Abstract. Building on recent studies, we attempt hemi-Warm Epoch (though Lamb, examining evidence mostly spheric temperature reconstructions with proxy data net-from western Europe, never suggested this was a global works for the past millennium. We focus not just on the phenomenon). We here apply the methodology detailed by reconstructions, but the uncertainties therein, and impor-MBH98 to the sparser proxy data network available prior tant caveats. Though expanded uncertainties prevent deci-to AD 1400, to critically revisit this issue, extending NH sive conclusions for the period prior to AD 1400, our results reconstructions as far back as is currently feasible. We also suggest that the latter 20th century is anomalous in the reevaluate earlier estimates of uncertainties in the NH series.context of at least the past millennium. The 1990s was the warmest decade, and 1998 the warmest year, at moderately high levels of confidence. The 20th century warming counters a millennial-scale cooling trend which is consistent with' long-term astronomical forcing.
Solar total and ultraviolet (UV) irradiances are reconstructed annually from 1610 to the present. This epoch includes the Maunder Minimum of anomalously low solar activity (circa 1645–1715) and the subsequent increase to the high levels of the present Modern Maximum. In this reconstruction, the Schwabe (11‐year) irradiance cycle and a longer term variability component are determined separately, based on contemporary solar and stellar monitoring. The correlation of reconstructed solar irradiance and Northern Hemisphere (NH) surface temperature is 0.86 in the pre‐industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55°C surface warming since 1860 and one third of the warming since 1970.
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