Environmental Engineering Reference
In-Depth Information
centuries can now be identified and estimated at different levels of warm-
ing. Many impacts can be shown to scale with warming (see Figure S.5).
Scientific progress has resulted in increased confidence in the understanding
how global warming levels of 2°C, 3°C, 4°C, 5°C, etc. (see Figure S.1) af-
fect precipitation patterns, extreme hot seasons, streamflow, sea ice retreat,
reduced crop yields, coral bleaching, and sea level rise. This increased con-
fidence provides direct scientific support for evaluating the implications of
different stabilization targets. However, other climate changes and impacts
are currently understood only in a qualitative manner. Many potential effects
on human societies and the natural environment cannot presently be quanti-
fied as a function of stabilization target (see Figure S.6). This shortcoming
does not imply that these changes and impacts are negligible. Some of these
impacts, such as species changing their ranges or behavior, could be very
important; indeed, some may dominate future risks due to anthropogenic
climate change. Uncertainty in the carbon dioxide emissions and concen-
trations corresponding to a given temperature target is large, and choices
about stabilization targets depend upon judgments regarding the degree
°C
°F
10
18
9
16.2
8
14.4
FIGURE S.1 Illustration of how temperature
change in degrees Celsius (left side of thermom-
eter) relates to temperature change in degrees
Fahrenheit (right side of thermometer). For ex-
ample, a warming of 5°C is equal to a warming
of 9°C. In this report estimates of temperature
change are made in degrees Celsius in accor-
dance with international scientific practice.
7
12.6
6
10.8
5
9
4
7.2
3
5.4
2
3.6
1
1.8
0
0
