Environmental Engineering Reference
In-Depth Information
Temperature change over past 22,000 years
Average temperature over past 900,000 years
2
17
Agriculture established
1
16
0
15
14
−
−
−
1
End of
last ice
age
13
12
Average temperature over past
10,000 years = 15
C (59
F)
11
°
°
−
4
−
5
10
9
20,000 10,000
2,000
1,000
200
100
Now
900
800
700
600
500
400
300
200
100
Present
Years ago
Thousands of years ago
Temperature change over past 1,000 years
Average temperature over past 130 years
1.0
15.0
14.8
0.5
14.6
14.4
0.0
14.2
14.0
−
0.5
13.8
13.6
−
1.0
1000 1100
1200 1300 1400 1500 1600 1700 1800 1900 2000 2101
Year
1860 1880
1900 1920 1940 1960 1980 2000 2020
Year
Figure 16-2
Science:
estimated changes in the average global temperature of the atmosphere near the
earth's surface over different periods of time. Although a particular place might have much lower or much
higher readings than the troposphere's average temperature, such averages provide a valuable way to
measure long-term trends. (Data from Goddard Institute for Space Studies, Intergovernmental Panel on
Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center
for Atmospheric Research, and National Oceanic and Atmospheric Administration)
The earth's natural greenhouse effect is one of the rea-
sons you are alive to read these words.
See how greenhouse gases trap heat in the atmosphere
and raise the earth's temperature at Environmental
ScienceNow.
Science: Major Greenhouse Gases
The two major greenhouse gases are water vapor and
carbon dioxide.
The two greenhouse gases with the largest concentra-
tions are
water vapor,
controlled by the hydrologic cy-
cle, and
carbon dioxide
(CO
2
), controlled by the carbon
cycle. Carbon dioxide is the major greenhouse gas that
humans have added to the troposphere (Table 16-1,
p. 370).
Scientists have analyzed the concentrations of
greenhouse gases such as CO
2
and CH
4
(methane) in
bubbles trapped at various depths in ancient glacial ice
(Figure 16-3). According to these measurements, the
Figure 16-3
Science:
ice cores such as this one extracted
by drilling deep holes in ancient glaciers at various sites in
Antarctica and Greenland can be analyzed to obtain informa-
tion about past climates.
changes in tropospheric CO
2
levels correlate fairly
closely with variations in the average global tempera-
ture near the earth's surface during the past 160,000
years (Figure 16-4, p. 370).
