Just for the heck of it I made 1 turn per year script

Code:
script
	suspend_during_battle on
	declare_counter loop
	set_counter loop 1
	monitor_event FactionTurnEnd FactionType slave
		console_command season winter
	end_monitor
	while I_CompareCounter loop = 1
	end_while
end_script
I guess it needs to be "installed" and run in same way as 4turn year script.

All turns will be summers, and aging effects will be normal (1 year per turn).