The Oligocene to the Quaternary: climate and biology - Climate Change: Biological and Human Aspects - page 129

4

2

0

-2

-4

-6

-8

-10

0 50 000 100 000 150 000

Years ago

Fig. 4.2 TemperaturechangesaroundAntarcticaasrevealedbydeuteriumanalysisoficecores.Basedondatafromthe

NationalOceanicandAtmosphericAdministration(seeAcknowledgements).

the annual variation in atmospheric carbon dioxide is too small to have a significant
climate effect. On the other hand, although ice albedo effects may possibly magnify
temperature changes (see Figure 1.8) the thermal inertia in the vast ice caps of the
Antarctic and Greenland means that they take longer to respond and so only respond
to sustained year-on-year climate forcing factors as opposed to factors that take place
within a year.
As we shall see in subsequent chapters, this is somewhat relevant to our current
anthropogenic release of carbon dioxide by fossil fuel combustion. The anthropogenic
future will be determined not so much by the weak Milankovitch forcing but our
effects on the carbon cycle on a year-on-year (as opposed to within-year) basis, as well
as albedo changes as glaciers and ice caps retreat. This makes policy decisions that
determine how much carbon dioxide we release, such as energy policy, of fundamental
importance should we be concerned about future climate change.

4.5 Thelastglacial

4.5.1 Overviewoftemperature,carbondioxideandtiming

The last glacial began about 115 000 years ago with temperatures that oscillated
towards ever-colder conditions. It reached its climax (the last glacial maximum;
LGM) some 18 000-22 000 years ago and ended (after a false start to the current
interglacial 14 000 years ago) approximately 12 000 years ago (see Figure 4.2).
The importance of understanding the last glacial-interglacial cycle is that it illu-
minates the planet's current climatic mode. It is also important because, being closest
to us in time, it has been the easiest era for which to gather data. Nonetheless,