Climate Change Will Happen to You - Stolen Future, Broken Present: The Human Significance of Climate Change - page 4

this topic. hese vicious circles emerge when the warming temperature
causes the release of more greenhouse gases into the atmosphere, which
cause a further increase in temperature, and on around again. Once these
vicious circles become strong enough, they constitute “tipping points”
that lead to an irreversible sequence of events and an unstoppable rise in
temperature. The more gases we emit and the longer we wait to change
our habits, the more likely we will cross these tipping points, making it
even more difficult to postpone the arrival of serious climate change with
all its consequences.
In his topic on the subject, With Speed and Violence: Why Scientists
Fear Tipping Points in Climate Change , Fred Pearce reviews a wide array
of potential “positive feedback loops” that could arise in a number of
regions of the world. Some of these tipping points may indeed be decades
away. But we threaten to cross others in the fairly near future, if we have
not done so already. 15
Several key examples of tipping points are those I explored at the
beginning of this topic. As I mentioned there, the stunning melt of the
Arctic sea ice in the summer of 2012 suggests to many observers that this
process has now crossed the tipping point and become irreversible.
A second example, also related to the discussion in the introduction,
is the possibility that the methane clathrates on the seabeds around the
globe will begin to melt and release gas into the atmosphere. 16 If this
feedback loop gets going on any large scale, we are in for big trouble, for
there are untold quantities of methane capable of being released in this
fashion. One estimate suggests that the methane in the clathrates in all
the world's oceans is around four thousand times the amount in today's
atmosphere. 17
Researchers typically guess that such a clathrate melt will take place
only at much later stages of climate change. In 2008, Mark Lynas sug-
gested that this potential clathrate melt might take place on an Earth
that had warmed 5° Centigrade over preindustrial temperatures. 18 But
already, as I mentioned above, the clathrate melt is beginning on a shal-
low continental shelf of the Arctic Ocean. That relatively local event does
not suggest that the clathrates around the world are about to melt as well.
But because clathrates exist in such huge numbers, even a melt in only
a small fraction of their total bulk would be enough to shift the Earth's