Geoscience Reference
In-Depth Information
report considers that thermal expansion is likely to add between one and two metres
on top of whatever ice-cap melt there is (but they do not give an estimate for this
last).
Finally, looking even more centuries ahead it is thought that once the sea level
has risen due to the Greenland and Western Antarctica ice caps melting, there would
be little scope for levels to decline completely to present values without the onset
of a proper glacial. For example, melting of the Greenland ice sheet alone would
raise sea levels by 7 m (ignoring thermal expansion or any other contribution, such
as from Antarctica). Furthermore, both geological evidence and computer models
(run in 2002) suggest that even if the Earth returned to 20th-century temperatures the
Greenland ice sheet would not reform (Toniazzo et al., 2004).
Given the latest science, the palaeo-analogues and separately that much of the
global economy is based on settlements that have been located for many centuries -
and so which are ill-suited to address some future climate change consequences -
the impact of climate change in purely human terms cannot be ignored. The IPCC
attempt to provide a comparatively near-future picture; the uncertainty relates to how
near a future, while planning arguably needs to be undertaken with a longer-term
perspective. We have considerable confidence that both warming and sea-level rise
will continue beyond the 21st century. So, while today we may build sea defences to
cope with the anticipated 21st-century rise plus a safety margin, we should perhaps
construct them in anticipation of their needing to be enhanced to cope with further
rise in the future. After all, many of today's rail networks are grounded in centuries-
old construction. Such planning will be far more cost-effective in the long term, and
allow us to better cope with a surprise rise in levels, as warned of by the IPCC.
The above multi-century scenario may sound sensationalist but it is not one of
doom and disaster. Many species on Earth survived the IETM, even if the planet
changed and there was a (primarily) marine extinction event. Indeed, modern humans
( H. sapiens sapiens ;or H. sapiens ) survived the considerable environmental changes
that have taken place since the last glacial maximum, even if some civilisations have
not survived subsequent regional climate change. Of course, earlier in history, our
planet did not have to sustain humans in the numbers it does do today (or is likely
to in the coming decades). Even so, to maximise the longevity of something similar
to modern global human society and some types of robust, biodiverse, biological
support system (but not necessarily their location) all that is required is understanding
(research), anticipation (planning) and application (implementation). Application is
beyond the scope of this text, but planning and policy concerns will be addressed in
Chapter 8, while climate-related biological and human impacts will be summarised
in Chapters 6 and 7, respectively. Meanwhile, there are further matters arising out of
the 2007 IPCC report, and subsequent science, to note.
5.4 Currenthumaninluencesonthecarboncycle
Human influences on the carbon cycle will, the IPCC concluded in 2001, continue to
change atmospheric composition throughout the 21st century. As the IPCC provide
Search WWH ::




Custom Search