Geology Reference
In-Depth Information
better at revealing climate changes on short time-scales than the ice cores from Antarc-
tica because of the way in which the Greenland ice was deposited. The ice from the north
holds unequivocal memories that climate during both the last glacial and the current in-
terglacial was highly unstable, with particularly rapid shifts from relatively warm to cold
even when the world was in the grip of the ice age. The periods of warmth were signi-
ficant, with the world warming within decades to temperatures close to those of today,
followed by a slower cooling back down to glacial conditions. The evidence suggests
that these temperature fluctuations were triggered by very small changes in solar lumin-
osity—another warning that seemingly insignificant changes can be amplified beyond
all recognition into huge effects by complex dynamical systems such as Gaia.
Scientists know only too well that irregular behaviour is a hallmark of complex sys-
tems. One particular event underscores this instability: the end of the Younger Dryas
cooling some 11,600 years ago, when global temperatures soared by 15°C in no less
than a decade. Why this happened is not totally clear, but emissions of methane either
from wetlands or from the huge store of undersea methane hydrates were almost cer-
tainly involved, together with the reorganisation of the circulation of the global ocean.
The messages from the ice are strikingly clear: stable climate is a myth. The Gaia into
which our species emerged is a wild, complex dynamic being, subject to sudden shifts
between multiple semi-stable states. At this time in her long life, small disturbances
can ramify through her vast body, growing larger and larger through positive feedback,
as our explorations of the effects of tiny increases in solar luminosity have so clearly
shown. There are tipping points beyond which climate can suddenly transmute from be-
nign to deadly, and there is no good reason for us to bask in the complacent idea that our
emissions of greenhouse gases will warm the planet gradually—that we will have time
to adapt. It is far more likely that we will trigger abrupt, catastrophic climate changes
that will push Gaia into a new hot state unsuitable for many of her life forms, including
ourselves.
Gaia and the Western World
So how are we changing Gaia's climate, and what are the likely consequences? The sci-
entific community has addressed this vital question in part through the IPCC (the Inter-
governmental Panel on Climate Change), which synthesises the work of thousands of
scientists around the world who contribute their supercomputer simulations and obser-
vational data of Gaia's past, present and future climates. In their most recent publication
to date, the Fourth Assessment Report published in 2007, the IPCC stated that warming
of the climate system is now “unequivocal”, and that there is “very high confidence” (a
