Terrestrial Palaeoecology and Global Change

Chapter 7. Climate change
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Fig. 90. The relative extent of the major biomes over the Carboniferous to Neogene: (AT) Arctic tundra, (DF)
Deciduous forest, (RF) Rainforest, (TF) Boreal forest (taiga), (XS) Xeric shrublands to grasslands.
history (Fig. 90). The Mediterranean-type climate is likewise persistent, formerly supported
by the vast extent of the Tethys seas. Its occasional excursions to high latitudes
(as in the Early Eocene) correspond to minimal ice caps.
VII.2. Causes and effects
Climate, as a complex system, comprises a number of subsystems with their own
dynamics. Climate affects, and is feedback affected by circulation of oceanic water
masses, carbonate deposition, burial of organic matter, weathering of geological substrates,
pedogenesis, vegetation changes, etc. In each subsystem, climatic evolution with
a positive feedback is directional (humidity promotes forestation that increases humidity)
while negative feedbacks generate cyclicity (CO 2
greenhouse enhances biotic production
that reduces atmospheric CO 2
).
Secular climates arise at the interference of directional and cyclic processes and are by
necessity less predictable than any of these. Critical for the understanding of climatic cyclicity