TEMPERATURE HISTORIES FROM TREE-RINGS AND CORALS

Recent temperature trends in long tree-ring and coral proxy temperatur e histories are evaluated and compared in an effort to objectively det ermine how anomalous twentieth century temperature changes have been. These histories mostly reflect regional variations in summer warmth fr om the tree rings and annual warmth from the corals. In the Northern H emisphere, the North American tree-ring temperature histories and thos e from the north Polar Urals. covering the past 1000 or more years, in dicate that the twentieth century has been anomalously warm relative t o the past. In contrast, the tree-ring history from northern Fennoscan dia indicates that summer temperatures during the 'Medieval Warm Perio d' were probably warmer on average than those than during this century . In the Southern Hemisphere, the tree-ring temperature histories from South America show no indication:of recent warming, which is in accor dance with local instrumental records. In contrast, the tree-ring reco rds from Tasmania and New Zealand indicate that the twentieth century has been unusually warm particularly since 1960. The coral temperature histories from the Galapagos Islands and the Great Barrier Reef are i n broad agreement with the tree-ring temperature histories in those se ctors, with the former showing recent cooling and the latter showing r ecent warming;that may be unprecedented. Overall, the region;il temper ature histories evaluated here broadly support the larger-scale eviden ce for anomalous twentieth century warming based on instrumental recor ds. However, this warming cannot be confirmed as an unprecedented even t in all regions.