For earlier periods (last ice age etc), models generally use time - slice experiments — these have been done for many different periods. (realclimate.org)
«New study shows influence on climate of fresh water during last ice age.» (sciencedaily.com)
Another explanation: Land bridge across Bosporus gets breached by slowly rising Mediterranean following last Ice Age, creating Black Sea out of an earlier low - lying land mass surrounding a smaller freshwater lake. (judithcurry.com)