Environmental Engineering Reference
In-Depth Information
as the excess greenhouse gases were slowly drawn out of the atmosphere by
reactions associated with rock weathering.
These geological examples strongly reinforce the modeled scenarios of
global warming for later this century. Crucially, such temperature surges show
the earth behaving in a non-linear fashion when reacting to environmental
stress: that is, it tends to ‗flip' from one quasi-stable state to another, and this
kind of behavior is inherently difficult to model or to predict.
Sea level has constantly fluctuated in the geological past: its highest
recorded level was in the Cretaceous Period, some 80 million years ago, when
CO
2
levels were considerably higher than at present, and ice-caps were
virtually absent from the earth . Then, sea level stood at least 200 meters
higher than today, with most of the UK being submerged.
Less well known are the variable sea levels recorded in previous warm
phases of the Ice Ages . For instance, in the most recent of these, some 125
000 years ago, sea level reached some 6 m higher than at present. Such a
difference is geologically modest, and reflects relatively minor differences in
the extent of melting of land ice. We emphasize that it occurred in a world
where levels of greenhouse gases, unaffected by humans, were lower than at
present.
The problem can only be marginally (i.e. ineffectually) addressed by
increases in alternative energy and energy efficiency, any likely savings being
offset by population and economic growth [6]. And, given the huge energy and
material demands in the construction of, say, wind farms, the ultimate value of
these is debatable. More radical solutions to humanity's dilemma are
necessary, and these might include:
•
massive underground sequestration of CO
2
. This is not yet a proven
method on anything like the scale needed, but needs to be pursued
with urgency.
•
large-scale capture of CO
2
from the air and its conversion into a
mineralized form, perhaps as carbonate minerals.
•
a large-scale switch to civil nuclear power. This has the benefit of
being proven technology. We are aware of the problems, and current
public unpopularity of this route, but we consider the dangers posed
by global warming to be orders of magnitude greater than those likely
to be caused by the controlled use of nuclear power. This energy
source, additionally, could lie at the heart of future hydrogen-based
transport systems.
