16 Engineering Response to Climate Change
1.3.3.6 Natural Variability
Perhaps a more detailed discussion of what is meant by natural variability
is called for. Both historical data and the results of GCMs show that both
the globally averaged temperatures and regional and local temperatures
will have their ups and downs. Historical changes that have occurred both
recently and over the past 1000 years bear out the fact that sizeable changes
in the climate might occur naturally in the climate system. This is what cli-
matologists call “natural variability.” For example, there was a relatively
cool period that occurred between about 4500 and 2500 years ago, ending
at about the time of the dawn of the Roman Empire. The decline and fall
of the empire ...