The eleven centuries-long African peoples' expropriation to Asia, Europe, the Americas , the Caribbean, from the 8th-19th centuries was a period of epochal global climate change, in Africa, and elsewhere, ranking with ice, desertification ages.
http://www.slate.com/articles/life/the_history_of_american_slavery/2015/06/animated_interactive_of_the_history_of_the_atlantic_slave_trade.html?wpsrc=sh_all_dt_fb_top