The disagreement, in certain locations, between the various re-analysis datasets is one of the main reasons that 3TIER has released a new product to make accessing, viewing and obtaining time series from the main re-analysis datasets much simpler. The selection of the appropriate method of creating a long-term reference from global re-analysis data is very complicated. If you look at only simple statistics (such as hourly or daily correlations against observed data, you can make very poor decisions. Success depends on a detailed knowledge not only of statistics (i.e. MCP) but a deep understanding of the underlying factors of climate variability along with access to numerous global datasets and post-processing techniques.