Geology Reference
In-Depth Information
According to James Lovelock, the fact that such a tiny change in solar energy can
have such drastic consequences is a sure sign that Gaia's temperature regulation is in
crisis—that she is experiencing some kind of pathology. As we have seen, during the last
3,500 million years Gaia has maintained habitable temperatures in the face of an ever-
brightening sun by gradually removing carbon dioxide from her atmosphere, thanks to
the ever more efficient life-assisted weathering of granite and basalt. By two million
years ago, so much carbon dioxide had gone that removing any more under a modern
and very bright sun has been of little help in Gaia's efforts to keep herself cool. Invent-
ors know only too well that cybernetic systems wobble from one state to another when
they are about to fail, just like a wildly oscillating top before it runs out of energy. For
Lovelock, Gaia's recent wobbles in and out of ice ages may be a clear sign that she
is struggling to keep cool under a bright sun—that she is overstretched to the point of
instability, with the glacial periods being her preferred state, and the interglacials her
fevers during which she hovers dangerously close to catastrophic climatic breakdown.
Without the small addition of solar energy given her by the eccentricity of her orbit Gaia
would probably have oscillated somewhat randomly between ice ages and interglacials
in her search for a comfortable coolness. If so, Gaia has driven her own shifts from cold
to warm, but the rhythmical expansion and contraction of her long trajectory around the
sun has imposed regularity on what might otherwise have been a far less predictable
plunging in and out of ice ages.
So how does a tiny increase in solar radiation trigger the end of an ice age? What
are the amplifiers? A hundred thousand years of ice have passed, and Gaia's orbit once
again contrives to bring her marginally closer to the sun. The dark oceans warm as they
soak up the tiny bit of extra solar energy. Molecules of carbon dioxide, methane and
water, picking up speed in the warmer water, leave the oceans to journey in the vast
expanses of the atmosphere as greenhouse gases, further amplifying the warming. The
ice, once safe in the grip of an ice age, is not immune from the warming. At last, after
100,000 years of torpor, huge numbers of its water molecules are liberated into the fluid-
ity of the liquid state. As the melting continues, more and more of the dark land and
ocean are exposed to the sun, and Gaia warms further. In the northern hemisphere, the
boreal forests advance, swallowing up the peat bogs, warming the region and the entire
world as their dark, snow-shedding leaves absorb the sun's warmth and as the dying peat
bogs release their immense stores of carbon to the air.
The additional warming affects the oceans, which release even more carbon dioxide
into the air. Plants grow well in the new high carbon dioxide atmosphere. They send
their roots deep in search of nutrients, cracking open rocks with sheer brute force and
with the subtle but relentless dissolving powers of their acidic chemical exudations. One
can almost hear the gentle grinding noise of the increased weathering as plants all over
