A data assimilation approach to last millennium temperature field reconstruction using a limited high-sensitivity proxy network

Abstract We use theNorthern Hemisphere Tree-RingNetwork Development (NTREND) tree-ring database to examine the effects of using a small, highly-sensitive proxy network for paleotemperature data assimilation over last millennium. first evaluate our methods pseudo-proxy experiments. These indicate that spatial assimilations this are skillful in extratropical Northern and improve on previous NTREND reconstructions based Point-by-Point regression. also find method is sensitive climate model biases when number sites becomes small. Based these experiments, we then assimilate real network. To quantify prior uncertainty, produce 10 separate reconstructions, each assimilating different model. most dissimilar 1100 CE, sparse, but show greater consistency as grows. Temporal variability underestimated before CE. Our produces uncertainty estimates identify treeline North America eastern Siberia regions would benefit from development new millennial-length temperature-sensitive records. compare multi-model mean reconstruction five existing paleo-temperature products range reconstructed responses radiative forcing. substantial differences patterns magnitudes volcanic eruptions transition between Medieval epoch Little Ice Age. extant uncertainties call paleoclimate intercomparison framework systematically examining consequences composition methodology continued expansion networks.