Global Climate Change
Passage #1:
Over the last 100 years, the global sea level has risen from 10 to 25 cm.
Sea level change is difficult to measure. Relative sea level changes have been
derived mainly from tide-gauge data. In the conventional tide-gauge system, the
sea level is measured relative to a land-based tide-gauge benchmark. The major
problem is that the land experiences vertical movements (such as tectonic effects
and sedimentation), and these get incorporated into the measurements. However,
improved methods of filtering out the effects of long-term vertical land
movements, as well as a greater reliance on the longest tide-gauge records for
estimating trends, have provided greater confidence that the volume of ocean
water has indeed been increasing, causing the sea level to rise within the given
range.
It is likely that much of the rise in sea level has been related to the concurrent rise
in global temperature over the last 100 years. On this time scale, the warming and
the consequent thermal expansion of the oceans may account for from 2 to 7 cm of the observed sea level rise, while the observed
retreat of glaciers and ice caps may account for from 2 to 5 cm.
Other factors are more difficult to quantify. The rate of observed sea level rise suggests that there has been a net positive contribution
from the huge ice sheets of Greenland and Antarctica, but observations of the ice sheets do not yet allow meaningful quantitative
estimates of their separate contributions. The ice sheets remain a major source of uncertainty in accounting for past changes in sea
level because of insufficient data about these ice sheets over the last 100 years.
Use information from reading passage #1 to answer questions 1 through 8.
1. Relative sea level changes have been derived mainly from
a.
b.
c.
d.
ice sheet melting
tide-guage data
global warming
none of these
2. The major problem with measuring sea level rise is
a.
b.
c.
d.
thermal expansion of the ocean
lack of ice sheet melting data
vertical movements of the land
none of these
3. It is likely that much of the rise in sea level has been related to
a.
b.
c.
d.
rise in global temp over the last 100 years
drop in the land-based tide-guage benchmarks
increases in Greenland and Antarctica ice sheets
none of these
4. Thermal expansion of the oceans by account for this amount of the observed sea level rise
a.
b.
c.
d.
25 cm
10 cm
2 to 5 cm
none of these
5. The Greenland and Antarctica ice sheets remain a major source of uncertainty because of
a.
b.
c.
d.
sedimentation
long-term vertical land movements
insufficient data
none of these
6. Over the last 100 years, the global sea level has risen from
a.
b.
c.
d.
10 to 25 cm
2 to 5 cm
5 to 7 cm
none of these
7. The sea level 5 year running mean became positive in
a.
b.
c.
d.
1960
1965
1970
1975
8. The independent variable on the graph above is
a.
b.
c.
d.
centimeters
sea level rise
years
none of these
Passage #2:
Global climate change is a very complex subject. All of Earth's spheres - the biosphere (living things), hydrosphere (water),
lithosphere (rock/soil), and atmosphere (air) - work together to create and maintain climate.
One way in which humans have affected the climate is by increasing emissions of greenhouse gases. Greenhouse gases absorb infrared
radiation. This is the form of the sun's energy reflected off the earth's surface. Greenhouse gases then radiate heat energy back toward
the earth. This heats the earth's atmosphere and ultimately contributes to increasingly warmer climates, a process known as global
warming. Common greenhouse gases include carbon dioxide (CO 2), chlorofluorocarbons (CFCs), methane (CH4), nitrous oxide
(N2O), and tropospheric ozone (O3).
Carbon dioxide (CO2) is a byproduct of the combustion - or burning. The following chemical equation describes the chemical process
of combustion:
6 O2 + C6H12O6
6 H2O + 6 CO2 + energy
Methane (CH4) production - methanogenesis - can occur in a number of ways. The one that may have the largest impact on the climate
occurs in freshwater wetlands.
During the microbial metabolic process of methanogenesis, acetate (CH 3COOH) is split into CO2 and CH4. The following chemical
equation describes the chemical process of methanogenesis:
CH3COOH
CO2 + CH4
Use information from reading passage #2 to answer qustions 9 through 14.
9. The Earth's "sphere" composed of rock and soil
a.
b.
c.
d.
biosphere
lithosphere
hydrosphere
none of these
10. Greenhouse gases absorb
a.
b.
c.
d.
infrared radiation
sunlight
heat
none of these
11. The number of oxygen molecules needed to combine with one molecule of C 6H12O6
a.
b.
c.
d.
1
3
5
none of these
12. Methane is produced by a process known as
a.
b.
c.
d.
global warming
combustion
methanogenesis
none of these
13. Acetate (CH3COOH) decomposes into
a.
b.
c.
d.
ozone and CFCs
carbon dioxide and methane
water and carbon dioxide
none of these
14. Which of these is NOT a greenhouse gas?
a.
b.
c.
d.
CFCs
N 2O
tropospheric O3
H 2O