The NASA/GISS temperature record is not actually a record of recorded temperatures. It is simply the most recent version of NASA’s adjustments to older adjustments. It is not thermometer readings. It is models all the way down.
In 2012, I wrote an American Thinker article on the status of global warming at the time. I used the latest available NASA/GISS data to do that analysis, which was the version NASA had on its website on April 30, 2012 (Land-Ocean Temperature Index [LOTI]).
At that time, the data from 1880 through 2011 showed a warming trend of 0.59 degrees Celsius per century.
What is that warming trend using the latest data from NASA’s website (December 30, 2017), using those same exact years (1880-2011)? The answer is 0.66˚ C.
How did warming accelerate if we are looking at the very same years?
Apparently, the Earth is getting warmer faster than it was five and a half years ago, but not because of actual recorded thermometer readings in those last five and a half years. It is getting warmer faster because NASA adjusted the data to show faster warming.
When you go to the NASA website, you can download temperature anomalies “1880-present.” But those data change every month. NASA adjusts it. You cannot find any older versions. NASA makes available only its most recent version. And NASA does not explain how it adjusts the data. You must simply trust it.
I still have the data from 2012 only because I downloaded them to a spreadsheet and kept that spreadsheet.
What are the differences between the two sets of data? See the first figure, which shows all adjustments to data from 1880 through 2011. NASA made these adjustments after April 2012.
Figure 1. NASA’s post-2012 adjustments to the 1880-2011 temperature record.
The black line shows the linear regression trend of the adjustments. To be clear, the trend is of the adjustments to temperatures, not actual temperatures. It is clear that NASA tends to adjust older temperatures down and recent temperatures up, to accelerate the overall warming trend: from 0.59 to 0.66˚ C per century, just since 2012.