From a November paper by Michael Mann and cohorts in Science, meticulously reconstructing the temperature record over the last fifteen hundred years, from proxies including tree rings, pollen, coral, oxygen isotopes, sediments, and so on.
The end point — in black — is from the instrumental record.
This gives us a familiar conclusion — since the Industrial Revolution, global atmospheric temperatures have warmed about .7 degrees C. But most interesting is Mann's argument, which he concludes this way:
If the tropical Pacific thermostat response suggested by our analyses of past changes applies to anthropogenic climate change, this holds profound implications for regional climate change effects such as future drought patterns.
In other words, expect decades-long California droughts.