Simplify the following text for a Grade 12 native English-speaking person.
Original: This graph differed from a schematic in the first assessment report which lacked temperature units , but appeared to depict larger global temperature variations over the past 1000 years , and higher temperatures during the Medieval Warm Period than the mid 20th century .
Simplified: This graph was different to the IPCC First assessment report which showed global temperature for the past 1000 years , and higher temperatures during the Medieval Warm Period .