The UK Climate Change Bill: Introduction from Defra

Introduction

The UK Government is committed to addressing both the causes and consequences of climate change and has published its proposals for a Climate Change Bill. We are consulting widely – with a closing date for comments of 12 June 2007.

Our objective is to ensure that all interested parties have the opportunity to contribute their opinions at an early stage of policy development. We are asking important questions about the shape of our policy proposals and what issues we should take into account, when developing the Climate Change Bill.

Comment on the draft Bill

Other documents

Several other documents have been published alongside the draft Bill as follows:

Background

The debate on climate change has shifted from whether we need to act to how much we need to do by when, and the economic implications of doing so. The time is therefore right for the introduction of a strong legal framework in the UK for tackling climate change. The draft Climate Change Bill is the first of its kind in any country.

The proposed Bill provides a clear, credible, long-term framework for the UK to achieve its goals of reducing carbon dioxide emissions and will ensure that steps are taken towards adapting to the impacts of climate change.

Key provisions of the Bill

Targets

  • This Bill puts into statute the UK’s targets to reduce carbon dioxide emissions through domestic and international action by 60% by 2050 and 26-32% by 2020, against a 1990 baseline.
  • Five-year carbon budgets, which will require the Government to set, in secondary legislation, binding limits on carbon dioxide emissions during five year budget periods, beginning with the period 2008-12. Three successive carbon budgets (representing 15 years) will always be in legislation.
  • Emission reductions purchased overseas may be counted towards the UK’s targets, consistent with the UK’s international obligations. This ensures emission reductions can be achieved in the most cost effective way, recognising the potential for investing in low carbon technologies abroad as well as action within the UK to reduce the UK’s overall carbon footprint.

Committee on Climate Change

  • A Committee on Climate Change will be set up as an independent statutory body to advise the Government on the pathway to the 2050 target and to advise specifically on: the level of carbon budgets; reduction effort needed by sectors of the economy covered by trading schemes, and other sectors; and on the optimum balance between domestic action and international trading in carbon allowances.
  • It will take into account a range of factors including environmental, technological, economic, fiscal, social and international factors, as well as energy policy, when giving its advice.

Enabling Powers

  • The Bill contains enabling powers to introduce new trading schemes through secondary legislation. This increases the policy options which Government could use to stay within budgets and meet emissions targets.

Reporting requirements

  • The Committee on Climate Change will have a specific role in reporting annually to Parliament on the UK’s progress towards achieving its targets and budgets. The Government will be required to lay before Parliament a response to this annual progress report.
  • Every five years, the Committee’s report will contain an explicit review of the UK’s performance over the last budget period, and the implications of this for keeping on track to meet future targets and budgets.

Reporting Progress on Adaptation

  • The Bill will also allow Parliament to monitor the Government’s proposals and policies for integrating adaptation to climate change into its work by establishing regular reporting to Parliament.

Consultation

It is right that It is right that the public, Parliament and a wide range of interested organisations have an opportunity to discuss and debate these proposals – as climate change is an issue which affects us all and this Bill is intended to create a framework that lasts for more than a generation. The Government therefore looks forward to receiving a wide range of views on its proposals.

The consultation document discusses the context and rationale behind the draft Climate Change Bill and sets out the main reasons why the UK Government considers legislation in this area is required. It outlines the background to and the proposed contents of the draft Bill, summarising its key elements and how they are expected to fit together.

Regulatory Impact Assessment

As part of this consultation a partial Regulatory Impact Assessment has been produced and provides initial assessments on the impact of the proposals in the draft Bill.

Strategy

The strategy document, published alongside the Bill, sets out the broader context for the Bill. It highlights some key announcements coming up in the next few weeks and months. And it gives the broader international context, where the UK will continue to press for action through the EU, the G8 and the UN.

Related information

Key material

What is Climate Change and What Can Be Done About it?

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.

For example:

  • There will be increased frequency of heat waves and droughts in already hot or dry areas. This may precipitate famine and conflict over scarce water supplies.
  • Hurricanes and other violent weather will increase in intensity. The 2005 Hurricane season was the most destructive on record with the greatest number of storms ever recorded.
  • Large parts of marginal semi-desert will turn into desert. In particular, much of the area directly south of the Sahara will be swallowed by the desert. Much of the Mediterranean (Spain, Italy, Greece) may become desert.
  • Sea levels will rise. Whilst this is a fairly slow process, once one of the various polar ice sheets starts to melt, it is difficult to arrest the process, since sea/rock absorbs more solar energy than white ice. The melting of the Greenland or west Antarctic ice sheets would each raise the sea level by 6.5m each (13m in total), drowning many islands and costal towns. If the East Antarctic ice sheet melted, the rise would be 84m. Melting in the ice sheets has recently accelerated.
  • The flow of cold melt water from the Arctic may interrupt the ‘gulf stream’ part of the heat conveyor that transports energy from the tropics to temperate areas. This will cause Europe and in particular NorthWest Europe to become locally much colder (perhaps 5C), and maybe to have a climate more similar to Newfoundland, Canada.
  • Tropical regions such as West Africa may become even warmer. In the last few months there has been evidence that the flow of the Gulf Stream may be as much as 30% less than previously.
  • There will be widespread changes in ecosystems including the collapse of the coral reefs (probably inevitable even with moderate climate change).
  • Increased disease frequency as e.g. malaria spreads to other areas.

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:

  • The melting of ice leads to a change in the colour of the earth’s surface from a reflective white, to black, which absorbs more heat.
  • Global warming may cause the collapse of rainforest ecosystems already ravaged by deforestation, releasing much stored CO2.
  • There are huge stores of Methane (a greenhouse gas) Siberia in permafrost. This permafrost may melt. (Recently scientists have seen that this may have started to happen).
  • Whilst moderate climate change (e.g. 1C) therefore may be counteracted by various natural systems, large climate change (>2C) may well be dangerous. It is clear that humans need to avoid highly polluting behaviour until and unless it is known with certainty that these effects are safe. If anything, the scientific evidence at present points to the reality of many of the proposed changes.

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.

The Case for a Zero Carbon Society

The government wants to get our emissions down to from 10 to 4 tonnes
of CO2 per person per year. But 4 tonnes CO2 per person per year is
the CURRENT global average of CO2 from fossil fuel alone…

Where the UK hopes to be in 2050, even if adopted by everyone, would
not reduce global emissions (and certainly not get them to a safe
level).

To keep global warming below 2 degrees, We need 1 tonne per person per
year (by 2030 if possible, but certainly before 2050). (See “how much
CO2 can we emit” attachment)

Anything above 2 degrees and we hit tipping points and we have a mass
extinction event (of plants, animals and the poor). (See “Six degrees
“attachment).

*We need a national campaign for 1 tonne per person per year, a 90% reduction on 1990 levels.

This can be achieved while maintaining a healthy and vibrant low-carbon economy.

China pollution fuelled by heavy industry

China pollution fuelled by heavy industry
By Richard McGregor in Beijing

China’s rapidly worsening pollution is being driven by a surge in
investment in energy-intensive heavy industry caused by cut-throat
competition among cities and provinces, according to a study released
Tuesday.
The study, by the Peterson Institute for International Economics in
Washington, says the huge investment in steel, aluminium, cement and
other plant has begun to reverse almost three decades of gains in
energy efficiency.

“It is not air-conditioners and automobiles that are driving China’s
energy demand but rather heavy industry,” say Daniel Rosen and Trevor
Houser of China Strategic Advisory, the authors. “Consumption-led
demand is China’s future energy challenge.”
China’s huge growth has made its economy a global issue because of
rising exports of steel, in particular, and the impact on
inter=ADnational markets for related commodities.
Greenhouse gases are also under scrutiny; the Inter=ADnational Energy
Agency predicts China could surpass the US as early as this year as
the largest emitter of CO2, a figure Beijing disputes.
Chinese leaders have set tough new targets to reduce the use of energy
per unit of economic output by 20 per cent and pollution by 10 per
cent, between 2006 and 2010. But the rise of heavy industry, which the
study says caught even Beijing by surprise, means China failed to meet
the benchmarks in 2006 and will find it hard to do so by the end of
the decade.
China now accounts for almost half of the world’s flat glass and
cement production, more than a third of steel output and 28 per cent
of aluminium. Heavy industry consumes 54 per cent of China’s energy,
up from 39 per cent five years ago.
A structural bias towards heavy industry, which dominated in the
centrally planned Maoist-era economy, means energy intensity has
worsened even though Chinese steel plants have become more efficient.
“A new steel plant, no matter how much more efficient than its peers,
uses substantially more energy than a garment factory,” the study
says.
The study blames the growth of heavy industry on cut-throat internal
competition. “The rules of competition are set not just by Beijing but
also by local interests, including state-owned heavy industrial
enterprises,” it says. “And regardless of who sets the rules, the
reality of how they are implemented is almost entirely a local
matter.”
The National Reform and Development Commission, the economic planning
agency also responsible for energy, has tried for years to curb
industrial expansion.
Although nominally all-powerful and with the right to stop projects
over a certain size on a range of grounds, the commission has been
largely helpless to stop the flood of new investment.
The commission’s power is not reflected in the size or skill of its
staff or in the research base and industry expertise from which it
operates. Its energy bureau has 100 staff and the State Energy Office
under the cabinet 30-40, in contrast to 110,000 at the US Department
of Energy.
Individual state companies are better equipped than the ministries.
The State Grid, which is responsible for power transmission, has more
research staff than the commission’s energy bureau.
Weak regulation also makes it difficult to cut pollution and
greenhouse gas emissions. Fewer than 15 per cent of coal-fired plants,
which generate 80 per cent of China’s electricity, have systems to
remove sulphur dioxide from emissions, and even fewer use them, the
report says. Most new plants have sulphur scrubbers.
The authors say that China will not make unilateral adjustments in the
absence of changes to US policy. “China is an 800lb gorilla on the
world energy stage that cannot be ignored, but there is a 1,600lb
gorilla in this room too: the US,” they said.

Biofuels Are Not the Answer

By Tim Joslin
Full Article (pdf)

The threat of global warming has led governments around the world to encourage the use of biofuel, in particular in the transport sector, in the hope of displacing fossil fuel. The UK, following an EU Biofuels Directive, is introducing a Road Transport Fuel Obligation (RTFO), requiring fuel providers to ensure that 5% of their total road transport fuel sales “is made up of fuels from renewable sources” by 2010.

It is already well-known, through the efforts of, in particular, George Monbiot, that a large-scale diversion of agricultural land to the production of biofuel will set up competition between food and fuel, between people and cars. Vast tracts of rainforest are already being cleared to create more land on which to grow biofuel crops, such as oil palm. Governments may argue that they can manage these problems, whilst continuing to promote biofuel use. This is doubtful.

But there are even more fundamental arguments against biofuels. This paper shows that the use of biofuel to supplement fossil fuel for vehicle transport is not only disastrous in practice, it is also flawed even on its own terms, in two distinct ways:

  1. plant-growth on land is one of the main ways in which CO2 is removed from the atmosphere. Land is therefore a resource in the fight against global-warming. Even under optimistic assumptions, growing biofuel crops will not reduce atmospheric levels of CO2 over any timescale of up to more than a century, compared to preventing deforestation or even simply leaving already cleared land alone and allowing natural plant growth to capture carbon.
  2. we know that within a few decades we must dramatically reduce our reliance on fossil-fuels, especially in the transport sector, where capturing and sequestering carbon emissions would be very expensive. In terms of achieving this objective, the use of biofuel is counter-productive. Instead of encouraging investment in energy supplies that are renewable for the long-term, measures such as the RTFO incentivise businesses and individuals to make further investments in technology for burning fossil fuels. Government should instead encourage a technological path from hybrid cars, through plug-in hybrids, to electric cars. Instead of continuing to burn carbon, our future transport energy needs can be met by the generation of electricity using true renewable and/or nuclear technologies.

Biofuels are not the answer.

Full Article (pdf)

Benefits of zero carbon

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: from real climate (2005)

http://www.realclimate.org/index.php?p=227

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
itself melting.

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
sediment.

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
methane concentration.

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
for peer review and publication, which can be accessed here.

Bala, G., K. Caldeira, A. Mirin, M. Wickett, and C. Delira,
Multicentury changes to the global climate and carbon cycle: Results
from a coupled climate and carbon cycle model, Journal of Climate, 18,
4531-4544, 2005.
Brewer, P.G., C. Paull, E.T. Peltzer, W. Ussler, G. Rehder, and G.
Friederich, Measurements of the fate of gas hydrates during transit
through the ocean water column, Geophysical Research Letters, 29 (22),
2002.
Bryn, P., K. Berg, C.F. Forsberg, A. Solheim, and T.J. Kvalstad,
Explaining the Storegga Slide, Marine and Petroleum Geology, 22 (1-2),
11-19, 2005.

Buffett, B., and D.E. Archer, Global inventory of methane clathrate:
Sensitivity to changes in environmental conditions, Earth and
Planetary Science Letters, 227, 185-199, 2004.
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