Earlier quoted context omitted.
Thanks for the links. I'll add one link, direct to the project page, since it has links to the actual data, as well as much more detail than is in the articles: http://berkeleyearth.org/ I note two things on a first read-through: (1) The project confirmed the data on temperature trends, but the error bar sizes are only reasonable back to about 1860; further back than that, the error bars get quite large. This is glos…
They looked at siting effects as well: http://www.scitechnol.com/2327-4581/2327-4581-1-107.php They used Watts own siting data and showed that both poor and good sites showed the same temperature trend over time. The data back to 1860 are also sufficient to establish the current warming trend and through other analysis (e.g. Meehl, et al's work) to establish the climate sensitivity. Climate science as a discipline do…
The data back to 1860 are also sufficient to establish the current warming trend
Only if you assume that there are no significant cyclic effects on longer time scales.
Climate science as a discipline does not hinge on knowing exactly how warm it was 250 years ago within +/- 0.5C.
It does if you're claiming, as the IPCC does based on the input of climate scientists, that temperatures now are warmer than they have been in at least several thousand years.