Here is the web site of the group that Muller is leading and here is its mission statement:
The most important indicator of global warming, by far, is the land and sea surface temperature record. This has been criticized in several ways, including the choice of stations and the methods for correcting systematic errors. The Berkeley Earth Surface Temperature study sets out to to do a new analysis of the surface temperature record in a rigorous manner that addresses this criticism. We are using over 39,000 unique stations, which is more than five times the 7,280 stations found in the Global Historical Climatology Network Monthly data set (GHCN-M) that has served as the focus of many climate studies.I disagree with the above. I believe that the oceans are a big heat sink that drive of climate. But I'm not a specialist so that is opinion and not necessarily scientific fact. What is a fact is that water can hold a heck of a lot more heat than air. From Wikipedia on "heat capacity" the volume specific heat capacity is:
Our aim is to resolve current criticism of the former temperature analyses, and to prepare an open record that will allow rapid response to further criticism or suggestions. Our results will include not only our best estimate for the global temperature change, but estimates of the uncertainties in the record.
air 0.001297or four thousand times as much!