The code for the GISTEMP temperature anomaly from NASA GISS has been available for some years from the GISS website. In November 2009, I downloaded, compiled, and ran the public code to reconstruct the GISTEMP gridded data for surface stations and the monthly global anomalies.
The following files were updated via retrieval from FTP and HTTP sites.
The following files are not updated and are included in the GISTEMP source.
combine_pieces_helena.in: contains parameters for special handling of station 147619010 (St Helena)
t_hohenpeissenberg_200306.txt_as_received_July17_2003: contains an unusually long lived record for central Europe (begins in 1781)
Ts.discont.RS.alter.IN: contains parameters for special handling of station 425911650 (LIHUE, KAUAI)
Ts.strange.RSU.list.IN_full: contains information for the exclusion of 65 records from 63 stations
v2.inv: similar to GHCN v2.temperature.inv but includes brightness information and Antarctic stations
9641C_200907_F52.avg: USHCN average of fully-adjusted monthly mean maximum and minimum temperatures (with estimates for missing values) (This file is OBE but is the one that the public code is hard coded to use. You can get a copy at the Clear Climate Code Project http://code.google.com/p/ccc-gistemp/downloads/list ccc-gistemp-test-2009-12-28.tar.gz (45mb))
GISTEMP Step 0
Step 0 takes the Antarctica files, parses them into a GHCN v2 format and merges them into the v2.mean file (v2.meanx). It then removes pre 1880 data (v2.meany). USHCN stations are parsed out of the GHCN data sets and replaced with USHCNv2 stations. (v2.meanz). Finally, the Hohenpeissenberg record is updated and the final file, v2.mean_comb, is placed into a directory for use in the next step.
It can be noted that the GISTEMP process to replace the US data has been changing over the last several years as described on the GISTEMP web page.
GISTEMP Step 1
Step 1 takes the multiple records found for many individual station ids and merges them into a single record. This process is handeled differently for overlapping and discontinuous records. GHCN v2 files listed Ts.strange.RSU.list.IN are excluded. Input from Ts.discont.RSU.list.IN, and combine_pieces_helena.in is used in this processing. The output is a single file, Ts.txt, with one data table for each station which includes a header line with some meta data.
GISTEMP Step 2
Step 2 is the homogenization step which includes the urban-rural adjustments as well as the ‘brightness’ adjustment. The file Ts.txt is parsed into 6 latitudinal zones and each is processed separately. Stations with less than 20 years of data are dropped. The result is six zonal files with individual station records before the urban adjustments, and six zonal files with individual station records after the urban adjustments.
GISTEMP Step 3
Step 3 is the global gridding and averaging step, the output of which includes the GLB.Ts.GHCN.CL.PA.txt file which is used in the following discussion.
More information regarding this process can be found at the GISTEMP sources web page:
Original Source Code for GISTEMP:
GISS Surface Temperature Analysis: Sources
GISS Surface Temperature Analysis: Output
Last update 20091226
J. Hansen, R. Ruedy, M. Sato, and K. Lo, 2010:Current GISS Global Surface Temperature Analysis (draft)
Hansen, J., R. Ruedy, J. Glascoe, and Mki. Sato, 1999: GISS analysis of surface temperature change., J. Geophys. Res., 104, 30997-31022, doi:10.1029/1999JD900835.
Hansen, J.E., R. Ruedy, Mki. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl, 2001: A closer look at United States and global surface temperature change. J. Geophys. Res., 106, 23947-23963, doi:10.1029/2001JD000354
Clear Climate Code’s Reconstruction of GISTEMP in Python (Nick Barnes)
E.M. Smith’s critical review of GISTEMP
Houston Chronicle: Atmo.Sphere blog: D’Aleo and Watts Report: Correction
(Brief Discussion on GISTEMP algorithm for combining multiple records for a single station ID)