Climate over past millennia

We review evidence for climate change over the past several millennia from instrumental and high‐resolution climate “proxy” data sources and climate modeling studies. We focus on changes over the past 1 to 2 millennia. We assess reconstructions and modeling studies analyzing a number of different climate fields, including atmospheric circulation diagnostics, precipitation, and drought. We devote particular attention to proxy‐based reconstructions of temperature patterns in past centuries, which place recent large‐scale warming in an appropriate longer‐term context. Our assessment affirms the conclusion that late 20th century warmth is unprecedented at hemispheric and, likely, global scales. There is more…