What field in earth sciences would use the most statistics to study?

Climate change is fertile ground for the use of statistics in earth science. Quantifying the effect of anthropogenic CO2 on climate boils down to detecting trends and means in noisy and non-stationary time series. The climate change literature has many many examples of esoteric statistical analyses that are used to tease out some facet or another of the signals of global warming on biogeochemical cycles and earth systems. Sadly, esoteric statistical methods are also used to some degree of success by climate skeptics, who use statistics to obfuscate faulty physical reasoning. So if you wanted to find something that was highly relevant, important, and probably really interesting, look into how statistics gets used in climate change research. A good place to start is the whole Michael Mann "hockey stick" controversy, which is not so much of a controversy anymore, since the "hockey stick" has been replicated at least a dozen times by other researchers who used correct statistical methods (and in fact, Mann got the right answer even though his methodology sucked because the right answer was so stunningly obvious it was impossible to get wrong (and the climate skeptics who try to disprove the hockey stick have to resort to scientific misconduct)).