Climategate: ... And Just Like That, the Warming's Gone (PJM Exclusive)
We now know that the Russian station count dropped from 476 to 121, meaning “over 40% of Russian territory was not properly included in global-temperature calculations for some other reasons, rather than the lack of meteorological stations and observations.”
In the IEA report, there is a chart showing CRU's selective use of 25% of the Russian data created 0.64C more warming than was exhibited by using 100% of the raw data. Given the huge area Russia represents (11.5% of global land surface area), this significantly affects global land temperatures.
We know from the maps that NASA produces -- produced using NOAA GHCN data -- that Canada is largely missing. As is Greenland. The Arctic. Much of Africa. Brazil. And parts of Australia. (See this post.)
To fill in these large holes, data was extrapolated from great distances away. Often the data came from lower latitude, lower elevation, and higher population centers. In addition to station dropout, the number of missing months increased by as much as tenfold in many of the remaining areas. This required filling in of data from surrounding stations, again sometimes considerable distances away from the missing location. Another opportunity for error, if not mischief.
These gaps allowed the data centers to extrapolate the data from the warm spots to the missing data grids, or to blend the warm stations with the fewer remaining cooler ones.
More reds and oranges.
There was indeed a global warming period from 1979 to 1998, thanks to the natural cycles of the oceans and sun -- which had produced a similar warming from around 1920 to 1940, and a cooling from the 1940s to the late 1970s. In the adjustments made by all the data centers, they cooled off the 1930s and 1940s warm blip by adjusting land and ocean temperatures down, and elevated the late 20th century and this decade.
Even with that, a cooling trend has been observed since 2001.
They applied no correction for urban growth or spread, which can produce an artificial but very localized warming (see recent Georgia Tech release here). And in the United States, Anthony Watts -- in a volunteer survey of over 1000 of the 1221 instrument stations -- had found 89% were poorly or very poorly sited, using NOAA’s own criteria. This resulted in a warm bias of over 1 degree C (earlier analysis here).
A few preliminary surveys in other parts of the world indicate the U.S. is not alone.
Satellites have measured global temperatures since 1979, and have shown warming. Originally the satellites were in close agreement with the data centers' global numbers, but gradually the data centers have diverged and are now approaching 0.5 degrees Celsius (see this post).
Given all this manipulation and cherry-picking, you should ignore the press releases that will undoubtedly be coming from NOAA (when they return from snowy, cold Copenhagen), NASA, and Hadley about how this has been among the warmest years, and how the last decade was the warmest on record.
There indeed has been man-made global warming -- but it's from the paint-by-numbers men and women at NOAA, NASA, and Hadley ... and now, just like that, it's gone.