考研考试

【单选题】
A、"radiative forcing" is any change imposed on theEarth that affect the planetary energy balance. Radiative forcings include changes in greenhouse gases (such as carbon dioxide and ozone), aerosols in the atmosphere, solar irradiance, and surface reflectivity.
A、forcing may result from either a natural or an anthropogenic cause, or from both, as in the case of atmospheric aerosol concentrations, which can be altered either by volcanic action or the burning of fossil fuels. Radiative forcings are typically specified for the purpose of theoretical global climate simulations. In contrast, radiative "feedbacks" are environmental changes resulting from climate changes and are calculated from scientific observation. Radiative feedbacks include changes in such phenomena as clouds, atmospheric water vapor, sea-ice cover, and snow cover.　　The interplay between forcings and feedbacks can be quite complex. For example, an increase in the concentration of atmospheric water vapor increases solar irradiance, thereby warming the atmosphere and, in turn, increasing evaporation and the concentration of atmospheric water vapor.
A、related example of this complex interplay also shows the uncertainty of future climatic changes associated with forcings and feedbacks. Scientists are unsure how the reduction of ozone will ultimately affect clouds and, in turn, theEarth temperature.Clouds trap outgoing, cooling radiation, thereby providing a warming influence. However, they also reflect incoming solar radiation and thus provide a cooling influence.Currents measurements indicate that the net effect of clouds is to cool theEarth. However, scientists do not know how the balance might shift in the future as cloud formation and dispersion are affected by ozone reduction.　　Contributing to this uncertainty is the complexity of the mechanisms at work in the process of ozone reduction. The amount of radiation reaching the earth’’s surface and the amount of reradiated radiation that is trapped by the greenhouse effect influence theEarth’’s temperature in opposite directions.Both mechanisms are affected by the vertical distribution of ozone.Also, the relative importance of these two competing mechanisms depends on the altitude at which ozone changes occur. In a recent NASA-sponsored aircraft study of theAntarctic ozone hole, chlorine monoxide was measured at varying altitudes. The measurements suggest that chlorine plays a greater role, and oxides of nitrogen a lesser role, than previously thought in the destruction of ozone in the lower atmosphere. The study concluded that simultaneous high-resolution measurements at many different altitudes (on the scale of 0.1 kilometer in vertical extent) are necessary to diagnose the operative mechanisms. These findings have called into question conventional explanations for ozone reduction, which fail to adequately account for the new evidence. (NASA=NationalAeronautics and SpaceAdministration <美>国家航空航天局)The example of ozone reduction is used to show the
A、complex operations of feedbacks and forcings
B．distinction between radiative feedbacks and forcings.
C． difficulty in balancing forcing-feedback interactions.
D．impact of cloud formation on global climate.

网考网参考答案：C
网考网解析：
第2段第3句的ozone reduction(臭氧减少)是作为证明forcings和 feedbacks相互作用的复杂性及其影响气候变化的不确定性提出来的。C项是此意的概括，其巾interaction=interplay(相互作用)。A项的operation(作用)不同于 interplay。B项distinction，文中未提。D项cloud formation不全面。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>