Climate change: ‘One [more] degree and we’re done for’
> New Scientist: 27 September 2006
> “Further global warming of 1
Climate change: ‘One [more] degree and we’re done for’
> New Scientist: 27 September 2006
> “Further global warming of 1
Fiddling with figures while the Earth burns
The Sunday Times May 6, 2007
The latest initiatives to stop global warming won’t save us, James Lovelock tells Jonathan Leake
If you want to get some idea of what much of the Earth might look like in 50 years’ time then, says James Lovelock, get hold of a powerful telescope or log onto Nasa’s Mars website. That arid, empty, lifeless landscape is, he believes, how most of Earth’s equatorial lands will be looking by 2050. A few decades later and that same uninhabitable desert will have extended into Spain, Italy, Australia and much of the southern United States.
“We are on the edge of the greatest die-off humanity has ever seen,” said Lovelock. “We will be lucky if 20% of us survive what is coming. We should be scared stiff.”
Lovelock has delivered such warnings before, but this weekend they have a special resonance. Last week in Bangkok, Thailand, the world’s governments finalised this year’s third and final report from the Intergovernmental Panel on Climate Change (IPCC) setting out how humanity might save itself from the worst effects of climate change.
In it was a message of hope, albeit a faint one. The report set out a complex mix of political, economic and technological solutions. If they all worked, said the report, they could achieve huge cuts in the 25 billion tons of carbon dioxide (CO2) released by humanity into the air each year, thus keeping global temperature rises below 3C.
At the same time in Cologne, Germany, 4,000 sharp-suited bankers, lawyers and financial traders at Carbon Expo 2007 were congratulating themselves on the booming new markets in carbon credits that will, they boasted, save the world as well as making them rich.
“I have a dream,” Yvo de Boer, executive secretary of the United Nations Framework Convention on Climate Change, told the delegates. He set out his belief that carbon trading will help stabilise greenhouse gas emissions and aid developing countries by transferring £50 billion a year to these nations from the First World to support green development.
For Lovelock, however, such dreams are dangerous nonsense on a par with a drowning man clutching at straws. “It’s all ridiculous,” he sighed. “These new markets do some good in that they generate wealth and keep these people employed, but they and the IPCC are just raising false hopes. We have done too much damage to the world and now it is changing too fast for us to make much difference.”
Lovelock’s view is that the world has two stable states: the “icehouse”, when ice covers both poles, sometimes extending far into lower latitudes in the form of ice ages; and the “greenhouse”, when all the ice melts. Both have already happened many times in the Earth’s history.
“Human outpourings of greenhouse gases have flicked the switch that turns the world from its colder to its warm state – and it is probably too late to stop it,” he said. “The warming impact of the carbon we have already released is such that the Earth has taken over and our greenhouse gas emissions are being amplified by nature itself.”
Lovelock believes that the transformation is happening far too fast for humanity to tackle, especially in a world that remains committed to economic growth and whose 6.5 billion population is predicted to reach more than 9 billion by mid-century.
For evidence, he points to Siberia where the melting of the permafrost, already widely reported in scientific literature, will enable bacteria to decompose organic matter that has accumulated in the soil over tens of millions of years – potentially releasing billions more tons of CO2 “I have just come back from Norway where the temperatures are even further above normal than Britain’s. The climate is changing every year now. Everyone can see it – as in this very warm April. By mid-century the heatwave [in Europe] that killed 20,000 people in 2003 will be a cool summer by comparison.”
At first sight Lovelock’s predictions seem wildly at odds with the IPCC’s reports, but in many ways the only difference is in the vividness of the language. “The progressive acidification of oceans due to increasing atmospheric carbon dioxide is expected to have negative impacts on marine shell-forming organisms (ie corals) and their dependent species,” said the IPCC report detailing the impacts of climate change – its careful language draining the drama from a warning that vast tracts of the ocean may turn so acidic that little life will be left in them.
It added: “At lower latitudes, especially seasonally dry and tropical regions, crop productivity is projected to decrease for even small local temperature increases (1-2C), which would increase risk of hunger.” What these measured tones imply, warns Lovelock, is that millions – perhaps hundreds of millions – of people living in equatorial lands will be forced from their homes, with most of them heading northwards. “The world will face mass shortages of food and water. That will lead to wars and the effective clearance of vast areas of land as the deserts spread,” he said.
Lovelock’s reputation as a scientific seer was founded four decades ago when he published his Gaia hypothesis. His idea, that the Earth’s chemistry, climate and life were all closely linked into a kind of self-sustaining system, is now received wisdom. It has become clear that the first life forms on Earth transformed its early climate and atmosphere, generating the oxygen that allowed life to evolve – eventually into us.
What’s more, that process continues. Oxygen is a reactive gas that would vanish from the atmosphere were it not for the plankton, and plants that keep topping it up.
Lovelock’s warnings may seem remote (and he hasn’t always been proved right) but with Britain basking in record spring heat he says our scepticism about the damage we can expect from global warming is understandable. “Britain and Scandinavia are becoming green oases. In 2050 or soon after, most of the world may be scrub and desert and most of the oceans will be denuded of life, but temperatures here will remain very tolerable. The downside of that is that we risk becoming like a lifeboat with millions of refugees trying to settle here.”
He is not alone in predicting a huge northwards shift in human populations: in his new book, How the World will Change with Global Warming, Professor Trausti Valsson, an Icelandic academic, predicts how population centres will move north.
“The Arctic ice cap is melting. When it goes it will open up new shipping routes, new fishing grounds and new oil fields,” said Valsson. “The Arctic Ocean will become the new Mediterranean with Siberia and Canada as the centres for human culture and civilisation.”
Lovelock is fond of recounting how, on a recent lecture tour of America, he was accosted by earnest academics seeking advice on whereabouts in Canada they should buy their second homes.
Behind such comic anecdotes, however, lies the grim possibility that billions of people face a miserable life and death as humanity finds a new equilibrium with the Earth. At 87 Lovelock acknowledges that he is unlikely to be one of them. His concern is for the generations represented by his nine grandchildren. “What we have lived through, the 20th century, has been like a great party. Adults now have had the best time humanity has ever had. Now the party is over and the Earth is reckoning up.”
Six steps to hell – Mark Lynas
By the end of the century, the Earth could be more than 6C hotter than
it is today, according to the Intergovernmental Panel on Climate
Change. We know that would be bad news – but just how bad? How big a
rise will it take for the Alps to melt, the oceans to die and desert
to conquer Europe and the Americas? Mark Lynas sifted through
thousands of scientific papers for his new book on global warming.
This is what the research told him …
Monday April 23, 2007 The Guardian
Nebraska isn’t at the top of most tourists’ to-do lists. However, this
dreary expanse of impossibly flat plains sits in the middle of one of
the most productive agricultural systems on Earth. Beef and corn
dominate the economy, and the Sand Hills region – where low, grassy
hillocks rise up from the flatlands – has some of the best cattle
ranching in the whole US. But scratch beneath the grass and you will
find, as the name suggests, not soil but sand. These innocuous-looking
hills were once desert, part of an immense system of sand dunes that
spread across the Great Plains from Texas in the south to the Canadian
prairies in the north. Six thousand years ago, when temperatures were
about 1C warmer than today in the US, these deserts may have looked
much as the Sahara does today. As global warming bites, the western US
could once again be plagued by perennial drought – devastating
agriculture and driving out human inhabitants on a scale far larger
than the 1930s “Dustbowl” exodus.
On the other side of the Atlantic, today’s hottest desert could be
seeing a wetter future in the one-degree world. At the same time as
sand dunes were blowing across the western US, the central Sahara was
a veritable Garden of Eden as rock paintings of elephants, giraffes
and buffalo, also dating from 6,000 years ago, attest. On the borders
of what is today Chad, Nigeria and Cameroon, the prehistoric Lake
Mega-Chad spread over an area only slightly smaller than the Caspian
Sea does now. Could a resurgent north African monsoon drive rainfall
back into the Sahara in a one-degree world? Models suggest it could.
Also in Africa, Mount Kilimanjaro will be losing the last of its snow
and ice as temperatures rise, leaving the entire continent ice-free
for the first time in at least 11,000 years. The Alps, too, will be
melting, releasing deadly giant landslides as thawing permafrost
removes the “glue” that holds the peaks together. In the Arctic,
temperatures will rise far higher than the one-degree global average,
continuing the rapid decline in sea ice that scientists have already
observed. This spells bad news for polar bears, walruses and ringed
seals – species that are effectively pushed off the top of the planet
as warming shrinks cold areas closer and closer to the pole.
Indeed, it is the ecological effects of warming that may be most
apparent at one degree. Critically, this temperature rise may wipe out
the majority of the world’s tropical coral reefs, devastating marine
biodiversity. Most of the Great Barrier Reef will be dead.
In the highly unlikely event that global warming deniers prove to be
right, we will still have to worry about carbon dioxide, because it
dissolves in the oceans and makes them more acidic. Even with
relatively low emissions, large areas of the southern oceans and parts
of the Pacific will within a few decades become toxic to organisms
with calcium carbonate shells, for the simple reason that the acidic
seawater will dissolve them. Many species of plankton – the basis of
the marine food chain and essential for the sustenance of higher
creatures, from mackerel to baleen whales – will be wiped out, and the
more acidic seawater may be the knockout blow for what remains of the
world’s coral reefs. The oceans may become the new deserts as the
world’s temperatures reach 2C above today’s.
Two degrees may not sound like much, but it is enough to make every
European summer as hot as 2003, when 30,000 people died from
heatstroke. That means extreme summers will be much hotter still. As
Middle East-style temperatures sweep across Europe, the death toll may
reach into the hundreds of thousands. The Mediterranean area can
expect six more weeks of heatwave conditions, with wildfire risk also
growing. Water worries will be aggravated as the southern Med loses a
fifth of its rainfall, and the tourism industry could collapse as
people move north outside the zones of extreme heat.
Two degrees is also enough to cause the eventual complete melting of
the Greenland ice sheet, which would raise global sea levels by seven
metres. Much of the ice-cap disappeared 125,000 years ago, when global
temperatures were 1-2C higher than now. Because of the sheer size of
the ice sheet, no one expects this full seven metres to come before
the end of the century, but a top Nasa climate scientist, James
Hansen, is warning that the mainstream projections of sea level rise
(of 50cm or so by 2100) could be dangerously conservative. As if to
underline Hansen’s warning, the rate of ice loss from Greenland has
tripled since 2004.
This melting will also continue to affect the world’s mountain ranges,
and in Peru all the glaciers will disappear from the Andean peaks that
currently supply Lima with water. In California, the loss of snowpack
from the Sierra Nevada – three-quarters of which could disappear in
the two-degree world – will leave cities such as Los Angeles
increasingly thirsty during the summer. Global food supplies,
especially in the tropics, will also be affected but while two degrees
of warming will be survivable for most humans, a third of all species
alive today may be driven to extinction as climate change wipes out
Scientists estimate that we have at best 10 years to bring down global
carbon emissions if we are to stabilise world temperatures within two
degrees of their present levels. The impacts of two degrees warming
are bad enough, but far worse is in store if emissions continue to
rise. Most importantly, 3C may be the “tipping point” where global
warming could run out of control, leaving us powerless to intervene as
planetary temperatures soar. The centre of this predicted disaster is
the Amazon, where the tropical rainforest, which today extends over
millions of square kilometres, would burn down in a firestorm of epic
proportions. Computer model projections show worsening droughts making
Amazonian trees, which have no evolved resistance to fire, much more
susceptible to burning. Once this drying trend passes a critical
threshold, any spark could light the firestorm which destroys almost
the entire rainforest ecosystem. Once the trees have gone, desert will
appear and the carbon released by the forests’ burning will be joined
by still more from the world’s soils. This could boost global
temperatures by a further 1.5=BAC – tippping us straight into the
Three degrees alone would see increasing areas of the planet being
rendered essentially uninhabitable by drought and heat. In southern
Africa, a huge expanse centred on Botswana could see a remobilisation
of old sand dunes, much as is projected to happen earlier in the US
west. This would wipe out agriculture and drive tens of millions of
climate refugees out of the area. The same situation could also occur
in Australia, where most of the continent will now fall outside the
belts of regular rainfall.
With extreme weather continuing to bite – hurricanes may increase in
power by half a category above today’s top-level Category Five – world
food supplies will be critically endangered. This could mean hundreds
of millions – or even billions – of refugees moving out from areas of
famine and drought in the sub-tropics towards the mid-latitudes. In
Pakistan, for example, food supplies will crash as the waters of the
Indus decline to a trickle because of the melting of the Karakoram
glaciers that form the river’s source. Conflicts may erupt with
neighbouring India over water use from dams on Indus tributaries that
cross the border.
In northern Europe and the UK, summer drought will alternate with
extreme winter flooding as torrential rainstorms sweep in from the
Atlantic – perhaps bringing storm surge flooding to vulnerable
low-lying coastlines as sea levels continue to rise. Those areas still
able to grow crops and feed themselves, however, may become some of
the most valuable real estate on the planet, besieged by millions of
climate refugees from the south.
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.
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
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
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
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.
Al Gore’s Plan for the “Climate Crisis”
Ronald Bailey | March 21, 2007, 11:07am
Gleanings from Gore’s testimony before Congress.
Gore: “We face a planetary emergency. I know it sounds shrill.”
He proposed a Marshall Plan to address climate change. “We do not have
time to play around with this,” Gore declared.
(1) We should immediately freeze CO2 emission in US. Begin sharp
reductions to by 90% by 2050. [In other words, emit only 10% of CO2
that we emit today–sorry for any confusion.] Freeze it right now.
(2) I believe we should start using the tax code to reduce taxes on
production and employment and substitute pollution taxes. We’re
discouraging work and encouraging the destruction of the planet’s
habitability. We should discourage pollution while encouraging work.
Carbon pollution is not currently priced into the marketplace. I
internalize air and water and I think that the economic system should
(3) A portion of those revenues must be earmarked for lower income
groups to make this transition
(4) I’m in favor of a strong global treaty to limit greenhouse gas
emissions=97I’m in favor of Kyoto=97I fully understand as a brand it’s
been demonized. I think we should work toward de facto compliance with
Kyoto. My formal proposal is to move forward the adoption of the next
treaty to 2010, not when Kyoto expires in 2012. We have to work to get
China and India in participate in some way, to make them part of this
(5) This Congress should enact a moratorium on all new coal fired
power plants not compatible with carbon capture and sequestration.
(6) This congress should develop a Electronet=97a smart grid. We ought
to have a law, allow people to put up photovoltaic and wind generation
and sell electricity into grid without any artificial caps.
(7) Must raise CAF=C9 standards for automobile and trucks. CAF=C9 must be
part of a comprehensive package. Don’t single out cars and trucks. The
problem is cars, coal and buildings, so must address all three
(8) Set a date for banning incandescent light bulbs.
(9) Carbon neutral mortgage association (Connie Mae) The idea is that
the market doesn’t properly price energy saving technologies, e.g.,
insulation, double paned windows, and so forth, so government should
create some kind of financial instrument to pay for these energy
saving techs. He claims that they will pay for themselves.
(10) The Securities and Exchange Commission ought to require
disclosure of carbon emissions in corporate reports. Because it’s a
material risk that companies face.
In his role as a lead author, Terry Barker is presently in Bangkok for the
IPCC Working Group III Meeting which precedes the release tomorrow
of the report “Mitigation of Climate Change” for the Panel’s 4th
outline of report:
There is an overwhelming scientific consensus that the earth’s atmosphere is warming up due to the release into the atmosphere of carbon dioxide and other greenhouse gases due to human activity. The atmospheric level of carbon dioxide is now far higher than any time in the last 400 thousand years (the last 4 ice age cycles). So far, the global temperature has risen by about 0.5C against the long run average. Over the next 100 years, global temperature is likely to increase by a further 1.5 to 6C (according to the UN panel the IPCC, although the UK’s Tyndall centre believes their is a potential for even higher rises of 8C, if positive feedback is taken into account).
Such climate changes will have widespread effects across the earth.
A complex physical system such as the earth’s climate contains both negative and positive feedbacks. For small perturbations, negative feedback effects may dominate; otherwise the system would not persist at this point. However, such systems may have a ‘tipping point’ past which the positive feedback effects may overwhelm the negative feedback loops.
Various potential positive feedback systems have been identified for the earth. For example:
Human activity takes time to adjust. We need to change our methods of transport and energy production so that we emit far less CO2.
It has been estimated that the sustainable level of energy consumption is about 20% of average UK consumption and about 10% of average US consumption. This can be accomplished using a ‘personal energy quota’. (The centre for alternative technology www.cat.org.uk has further info). In particular, we need to insulate our houses well, avoid low occupancy car use, dress up warmly rather than relying excessively on heating, and particularly avoid unnecessary air travel. (E.g. see www.raileurope.co.uk). In fact, this is merely a reversal to habits of a decade or two ago, where people were not noticeably less content than they are today. The author has adopted such a ‘sustainable Carbon Dioxide quota’ without much trouble. It takes a little time to adapt habits but it is not difficult to do. Those with international jobs courses, or families would have twice the usual quota (to allow for the possibility of one intercontinental flight per person per year).
We need to lobby our governments to produce energy through methods that produce little or any carbon dioxide. For example in the UK, and the other major economies with pre-existing nuclear industries (US, Canada, Europe, Japan, Russia, India and China) the ‘baseload’ energy (75% of total) that is needed 24 hours a day can be produced by nuclear energy, as a ‘stopgap’ until renewable energy or fusion power is available. (Economical, technically advanced, efficient and safe. Arguably it is safer to have a well-funded nuclear industry with new and safe reactors rather than to have many demoralised and unemployed nuclear scientists, with poorly funded and/or derelict nuclear facilities. Nuclear reactors design has improved massively over the last decades). Wind power can be used in UK (but requires some backup for when the wind isn’t blowing such as pumped storage hydro plants). Solar energy can be harnessed in other countries without pre-existing nuclear infrastructure. Once energy production is non-CO2 emitting, cars can be converted to being run from electricity, further cutting emissions.
Finally, we need to lobby our governments (particularly in the US but globally as well) to support treaties that cut carbon dioxide emission. The European Union has pioneered an emissions trading scheme which caps total emissions and then charges for permits to emit carbon dioxide. Since low carbon technologies are immature – they can still be improved, (whereas polluting technologies have little scope for improvement)- it may be that action to change energy and transport systems will pay for itself by increasing the economy’s productive capacity.
A guaranteed minimum electricity price (indexed and time-averaged over each 5 year period, for the design life of each project) for long-term investors in carbon free (<50gCO2/kWh) electricity generation capacity.
The investment required to decarbonise the energy system (for the UK, about £10billion per year for 25 years) can help to provide for the retirement of the baby boomer generation. By guaranteeing future electricity prices, private sector investment can provide energy security and avoid war. We can eliminate taxes on working families and business investment and instead penalise coal, crude oil, and gas as they enter the country.
Methane hydrates and global warming (2005)
There is an enormous amount of methane (CH4) on earth frozen into a
type of ice called methane hydrate. Hydrates can form with almost any
gas and consist of a ‘cage’ of water molecules surrounding the gas.
(The term ‘clathrate’ more generally describes solids consisting of
gases are trapped within any kind of cage while hydrate is the
specific term for when the cage is made of water molecules). There are
CO2 hydrates on Mars, while on Earth most of the hydrates are filled
with methane. Most of these are in sediments of the ocean, but some
are associated with permafrost soils.
Methane hydrates would seem intuitively to be the most precarious of
things. Methane hydrate melts if it gets too warm, and it floats in
water. Methane is a powerful greenhouse gas, and it degrades to CO2,
another greenhouse gas which accumulates in the atmosphere just as
fossil fuel CO2 does. And there is a lot of it, possibly more than the
traditional fossil fuel deposits. Conceivably, climate changes could
affect these deposits. So what do we know of the disaster-movie
potential of the methane hydrates?
Ocean hydrates. Most of the methane hydrate is in sediments of the
ocean. Of that, most is what can be called the stratigraphic-type
deposits. Organic carbon from plankton is buried over millions of
years. Hundreds of meters below the sea floor, bacteria produce
methane from the dead plankton. If methane is produced quickly enough,
some of it will freeze into methane hydrates. This type of deposit
holds thousands of gigatons of carbon as methane [Buffett and Archer,
2004; Milkov, 2004]. For comparison, the most abundant type of
traditional fossil fuel is coal, which is typically credited with
about 5000 Gton C [Rogner, 1997].
Sometimes the methane moves around in the earth, and collects
someplace, forming what are called structural hydrate deposits. The
Gulf of Mexico, for example, is basically a leaky oil field [MacDonald
et al., 2005]. One implication of gas moving around and pooling like
this is that the hydrate concentration can be higher, even to the
point of what they call massive deposits, lumps of nearly pure
hydrate. The second bottom line is that the hydrate can be found much
closer to the sea floor, and even on the sea floor.
Hydrate melts if it gets too warm. The ocean is cold enough in a depth
range from say 500 meters down (200 meters in the Arctic). Below the
sea floor, the temperature increases with depth, along the geothermal
temperature gradient. At some depth it becomes too warm for hydrate,
so hydrate melts if it becomes buried deeper than this depth. There is
often a layer of bubbles beneath the hydrate stability zone. The
bubbles reflect seismic sound waves, and show up clearly in seismic
surveys around the world [Buffett, 2000]. Hills and valleys of the
bubble layer follow hills and valleys of the sea floor, so this layer
is called a bottom-simulating reflector (BSR).
Now let’s warm up the water at the top of the sediment column.
Ultimately, the new temperature profile will have nearly the same
slope as before, the geotherm. The hydrate stability zone will get
thinner with an increase in the sediment column temperature. The
important thing to note is that it gets thinner from the bottom, not
from the top. Hydrate at the base of the original stability zone finds
If the stability zone still exists, it will be shallower in the
sediment column than the newly released methane bubbles, and so it
could act like a cold trap to prevent the released methane gas from
escaping. However, seismic studies often show ‘wipeout zones’ where
the BSR is missing, and all of the layered structure of the sediment
column above the missing BSR is smoothed out. These are thought to be
areas where gas has broken through the structure of the sediment to
escape to the ocean [Wood et al., 2002]. One theory is that upward
migration of fluid carries with it heat, preventing the methane from
freezing as it travels through the nominal stability zone. The
sediment surface of the world’s ocean has holes in it called pockmarks
[Hill et al., 2004], interpreted to be what these gas explosions look
like from the surface.
And there is the possibility of landslides. When hydrate melts and
produces bubbles, there is an increase in volume. The idea is that the
bubbles might lift the grains off of each other, destabilizing the
sediment column. The largest submarine landslide known is off the
coast of Norway, called Storegga [Bryn et al., 2005; Mienert et al.,
2005]. The slide excavated on average the top 250 meters of sediment
over a swath hundreds of kilometers wide, stretching half-way from
Norway to Greenland. There have been comparable slides on the
Norwegian margin every approximately 100 kyr, synchronous with the
glacial cycles [Solheim et al., 2005]. The last one occurred 2-3 kyr
years after the stability zone thinned due to increasing water
temperature [Mienert et al., 2005], about 8150 years ago. The slide
started at a few hundred meters water depth, just off the continental
slope, where Mienert calculates the maximum change in HSZ. The
Storegga slide area today contains methane clathrate deposits as
indicated by a seismic BSR corresponding to the base of the HSZ at
200-300 meters, and pockmarks indicating gas expulsion from the
However, there is another also apparently plausible hypothesis for
Storegga, which doesn’t involve hydrates at all. This is the rapid
accumulation of glacial sediment shed by the Fennoscandian ice sheet
[Bryn et al., 2005]. Rapid sediment loading traps pore water in the
sediment column faster than it can be expelled by the increasing
sediment load. At some point, the sediment column floats in its own
porewater. This mechanism has the capacity to explain why the
Norwegian continental margin, of all places in the world, should have
landslides synchronous with climate change.
The Storegga slide generated a tsunami in what is now the United
Kingdom, but it does not appear to have had any climate connections.
It was not a catastrophic amount of methane loss. The volume of
sediment moved was about 2500 km3. Assuming 1% hydrate by pore water
volume were released on average from the slide volume, you get a
methane release of about 0.8 Gton of C. Even if all of the hydrate
made it to the atmosphere, it would have had a smaller climate impact
than a volcanic eruption (I calculated the methane impact on the
radiative budget here). Actually, the truth be told, the Storegga
slide occurred spookily close in time to the 8.2k climate event, but
there doesn’t appear to be any connection. The 8.2k event was a
century-long cool interval, most probably in response to fresh-water
release from Glacial Lake Aggasiz to the North Atlantic and was
coincident with a ~75 ppbv drop in methane, not a rise.
Methane can leave the sediment in three possible forms: dissolved,
bubbles, and hydrate. Dissolved methane is chemically unstable in the
oxic water column of the ocean, but it has a lifetime of decades
(shorter in high-flux environments) [Valentine et al., 2001], so if
the methane is released shallow enough in the ocean, it has a good
chance of escaping to the atmosphere. Bubbles of methane are typically
only able to rise a few hundred meters before they dissolve. Hydrate
floats in water just like regular ice floats in water, carrying
methane to the atmosphere much more efficiently than bubbles [Brewer
et al., 2002].
For most parts of the ocean, melting of hydrates is a slow process. It
takes decades to centuries to warm up the water 1000 meters down in
the ocean, and centuries more to diffuse that heat down into the
sediment where the base of the stability zone is. The Arctic Ocean may
be a special case, because of the shallower stability zone due to the
colder water column, and because warming is expected to be more
intense in high latitudes.
Permafrost. You’ve maybe read about permafrost in the paper a lot
lately. Permafrost soils are defined as those which remain frozen
year-round (actually, the technical definition is a soil which has
been frozen for the last two years). There is sometimes a zone near
the sediment surface that thaws in the summer. In the permafrost
literature, this zone is called the active zone, and it has been
observed to be getting larger with time [Sazonova et al., 2004].
Melting of surface soils is one reason why the high latitude Arctic is
expected to be a part of the land surface that responds most
dramatically to climate change [Bala et al., 2005]. The other reason
is that temperature changes are more dramatic in high latitudes than
the global average, especially high northern latitudes. There has been
a stream of anecdotal reports of the effects of melting permafrosts on
the Arctic landscape, tilted buildings and “drunken forests” near
Fairbanks, for example [Pearce, 2005; Stockstad, 2004]. Much of the
Alaskan oil pipeline is anchored in permafrost soils.
Hydrates are sometimes associated with permafrost deposits, but not
too close to the soil surface, because of the requirement for high
pressure. The other factor that determines whether you find hydrate is
the permeability of the soils. Sometimes freezing, flowing groundwater
creates a sealed ice layer in the soil, which can elevate the pressure
in the pore space below. Hydrate in a one permafrost core [Dallimore
and Collett, 1995] was reported below sealed ice layers. Lakes have
been reported to suddenly drain away as some subsurface sealed ice
layer is apparently breached.
The grand-daddy of subsurface sealed ice layers is a very large
structure in Siberia called the ice complex [Hubberten and
Romanovskii, 2001]. The most important means of eroding the ice
complex is laterally, by a melt-erosion process called thermokarst
erosion [Gavrilov et al., 2003]. The ice layer is exposed to the
warming waters of the ocean. As the ice melts, the land collapses,
exposing more ice. The northern coast of Siberia has been eroding for
thousands of years, but rates are accelerating. Entire islands have
disappeared in historical time [Romankevich, 1984]. Concentrations of
dissolved methane on the Siberian shelf reached 25 times higher than
atmospheric saturation, indicating escape of methane from coastal
erosion into the atmosphere [Shakhova et al., 2005]. Total amounts of
methane hydrate in permafrost soils are very poorly known, with
estimates ranging from 7.5 to 400 Gton C (estimates compiled by
[Gornitz and Fung, 1994]).
The Future. The juiciest disaster-movie scenario would be a release of
enough methane to significantly change the atmospheric concentration,
on a time scale that is fast compared with the lifetime of methane.
This would generate a spike in methane concentration. For a scale of
how much would be a large methane release, the amount of methane that
would be required to equal the radiative forcing of doubled CO2 would
be about ten times the present methane concentration. That would be
disaster movie. Or, the difference between the worst case IPCC
scenario and the best conceivable ‘alternative scenario’ by 2050 is
only about 1 W/m2 mean radiative energy imbalance. A radiative forcing
on that order from methane would probably make it impossible to remain
below a ‘dangerous’ level of 2 deg above pre-industrial. I calculate
here that it would take about 6 ppm of methane to get 1 W/m2 over
present-day. A methane concentration of 6 ppm would be a disaster in
the real world.
The atmosphere currently contains about 3.5 Gton C as methane. An
instantaneous release of 10 Gton C would kick us up past 6 ppm. This
is probably an order of magnitude larger than any of the catastrophes
that anyone has proposed. Landslides release maybe a gigaton and
pockmark explosions considerably less. Permafrost hydrates are
melting, but no one thinks they are going to explode all at once.
There is an event documented in sediments from 55 million years ago
called the Paleocene Eocene Thermal Maximum, during which (allegedly)
several thousand Gton C of methane was released to the atmosphere and
ocean, driving 5 degrees C warming of the intermediate depth ocean. It
is not easy to constrain how quickly things happen so long ago, but
the best guess is that the methane was released over perhaps a
thousand years, i.e. not catastrophically [Zachos et al., 2001;
Schmidt and Shindell, 2003].
The other possibility for our future is an increase in the year-in,
year-out chronic rate of methane emission to the atmosphere. The
ongoing release of methane is what supplies, and determines the
concentration of, the ongoing concentration of methane in the
atmosphere. Double the source, and you’d double the concentration,
more or less. (A little more, actually, because the methane lifetime
increases.) The methane is oxidized to CO2, another greenhouse gas
that accumulates for hundreds of thousands of years, same as fossil
fuel CO2 does. Models of chronic methane release often show that the
accumulating CO2 contributes as much to warming as does the transient
Anthropogenic methane sources, such as rice paddies, the fossil fuel
industry, and livestock, have already more than doubled the methane
concentration in the atmosphere from pre-industrial levels. Currently
methane levels appear stable, but the reasons for this relatively
recent phenomena are not yet clear. The amount of permafrost hydrate
methane is not known very well, but it would not take too much
methane, say 60 Gton C released over 100 years, to double atmospheric
methane yet again. Peat deposits may be a comparable methane source to
melting permafrost hydrate. When peat that has been frozen for
thousands of years thaws, it still contains viable populations of
methanotrophic bacteria [Rivkina et al., 2004] that begin to convert
the peat into CO2 and CH4. It’s not too difficult to imagine 60 Gton C
over 100 years from peat, either. Changes in methane production in
existing wetlands and swamps due to changes in rainfall and
temperature could also be important. Ocean hydrates have also been
forecast to melt, but only slowly [Harvey and Huang, 1995]. Places to
watch would seem to be the Arctic and the Gulf of Mexico.
So, in the end, not an obvious disaster-movie plot, but a potential
positive feedback that could turn out to be the difference between
success and failure in avoiding ‘dangerous’ anthropogenic climate
change. That’s scary enough.
I have submitted a more detailed review of hydrates and climate change
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