What does the Fourth Report of the IPCC say about average Northern Hemisphere temperatures?

The Fourth Report of the IPCC (The United Nations' Intergovernmental Panel on Climate Change), Climate Change 2007, said:

Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years (including both theMedieval Warm Period and the Little Ice Age).