GRE-Verbal Latest Exam Braindumps
Question 9: Radiative forcings are changes imposed on the planetary energy balance; radiative feedbacksare
changes induced by climate change. Forcings can arise from either natural or anthropogenic causes.
For
example, the concentration of sulfate aerosols in the atmosphere can be altered by volcanic action or
by
the burning of fossil fuels. The distinction between forcings and feedbacks is sometimes arbitrary;
however, forcings are quantities normally specified in global climate model simulations, while
feedbacks
are calculated quantities. Examples of radiative forcings are greenhouse gases (such as carbon
dioxide
and ozone), aerosols in the troposphere, and surface reflectivity. Radiative feedbacks include clouds,
water vapor in the troposphere, and sea-ice cover. The effects of forcings and feedbacks on climate
are
complex. For example, clouds trap outgoing radiation, thus providing a warming influence, while also
reflecting incoming solar radiation and, thereby, providing a cooling influence. Current
measurements
indicate that the net effect of clouds is to cool the earth. However, scientists are unsure if the
balance will
shift in the future as the atmosphere and cloud formation are altered by the accumulation of
greenhouse
gases. Similarly, the vertical distribution of ozone affects both the amount of radiation reaching the
earth's
surface and the amount of reradiated radiation that is trapped by the greenhouse effect. These two
mechanisms affect the earth's temperature in opposite directions.
Based solely on the information in the passage, which of the following research methods, if
implemented,
would be most likely to yield a more accurate prediction of the extent and direction of the
greenhouse
effect?
A. Monitoring radiative feedbacks and forcings over a longer time period
B. Measuring variations in cloud density in relation to air temperature
C. Isolating ozone changes caused specifically by anthropogenic factors
D. Accounting for the altitude at which cloud formations appear
E. Isolating the cooling influence1 of ozone changes from their warming influence
Correct Answer: E
Explanation:
According to the passage, a given vertical distribution of ozone affects atmospheric temperatures in
both
directions at once. Accordingly, by isolating the cooling influence of a given distribution of ozone
from its
warming influence, scientists might better predict whether changes in the vertical distribution of
ozone will
have a net cooling or a net warming effect.
