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Global warming warning
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A landmark report says scientists are 95% certain that humans are the "dominant cause" of global warming since the 1950's the UN's climate panel details the physical evidence behind climate change.

On the ground, in the air, in the oceans, global warming is "unequivocal", it explained.

It adds that a pause in warming over the past 15 years is too short to reflect long-term trends.

The panel warns that continued emissions of greenhouse gases will cause further warming and changes in all aspects of the climate system. Stocker says to limit climate change will require substantial and sustained reductions of greenhouse gases. Finishes to applause.Very simple statement says Dr stocker, human influence on the climate system is clear, adopted by 110 governments by consensus not about headlines, but scientific assessment says Dr Thomas Stocker, wg1 co chair Wg1 co chair Thomas Stocker giving presentation on the new summary. Says he's slept only six hours in the last two days!

To contain these changes will require "substantial and sustained reductions of greenhouse gas emissions".

After a week of intense negotiations in the Swedish capital, the summary for policymakers on the physical science of global warming has finally been released.

The first part of an IPCC trilogy, due over the next 12 months, this dense, 36-page document is considered the most comprehensive statement on our understanding of the mechanics of a warming planet.

It states baldly that, since the 1950s, many of the observed changes in the climate system are "unprecedented over decades to millennia".

Each of the last three decades has been successively warmer at the Earth's surface, and warmer than any period since 1850, and probably warmer than any time in the past 1,400 years.

"Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and that concentrations of greenhouse gases have increased," said Qin Dahe, co-chair of IPCC working group one, who produced the report.

Speaking at a news conference in the Swedish capital, Prof Thomas Stocker, another co-chair, said that climate change "challenges the two primary resources of humans and ecosystems, land and water. In short, it threatens our planet, our only home".

Since 1950, the report's authors say, humanity is clearly responsible for more than half of the observed increase in temperatures.

But a so-called pause in the increase in temperatures in the period since 1998 is downplayed in the report. The scientists point out that this period began with a very hot El Nino year.

What is the IPCC?

In its own words, the IPCC is there "to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts".

The offspring of two UN bodies, the World Meteorological Organization and the United Nations Environment Programme, it has issued four heavyweight assessment reports to date on the state of the climate.

These are commissioned by the governments of 195 countries, essentially the entire world. These reports are critical in informing the climate policies adopted by these governments.

The IPCC itself is a small organisation, run from Geneva with a full time staff of 12. All the scientists who are involved with it do so on a voluntary basis.

"Trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends," the report says.

Prof Stocker, added: "I'm afraid there is not a lot of public literature that allows us to delve deeper at the required depth of this emerging scientific question.

"For example, there are not sufficient observations of the uptake of heat, particularly into the deep ocean, that would be one of the possible mechanisms to explain this warming hiatus."

"Likewise we have insufficient data to adequately assess the forcing over the last 10-15 years to establish a relationship between the causes of the warming."

However, the report does alter a key figure from the 2007 study. The temperature range given for a doubling of CO2 in the atmosphere, called equilibrium climate sensitivity, was 2.0C to 4.5C in that report.

In the latest document, the range has been changed to 1.5C to 4.5C. The scientists say this reflects improved understanding, better temperature records and new estimates for the factors driving up temperatures.

In the summary for policymakers, the scientists say that sea level rise will proceed at a faster rate than we have experienced over the past 40 years. Waters are expected to rise, the document says, by between 26cm (at the low end) and 82cm (at the high end), depending on the greenhouse emissions path this century.

The scientists say ocean warming dominates the increase in energy stored in the climate system, accounting for 90% of energy accumulated between 1971 and 2010.

For the future, the report states that warming is projected to continue under all scenarios and is likely to exceed 1.5C by 2100.

"We have found in our assessment analysing these model simulation[s] that global surface temperature change for the end of the 21st Century is likely to exceed 1.5 degrees Celsius relative to 1850 for all scenarios. This is a statement that is adopted by the governments of the world," Prof Stocker told reporters.

Prof Sir Brian Hoskins, from Imperial College London, "We are performing a very dangerous experiment with our planet, and I don't want my grandchildren to suffer the consequences of that experiment."

 
Fusion future plans
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The world's largest bid to harness the power of fusion has entered a "critical" phase in southern France.

The Iter project at Cadarache in Provence is receiving the first of about one million components for its experimental reactor.

Dogged by massive cost rises and long delays, building work is currently nearly two years behind schedule.

The construction of the key building has even been altered to allow for the late delivery of key components.

"We're not hiding anything - it's incredibly frustrating," David Campbell, a deputy director, told BBC News.

"Now we're doing everything we can to recover as much time as possible.

"The project is inspiring enough to give you the energy to carry on - we'd all like to see fusion energy as soon as possible."

 

Fusion facts

 
  • Fusion is the process that powers the stars including the Sun
  • One litre of water contains enough deuterium, when fused with tritium, to produce the equivalent energy of 500 litres of petrol
  • A 1,500MW fusion power station would consume about 600g of tritium and 400g of deuterium a day
  • The first large-scale use of fusion was by the US military with the detonation of Ivy Mike, a hydrogen bomb, on 1 November 1952.
  • Iter's design involves a tokamak, the Russian word for a ring-shaped magnetic chamber
  • The magnetic field is designed to contain 100 million degree plasma, the temperature required for the fusion process
  • The US, while supporting Iter as a partner, is also funding the National Ignition Facility, which uses lasers to heat and compress hydrogen to the point of fusion
  • South Korea, another Iter partner, is investing $941m in a fusion technology demonstrator, K-DEMO, which could be the first to generate Grid power
  • Critics object to further research into nuclear power and question the likely costs of commercial operations

 

After initial design problems and early difficulties co-ordinating this unique international project, there is now more confidence about the timetable.

Since the 1950s, fusion has offered the dream of almost limitless energy - copying the fireball process that powers the Sun - fuelled by two readily available forms of hydrogen.  

The attraction is a combination of cheap fuel, relatively little radioactive waste and no emissions of greenhouse gases. 

But the technical challenges of not only handling such an extreme process but also designing ways of extracting energy from it have always been immense. 

In fact, fusion has long been described as so difficult to achieve that it's always been touted as being "30 years away".

Now the Iter reactor will put that to the test. Known as a "tokamak", it is based on the design of Jet, a European pilot project at Culham in Oxfordshire.

It will involve creating a plasma of superheated gas reaching temperatures of more than 200 million C - conditions hot enough to force deuterium and tritium atoms to fuse together and release energy.  

The whole process will take place inside a giant magnetic field in the shape of a ring - the only way such extreme heat can be contained.  

The plant at JET has managed to achieve fusion reactions in very short bursts but required the use of more power than it was able to produce.  

The reactor at Iter is on a much larger scale and is designed to generate 10 times more power - 500 MW - than it will consume.

France's fusion reactor would work like the sun

Iter brings together the scientific and political weight of governments representing more than half the world's population - including the European Union, which is supporting nearly half the cost of the project, together with China, India, Japan, Russia, South Korea and the United States.

Contributions are mainly "in kind" rather than in cash with, for example, the EU providing all the buildings and infrastructure - which is why an exact figure for cost is not available. The rough overall budget is described as £13bn or 15bn euros.

But the novel structure of Iter has itself caused friction and delays, especially in the early days.  

Each partner first had to set up a domestic "agency" to handle the procurement of components within each member country, and there have been complications with import duties and taxes.  

Further delay crept in with disputes over access to manufacturing sites in partner countries. Because each part has to meet extremely high specifications, inspectors from Iter and the French nuclear authorities have had to negotiate visits to companies not used to outside scrutiny.

The result is that although a timeline for the delivery of the key elements has been agreed, there's a recognition that more hold-ups are almost inevitable.   

The main building to house the tokamak has been adjusted to leave gaps in its sides so that late components can be added without too much disruption.

The route from the ports to the construction site has had to be improved to handle huge components weighing up to 600 tonnes, but this work too has been slower than hoped. A trial convoy originally scheduled for last January has slipped to this coming September.

Under an initial plan, it had once been hoped to achieve the first plasma by the middle of the last decade.

Then, after a redesign, a new deadline of November 2020 was set but that too is now in doubt. Managers say they are doubling shifts to accelerate the pace of construction. It's thought that even a start date during 2021 may be challenging.

The man in charge of coordinating the assembly of the reactor is Ken Blackler.

"We've now started for real," he told me. "Industrial manufacturing is now under way so the timescale is much more certain - many technical challenges have been solved.

"But Iter is incredibly complicated. The pieces are being made all around the world - they'll be shipped here.

"We'll have to orchestrate their arrival and build them step by step so everything will have to arrive in the right order - it's really a critical point."

Command and control

While one major concern is the arrival sequence of major components, another is that the components themselves are of sufficiently high quality for the system to function.

The 28 magnets that will create the field containing the plasma have to be machined to a very demanding level of accuracy. And each part must be structurally sound and then welded together to ensure a totally tight vacuum - without which the plasma cannot be maintained. A single fault or weakness could jeopardise the entire project. 

Assuming Iter does succeed in proving that fusion can produce more power than it consumes, the next step will be for the international partners to follow up with a technology demonstration project - a test-bed for the components and systems needed for a commercial reactor.  

Ironically, the greater the progress, the more apparent becomes the scale of the challenge of devising a fusion reactor that will be ready for market.

At a conference in Belgium last September, I asked a panel of experts when the first commercially-available fusion reactor might generate power for the grid. 

A few said that could happen within 40 years but most said it would take another 50 or even 60 years. The fusion dream has never been worked on so vigorously. But turning it into reality is much more than 30 years away.

 
Fusion still the magic bullet
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In the era of global climate change, and concerns about humanity's long-term reliance on fossil fuels, many think the solution lies in alternative sources of energy, including nuclear power. All our nuclear power plants are based on fission: splitting heavy atoms into lighter components in a controlled fashion. Though fission is safe when all goes well, the fuel is radioactive, waste disposal can be problematic, and as the Fukushima disaster showed there is a high cost to accidents.

Nuclear fusion is in principle cleaner and comes from a cheaper, more abundant fuel source: an isotope of hydrogen called deuterium can be extracted from water and only helium is produced as waste. From The Matrix to SimCity 2000 to political dreamers, fusion has often been seen as an inevitability for society. However, despite decades of work nuclear fusion remains a dream. As the joke goes fusion is the power of the future – and always will be.

That's not because creating a sustained fusion reaction – in which more energy is produced than is required to start and maintain the process – is impossible or even terribly hard to achieve (at least by high-energy particle physics standards). The most infamous example of a fusion reaction is the hydrogen bomb, which sacrificed control and safety for the sake of violence and death. Fusion reactors obviously need to have more stringent requirements.

Cosmic collider

To see what's needed to create a sustained reaction, let's look to the best-known fusion reactors of all: stars. In the core of a star like the Sun, strong gravitational pressure forces together hydrogen plasma – an equal mixture of protons and electrons. Extreme conditions of 15 million-degree-temperatures and high pressures mean that protons have enough energy to overcome their mutual repulsion for each other, allowing the attractive forces to kick in. When protons fuse together they are converted into neutrons and release a lot of energy.

Bluntly stated, we can't recreate those conditions, even if we wanted to. Stars have a sufficiently large mass to contain the hydrogen plasma by the force of gravity alone, but we don't have that option, so physicists have to confine plasma using electromagnetism instead. Researchers can also start with deuterium or tritium plasma instead of hydrogen to lower the energy required to start fusion. (Tritium is a hydrogen isotope consisting of a proton and two neutrons; unlike normal hydrogen and deuterium, it's unstable and therefore harder to keep around.) However, the temperature and pressure still needs to be high, so it requires a larger energy input than fusion liberates, which defeats the purpose.

Part of the difficulty lies in the nature of plasma. If you put a normal neutral gas, such as oxygen, in a container you can increase both pressure and temperature by compressing it. Plasma, on the other hand, consists of charged particles at sufficiently high temperatures to melt the container walls. Also, without maintaining conditions carefully, the electrons tend to reunite with protons, creating a neutral hydrogen gas that's useless for fusion; it's imperative that the container trapping the plasma contain no gas, for similar reasons.

Some hope lies in using elements other than hydrogen, as these contain more than one proton per nucleus. That increases the electric repulsion and in some cases can make the energy barrier to fusion even higher. While some fusion reactions involving helium, lithium, or boron are areas of active research, a major problem is that these materials are far rarer on Earth than hydrogen.

Hot doughnuts

All is not lost, however. Researchers are pursuing several possible solutions to the fusion problem, mostly based on clever methods for confining or compressing deuterium. The oldest of these is magnetic confinement, in which strong magnetic fields act as the “walls” of a container.

The best-known incarnation of this is the tokamak, first built in the Soviet Union in the 1950s. In a tokamak, deuterium and tritium are injected into a doughnut, or torus-shaped chamber, and heated to the point at which its electrons break free. Magnetic fields running along the centre contain and squeeze the plasma, and the high temperatures within the plasma then facilitate fusion. However, even the best tokamak designs – including the Joint European Torus (JET) in the United Kingdom and the Tokamak Fusion Test Reactor (TFTR) in the United States – haven't broken the barrier of making more energy than is required to keep the plasma hot and trapped. Much hope is being placed on Iter (International Thermonuclear Experimental Reactor), a €15 billion ($22 billion) project designed to build the world’s largest tokamak in the south of France. Iter is expected to commence operation at the end of this decade, with the first proper fusion tests scheduled for 2028. But it has been dogged by logistical issues – last month the US Senate spending panel voted to stop contributions to the project.

Many think another method called inertial confinement provides the best hope for a workable fusion reactor. This uses bombardment by high-energy photons – X-rays – to confine and compress a pellet of hydrogen and its isotopes. Successive X-ray pulses emanate from a large number of lasers completely surrounding the pellet, doing the work of heating, ionising, and compressing the hydrogen to the point where it can fuse. The biggest barrier to a working model lies in the X-ray lasers, which require a lot of energy to operate, but researchers at laboratories such as SLAC in the United States and the European X-ray Free Electron Laser are actively working to solve the problem.

The Z Machine at Sandia National Laboratory in the United States is a hybrid between magnetic and inertial confinement. Though the Z Machine itself is not a fusion reactor (and in fact is partly used for developing models for nuclear weapons), the powerful magnetic fields and X-rays it produces are part of a project in which a pellet of hydrogen is repeatedly bombarded with intense pulses of light to compress it.

There are other methods for confinement and compression, and more will no doubt be developed. Another path is aimed at lowering the energy barrier to deuterium fusion: forming molecules using muons instead of electrons. Muons are the heavier, unstable cousins of electrons. (We all have family members like that, I think.) Their presence in a molecule of two deuterium atoms brings the nuclei much closer together, consequently making fusion much more likely. However, once the energy cost of making muons and creating molecules using them is added in, muon-catalysed fusion no longer becomes cost-effective.

So the question is will we find a way around any of these problems? As with many things, it depends on human scientific ingenuity, and the practical limits placed upon it. Fusion research is relatively expensive, so investing in it is an exercise in hope. More precisely it is hope that once a sustainable fusion reactor is invented, it will repay the investment many times over.

 
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