If you aren’t worried about the integrity of historical temperature data under the care of folks like James Hansen, then you will be after reading this at Climate Audit.

Since August 1, 2007, NASA has had 3 substantially different online versions of their 1221 USHCN stations (1221 in total.) The third and most recent version was slipped in without any announcement or notice in the last few days – subsequent to their code being placed online on Sept 7, 2007. (I can vouch for this as I completed a scrape of the dset=1 dataset in the early afternoon of Sept 7.)

We’ve been following the progress of the Detroit Lakes MN station and it’s instructive to follow the ups and downs of its history through these spasms. One is used to unpredictability in futures markets (I worked in the copper business in the 1970s and learned their vagaries first hand). But it’s quite unexpected to see similar volatility in the temperature “pasts”.

For example, the Oct 1931 value (GISS dset0 and dset1 – both are equal) for Detroit Lakes began August 2007 at 8.2 deg C; there was a short bull market in August with an increase to 9.1 deg C for a few weeks, but its value was hit by the September bear market and is now only 8.5 deg C. The Nov 1931 temperature went up by 0.8 deg (from -0.9 deg C to -0.1 deg C) in the August bull market, but went back down the full amount of 0.8 deg in the September bear market. December 1931 went up a full 1.0 deg C in the August bull market (from -7.6 deg C to -6.6 deg C) and has held onto its gains much better in the September bear market, falling back only 0.1 deg C -6.7 deg C.

Note the volatility of historic temperature numbers.  Always with a steady bias – recent temepratures are adjusted up, older temperatures are adjusted down, giving a net result of more warming.  By the way, think about what these adjustments mean — adjusting recent temperatures down means that our growing urban society and hot cities are somehow introducing a recent cooling bias in measurement.  And adjusting older temepratures down means that in the more rural society of 50 years ago we had more warming biases than we have today.  Huh?