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The debate concerning the causes of the global temperature increase of the past century results in part from the difficulty in establishing the magnitude of surface temperature change that can be attributed to natural climate variability and that caused by human impact through greenhouse gas emissions. Recent high-resolution paleoclimate reconstructions of the past two millennia using tree-ring and other proxies correlated well in structure and in timing, however, the magnitude of temperature change in these studies divert from one another. This remains a problem that has plagued these studies and the current debate over how much of the recent surface temperature change can be attributed to human impact. We present a new high-resolution summer temperature reconstruction for North America using an extensive network of pollen records. When compared with northern hemispheric temperature anomaly …