Environmental Engineering Reference
In-Depth Information
changes in land use have resulted in more energy being refl ected from the
surface of the earth.
Section 4
The climate
Is the climate changing? Is the climate changing because of human activ-
ity? These questions have been addressed by many scientists and have
been documented in many reports. The answers are “yes” and “yes.” Here
we discuss some of the relevant data, mainly to illustrate that the notion of
climate change is not based on a single observation, but rather on many
independent measurements that point consistently in the same direction.
Climate and temperature
Before we do this, we need to defi ne climate. Climate is the long-term aver-
age of the weather (including temperature, cloud cover, rainfall, drought,
etc.). Weather would suggest, for example, that on some days it is cooler
in Berkeley in California than it is in Anchorage in Alaska. Climate tells us
that Anchorage is colder than Berkeley. Public opinion tends to be easily
swayed by the weather, making discussion of climate change problematic
for scientists and policy makers. Because the weather fl uctuates signifi -
cantly, it is impossible to associate a single weather event with climate
change. A good illustration of this is given in Figure 2.4.1 from the National
Oceanic and Atmospheric Administration (NOAA) [2.3]. The year 2012 was
the eighth warmest on the record, yet Figure 2.4.1 shows that in many
places on the planet the average temperature in 2012 was actually below
the 30-year average. Figure 2.4.2 shows selected signifi cant climate
anomalies and events in October 2012 [2.3].
The most famous curve indicating climate change is the “ hockey
stick curve ” from the 2001 IPCC report [2.4], which is shown in
Figure 2.4.3. This fi gure shows the deviation from the 1961-1990
average temperature on the Northern hemisphere. The importance of the
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