Interesting:

A stalagmite from an Alpine cave may indicate that global warming is not as unusual as many think.
Deposits laid down in the stalagmite have enabled a European team to probe past climates confirming a Medieval Warm Period between AD 800 and 1300.
The warm spell is also indicated in some studies of tree-rings, ice-cores and coral reef growth records.
Writing in Earth and Planetary Science Letters the researchers suggest that global warming is a natural process.
Other scientists, however, say phenomena such as the Medieval Warm Period become less significant when broad sets of so-called “proxy data” are calibrated and synthesised to give a truly global picture – not just regional ones.
When this is done, they argue, the warming witnessed in the past few decades appears to be very unnatural….