托福阅读真题+题目+答案：The Atmospheric Greenhouse Effect

托福阅读真题+题目+答案：The Atmospheric Greenhouse Effect

The atmospheric greenhouse effect is the result of electromagnetic energy from the Sun that is trapped in a planet's atmosphere. Atmospheric gases freely transmit visible- -short wavelength- solar energy, warming the planet's surface. The warmed surface tries to radiate the excess energy back into space, but because the planet is much colder than the Sun, it radiates at much longer, infrared (IR) wavelengths. But carbon dioxide and water vapor strongly absorb IR radiation, converting it to thermal (heat) energy. They subsequently re-radiate this thermal energy in all directions; some of the thermal energy continues into space, but much of it returns to the ground. The planetary surface receives thermal energy both from the Sun and from the atmosphere, and consequently it heats up.

1.The word “subsequently”in the passage is closest in meaning to

A often

B later

C partially

D gradually

2.According to paragraph 1, why is there a difference between the length of the wavelengths the Sun transmits to a planet and the length of the wavelengths the planet radiates back?

A Because the temperatures of the planet and the Sun are very different

B Because the carbon dioxide and water vapor on the planet convert solar energy to thermal energy

C Because the planet re-radiates energy in all directions

D Because the surface of the planet heats up before it radiates energy back

Why does the atmospheric greenhouse effect make the composition of Earth's atmosphere so different from that of Venus? The answer lies in Earth's location in the solar system. Consider early Earth and early Venus, each having about the same mass, but with Venus orbiting somewhat closer to the Sun than Earth does. Volcanoes and comet impacts poured out large amounts of carbon dioxide and water vapor to form early atmospheres on both planets. Most of Earth's water quickly rained out of the atmosphere to fill vast ocean basins, but Venus was closer to the Sun, and its surface temperature was higher than Earth's, so most of the rainwater on Venus immediately re-evaporated. Venus was left with a surface containing very little liquid water and an atmosphere filled with water vapor. The continuing buildup of both water vapor and carbon dioxide in the atmosphere of Venus then led to a runaway (out of control) atmospheric greenhouse effect that drove up the surface temperature of the planet. Ultimately, the surface of Venus became so hot that no liquid water could survive there.

3.The word "Consider" in the passage is closest in meaning to

A Identify

B Separate

C Compare

D Think about

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