Reflections on the Surface

July 10, 2007

Wildfires in the West (the other three degrees)

Filed under: Environment,global warming,insanity,Life,Nature,Thoughts — asharpminor @ 12:52 pm

Courtesy of Mark Lynas and the Guardian.

Six degrees to Hell (continued).

4ºC
At four degrees another tipping point is almost certain to be crossed; indeed, it could
happen much earlier. (This reinforces the determination of many environmental groups, and
indeed the entire EU, to bring us in within the two degrees target.) This moment comes as
the hundreds of billions of tonnes of carbon locked up in Arctic permafrost – particularly in
Siberia – enter the melt zone, releasing globally warming methane and carbon dioxide in
immense quantities. No one knows how rapidly this might happen, or what its effect might
be on global temperatures, but this scientific uncertainty is surely cause for concern and not
complacency. The whole Arctic Ocean ice cap will also disappear, leaving the North Pole as
open water for the first time in at least three million years. Extinction for polar bears and
other ice-dependent species will now be a certainty.
The south polar ice cap may also be badly affected – the West Antarctic ice sheet could lift
loose from its bedrock and collapse as warming ocean waters nibble away at its base, much
of which is anchored below current sea levels. This would eventually add another 5m to
global sea levels – again, the timescale is uncertain, but as sea level rise accelerates
coastlines will be in a constant state of flux. Whole areas, and indeed whole island nations,
will be submerged.
In Europe, new deserts will be spreading in Italy, Spain, Greece and Turkey: the Sahara will
have effectively leapt the Straits of Gibraltar. In Switzerland, summer temperatures may hit
48C, more reminiscent of Baghdad than Basel. The Alps will be so denuded of snow and ice
that they resemble the rocky moonscapes of today’s High Atlas – glaciers will only persist on
the highest peaks such as Mont Blanc. The sort of climate experienced today in Marrakech
will be experienced in southern England, with summer temperatures in the home counties
reaching a searing 45C. Europe’s population may be forced into a “great trek” north.

5ºC
To find out what the planet would look like with five degrees of warming, one must largely
abandon the models and venture far back into geological time, to the beginning of a period
known as the Eocene. Fossils of sub-tropical species such as crocodiles and turtles have all
been found in the Canadian high Arctic dating from the early Eocene, 55 million years ago,
when the Earth experienced a sudden and dramatic global warming. These fossils even show
that breadfruit trees were growing on the coast of Greenland, while the Arctic Ocean saw
water temperatures of 20C within 200km of the North Pole itself. There was no ice at either
pole; forests were probably growing in central Antarctica.
The Eocene greenhouse event fascinates scientists not just because of its effects, which also
saw a major mass extinction in the seas, but also because of its likely cause: methane
hydrates. This unlikely substance, a sort of ice-like combination of methane and water that
is only stable at low temperatures and high pressure, may have burst into the atmosphere
from the seabed in an immense “ocean burp”, sparking a surge in global temperatures
(methane is even more powerful as a greenhouse gas than carbon dioxide). Today vast
amounts of these same methane hydrates still sit on subsea continental shelves. As the
oceans warm, they could be released once more in a terrifying echo of that methane belch of
55 million years ago. In the process, moreover, the seafloor could slump as the gas is
released, sparking massive tsunamis that would further devastate the coasts.
Again, no one knows how likely this apocalyptic scenario is to unfold in today’s world. The
good news is that it could take centuries for warmer water to penetrate down to the bottom
of the oceans and release the stored methane. The bad news is that it could happen much
sooner in shallower seas that see a stronger heating effect (and contain lots of methane
hydrate) such as in the Arctic. It is also important to realise that the early Eocene greenhouse
took at least 10,000 years to come about. Today we could accomplish the same feat in less
than a century.

6ºC
If there is one episode in the Earth’s history that we should try above all not to repeat, it is
surely the catastrophe that befell the planet at the end of the Permian period, 251 million
years ago. By the end of this calamity, up to 95% of species were extinct. The end-Permian
wipeout is the nearest this planet has ever come to becoming just another lifeless rock
drifting through space. The precise cause remains unclear, but what is undeniable is that the
end-Permian mass extinction was associated with a super-greenhouse event. Oxygen
isotopes in rocks dating from the time suggest that temperatures rose by six degrees,
perhaps because of an even bigger methane belch than happened 200 million years later in
the Eocene.
Sedimentary layers show that most of the world’s plant cover was removed in a catastrophic
bout of soil erosion. Rocks also show a “fungal spike” as plants and animals rotted in situ.
Still more corpses were washed into the oceans, helping to turn them stagnant and anoxic.
Deserts invaded central Europe, and may even have reached close to the Arctic Circle.
One scientific paper investigating “kill mechanisms” during the end-Permian suggests that
methane hydrate explosions “could destroy terrestrial life almost entirely”. Acting much like
today’s fuel-air explosives (or “vacuum bombs”), major oceanic methane eruptions could
release energy equivalent to 10,000 times the world’s stockpile of nuclear weapons.
Whatever happened back then to wipe out 95% of life on Earth must have been pretty serious.
And while it would be wrong to imagine that history will ever straightforwardly repeat itself,
we should certainly try and learn the lessons of the distant past. If they tell us one thing
above all, it is this: that we mess with the climatic thermostat of this planet at our extreme –
and growing – peril.

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