Read and Choose. 读短文,选择正确答案。 The "greenhouse effect" is often associated with global warming, but the truth is we couldn't live without it. The "greenhouse gases" include water vapor, carbon dioxide (CO2), and so on. Although they make up only about 1 percent of the Earth's atmosphere, the greenhouse gases regulate our climate. They hold heat in a kind of warm-air blanket that surrounds the Earth. This phenomenon is what scientist call the "greenhouse effect". Without it, scientists estimate that the average temperature on the Earth would be colder by about 30 degrees Celsius (54 degree Fahrenheit), which would be too cold to sustain our current ecosystem.