kottke reports: [edited]
For the first time, researchers have put together all the climate data they have (from ice cores, coral, sediment drilling) into one chart that shows the 'global temperature reconstruction for the last 11,000 years'.
The climate curve looks like a "hump". At the beginning of the Holocene - after the end of the last Ice Age - global temperature increased, and subsequently it decreased again by 0.7°C over the past 5000 years.
The transition from the relatively warm Medieval into the 'little ice age' turns out to be part of a much longer-term cooling, which ended abruptly with the rapid warming of the 20th Century. Within a hundred years, the cooling of the previous 5000 years was undone.