mini还是全文听写模式，很多童鞋可能进来看到【专八】可能会有点胆怯，刚开始是会感觉到有点吃力哦，但这就是专八。希望大家可以耐心的认真听写O(∩_∩)O~

Today's lecture is about the Greenhouse Effect.

hints:
Celsius
This phenomenon is what scientists call the "greenhouse effect." Without it, scientists estimate that the average temperature on Earth would be colder by approximately 30 degrees Celsius, far too cold to sustain our current ecosystem. Second, we need to clarify the ways humans contribute to the greenhouse effect. While the greenhouse effect is an essential environmental prerequisite for life on Earth, there really can be too much of a good thing. The problem begin when human activities distort and accelerate the natural process by creating more greenhouse gases in the atmosphere than are necessary to warm the planet to an ideal temperature, for example, burning natural gas, coal and oil - including gasoline for automobile engines - raises the level of carbon dioxide in the atmosphere; some farming practices and land-use changes increase the levels of methane and nitrous oxide.