ahh we have a critic.. very well, here, a very quick search provides the following references:
In Europe earlier puberty has also been reported, particularly in warmer climates 7
source: [Precocious Puberty]Health Topics]Precocious Puberty](Health Topics)
In warmer climates, puberty often occurs earlier, and in the Artic regions, one or two years later
source: (http://www.yale.edu/ynhti/curriculum/units/1988/5/88.05.04.x.html)