of autonomous variability, including the approximately 11-year sunspot cycle and the reversals of the Earth's magnetic field every couple of hundred thousand years or so. In this respect, the climate system is no different from other natural systems.
"Now here is the currently popular narrative concerning this system. The climate, a complex multifactor system, can be summarized in just one variable, the globally averaged temperature change, and is primarily controlled by the 1-2% perturbation in the energy budget due to a single variable - carbon dioxide - among many variables of comparable importance.
"This is an extraordinary pair of claims based on reasoning that borders on magical thinking. It is, however, the narrative that has been widely accepted, even among many sceptics.
"Many politicians and learned societies go even further: They endorse carbon dioxide as the controlling variable. And although mankind's CO2 contributions are small - compared to the much larger but uncertain natural exchanges with both the oceans and the biosphere - they are confident that they know precisely what policies to implement in order to control CO2 levels."
Sea level has been increasing by about 8 inches per century for hundreds of years, and we have clearly been able to deal with it. In order to promote fear, however, those models that predict much larger increases are invoked. As a practical matter, it has long been known that at most coastal locations, changes in sea level, as measured by tide gauges, are primarily due to changes in land level associated with both tectonics and land use.
The small change in global mean temperature (actually the change in temperature increase) is much smaller than what the computer models used by the IPCC have predicted. Even if all this change were due to man, it would be most consistent with low sensitivity to added carbon dioxide, and the IPCC only claims that most (not all) of the warming over the past 60 years is due to man's activities. Thus, the issue of man-made climate change does not appear to be a serious problem. However, this hardly stops ignorant politicians from declaring that the IPCC's claim of attribution is tantamount to unambiguous proof of coming disaster
Cherry picking is always an issue. Thus, there has been a recent claim that Greenland ice discharge has increased, and that warming will make it worse. Omitted from the report is the finding by both NOAA and the Danish Meteorological Institute that the ice mass of Greenland has actually been increasing. In fact both these observations can be true, and, indeed, ice build-up pushes peripheral ice into the sea.
Misrepresentation, exaggeration, cherry picking, or outright lying pretty much covers all the so-called evidence.
Lindzen's entire speech is much needed and worth reading. Simply because the IPCC names its process as science, does not make it science.