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Following the suggestions of a recent National Research Council report [NRC (National Research Council) (2006) Surface Temperature Reconstructions for the Last 2,000 Years (Natl Acad Press, Washington, DC).), we reconstruct surface temperature at hemispheric and global scale for much of the last 2,000 years using a greatly expanded set of proxy data for decadal-to-centennial climate changes, recently updated instrumental data, and complementary methods that have been thoroughly tested and validated with model simulation experiments. Our results extend previous conclusions that recent Northern Hemisphere surface temperature increases are likely anomalous in a long-term context. Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used. If tree-ring data are used, the conclusion can be extended to at least the past 1,700 years, but with additional strong caveats. The reconstructed amplitude of change over past centuries is greater than hitherto reported, with somewhat greater Medieval warmth in the Northern Hemisphere, albeit still not reaching recent levels. [ABSTRACT FROM AUTHOR]

Examines the phase evolution of precession and semiprecession cycles in the tropical and extra-tropical Atlantic Ocean. Purpose of the study to explain changes in the Earth's glacial cycles during the Pleistocene epoch; Conclusion that heat flow across the equator to higher latitudes strengthened the semiprecession cycle in the Northern Hemisphere and triggered the transition to sustained glacial cycles.