BT’s wind farm proposals

BT uses over half of 1% of the UK’s electricity and is the single largest purchaser of green electricity in the UK. It buys over 10% of the country’s total supply of renewable electricity. It now seeks to develop wind turbines on some of its own sites. It intends to invest in about 120 2MW turbines to produce about a quarter of its own electricity or between 0.1 and 0.2% of the UK’s total need. This is an impressively large plan. The cost is about £250m. The financial return will depend on how much of the electricity replaces power BT would have bought from other suppliers and how much is ‘exported’. Assuming very little is used by BT itself, the return will be approximately £50m a year, yielding a return of about 20% on the initial investment. These figures assume that BT gets a yield of about 28% of the rated capacity of the turbines, which is about the UK average.

These figures depend entirely on finding sites. I think that BT may well have substantial difficulties finding as many 120 places where it can capture enough wind to average 28%. Perhaps more importantly, at many of those sites which do have enough wind, I think it will have problems getting connections to the local distribution network. Two of the three initial sites identified by BT are in the Scottish Islands. Although a typical 2MW turbine is not a huge generator to add to the local network, the islands have quite limited electricity needs. Scottish and Southern may not easily be able to add these turbines to their network.

When I asked BT whether it had approached the local distribution companies to check on this point, I was not given an affirmative answer. This raises the possibility that BT announced these plans before detailed consideration of whether its aspirations are technically feasible. So it may be a great idea to erest wind turbines, but it looks like it will be much more difficult than BT realises. Companies like Ecotricity have been developing wind turbines on industrial sites for years. Though planning permission is easier, there are still huge obstacles to overcome. BT needs Ecotricity's expertise immediately, but it will still struggle to meet its aspirations to grow its wind power capacity.

E.ON and tidal stream technology

It is adventurous of E.ON to decide to invest in tidal stream generator farm. The announcement in the last few days confirmed that the company intended to put a tidal plant off the coast of Wales in a partnership with Lunar Energy. The Severn barrage scheme (see Carbon Commentary Newsletter #3) is a ‘tidal range’ scheme. The electricity is generated by damming the river at high tide and then letting the water flow out through turbines as the tide falls. Tidal stream technology captures the energy of the tide as it flows through constricted channels. The UK has many potential sites for tidal stream power stations, but the best locations are off the north coast of Scotland and around Alderney in the Channel Islands.

Why then has E.ON chosen Wales? Perhaps the company doesn’t want to test the technology in the toughest conditions. An attempt to use similar underwater turbines in New York’s East River has been frustrated by the breaking off of the tips of the turbine blades in the fast flowing tides. The UK’s offshore conditions will be far tougher. Or it might be that E.ON knows that it would be expensive or impossible to connect the turbines to the distribution grid in the locations of highest energy potential (see the news story in this section on BT’s plans for wind turbines in Orkney and Shetland). Previous rumours have suggested that the eventual site chosen will either be off the coast of Pembrokeshire or off Anglesey.

The recent report into the Severn barrage noted that there at least 24 different technologies for capturing tidal stream energy in the UK. The device promoted by Lunar Energy sits on the sea floor, is about 20m long and has a turbine diameter of about 12m. The blades sit within a case which focuses the tidal flow. As a Venturi device, the speed of the water flow within the case is greater than the flow outside, adding to the amount of energy that can be captured.

Is wave power economic? It is probably too early to say. The UK has excellent tidal streams around the country, but even this advantage may not be enough. Lunar Energy optimistically quotes figures of around 2.5p to 5p per kilowatt hour, which would make the technology extremely attractive, but these figures appear only to be based on some guesses made in the US. The Carbon Trust’s recent report suggested figures at least three times as much for the first implementations of tidal stream power plants. On the other hand, informal figures from the New York project have suggested figures close to the Lunar Energy estimates.

E.ON has been working with Lunar Energy for some time. It had been thought that the generator would not commit until after sea trials of the first Lunar device in Scotland next year. Last week’s announcement suggests that E.ON’s confidence in the technology and Lunar Energy is high.

The Severn barrage

Nobody expects a Severn barrage to be built soon. But government opinion appears to be swinging in favour of the idea. The independent Sustainable Development Commission has just brought out a report that broadly supports a barrage. Though the environmental costs will be high, it says that mitigation measures will counterbalance some of the damage. We now also have a better feel for the economics of the scheme or, more correctly, for both of the two main options for blocking the Severn. The bigger scheme blocks the estuary between Cardiff and Weston-super-Mare. It will cost about £15bn and deliver just under 5% of the UK’s electricity. The smaller – just downstream of the Severn bridges – will cost a tenth as much, or £1.5bn, but will provide a sixth as much power as the bigger project.

£15bn to build a barrage that decarbonises less than 5% of the UK’s electricity supply is a high price to pay. Scaled up to the whole of the electricity business, this is about 20% of one year’s GNP to replace coal and gas power stations. Even over twenty years, this cost is similar to Stern’s estimate of the cost of reducing the UK’s emissions for the economy as a whole. The smaller barrier delivers much less electricity, but at a capital cost per kWh of little more than half its larger cousin.

The Sustainable Development Commission acknowledges that private financiers are unlikely to put up the cash for the bigger scheme. The report doesn’t really discuss the viability of the smaller barrage but it is much more financially attractive. In terms of total capital cost and expected yearly output, the upstream barrage is very similar to the huge wind farm development called the London Array. The Array will be constructed with private capital. I believe that if the current renewable electricity support scheme remains in place a barrage across the upper Severn can be built with risk capital.

The Sustainable Development Commission thinks that the bigger scheme should be built with public funds. I am not convinced by this. The offshore wind resources around the UK are orders of magnitude greater than the useful energy of Severn tides. If the larger Severn barrage has construction costs of nearly twice the typical figures for offshore wind, wouldn't it be better simply to speed up the licensing of wind farms?

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Bjørn Lomborg's new book Cool It

Bjørn Lomborg, a professor at Copenhagen Business School, is the most formidable critic of those who think that cutting climate-changing gases is the most important problem the world faces. He made his name with 'The Skeptical Environmentalist' and his new book continues his drive to get the world to see global warming as just one of the world's important problems. Lomborg believes climate change is happening, and that mankind’s activities are responsible. But he tells that we shouldn’t do much about global warming because the costs are very high and the benefits low and far-off. Like most books written by partisans in this impassioned debate, much of what he says can be questioned.

Nevertheless, this is an extremely valuable polemic: it stresses repeatedly that taking action to stop climate change may have very high short-term costs. If by clumsy attempts to hold down emissions we stunt the prospects for global economic growth, we may do more harm to the world’s poor than would be inflicted by climate change. It needs to be said time and time again that disease and malnutrition are killing far more people today than climate change. We are making progress diminishing the impact of these scourges. Despite what you sometimes read in the newspapers, world food supply and life expectancy are improving. Panic-stricken action on climate change must not be allowed to halt this progress. We need a rational assessment of whether it is best to spend money on slowing climate change or to whether we would achieve better effects from focusing resources elsewhere.

Bjørn Lomborg is an able debater with a passionate interest in his subject. But he overstates his case, focuses on only parts of the issue and avoids any discussion of a possible future acceleration of global warming. Even with these weaknesses Cool It needs to be part of the continuing debate on how to respond to the climate threat without crippling the poorest economies of the world.

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The Treasury's Pre-Budget review

The Pre-Budget review in early October disappointed green activists. Environmental measures formed a small fraction of the government’s initiatives. It doesn’t look as though Alistair Darling sees climate change as one of the priorities of this administration. But there were two important commitments: a revision to Air Passenger Duty (APD) and (via BERR) a competition to run a commercial-scale carbon capture project. The APD proposal attracted most attention. The government intends to change the duty so that it is levied on aircraft movements and not on individual travellers. Commentators, and the two main opposition parties, have long suggested that this would be a sensible change. Carbon Commentary disagrees. The proposed revision cannot be implemented without infringing international treaties on the taxation of air travel. The chancellor’s proposed consultation will eventually conclude that APD should remain substantially as it is now.

In the article, we briefly analyse the effects of APD and also show that the duty imposes an effective tax on airlines that is greater than would be levied if air travel were fully included in the European Emissions Trading Scheme (ETS).

The BERR Carbon Capture and Storage (CCS) announcement was worryingly unspecific. It did not even bother to mention a figure for the value of the financial support. It also upset some major companies by only allowing entries for the competition from a limited range of technologies. The government is extremely vulnerable to the charge that it is back in the business of picking winners.

CCS is an extremely important part of any strategy for national reduction of emissions. The UK should be throwing far more money at research and development into the various forms of CCS. The simplest and quickest way to get innovation in CCS would be to include carbon storage as a technology that qualifies under the renewable obligation rules. We need to remove the difference between the financial treatment of renewable power generation and carbon capture. Both achieve the same outcome and both should have the same reward.

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26m servers in data centres use 2% of world electricity

BT’s green credentials are well established. It is the largest commercial buyer of renewable electricity in the UK, emphasises the importance of carbon reduction across the organisation, and pushes voice and video conferencing at an unconvinced customer base. In any international ranking, BT’s sustainability measures get high marks. But BT has the same problem as many other organisations: its server farms are growing in number and size. The increased power consumption in its data centres explains why the organisation’s electricity demand is growing. Eventually, its brand image will suffer as critics suggest that its public stance on green issues is not matched by its internal behaviour.

BT’s electricity use is about half a percent of the UK’s total, and its server farms represent over 10% of its energy consumption. BT says that data centre use is rising at 40% a year, and the company’s emphasis on growing video businesses, such as BT Vision, is likely to increase data storage and transmission demands into the foreseeable future.

BT’s response has been to attack the power use of the server with radical measures that set best practice elsewhere in the world. Its new data centres use fresh air cooling, not air conditioning, and the company runs its machines at much higher temperatures than used to be considered possible. Since cooling servers uses at least as much power as running them, this is an important step. The second major innovation is to run the farms on DC power, cutting the very significant losses in the multiple AC to DC conversions in a conventional centre. Better ‘loading’ of the computers helps as well. A well-utilised machine uses only a little more power than an intermittently under-employed server. BT claims that these measures can reduce the typical power consumption of a server farm by 60%.

Across the world, data centre energy consumption is becoming a bigger issue. The world has about 26m servers pumping out data day and night. Estimates suggest that they use about 2% of all electricity produced and global growth is probably around 15% a year. BT’s innovations may be a useful model for others to follow. But the unfortunate fact is that at current growth rates the maximum efficiency gains will be wiped out in less than four years.

In an intriguing trend, some companies are dealing with apparently unquenchable growth in data traffic by beginning to move away from thousands of servers based on PC technology towards huge single computers with lower total energy costs. Who said the mainframe was dead?

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If biofuels are the answer, we are asking the wrong question

Many agricultural crops can be turned into fuels. Diesel substitutes can be made from the oil in seeds. The sugars in cereals and tubers can be fermented into ethanol. At first examination, biofuels look as though they might significantly reduce carbon emissions. An agricultural crop takes carbon from the air through the photosynthesis process. When the harvest is processed, and the output used as a fuel, the carbon returns to the atmosphere. Proponents sometimes said that agricultural crops make ‘carbon-neutral’ fuels.

Over the last two years, this simple optimism has been eroded. Two further blows have fallen in recent weeks:

  • Nobel winner Paul Crutzen and his team showed that we may have been underestimating greenhouse gas emissions from using fertiliser. The work suggested that emissions of nitrous oxide may be far higher than previously thought.
  • Richard Doornbusch, who is attached the OECD, wrote a paper which said: ‘The conclusion must be that the potential of the current technologies of choice – ethanol and biodiesel – to deliver a major contribution to the energy demands of the transport sector without compromising food prices and the environment is very limited.’

The balance of evidence is that biofuels produced from crops grown in temperate climates save very small amounts of emissions. Moreover, the land used for biofuel crops could be used for food or biomass for energy. In tropical lands, biofuel crops may save carbon emissions. But the energy policies of richer countries may be incentivising tropical farmers to cut down forest to grow fuel crops. The effect of this almost certainly outweighs any emissions reductions.

Despite the increasingly prevalent view that biofuels are little or no improvement on fossil fuels, both the EU and the US are obliging retailers to increase the percentage of motor fuels derived from agricultural sources. This is a mistake.

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Holding back the unstoppable tide of green claims

The Advertising Standards Authority is struggling to hold the line on the advertising of environmental benefits. In June, the Authority put out a series of instructions trying to impose clearer conditions on advertisers. But it continues to have to adjudicate on a series of difficult decisions. Last week saw a wind power developer taken to task for over-estimating the carbon savings from turbines. The Authority had to decide which type of power station would produce less power as a result of a new wind farm – coal or gas. It took advice from the National Grid and proceeded to tick npower off, even though the power company was following rules previously set down by the ASA itself. In at least one other country, the advertising regulator has thrown in the towel and told some advertisers simply to stop advertising green claims. Reuters reports that Norway’s Consumer Ombudsman has told car advertisers that ‘We ask that…phrases such as “environmentally friendly”, “green”, “clean”, “environmental car”, “natural” or similar descriptions not be used in marketing cars.’

We cannot be far away from this sort of rule in the UK. Green claims are almost invariably contentious and difficult to prove. We simply don’t have an accounting system that can deal yet with carbon. Advertisers are going to be forced to avoid any but the most clear-cut and well-documented savings.

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Consumer segmentation: Research from the Henley Centre and Marks and Spencer

Many companies selling to UK families have a strong sense that consumer demands are shifting rapidly. M&S recently talked to Carbon Commentary about its perceptions of changes in attitudes and behaviour. This article compares its results with those of a survey by the Henley Centre in summer 2007. During the last year or so, the percentage of 'green zealots' in M&S research has risen from 3-4% to nearer 8%. Henley also sees a figure of 8% for the two greenest groups 'principled pioneers' and 'vocal activists'. A further 31% (Henley Centre) or 30-35% (M&S) are actively concerned and want to adjust their behaviour. There has also been a big growth in this group in the last year.

In both surveys another third are aware of environmental and ethical issues, but are unlikely to take active steps unless pushed. A final quarter or so don't care very much. M&S says that they are 'struggling'. Henley calls them 'disengaged'.

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Domestic Combined Heat and Power

Ceres Power, a £150m AIM-listed company, recently demonstrated its new Combined Heat and Power product. This power plant is targeted at ordinary domestic homes. Combining an efficient central heating boiler with a fuel cell that converts gas to electricity, the new product has excited the City. Ceres is extremely optimistic about sales of the device, based on the cash and carbon dioxide savings it says can be achieved.

The Ceres fuel cell (on the left) is incorporated into an ordinary domestic condensing boiler (on the right)

Ceres promises reductions in utility bills of £300 a year and 2.5 tonnes savings in carbon dioxide for the typical UK house. Our short report shows why we think that these savings are unlikely even in the most appropriate UK installation. In fact, the emissions reductions are likely to be minimal and the reductions in the electricity bill will not easily justify the approximately £1,000 extra cost of the CHP cell.

Micro CHP is a difficult proposition. Other companies have found that it is hard to make substantial savings in domestic installations. CHP is not well suited to rapidly fluctuating and unpredictable demand for electricity and hot water.

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Geo-engineering

Some scientists think that the world's halting attempts to reduce carbon emissions are bound to fail. So they have proposed various schemes for counteracting the global warming impact of fossil fuels. The Gaia scientist James Lovelock proposed an unusual and untested idea in a recent paper. He suggested that we install millions of pipes to bring nutrient-rich water to the surface to feed carbon sequestering organisms. Other scientists are working on schemes as diverse as mirrors that reflect part of the sun's energy, increased aerosol pollution to stop sunlight getting to the earth, and improving plankton growth by adding iron to the oceans. All these schemes are 'offsets'; they seek to counter-balance the impact of human activities with schemes to reduce CO2 elsewhere. The technology optimists believe that one or more of these techniques can completely counteract human effects. The cost often seems very reasonable – in the billions rather than the trillions – and the technological challenges seem not insuperable. The pessimists say these schemes will have huge unintended effects, possibly worse than climate change itself, and that toying with 'geo-engineering' projects, as they are called, simply delays the day that the world starts to realise it must cut fossil fuel use. Geo-engineering deals with the symptoms, not the causes, of global warming. And none of the proposed schemes deal with the adverse effects of higher CO2 concentrations, such as increased ocean acidity.

This article argues that all the major geo-engineering proposals have substantial pitfalls, but that it makes clear sense to increase the research funding into these schemes. The opponents and proponents of geo-engineering have got locked into an almost theological debate as to the ethics of climate modification but this argument should be secondary to the need to have well-defined back-up plans in the event of increasingly rapid deterioration of the global climate.

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The eco-homes at Bladon, near Oxford

New UK housing has insulation standards that do not come close to matching the best northern European levels. Individual homeowners and ethical investors have built single 'eco-homes' but a small new development in Bladon, Oxfordshire is among the first to be speculatively built by a mainstream housebuilder. The new houses are not 'zero-carbon' and do not use the Passiv Haus technologies pioneered for low-emissions housing in Germany. But they are a substantial improvement on most mass-produced homes. Will they make the builder more money? No, says the company, but the experience it has gained will enable it to build eco-homes at a more competitive price in the future. These nine houses each cost over £40,000 more than their draughty Persimmon equivalents. The builder expects the price premium to be slightly less.

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Straws in the wind: The Lib Dems' climate change paper

Both the Conservative and Lib Dem parties have produced position papers on climate change in the last few weeks. The Conservative document is over 500 pages long but contains very few specific proposals. To be harsh, it is little more than a prolonged agonising over whether the climate change problem can be addressed using conventional free-market mechanisms. The Lib Dem paper is a tenth of the length but does contain the outlines of a coherent set of policies. This article analyses the Lib Dem proposals. It shows that the Lib Dems are prepared to use the price mechanism to choke off increasing demand for aviation. The party also contemplates extending the Emissions Trading Scheme beyond the 50% of the economy currently covered. On the other hand, it makes completely clear that it has no intention of raising the prices of energy and fuels to domestic consumers.

Although the party presents itself as the only UK political institution ready to grasp the need for an economy-wide carbon price that will bring down emissions by 30% in 2020, the detailed proposals are far less radical. In the material that follows, I try to tabulate the Lib Dem ideas, focusing on whether they use price, regulatory fiat or pious hope as the proposed means of emissions reductions. As in the Conservative paper, estimates of the costs and benefits of their policies are almost completely absent from the Lib Dem paper. It is a shocking commentary on British politics that no major party is prepared to quantify exactly how it proposes to shift taxes towards polluting activities and away from other sources.

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Tesco vs. Wal-Mart vs. carbon emissions

The rivalry between Tesco and Wal-Mart is well known. Tesco's imminent entry to the US heartland of the world's largest retailer may have created an extra edge to the battle. And, unsurprisingly, the two giants are squaring up over carbon issues as well as over such things as employee conditions and global sourcing policies. Tesco said earlier this year that it would eventually put carbon labels on all its 70,000 food lines. It has been trying to find way of doing this using Life Cycle Analysis, putting a greenhouse gas cost on every element of a product's move from farm to plate. This was always a hugely over-ambitious project and recent weeks have seen the company drift back from its early optimism. Now Wal-Mart has come up with a similarly impossible dream – to use the Carbon Disclosure Project (CDP) to assess and manage the energy footprint of its suppliers. These big retailers know that they have to be seen to be doing something about greenhouse gases, so they have both launched incomplete schemes that will achieve little.

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British Gas's new Zero Carbon tariff

British Gas has launched a consumer gas and electricity tariff that will cost 10% more than its standard rates but which offers better green credentials than any other consumer utility tariff in the UK market. The product has the following important features:

  • The electricity is derived from renewable sources. The company says that this is not the key ingredient of the tariff. Later in this note I try to explain why.
  • British Gas will buy and retire Renewable Energy Certificates for 12% of the electricity it supplies. This is probably the most important aspect of the proposition.
  • British Gas will 'offset' all of the carbon dioxide produced as a result of each household's purchases. This is the most expensive part of the deal for British Gas.
  • There will be a small donation to a green education fund for schools.

BG says that it makes no extra money from the sale of its Zero Carbon product. This looks a justifiable statement to us. The important other questions to ask are:

  • Why did BG decide that 10% was the appropriate premium to its main tariff? It could have designed a less costly offering with reasonably strong green features. Do mainstream 'concerned consumers' regard 10% as an acceptable price increment? Did BG need to 'gold plate' the new product to avoid any criticism that it was a proper green tariff?
  • How will the company manage to ensure that it buys high quality offsets, and not the dubious offerings sold by consumer offsetting companies?
  • The product is slightly complex and difficult to explain. Can BG cut through the competing claims of other green suppliers to build a large customer base for this high quality offering?
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Tyndall Centre report on aviation and emissions trading

In early September, researchers from the Tyndall Centre in the UK put out a report that said that incorporation of the airline industry into the Emissions Trading Scheme (ETS) will not provide significant incentive to cut emissions. The big polluters today are paying about €20 per tonne for their emissions. When aviation joins the scheme in 2012, this price would add about €5 for a flight to Barcelona. Tyndall argues that the EU and national governments cannot escape the conclusion that the ETS is not enough and that aviation must be constrained by other fiscal or legislative measures as well as by inclusion in the carbon tax net. Tyndall has acquired an excellent reputation for its informed and passionate stance on aviation. Broadly speaking, its view has been that continued expansion of aviation is incompatible with the tight emissions targets that the EU and other bodies have set for the years to mid-century. It has consistently said that by 2050 unconstrained air travel will be using up most of the total carbon emissions that the world can allow itself. Aviation expansion will drown out emissions reductions in other areas.

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Is organic food better for the climate?

The evidence is not quite clear enough that organic food is better for the atmosphere. The debate on whether organic agriculture reduces greenhouse gas emissions is a lively and sometimes acrimonious affair. The calculations are complex, the results depend on myriad factors that are difficult to quantify, and much research remains to be done. Those who give unequivocal answers to the question 'is organic better?' may not be recognising the extraordinary uncertainty that still surrounds many aspects of agriculture. Rather than produce a simple answer, this note offers a statement of the competing cases.

This topic has been widely researched but has produced very varying answers. There is certainly no consensus. In general, organic farming seems to be slightly better for the atmosphere than conventional cultivation, but for every ten studies that say this, five say something different. Almost all the conclusions are the subject of passionate debate.

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E.ON's new wood-burning power stations

Do dedicated biomass electricity generating plants make financial sense? E.ON UK has recently announced a plan to build a second power station using 100% energy crops as fuel. The first investment – a £90m power plant at Lockerbie in Scotland – will open within the next few months. The second plant, still only in the planning stage, will be in Sheffield on the site of a previous generating station. Both power plants will use wood from forestry and specially planted willow but Sheffield will also burn waste wood from other sources, such as industrial pallets. These are the first two large-scale plants in the UK if we exclude the ill-fated Arbre plant of several years ago. (Arbre was an extremely advanced wood chip gasification plant built in Yorkshire. It was never fully commissioned.)

By the standards of the electricity industry, the E.ON investments are tiny. The proposed Sheffield plant has a price tag of £44m compared to £1bn for E.ON's intended investment in the new super-critical low(ish) emissions coal power plant at Kingsnorth in Kent. Nevertheless, Lockerbie and Sheffield do appear to make good financial sense, at least in part because of the revisions to the renewable energy subsidy scheme announced in the government's June 2007 Energy White Paper.

This article looks at the prospective financial return from operating a power plant burning wood and other energy crops.

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HSBC's international opinion survey into climate change

The key conclusions from a good piece of market research HSBC's July 2007 survey entitled the Climate Confidence Index contained many surprising results. Carried out in nine major countries around the world, it showed that concern about climate change is far higher in developing countries than in the UK or the USA. As importantly, the inhabitants in these countries also think that the world is more likely to find ways to avert climate change problems.

Almost 60% of people in Brazil, Mexico and India see global warming as one of the most pressing problems the world faces, compared to little more than 20% in the UK. Broadly speaking, the richer countries tend to see terrorism as a bigger threat to the world than climate change. In all nine nations bar the US, the level of concern tends to rise quite sharply with age. (This result is also seen in most other surveys of UK opinion.)

Confidence that climate change will be successfully addressed by existing institutions is low in most places around the world. It falls to its lowest level (5%) in the UK. The UK also has the lowest level of people saying that they personally are making a significant effort to reduce climate change at 19%, compared to levels above 40% in developing countries. Fatalistic Britons are also almost the most pessimistic about whether global warming will be stopped, with only 6% of people saying 'I believe we will stop climate change,' compared to 45% in India and 39% in China.

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Science news: Greenland's melting ice

The glacier at Ilulassit in Western Greenland Photo: the glacier at Ilulassit in Western Greenland

In early September, leaders from the major faiths came together in Greenland to pray for the future of the planet. They may well have chosen Greenland because of the visible and deeply worrying changes in the glaciers and ice fields that cover almost all its vast area. The melting of the ice sheet has speeded up dramatically since 2000.

The state of Greenland's glaciers is critical to the rate of global sea level rise. A complete melting of the island's ice would raise water levels by about 7 metres, enough to flood much of the world's inhabited land. To give one example, 15% of Bangladesh's population would be displaced by a rise of just 1.5 metres. Almost all the country's habitable land would disappear if the water level rises by 7m.

The religious leaders went to the town of Ilulissat on Greenland's western coast. Here a rapidly retreating glacier calves icebergs into a fjord at a rate of 35bn tonnes of water a year. The daily water loss would provide all the water London or New York needs for a year. Estimates suggest that between 6.5% and 10% of all the ice flowing off the interior icefields of Greenland melts into this fjord. This means that the increase in the rate of melt of this one glacier is adding about 0.06mm a year to the global sea level, 4% of the rate of rise during the 20th century.

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