Figure 1: The temperature evolution of 10 different global temperature indices. (niskanencenter.org)
Quayle, R.G., T.C. Peterson, A.N. Basist, and C. S. Godfrey, 1999: An operational near - real - time global temperature index. (ncdc.noaa.gov)
The accuracy of HQ and ACORN datasets can be questioned but they are accepted as the official yardsticks and ACORN feeds global temperature indices. (waclimate.net)