Quote Originally Posted by S Landreth View Post
Late 20th century was warmest in 1,400 years
related,.........

Major PAGES 2k Network Paper Confirms the Hockey Stick

PAGES (Past Global Changes) is a scientific network which supports research aimed at understanding the Earth’s past environment in order to make predictions for the future. It's funded by the U.S. and Swiss National Science Foundations, and the National Oceanic and Atmospheric Administration (NOAA). Over 5,000 scientists from more than 100 countries subscribe to PAGES, which is essentially an organizational group to bring international scientists together.

In 2006, scientists in the PAGES network decided to organize an initiative to reconstruct the climate of the last 2,000 years, which they called The PAGES 2k Network. This network consists of scientists from 9 regional working groups, each of which collects and processes the best paleoclimate (past climate change) data from their respective region. It's a clever approach because it allows the experts in their local proxy data to contribute to a much larger global project.

The 2K Network has just published a major paper in Nature Geoscience (abstract and figures here), with 78 researchers contributing as co-authors from 60 separate scientific institutions around the world. The analysis combines records from tree rings, pollen, corals, lake and marine sediments, ice cores, stalagmites and historical documents from 511 locations across seven continental-scale regions to reconstruct past global surface temperature changes over the past 2,000 years.

Their two main results are a confirmation that current global surface temperatures are hotter than at any time in the past 1,400 years (the general 'hockey stick' shape, as shown in Figure 1), and that while the Medieval Warm Period (MWP) and Little Ice Age (LIA) are clearly visible events in their reconstruction, they were not globally synchronized events.


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Conclusions

Overall, the PAGES 2k paper provides the best overall reconstruction of local and global surface temperature changes over the past 1,000–2,000 years. As illustrated in Figure 1, their overall results are largely consistent with previous millennial temperature reconstructions like those by Mann et al. (2008), Ljungkvist (2010), Moberg et al. (2005), and Hegerl et al. (2006).

They find that over the past 2,000 years, until 100 years ago, the planet underwent a long-term cooling trend. There was a 'Medieval Warm Period', but different regions warmed at different times, and overall global surface temperatures were warmer at the end of the 20th century than during the MWP peak. The 2,000-year cooling trend has been erased by the warming over the past century. And of course more warming is yet to come from continuing human greenhouse gas emissions.