VOA慢速英语:Climate Change May Turn Africa’s Dry Sahel Green

pattern – n. a repeated form or design; something used as a model

mind-boggling – adj. emotionally or mentally exciting

tip – v. to move the balance of power or influence

erratic – adj. having no fixed path or direction

challenge – n. a difficult problem or issue

fossil fuel – n. a fuel formed in the earth from plant or animal remains