environmentalresearchweb blog
May 19, 2012
Green Heat 2
The governments new Heat Strategy review took on board many of the arguments for district heating, and even the use of solar, that previously had been rather marginalised. It identified pathways for the transition of the UK’s heat supply to low- and zero-carbon energy sources in the domestic and industrial sectors.
The Combined Heat and Power Association (CHPA) was delighted. It said that ‘the Strategy points the way to a major expansion of new district heating networks in towns and cities, driving a multi-billion pound investment programme in green infrastructure and creating an additional 40,000 jobs in construction and engineering’.
The CHPA noted that previous Government studies had suggested that 8 million dwellings could be connected to district heating at reasonable cost, along with a major share of commercial and public buildings, through a 25 year capital programme, investing £2bn p.a. in new district heating infrastructure. Through this programme carbon emissions from heating would be halved and reduced to around 9 million tonnes per annum. It added ‘Networks could adapt to obtain heat from gas-fired CHP plant, biomass and biogas, heat pumps, energy-from-waste, solar thermal, along with heat rejected from industrial processes and power stations. This approach, which is commonplace in continental Europe and Scandinavia, delivers reliability and security to energy users and provides a credible and practical pathway to decarbonisation.’
However the policy shift wasn’t that large: the Heat Review still backs electrification as the main supply focus, since ‘electricity is universally available’ and, in well insulated houses, heat pumps can make using it for heating relatively economic. But it did admit that gas grids act as energy stores and are better at coping with variable demand, so that there would, in an electrified system, be more need for storage and demand management, as well as a lot more green generation capacity- almost double the present amount, given electrification of transport as well! Basically from nuclear and offshore wind, plus gas CCS.
Even so, it looks to biomethane and hydrogen, as new fuels, sourced from biomass, that could be used for heating, although it warns that biomass resources will be ‘constrained and contested’ and probably best used for industry and transport, where higher energy intensities are important. And, a little provocatively, it says large-scale biomethane injection into the gas grid is not realistic ‘when efficiency losses are taken into account’.
So, apart from some direct use by industry for process heating and for local district heat networks, it sees gas delivery on a national scale is being phased out, with cooking being done by electric hobs and perhaps induction heaters. A big change for many people. Interestingly, micro CHP is seen as just a transitional option, but solar heating is seen as valuable, especially if combined with interseasonal storage, implying large scale ‘heat accumulators’ /community heating systems. The industry section is useful, with, in addition to improved process efficiency, gas and biomass CCS seen as a possible option.
Overall interesting then, still wedded mainly to electricity, plus some heat networks. But there are few actual commitments or future supply numbers, just a general plan: a full policy is promised within a year.
www.decc.gov.uk/en/content/cms/news/pn12034/pn12034.aspx
Things do seem to take time! The Renewable Heat Incentive for example- which was meant to start the ball rolling. It was set up in two parts, with support of larger business schemes already established, along with an interim domestic-scale grant competition, the Renewable Heat Premium Payment scheme (RHPP), offering one-off payments for homeowners wishing to install green heating systems. DECC had been expected to launch the full domestic RHI in October this year, alongside the Green Deal loan scheme, but it has now decided to delay it until summer 2013, and will instead inject an extra £10m into the budget for the interim RHPP, taking it up to £25m, while reviewing cost control measures.
After its run-in with the PV solar Feed-In Tariff, the government is clearly worried that the projected costs of the RHI scheme, which unlike the FiT, will be met out of government funds, i.e. from taxes, will need to be controlled and kept below the fixed £860m budget. So it’s launched proposals to carefully manage the RHI budget. For the existing business scheme, as a temporary measure, it will suspend registrations at one month’s notice once 80% of the budget has been allocated. DECC said it will introduce proposals for a permanent cost-control mechanism by the end of the financial year, which could see tariffs fall in line with increased uptake.
Meanwhile, under the new extended RHPP, for the first time, communities seeking to install renewable heating systems will be able to take advantage of the scheme, with around £8m of the budget set aside for local projects. DECC has also earmarked £10m for social landlords to upgrade heating systems, after the social landlord competition last year received such a strong interest that DECC increased the initial £3m budget to £4m.
The Government said it wanted at least 25,000 households to take up RHI offers in the first year. So far, under the first phase of the RHPP, £4.8m has been cashed in by housholders, and 37 social housing schemes have also registered But, given the new review, Gaynor Hartnell, Renewable Energy Association CEO, feared the market will be killed off before it even starts: ‘To launch an official consultation on bringing the shutters down, having only just fired the starting gun on the RHI, is premature to say the least’.
www.decc.gov.uk/assets/decc/11/meeting-energy-demand/heat/4805-future-heating-strategic-framework.pdf
Some of the heating issues were followed up in the subsequent DECC, DEFRA and DfT Bioenergy strategy, which backs the ‘use of biomass to provide low carbon heat for buildings and industry (process heating), through either biomass boilers or through use of biomethane’. It adds ‘Use of recoverable waste heat from low carbon power generation or industrial processes is also an important component of this pathway’, noting that ‘combined heat and power generation offers more efficient use of the biomass resources and should be promoted where possible’.
It also notes that Bioenergy carbon capture and storage (BE-CCS) offers net carbon removal from the atmosphere or ‘negative emissions’, which ‘could then be used to offset fossil fuel emissions from other harder to decarbonise sectors. This makes BE-CCS an exceptionally valuable technological option’
The Combined Heat and Power Association was again delighted, noting that the stress had shifted to the use of heat networks rather than individual boilers to provide domestic heat, and the recovery of waste heat when used in an industrial setting. www.decc.gov.uk/en/content/cms/news/charleshbgbio/charleshbgbio.aspx
It does seem that, for once, new ideas are beginning to be listened to. I will be exploring some of them in my next Blog.
May 12, 2012
Green Heat 1
I have often been less than impressed by reports from the Royal Academy of Engineering (RAE) , which usually seems to take a conservative line on energy issues, but their new report on heating for buildings seems overall very well done, although with lapses. It makes the sensible point that we need to deal with the building envelop first, but also notes that most of the houses that will be lived in by 2050 have already been built, so we must look to remedial measures. It also notes that ‘Manchester isn’t Leipzig’, and looks at patterns of heating need and perceptions of comfort. It assumes we are talking about well insulated buildings, and familiar levels of comfort, and it reviews the energy supply options for supporting that.
It sets the scene by pointing out that ‘If space heating could be decoupled from water heating it would change the selection criteria for heating appliances and boilers. There would no longer be a need for the heating system (as opposed to the hot water system) to be on standby during summer months or to be capable of operating at a sufficiently high temperature to prevent Legionella developing in water systems. All domestic heating is currently thought of as low-grade heat requirement, but there is a case for distinguishing space heating as low grade and hot water as medium grade. A policy for heat should separate these two different uses’.
It looks at heat pumps as a possibility, but is not too convinced. ‘While the general reduction in carbon intensity of grid electricity makes the use of electric heating (direct or via a heat pump) more attractive, peak heat loads tend to coincide with peak electricity loads. There is, therefore, a significant likelihood of heating demand being met by high carbon electricity generation brought onto the system to meet peak loads over and above the capacity of low carbon generators’.
It goes on ‘Air source heat pumps have been rising in popularity for new build in the UK, but this is partly an effect of the way in which electrical energy is treated in the regulations that makes CO2 targets more lenient than for gas systems.’ While it admits that ‘Air source heat pumps integrate well with well insulated dwellings, if properly sized and installed,’ and it suggests that ‘micro-CHP complements and could balance some of the properties of heat pumps’, it also notes that ‘several reports discuss inadequacies of the application or system engineering in heat pump installations. It is clear that heat pumps are not forgiving if installed inappropriately.’
By contrast, it’s much happier will larger-scale communal system. ‘Communal air source heat pumps are an interesting area of development with some new configurations of systems coming to market. Central systems may be more efficient and are likely to offer much greater energy storage than do systems designed for individual household’.
It adds ‘Larger district systems, incorporating a CHP facility and providing heating are significantly more efficient than domestic level installations. This is because waste heat can be used in district heating after it has generated an element of electricity. Such district heat is therefore always of significantly lower CO2 emissions than any heat only production utilising the same fuel’. And that, it seems, includes domestic scale heat pumps.
The RAE does seem to been moving towards community- scaled system across the board. However, it is less happy with renewables. Although it sees some potential for bioenergy e.g for CHP/District Heating , it is not very impressed with solar, and overall treats renewables as problematic in terms of grid power supply, reverting to the traditional RAE line on the problems of intermittency and the delights of nuclear: ‘During the summer months, most of the night-time load could be provided by nuclear power with renewables providing additional power during the day’, while in winter ‘we would need sufficient renewables to guarantee 40GW during the evening peak. As wind, tides and the sun are intermittent, that would require significantly higher installed capacity of renewables or thermal back-up capacity, much of which would be unused for long periods in the summer’ making renewables uneconomic.
Nevertheless, it does look at smart grid /load management options which might change the situation radically, helping to deal with intermittency. A bit grudging, but at least there is now some recognition that a new interactive supply and demand system might be viable. It’s taken decades to get the community CHP/DH message across to the traditionalist engineers, so maybe it’s too early for idea of smart dynamic grids to have got through! And it may take even longer for them to give up on ‘baseload’ nuclear, which they still see as essential, rather than as getting in the way of a more interactive flexible system based on renewables ( which is the view emerging from Germany) .
However, as far as CHP/DH in concerned, the RAE is now full of praise. It says that ‘CHP plants, biomass combustion, and heat pumps are more efficient, reliable and cheaper at scales larger than a single dwelling. The costs of large scale heat pump installations per kW are a quarter of that for domestic-scale installations.’ It adds that ‘it is more efficient to use the available skills for fewer large systems than for many individual units’, and that, since energy storage will be needed ‘district heating systems have another important benefit - the mass of water in the underground pipes provides a heat store that evens out daily peaks and troughs in demand. This can be supplemented by hot water tanks to increase energy storage’. And taking it one step further, it points out that ‘well insulated hot water tanks or underground inter-seasonal thermal stores will be simpler to provide on a community basis given the small (and reducing) size of most UK homes’.
Some sense last! And DECC seem to be taking notice, in their new Heat strategy- see my next Blog.
‘Heat: degrees of comfort?’ Royal Academy of Engineering www.raeng.org.uk/heat
May 5, 2012
Biomass - on a slow burn
The Climate Change Committee’s report on bioenergy earlier this year was somewhat more cautious than many previous studies, arguing that, at best, the UK might only get 10% of its energy from bio-source by 2050. The CCC saw bioenergy as a scare resource, with significant constraints, not least land use. This of course is a global issue, with for example, in terms liquid biofuels, there being many concerns about the environmental and social impacts of large plantations around the world. It’s not just direct land use, it’s the impacts of land use changes (‘ILUC’) that matter, which CCC say must be included, though they are hard to assess. But if at least a 50% emission reduction, below that from fossil fuels, is set as a target, there’s less room for manoeuver.
When it comes to solid biomass for heat and power production, things get a little easier in terms of land use. CCC say ‘Our core scenarios focus on the use of abandoned agricultural land’, with a range of energy crops being viable: ‘We assume in the longer term dedicated energy crop feedstocks are a mix of fast growing trees and grasses, as these crops are potentially more suitable to land of low productivity, have low lifecycle emissions and can be converted for use across the range of sectors’. But CCC see Carbon Capture and Storage as vital in many cases: ‘If CCS is not available at the scale envisaged, the amount of bioenergy required to meet the 2050 target would have to be significantly higher than 10% of primary energy demand, and would imply land use change exceeding currently estimated sustainability limits.’
They also warn that ‘given limits on domestic supply, much of the forest biomass for power and heat used in the UK will have to be imported’. Nevertheless they feel able to conclude that ‘Scenarios for global land use which take account of required food production suggest that a reasonable UK share of potential sustainable bioenergy supply could extend to around 10% (200 TWh) of primary energy demand in 2050. However, it would be unsafe at present to assume any higher levels of bioenergy supply, and even the 10% level might require some trade-offs versus other desirable environmental and social objectives (e.g.through energy crops production encroaching on land of high biodiversity value).’ But they want tighter limits: ‘the threshold for use of biomass to meet the RO should be tightened to 200 gCO2/kWh. This would represent a significant enough saving relative to gas-fired generation, allowing a margin for emissions from possible indirect deforestation.’
Clearly they do not see biomass as likely to play a major role, although they suggest that there might be range of ‘sensible smaller-scale local uses’ - such as making use of old cooking oil to run buses, using food or farm waste in anaerobic digestion plants, or using woodchip from tree surgery waste in biomass boilers. Pretty marginal then, with CCC concluding ‘The role for use of biomass in heating buildings is likely to be relatively limited in the longer term, given alternative low-carbon options such as air-source and ground-source heat pumps. Where these are not feasible, there may be opportunities for district heating using waste heat from large-scale low-carbon thermal power plants (potentially including biomass CCS) or CHP using local waste or biomass, and for biomass boilers using local biomass in rural homes.’
This may be too dismissive a view. Certainly, in practice, biomass/biogas energy options are still struggling to get going on a significant scale in the UK, with objections still emerging to some large-scale power projects, but some are still moving ahead.
E.ONs controversial 150MW biomass power station in the Royal Portbury Docks, near Bristol, has got the go ahead, despite concerns about its part reliance on imported virgin wood. It will also use dedicated energy crops, and locally sourced waste wood. E.ON has said it would set up a community investment fund, contributing £50,000 per year for charitable and educational community projects in the area, while a further £75,000 would also be set aside to trial green buses and improve cycle routes in the area.
However, E.ON told BusinessGreen that it was reviewing its plans for this and other renwable energy projects, in light of proposed changes to subsidies offered under the government’s Renewable Obligation scheme. Drax also seem to be having second thoughts again about their biomass co-firing projects, complaining that there was not enough RO support
Meanwhile, Sheffield Council is looking at plans for a £20m waste wood CHP project in the Holbrook area , following on from the agreed E.ON’s £120m 30MW waste wood biomass plant on the site of the old Blackburn Meadows power station next to the M1, now under construction. In addition, RES has plans for a 100MW biomass plant in Northumberland on Blyth River.
An energy from waste/biomass complex has also been proposed for the Ince Park development located at the Manchester Ship Canal, as a joint venture between Peel Environmental and Covanta Energy. Construction of the EfW facility is set to begin soon aiming for operation in 2015. Peel Energy has also got planning permission for a separate 20MW biomass energy facility on the site, with construction scheduled to start early next year. Plants like this, which involve combustion, are often opposed by environmentalists due to possible emissions (especially if wastes are used) and also the land-use/ biodivesity implications of large scale biomass growing/importation
In Wales, in a novel project which should avoid these issues, BiogenGreenfinch have been appointed by Gwynedd Council as the preferred bidder for the construction of a new green energy plant which will take council collected food waste and turn it into renewable energy via Anaerobic Digestion. The new AD plant, which should be running soon, will process around 11,000 tonnes of food waste each year; converting it into renewable electricity and biofertiliser for use on nearby farmland. The food waste will be collected from local homes and businesses via a collection scheme run by Gwynedd Council. The new plant will replace the existing landfill site currently situated in Llwyn Isaf and should play a major role in helping the Council meet their statutory recycling targets. It will be the second waste-fed anaerobic digestion plant built in Wales, following the construction of the Premier Foods plant last year near Newport.
In this case, the biogas is burnt to produce electricity, but AD biogas can also be added to the gas main, with, despite CCC’s rather negative assessment, the prospects for ‘green gas’ from waste AD being increasingly seen as a new possible direction for green heat supply-in Germany especially. For more: www.biogas-info.co.uk.
While CCC may be a little sniffy about biogas, the new DECC/DEFRA/DfT Bioenergy Strategy is a lot more positive, as is the parallel DECC Heat Strategy. Although they do not see biogas playing a role in domestic heating directly, they do envisage biomass and biogas being used for community heating via CHP plants linked to district heating networks. I will be exploring this, and the green heating options. in my next few Blogs.
CCC report: www.theccc.org.uk/reports/bioenergy-review
May 3, 2012
Urban transport in the developing world
Walking and cycling dominate urban transport in Asia and Africa.
This statement is worth repeating. Walking and cycling dominate urban transport in Asia and Africa. It is one of the key statements in the book “Urban Transport in the Developing World”, subtitled “A Handbook for Policy and Practice”, edited by Harry Dimitriou and Ralph Gakenheimer. But it is much more than a handbook. It is the most comprehensive overview on the topic. With more than 600 pages, take your time reading it. While there is some redundancy, reading this book carefully will provide you with a superb, encompassing understanding of urban transport in the developing world.
Here is the book’s story. 60% of the world’s population live in Asia, and Asia is the epicenter of the global urbanization wave. Asia is also the focal point of incredible motorization with China alone being projected to have in 2050 nearly as many cars, as the world has currently on its roads, in totol: 700 million cars. An Asian city also gives its name to one of the key concepts I extracted from the book: the Bangkok syndrome. Similar to their OECD counterparts, Asian and African cities start with dense, walkable city cores. At the beginning of the last century, OECD cities invested in the then upcoming rail-based transport infrastructure, shaping cities profoundly. With the relatively slow but profound rise of automobility, American cities developed into low-density automobile cities, while European cities kept their inner cities served with public transit. Asian and African cities seem to be mostly on a different trajectory: They skip the stage of public transport infrastructures and move directly into individualized motorized mobility. This is too some degree quite surprising: Relative to their GDP, cities of the developing world invest much more into highways, citizens proportionally much more into personal transport than their OECD counterparts do and have done (see e.g. Jeffrey Kenworthy’s contribution). Inversely, these developing cities have high population density and are unsuitable for car transport. As a result, especially Asian cities develop into ‘motorcycle’ cities (Barter, 2000): motorized two-wheelers are best adapt to navigate the traffic disasters, but are subject to high accident rates and still face congestion.
Distribution and accessibility is another, related theme that develops continously across chapters. As the introductary statement indicates, paraphrased from Setty Pendakur’s chapter, non-motorized transport is the starting point of analysis, for transport efficiency and transport equity matters alike. Urban transport planning is often technocratically framed as ‘apolitical intervention’ (Eduardo Vasconcellos), where in fact it is top income segment who by driving their cars consume 10 times more space than the urban poor, consume a largest part of transport energy, and are responsible for most of street-level air pollution. It is then quite clear that a suitable normative objective for urban transport is reasonable accessibility for all, possibly emphasizing the urban poor (the concept itself actually may need to be qualified, see Xavier Godard’s chapter). Accesssibility itself is a highly interesting concept: Some cities, such as Dakar, seem to have high accessibililty - walkability - for the poorest quantile. In contrast, in cities like Buenos Aires the lowest income quintile pays proportionally to income much more than the richest quantile. Poverty may also directly reduce social contact by rendering visits to family or friends infeasible.
In line of the this comprehensive analysis, it then follows naturally to require comprehensive assessments of urban transport projects and plans, relying on strategic environmental assessments (Michael Replogle), inclusive equity evaluation (Eduardo Vasconcellos), and context-specific economic appraisal (Walter Hook). The key conundrum, however, is then in the meta-level of institions (Elliott Sclar and Julie Touber). In the dense urban environment of Asian and many African cities, the traffic disaster of the Bangkok syndrome can only be tackled with efficient public transport. But public transport can be regarded as a quasi-public good, and will not emerge from demand-side focussed market outcomes. Hence institutional capacity, a governance framework of promoting public goods and better public transport and non-motorized transport system need to coevolve simultenously. Transport planning alone is not enough.
April 28, 2012
Green energy retailing
Some consumers have been able to make use of the ‘Clean Energy Cashback’ Feed In Tariff scheme to get paid for generating their own renewable electricity , and exporting any excess to the grid. Around 1GW of solar PV has now been installed in the UK as result. But not everyone can afford the large capital outlay for PV solar or other domestic-scale renewables. For those still keen to use green energy, one option is to buy it in via a green retail scheme. There are a lot on offer, but it is sometimes hard to decide how reliable they are- how can consumers be sure they are really getting green power?
To try to help, an independent voluntary Green Energy Supply Certification Scheme was set up for domestic consumers and small businesses, and has been running since Feb. 2011, with 13 UK green electricity tariffs certified by August 2011. The Scheme is bound by Ofgem’s Green Supply Guidelines. It is overseen by an independent panel of experts with the National Energy Foundation as Panel Secretariat.
The Scheme awards a ‘green label’ to electricity tariffs that deliver a real, measurable green gains. Not all tariffs marketed as green in the UK are certified by the voluntary Scheme but evidently all those who have applied has been given certification without the need for major adjustments. However, despite relatively high public awareness of environmental issues, green tariffs still account for only 1% of demand. In part that is because of some confusion- and cynicism- as to what green power really is.
The basic initial idea was that suppliers would contract with consumers to match the electricity they use with electricity from renewable sources, and set green tariff rates, which were likely to be higher than normal rates. So it was voluntary scheme for those who wanted to support renewables more, since they cost more at present.
However it was complicated by the advent of the Renewables Obligation (RO) which requires suppliers to source increasing proportions of the electricity they sell to all consumers from renewable source, with the extra cost passed on to all comsumers. It would be unfair for the same electricity also to be sold under the voluntary scheme- those consumers would then in effect be charged twice. So it was proposed that the electricity had to come from projects that were outside/additional to those operating under the RO scheme. The problem was that there weren’t many of them and they tend to be the higher cost projects, so pushing the voluntary green tariff level even further up.
Some critics also argued that, as far a developing renewables rapidly on a large scale was concerned, it was far better to go for the RO, which passed the extra cost on to all electricity consumers, than the rely on voluntary support from a small minority, who would otherwise be in effect subsidising others not to bother. But then that’s the nature of charity, and if some are willing to pay more, altruistically, then it all helps. A more fundamental issue was that, as a Datamonitor Survey reported, 27% of respondents did not trust their energy company, and did not believe that their energy would actually come from (or be matched by) a renewable source. The Green Energy Supply Certification Scheme aimed to try to resolve that credibility issue.
In terms of the green tariffs on offer now, what has emerged is something of a compromise. Some green suppliers do supply 100% green power at a premium price from fully additional sources, or like Good Energy, ‘retire’ the ROCs they get from RO credited projects. But some don’t charge more and don’t use additional sources- in which case additionality is achieved by offering other, indirect, green benefits- specially established funds fed from a percentage from the sales receipts, for the development of renewable energy projects (e.g. the Juice fund for marine renewables) energy efficiency projects or eco/offset projects e.g. reafforestation.
The Green Energy Supply Certification Scheme requires that these projects must result in the abatement of at least a minimum level of carbon dioxide equivalent (CO2e) emissions- set at 50 kg p.a per tariff for funds/efficiency projects and 1 tonne for offsets. There has recently been a consultation on whether these levels should now be raised, and on other aspects of the scheme. The main concern however for it to be better known and used!
- Next year consumers should be able to get support for installing heat producing renewables, under the proposed Renewable Heat Incentive domestic tariff scheme, but there are already some voluntary green heat retail schemes on offer.
April 27, 2012
EGU 2012: Arctic vies with Greenland on sea-level
Arctic glaciers and ice caps cover an area of 402,000 square km, roughly 55% of the world’s total. But they’re punching above their weight when it comes to sea level rise - although Greenland’s ice sheet is four times larger, it contributes roughly the same amount of melted ice to the world’s oceans. That’s according to Jon Ove Hagen of the University of Oslo, Norway, speaking at the EGU meeting in Vienna.
For example from 2006-2010, around 200 Gigatonnes of ice per year melted from the Greenland ice sheet while the equivalent figure for glaciers and ice caps in the Arctic was 160 Gigatonnes. That said, there is considerable variability around the Arctic region, with some glaciers and ice caps losing mass rapidly and a few growing slightly.
As part of the ice2sea programme, Hagen and colleagues have taken continuous GPS measurements on two fast-flowing outlet glaciers of the Austfonna ice cap in northeastern Svalbard since April 2008. The data indicate that the ice is now moving between two and three times faster than four years ago.
What’s more, around 30-40% of the total ice mass loss is due to calving. Hagen said the ice cap is exhibiting unstable dynamics and the study shows the importance of monitoring calving.
April 26, 2012
EGU 2012: Mann upsets dendroclimatologists
Michael Mann of Penn State University, US, is used to attack from climate contrarians. But his latest work, as he told environmentalresearchweb at the EGU 2012 Assembly in Vienna, has received more interest from dendroclimatologists who “feel our paper [in Nature Geoscience] exposes a problem with their approach”.
The research indicates that growth-rings from trees at the far north of their range may not have picked up the fast cooling caused by major volcanic eruptions in the past. Such trees are particularly sensitive to temperature change, which is why they are used so often in palaeoclimate reconstructions. But there’s a snag - temperature drops of a couple of degrees may push them outside their growth range. That could mean a year without growth and a missing growth ring. Not only does this fail to record the temperature drop but it can also “smear” the chronology, explained Mann.
Mann, however, feels his research shows dendroclimatologists are doing a “good job” at reconstructing long-term temperature changes in the past - it’s only detection of short-term cooling responses to volcanic eruptions that is an issue.
“Ironically this points to some past work [on climate sensitivity] as biased on the low side and maybe contrarians don’t like that,” he said. Mann believes the work indicates that climate sensitivity - the increase in temperature for a doubling of atmospheric carbon dioxide - is closer to 3 °C than 2 °.
• Mann was awarded the EGU’s Hans Oeschger Medal.
EGU 2012: four in five heat records due to climate change
This year’s EGU General Assembly in Vienna is not currently experiencing heat extremes. But worldwide the number of local monthly record-breaking temperature extremes is now five times on average what would be expected if the climate was stable. This means that four out of five recent records would not have taken place without climate change, said Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research Germany, in a meeting presentation so early in the morning that he dubbed the attending delegates “heroic”.
Rahmstorf calculated the monthly heat record ratio - the number of records divided by the number expected in a stationary climate - for the last 131 years of temperature observations. The global mean ratio was roughly five, but parts of Africa and South America experienced 20 times more records than expected.
The high number of records in the tropics is because these areas normally experience a small temperature variance, even though the trend in temperature rise in the region is relatively low, Rahmstorf explained. The Arctic also has a high record ratio, but this is due to its larger temperature trend.
Rahmstorf’s analysis showed that the increase in heat extremes can be explained by a simple stochastic model - a linear trend of increasing temperature combined with uncorrelated noise.
April 25, 2012
EGU 2102: it’s an ill wind for Antarctica’s ice shelves
Changes in the wind circulation around Antarctica are causing the region’s ice shelves to lose ice, explained David Vaughan of the British Antarctic Survey to journalists at the EGU 2012 assembly in Vienna. But the mechanism is different, depending on where the ice shelves are located.
As detailed in a publication in Nature today, of which Vaughan is a co-author, in West and East Antarctica ocean-warming caused by wind changes is melting ice shelves from below. And where ice shelves have thinned, glaciers inland have accelerated as the buttressing effect of the ice shelf is removed.
On the eastern Antarctic Peninsula, on the other hand, it looks like wind-induced atmospheric warming is the culprit - it’s melting snow on the surface of the ice shelves. Some thinning in this region is also due to loss of air compacting the ice.
The team used laser measurements from NASA’s ICESat satellite for 2003-2008 to look at 54 - almost all - of Antarctica’s ice shelves. Warm ocean currents were pinpointed as melting 20 of the ice shelves, mainly in West Antarctica. Indeed the researchers ascribed the majority of Antarctica’s ice loss to ocean change.
EGU 2012: glaciers playing catch-up set to lose 40% of their ice
For the world’s glaciers and ice caps to catch up with the temperatures of the last ten years, they need to lose 38% of their ice volume, on average, and 30% of their area. That’s equivalent to 228 mm of sea-level rise over the next few decades, even without any additional climate change, according to Sebastian Mernild of Los Alamos National Laboratory, US, who presented his work at the EGU 2012 meeting in Vienna.
Mernild studied the mass balance of 124 glaciers and 19 icecaps worldwide, using three averaging methods. The results compared well with earlier studies, which incorporated fewer glaciers, he said.
In Central Europe, Svalbard and Greenland, glaciers and ice caps were more out of balance with their surroundings than the global average. Mernild reckons that glaciers in the Alps are likely to lose most of their mass by 2100.
If recent climate trends continue, by around 2040 glaciers and ice caps will lose at least half of their volume.
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