2017--2018学年人教版选修六 unit 4 global warming warming up and reading课件(39张)
2017--2018学年人教版选修六 unit 4 global warming warming up and reading课件(39张)第3页

Think about :

What causes global warming? Human activity or a random but natural phenomenon?

When we talk about this problem, we naturally link it to the use of energy and the environmental pollution.