Guest post by Samuel I. Outcalt, Professor Emeritus of Physical Geography, The University of Michigan, Ann Arbor
Abstract: After noticing the strange time dependent behavior of the difference between the NOAA USHCN Average Annual Temperature data in the unadjusted RAW data. The RAW data was plotted for the 1965-2011 time period. The RAW data plot revealed the start and end of the Modern Warm Regime, which lasted from 1976 (the base of the “hockey stick”) until the onset of the 21st Century. The footprint of the regime in the area is validated by mean annual geothermal data from 3 boreholes along Trail Ridge Road in Rocky Mountain National Park.
Background: The strange behavior of the NOAA difference between the NOAA USHCN average annual temperature [AAT] and the raw data [AATRAW] at Boulder, Colorado is presented as Figure 1.
Figure 1. The trace of the RAW and adjusted Average Annual Temperatures at Boulder, Colorado display sectors of high amplitude variation interlaced with long runs of uniform adjustments.
Previous investigations of the adjusted Boulder average annual temperature data indicated that the Modern Warm Regime was not viable on the integral trace of that record. This was considered unusual as inflections of major regime events are known to produce inflections and extreme values of the integral trace in serial data (Outcalt et.al.(1997)). The integral trace of the USHCN Average Annual temperature data is presented as Figure 2.
Figure 2. The Integral Trace of the Average Annual Temperature does not indicate the onset of the Modern Warming Regime.
In summary, the RAW and Adjusted Average Temperature [ATA] data over the record length 1898-2012 displays interlaced sequences of large amplitude and uniform adjustments rather than a pattern of smooth transitions and the Adjusted Data does not even hint at the wide spread 1976 climate regime change which is a major feature of global climate data (see Figure 3).
Figure 3. The integral traces of three global climate series all show major inflections near the 1976.
The missing 1976 onset of the Modern Warming might be present in the RAW data integral trace for the 1965-2011 time period if rather heavy handed adjustments to the AAT data had masked or attenuated the inflection.
The 1965-2011 ATTRAW Data: The 1965-2011 RAW data is displayed as Figure 4.
Figure 4. The RAW data for 1965-2011.
In Figure 4. The integral trace displays a minimum in 1979 near the 1976 global climate transition and a minimum a 1999 near the end of the Global Warming Regime. Further, the 5 year running mean and integral trace display downturns in 2005 and 2008. These results appear to support the hypothesis that heavy handed adjustment had masked or attenuated the signature of the beginning and end of the Period of Modern Warming in the USHCN ATT data.
It should be noted that the method if Hurst Rescaling introduced in an paper by Outcalt et.al.(1997) is exceedingly robust and has been used by Runnals and Oke (2006) to detect weather station site moves.
The method unfortunately also detects transitions introduced by data adjustment which seems be true in the case of the Boulder Annual Average Temperature [ AAT ] data.
A further indication of the footprint of the modern warming data can be found in the thermal profiles of mean annual temperatures derived from hourly observations at probes placed in at 1 m intervals in three 6 m boreholes along Trail Ridge Road in Rocky Mountain National Park. The boreholes are approximately 39 miles northwest of the Boulder Weather Station at the Boulder Municipal Airport. These mean annual temperatures are extremely robust as they were derived from probes recording at an hourly interval for a calendar year (Janke (1911)). In addition, the annual mean temperatures were calculated at all the measurement levels by the author and dated using the thermal disturbance methods published by Terzaghi(1970). These data are presented as Figure 5.
Figure 5. The Trail Ridge Mean Annual Temperature Geothermal Profiles.
Using the inflection produced by the 1976 global regime transition at 6 meters in BH2 the overlying inflections dated at 9.3, 2.2 and 0.3 years BP. As the data were taken during a calendar year from the summer of 2010 to 2011 the inflections date from the turn of the century to 2011. The range of inflection dates may be artifacts introduced by local site effects (slope, exposure, winter snow cover, ground water migration etc..) as well as the assumption of the same apparent thermal diffusivity at all the sites.
Conclusions: The footprint of the Modern Warming Regime that was recovered in the RAW data from the Boulder Weather Station is the probable result of the heavy handed uncritical adjustment of the AAT data set. Hurst Rescaling is a powerful method for detecting regime transitions in climatic data. However, the method is also sensitive to uncorrected site moves and adjustment artifacts. The alteration of the Boulder RAW data set was so severe that it masked and attenuated both the onset and end of the Modern Warming Regime.
Another aspect of Hurst Rescaling is the difficulty of introducing false regime inflections into serial climate data. One must first alter the data integral and differentiate the integral to a synthetic data set. However, the differential would probably not remotely resemble the initial data. The perpetrator would then be faced with nearly infinite iterations to fine tune the data.
The author is indebted to Dr. Jason Janke of a Metropolitan State College in Denver for giving him access to the rather unique borehole data from Trail Ridge Road.
Janke, J (2011) personal communication.
Outcalt,S.I.,Hinkel,K.M.,Meyer,E . and Brazel,A.J.(1997) The application of Hurst rescaling to serial geophysical data. Geographical Analysis 29, 72-87.
Runnalls,K.E. and Oke,T.R.(2006) A technique to detect micro-climatic inhomogeneities in historical records of screen-level air temperature. Journal of Climate 19: 959-978.
Terzaghi,K (1970) Permafrost, J. Boston. Soc. Civil Eng. 39(1): 319-368