A preliminary analysis of 2% of the Berkeley Earth dataset shows a global temperature trend that goes up and down with global cycles, and does so broadly in sync with the temperature records from other groups such as NOAA, NASA, and Hadley CRU. However, the preliminary analysis includes only a very small subset (2%) of randomly chosen data, and does not include any method for correcting for biases such as the urban heat island effect, the time of observation bias, etc.Gee, like, what a surprise. I don't know why a scientist like Muller even thought that this worth checking. The data showing that the earth has been getting warmer for the past century is solid. So is the data showing that the amount of CO2 in the atmosphere has been going up. So is the basic science showing that CO2 in the atmosphere traps heat.
The complications come in at the next level, trying to understand what the effect of increased CO2 emissions will be on the extremely complex system of the earth's climate, and how human-caused climate change might interact with the cyclical system driving our repeating Ice Ages. Higher level analysis, however, doesn't even seem to be part of Muller's plan for his organization,. According to its web site, BEST is focused on generating a good data set showing how the earth's mean surface temperature has really changed over time. Nothing wrong with that -- it is a hard problem, and Muller might eventually come up with values different from those of other scientists. But he won't find that the earth is really getting cooler, and he won't find an excuse for not wondering what massive CO2 emissions will do to the planet.