Simplify the following text for a Grade 11 native English-speaking person.
Original: The Medieval Warm Period ( MWP ) or Medieval Climate Optimum was a time of warm climate in the North Atlantic region , that may also have been related to other climate events around the world during that time , including in China , New Zealand , and other countries lasting from about AD 950 â `` 1250 .
Simplified: The Medieval Warm Period ( MWP ) or Medieval Climate Optimum was a time of unusually warm climate in the North Atlantic region .