Geology Reference
In-Depth Information
which splashed slowly back into the river. Her gaze lasted a few seconds, but is
there in us still to this day, for such blessings are eternal. Then, as we drifted
closer, Puma slowly turned, and with exquisite grace, vanished into the forest.
It isn't just the tropical forests which emit cloud-seeding chemicals; the great temperate
forests do it too, and so do the moss-covered peat bogs, and to a far lesser extent,
the great northern boreal forests—the nearly continuous belt of coniferous trees that
stretches across the far north of the American continent and Eurasia. In all, clouds
seeded by life cool the planet by up to a staggering 10
0
C, about twice the temperature
difference between a cold ice age and a warm interglacial period such as the one in
which we are living now.
Since I learnt these amazing facts, I have seen clouds differently, through Gaian eyes.
Once, they were for me the product of physics, now they are like fur or hair, not biolo-
gically alive in themselves, but the product of life nonetheless. They are the great dis-
persal buses of the microbial world that cool the planet, helping to keep it habitable
overall, but also helping to trigger ice ages. Contemplating how most of Gaia's clouds
are seeded by life gives us a taste of her animate presence, of her skill at handling the
ever-brightening sun. Even clouds and the very wind itself are animate powers that liv-
ing organisms have helped to set in motion.
Land and Ocean Working Together
We've seen how organisms on land and in the ocean help to regulate our planet's surface
temperature, but could it be that these two great Gaian realms work together? To explore
this question, Lovelock and his colleague Lee Kump made a model with land plants and
oceanic algae coupled together. In the model, marine algae seed a dense sunshade of
clouds, whilst on land great forests remove carbon dioxide from the air by enhancing
the weathering of granite and basalt. These two great biotic communities cool the planet
in tandem, but things change if a temperature increase is 'forced' through the gradual
addition of carbon dioxide to the atmosphere. In this model, with 500 ppm (parts per
million) of carbon dioxide in the air, the ocean temperature reaches 10
0
C, and the mar-
ine algae vanish exponentially fast as a cap of warmer water develops on the sea sur-
face. This starves the algae by preventing nutrient-rich currents, which sweep up from
the sediments below, from reaching them. As the clouds above the ocean vanish and the
dark blue sea is exposed to the warming rays of the sun, the planet warms rapidly to a
new, hotter steady state, held there by the land plants working without the help of the
algal denizens of the oceans.
