During earlier strong African Humid periods, the now-desiccated regions of northern Africa were well-watered, bearing lakes, swamps, and river systems that no longer exist.
What is now the Sahara Desert supported typical African wildlife of grassland and woodland environments: herbivores from gazelle to giraffe to ostrich, predators from lion to jackal, even hippopotamus and crocodile, as well as extinct forms like the Pleistocene camel.
Growing ice sheets in North America and Europe displaced the standard climatic zones of the northern hemisphere southward.
In the period of its fullest development from 30,000 to 18,000 BP, the Laurentide Ice Sheet not only covered an enormous geographic area but also increased its altitude to 1750 m (1.1 mi).
The jet stream effectively split into two, which created a new dominant weather pattern over the northern hemisphere that brought harsher conditions to several regions (including parts of Central Asia and the Middle East).
It is now understood that the major African humid period events were caused by increased insolation in the northern hemisphere and the impact of continental surface warming on the tropical monsoons.