Their new data set shows much higher trends than the GHCN-only data, especially since 1998. Their analysis shows >2x the warming since 1998 (0.086ºC/decade) as the GHCN-only data (0.039ºC/decade).
|Figure 1 from Karl et al. 2015 showing the trends over selected time periods as calculated using GHCN-only data (circles), their new data (squares), and their new data combined with polar interpolation (triangles).|
The main conclusions from Karl et al. is that the appearance of a pause was due to a) a short time period (changing the period by just two years had a significant impact on the calculated trend) and b) a cherry-picked start year (1998, the warmest El Niño currently on record), and c) artifacts due to incomplete data. This matches the main thrust of other research into global temperature data (i.e. Foster and Rahmstorf 2011, Rahmstorf et al. 2012, Rohde et al. 2013, Cowtan and Way 2014, the various Berkeley Earth papers) and various blog posts (i.e. Tamino and my own writings).
The "pause since 1998" is dead. Long live the "pause since ______" that deniers come up with next.