Global Warming in an Independent Record of the Past 130 Years

Criticism of the thermometer-based global surface temperature time series (GST) motivated us to develop a completely independent dataset from climate proxy archives. The paleo index is compiled from 117 temperature-sensitive proxy records including corals, ice cores, lake and ocean sediments, and historical documents. The individual series are globally-distributed with inter-annual to sub-annual resolution. Each series was normalized to produce index values of change relative to a 1901-2000 base period; the index values were then averaged. From 1880 to 1995, the index trends significantly upward, similar to the GST. Small-scale aspects of the GST including two warming trends and a warm interval during the 1940s are also observed in the paleo index. The paleo index continuously extends back to 1730 with 45 records and reveals that the upward trend observed in the GST began in the early 19th century. The paleo index supports the fidelity of the GST and confirms the global extent of the warming trend of the past century.