Sustainability and policy - Climate Change: Biological and Human Aspects - page 461

tar sand and orimulsion exploitation, etc.), is likely to raise global temperatures by
easily over 6 ◦ C and so have a palaeo-analogue earlier in the Cenozoic than a Pliocene
palaeo-analogue. This last itself might be expected somewhere towards the end of
the 21st century with just the 2007 IPCC's anticipated 2-5.4 ◦ C rise. Whether enough
of this 6 ◦ C or more will by then sufficiently penetrate the oceans to disrupt methane
hydrates is not known with certainty (yet), but it is almost certain to release some car-
bon in soil, so compounding warming. For the palaeobiologist the nightmare scenario
is that we might release enough carbon directly (through fossil fuel and land use) and
indirectly (due to soil carbon and possibly methane hydrates) to incur an extinction
event. This may sound dramatic, and it is, but remember equally that we are already in
the midst of a human-induced (anthropogenic) extinction event through biodiversity
loss that is distinct from extinction by anthropogenic climate change. The majority of
the population do not perceive this as serious because the human species continues
to flourish, as do the major commercial species on which we depend.
It is important to remember that the above discussion is based on rates of emission in
2001. As was noted in the previous chapters, the twin drivers of increasing per-capita
energy demand and increasing global population synergistically conspire to drive up
emissions beyond the 2001 level. (Indeed, in 2007 it looks like this is happening and
will continue to do so unless we switch our energy dependence away from carbon;
clean-carbon technologies notwithstanding.) In short, should emissions continue to
rise this increase in mean global temperature of 6 ◦ C or more will happen long before
two centuries are up.
However, if a major (6 ◦ C ) climate-driven event were to occur, what would be

the consequence? Well, we can with a fair degree of confidence rule out turning our
Earth into a Venus-like planet. Yet this does not mean that we can be excused from
striving for greater energy sustainability that relies less on fossil carbon, or from
adopting carbon-mitigation strategies. The palaeo-analogue of continued substantial
atmospheric fossil carbon accumulation is likely be the carbon isotope excursions
associated with the Initial Eocene Thermal Maximum/Palaeocene-Eocene Thermal
Maximum (IETM/PETM) and, worse, the Toarcian event (see Chapters 3 and 6).
Should we see a future event analogous to the IETM (let alone the Toarcian event)
then this would have a profound effect on most of the planet's ecosystems. As it stands,
the IETM did have a considerable ecological effect some 55 mya, even though glob-
ally much biodiversity was maintained (the marine extinction notwithstanding). Yet
this maintenance of global biodiversity only took place because of biome (hence
ecosystem) shift. However, such an ecological response would not be analogous to
the situation today. To begin with, present-day ecosystems arose (up to the so-called
present Anthropocene era) in a cooler Pliocene and ice-age Pleistocene of alternating
glacials and interglacials: our current interglacial climate is already at the warm
end of the Quaternary spectrum of global temperature in which present ecosystems
evolved. So, further warming of more than a few degrees takes us into a new temper-
ature realm for these ecosystems. Additionally, as mentioned in previous chapters,
current human ecosystem management to our species' own ends means that options
for natural ecosystems to shift and evolve with climate are restricted due to human
fragmentation of the landscape, which was not the case back in the Eocene. Further-
more, the ecological disruption of the IETM resulted in subsequent opportunities for

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