Geoscience Reference
In-Depth Information
(methane), and the climatic consequences that follow: global
warming, local modification of the climate, the melting of glaciers and
ice caps, a rise in the average sea level, acidification of the oceans,
possible destabilization of hydrates of methane in oceanic sediments
at depth, positive retroaction by an increase in albedo, etc.
Despite its enormous power as a buffer, the ocean cannot regulate
in the short-term the disturbance due to the current rate of
anthropogenic greenhouse gas emissions. We are therefore in a
transitional phase in the course of which the climate is modifying as a
result of human activity. The consequences are already perceptible in
numerous parts of the world. Beyond the immediate adaptation of
human societies, man should also make sure not to modify the climate
in an irreversible manner (threshold effect, irreversible melting of
polar caps) so that a future way of energetically sustainable life can be
established in habitable climatic zones as widespread as they are
today.
On geological timescales, the Earth as a whole system, including
the presence of life forms, will adapt itself and will pursue its
existence, with or without mankind.
1.6.3.
And life among all that?
In this chapter, the use of the term “life” has been carefully
avoided, preferring that of “life forms” or “living things” or “living
beings”. As already underlined at the beginning (section 1.2.5), life is
a concept much richer and more complex than the simple arbitrary
definition that can be given to the term “alive” or “biological”.
Before asking ourselves about the profound nature of life, it is
sensible to ask what, among its characteristics, can differentiate it
from “living”.
As far as we presently know, terrestrial life has been uninterrupted
for more than 3.5 billion years. This continuity is partly due to the
phylogenetic link between all living beings. Life never ceases with the
death of living beings; it is transmitted into new living beings. Even if
