cbc13be1_Surface_Temperature_Initiative__0
[1] Ongoing throughout but will have formed the basis for defining error model spread. [2] Benchmarking and Assessment working group led by Kate Willett [3] Ongoing [0] 
Up to date reference list of work on inhomogeneities in surface temperatures on the website (www.surfacetemperatures.org/benchmarking-and-assessment-working-group)
Benchmarking and Assessment - International Surface Temperature Initiative
0