Much of the reported warming from the 20th century was due to upwards adjustments of recent temperatures, and downwards adjustments of older temperatures.
This worked pretty well until satellites showed up and provided some badly needed checks and balances on the adjusters. Since 1990 it has been tougher to justify any further upwards adjustments to the data.
For the claimed warming since 2000, GISS has relied on their data free Arctic hole.
Essentially all of the warming which GISS reports since 2000 has been due to imaginary extrapolated Arctic data. The animation below shows GISS 2000-2009 trends, alternating between measured data and extrapolated data.
GISS shows between 2 and 4C warming at the pole, without a single thermometer reading within 800 km. This heavily skews the global trend data, because places which actually have thermometers show little or no warming.
So how does Hansen’s 2-4C Arctic warming compare with satellite data? UAH shows about one tenth of Hansen’s imaginary Arctic trend – at 0.25C.
Bottom line. Other than the 1979-2000 (0.2C) warming confirmed by satellites, much of the claimed global warming is based on tainted and probably useless data. Why is this nonsense allowed to continue? It isn’t science.