【单选题】

The molecules of carbon dioxide in theEarth’s atmosphere affect the heat balance of theEarth by acting as a one-way screen. (1) these molecules allow radiation at visible wavelengths, where most of the energy of sunlight is concerned, to pass (2) , they absorb some of the longer-wave length, infrared emissions radiated from theEarth’s surface, radiation that would (3) be transmitted back into space. For theEarth to maintain a constant average temperature, such emissions from the planet must (4) incoming solar radiation. If there were no carbon dioxide in the atmosphere, heat would (5) from theEarth much more easily.

Today, (6) , the potential problem is too much carbon dioxide.Could the increase in carbon dioxide (7) a global rise in average temperature, and could such a rise have serious (8) for human society Mathematical models that allow us to calculate the rise in temperature as a function of the increase (9) that the (10) is probably yes.
One mathematical model (11) that doubling the atmospheric carbon dioxide would raise the global mean surface temperature by 2.5℃. This model assumes that the atmosphere’s relative humidity remains constant and the temperature decreases with altitude at a (12) of 6.5℃ per kilometer. The assumption of constant relative humidity is important, because water vapor in the atmosphere is another (13) absorber or radiation at infrared wavelengths.Because warm air can hold more (14) than cool air, the relative humidity will be constant (15) the amount of water vapor in the atmosphere increases (16) the temperature rises. (17) , more infrared radiation would be absorbed and reradiated (18) to theEarth’s surface. The resultant warming at the surface could be expected to melt snow and ice, (19) theEarth’s reflectivity. More solar radiation would be absorbed, (20) to a further increase in temperature.
A．leading
B．coming
C．amounting
D．adding