By Steven Goddard
GISS has explained their steeper temperature slope since 1998 vs. Had-Crut, as being due to the fact that they are willing to extrapolate 1200 km across the Arctic into regions where they may have no data – whereas Had-Crut prefers to work with regions of the Arctic where they actually have thermometers. WUWT reader “Wren” suggested that I compare GISS Arctic trends vs other sources to see how they compare. GISS has been showing Arctic temperatures rising very fast, as seen below.
And the same graph for UAH.
Conclusions: GISS explains their increases vs. Had Crut as being due to their Arctic coverage. Their Arctic coverage is poor, and they rely on extrapolations across large distances with no data. Comparisons with other data sources show that GISS extrapolations across the Arctic are likely too high. In short, GISS trends over the last decade are most likely based on faulty extrapolations in the Arctic, and are probably not reliable indicators of global or Arctic temperature trends during that time period.