Climate reconstruction from tree rings: Part 2, spatial reconstruction of summer mean sea‐level pressure patterns over Great Britain

We present a methodology for the reconstruction of spatial climate patterns over the British Isles using tree rings. The predictands are mean sea‐level pressures averaged over May to July for a 16‐point grid centred over the British Isles. The predictors are ring widths from a network of 14 oak tree‐ring chronologies ( Quercus petraea Liebl. and Q. robur L.) in Britain and northern France. Major spatial modes of variance in the climate data are linked directly with those of the ring‐width data via a series of principal component regressions. Reconstruction performance is assessed by examining calibration and verification statistics at individual grid points and for individual pressure principal component amplitudes. The reconstruction equations are examined in order to identify, region by region, which chronologies are most valuable. This diagnostic approach to reconstruction assessment, when coupled with information on the statistical quality of the chronologies themselves, can suggest areas where future field‐work would be most valuable. Though limited in scale, these pressure reconstructions are the first to have been made using trees from maritime sites, and are the first to be comprehensively verified using independent pressure data.