Robert Rohde, the chief data analyst behind the Berkeley Earth Surface Temperature project: "...we can’t use the analysis of Marcott et al. to draw any firm conclusions about how unique the rapid changes of the twentieth century are compared to the previous 10,000 years"

Scientists Find an Abrupt Warm Jog After a Very Long Cooling - NYTimes.com

Because the analysis method and sparse data used in this study will tend to blur out most century-scale changes, we can’t use the analysis of Marcott et al. to draw any firm conclusions about how unique the rapid changes of the twentieth century are compared to the previous 10,000 years.