The answer is a political system
There can be many caused to the change of Earths temperature but one would be the use of fossil fuels. This is because when burned it releases Greenhouse gasses which are trapped in the atmosphere and causes heat. Which eventually leads to Global Warming. (Hopes this helps! )
The Sahel is located in Africa. It is the region in Africa that transitions from the Sahara to the Sudanian Savanna. It stretches across in the region from the West of Africa to the East and includes parts of Senegal, Mauritania, Mali, Burkina Faso, Algeria, Niger, Nigeria, Chad, Sudan, South Sudan, Eritrea, CAR, Cameroon, and Ethiopia.
The answer is 300.
Sorry this answer is so late, I was just learning about it! Hope it helps. :)
