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expert reaction to IPCC AR5 WG3

The UN’s Intergovernmental Panel on Climate Change (IPCC)  released its third and final report of the current series, looking at strategies for mitigating global warming and recommending a rapid move away from fossil fuels.


Prof Peter Styring, Director of the UK Centre for Carbon Dioxide Utilization at the University of Sheffield and Chair of the EPSRC CO2Chem Grand Challenge Network, said:

“The IPCC report makes it clear that CO2 mitigation is a priority if temperature rises are to be avoided. CCS is still regarded as a technology to achieve this in the short term although only medium confidence is applied to these assumptions. The main reason is despite the technology reaching a degree of maturity, it has not been demonstrated on a commercial scale globally.

“It is also clear that additional strategies may be required to remove CO2 from the atmosphere as well as at the end of pipe in the power and industrial sectors. Air capture poses technological challenges due to relatively low concentrations when compared to post combustion flue gas sources. While there is some evidence to support materials that can achieve air capture at the pilot scale, these are again a way off maturity.

“What the report fails to recognise is the growing importance of carbon capture and utilization (CCU) or carbon dioxide utilization (CDU) as it is otherwise known. With CCU the CO2 is transformed into value added products. While CCS is a waste mitigation technology so cannot yield a profit, CDU will eventually produce profits once capital expenditure has been recovered. The rapid advancement in CDU has shown many processes developed to turn CO2 into products such as polymers and cement and aggregates, fuels and chemical intermediates.  CDU is also a means for energy storage, taking renewable, intermediate energy sources and storing the energy at times of low demand: times at which the power sources would otherwise be switched off.

“This is backed up by the World Economic Forum who have identified carbon dioxide utilisation as one of the Top 10 Emerging Transformative Technologies.”


Dr Dan Osborn, independent consultant and former chair of the evaluation panel for the AVOID research programme, said:

“This report illustrates the challenges the world faces on mitigation but it could be good news for those businesses and countries willing to lead the way on all kinds of low-carbon technologies. Burning oil and gas will be frowned on by future generations because this resource is valuable for other purposes. The sooner we start on mitigation the lower adaptation costs will be. Relying on a non-existent Plan B is not a wise option. Time to act is limited. The world must not put its head in the sand. Global action is needed to reduce emissions whilst there is still time.”


Dr Neil Edwards, Reader in Earth Systems Science at the Open University, said: 

“The WG3 SPM highlights a number of key issues: Firstly, where we are in terms of mitigation and where we need to be (to have a good chance of respecting the 2C limit) are still a long way apart. The changes needed to bridge the gap include transformative, non-incremental changes, particularly of the energy system and behaviour in areas such as energy efficiency, modes of mobility, and potentially diet changes. Such transformative changes remain eminently possible, but concerted action is needed. In particular, BECCS (bio-energy with carbon capture and storage) is a critical component of most strong mitigation scenarios, allowing negative effective emissions, but is still not demonstrated at large scale.

“These results have been seen in many studies including the ERMITAGE project ( which I coordinated from the OU, just finished, which addressed (amongst other things) the conflicting demands for food, energy and forest conservation that complicate mitigation measures related to bioenergy.

“Another key issue to point out is that the current generation of modelling studies, as well as not properly accounting for the economic benefits of avoiding the impacts of climate change, cannot properly address the potential for green growth opportunities because their underlying structure, which generally assumes full employment and optimal use of resources. For this reason non-optimal models tend to be more optimistic.”


William Powrie FREng, Dean of the Faculty of Engineering and the Environment, University of Southampton, UK   

“The report presents powerful and comprehensive evidence of the urgent need to curb greenhouse gas emissions by reducing energy use, increasing energy efficiency and an increasing the proportion of our energy that is generated from renewable resources. It also sets out ways in which this can be achieved – for example in the built environment, through appropriate urban and land use planning, demand management and investment in public transport.

“Behaviour change and economic instruments will be as important as technological innovation; all should be viewed as opportunities rather than threats. Action must be swift, decisive and above all global. The report leaves no doubt that we really are in the last chance saloon as far as addressing climate change is concerned.”


Prof Stephen Long, from the Department of Crop Sciences at the University of Illinois, said:

“In ‘approaches to climate change mitigation’ the report espouses high ideals to which we can all agree, and that no policymaker would dare deny.  However, these ideals are far from achieved in today’s business-as-usual operations.  The danger here is that we will be, and as evidenced by much legislation around biofuels and bioenergy between AR4 and AR5, holding new mitigation options to higher standards than business-as-usual.  Such statements also encourage development of policies around imagined rather than proven issues.  The result is obvious, maintain business-as-usual – it is so much easier. 

“The section on ‘Agriculture, Forestry and Other Land Uses (AFOLU)’  clearly failed to see the elephant in the room.  Output of primary foodstuffs such as grain and seed needs to increase 70% by 2050 to keep pace with demand.  We are failing to increase yields per unit land area to achieve this goal.  If we do not address this problem first, then the result is obvious: we will spill over on to less productive and less sustainable land which will prevent or even reverse other mitigation options of afforestation, bioenergy, and soil improvement. 

“The report tells policymakers that ‘the most cost-effective effective options in forestry are afforestation’ – i.e. planting land currently in other uses with trees and then forgoing all other potential uses of that land.  Measures under the Common Agricultural Policy reform of the EU in particular are intended to continue to promote the reafforestation of agricultural land, which began in the 1990s.  Ironically this conversion of land has coincided with a doubling of net imports of primary foodstuffs by the EU. 

“The report for policymakers fails to expose the major caveats of afforestation.  First, it is one off, once the forest reaches maturity it is no longer a sink for carbon, but a store that will be lost with the next fire or insect attack.  Second the land could be used far more effectively in providing a continuous supply of energy, e.g. as coppice for combustion, which over a period of years would continually displace fossil fuel emissions.  By contrast, the section on bioenergy where we have real evidence of benefits is submerged in inhibitory caveats, which will hardly be enticing to policymakers. 

“While reafforestation of agricultural land is not flagged as competition with food, bioenergy is.  Yet it fails to note the many opportunities outside of the relatively small area of land suited to food production.  In particular, the report fails to give emphasis to the real successes and need of analysis of the bases of these successes.  The example of the Brazilian sugarcane ethanol industry which resulted in more ethanol than gasoline use in 2010 (between AR4 and AR5) is not noted.  The report casts doubt on its value (with ‘high certainty’).  Yet no one can deny it has resulted in large scale mitigation of fossil fuel consumption, achieved at a time when the country has massively increased food crop productivity per unit area of land. 

“It has also provided the best example of how learning by doing has continually improved GHG balance, so that more realistic estimates of technology gain in the bioenergy sector could be generated and applied in the models.  With the area now mapped by the Brazilian government, ethanol produced here could equal 15% of current global liquid fuel use.  With significant areas of the globe’s former sugarcane lands abandoned and many other areas of marginal land available in the tropics, what options are there to expand this successful model?  Biomass for combustion, like ethanol, is low hanging fruit, it can be implemented and used on a short time scale, perhaps buying time for more sophisticated and ultimately better technologies to develop. 

“There are many opportunities here that would be win-win for society and mitigation, such as use of lands that have become salinated or are too arid for food production, but would support biomass production – giving employment back to decimated communities.  But instead of picking the low hanging fruit, the report is a thinly veiled attempt to sell carbon dioxide capture and storage (CCS), giving the impression that bioenergy only has value if it can be combined with CCS. 

“This will be highly inhibitory to achieve mitigation through bioenergy.  Unlike bioenergy, with many mature technologies from planting to heat and electricity generation, CCS is still in the gestation phase.  There is little practical evidence of whether it will be acceptable and safe, or even economically viable.  It is clear that it will be far too expensive for any small scale rural energy projects.  The report is wrong to tie CCS so strongly to bioenergy – it is a laudable goal, but will be inhibitory to a mitigation option that we can achieve within out life times; and one that could bring employment and development opportunities to poor communities.”


Prof Godfrey Boyle, Emeritus Professor of Renewable Energy at The Open University and reviewer for parts of the WG3 report, said:

“Encouragingly, the IPCC AR5 WG3 Summary Report acknowledges the rapid performance improvements and cost reductions that have been seen in renewable energy technologies since the AR4 Report in 2007.  It observes that in 2012, renewables (mainly wind, solar and hydro) contributed just under half the world’s new electricity generating capacity. It sees the renewable sector playing a leading role in boosting the world’s share of low carbon electricity to at least 80% by 2050, and stresses that policy support for renewables should be maintained.

“In the light of this enthusiastic IPCC endorsement, it is disappointing that the European Commission’s recent policy proposals for growth in renewables are unambitious and unspecific. Post-2020, the EU will abandon its existing country-specific renewable targets, aiming instead for a modest Europe-wide target of 27% of energy from renewables by 2030. So instead of setting a leading example to the world by moving rapidly towards a low carbon future, the developed nations of Europe are in danger of falling well short of the IPCC’s latest standards.”


Dr Matt Watson, Senior Lecturer in Natural Hazards at the University of Bristol, said:

“Working group 3’s summary for policy makers is a comprehensive review of mitigation options including scenarios that assume the removal of carbon dioxide both at source and from the dilute atmosphere.

“Carbon Dioxide Removal (CDR) is one type of climate engineering that might be used to curb increasing concentrations and potentially keep temperature increases bearable and/or to compensate for overshoot under circumstances of lesser political and personal action. The IPCC rightly highlights the risks associate with CDR strategies and points out that none of the technologies are ready to be deployed at suitable spatio-temporal scales.  This points to the need for thoughtful, open and transparent research into climate engineering. 

“Anyone that suggests CDR is a distraction and a potential moral hazard does not understand the extent to which these imaginaries are already embedded in climate scenarios and should also better consider the severity of the peril we face.  Conversely, anyone touting CDR technologies as a panacea is not being realistic about the cost and timescales involved in their deployment.

“The only sensible policy option, as stated by the IPCC in the summary, is the rapid and wholehearted transition to renewables and less selfish lifestyles.”


Dr Jeremy Leggett, Associate Fellow at Oxford University’s Environmental Change Institute, said:

“It is useful to see so many experts agree that the electricity sector can completely decarbonised as a major contribution to keeping global warming below unacceptable danger levels, but many of us on the front lines of renewable energy would say that the IPCC has underestimated the speed with which our technologies, in concert with energy efficiency, can displace fossil fuels in the years ahead.

“Similarly, growing numbers of financial analysts would say that the IPCC has given inadequate consideration to the soaring capital expenditures of carbon-fuel companies, and the extent to which that constraint can help drive capital to the declining-cost technologies that dominate the renewables family.”


Prof Andrew Watson FRS, Royal Society Research Professor at the University of Exeter, said:

“This is a very responsible report. It has a clear message that there is no painless or risk-free approach to the problem we face.  For sure, there are economic and societal risks involved with mitigation approaches, whether these involve reducing fossil fuel burning, or the use of carbon dioxide sequestration and removal techniques. However, there are even bigger risks if we do nothing and rely exclusively on being able to ride out climate change and adapt to it – which is what will happen unless governments take stronger steps to slow the increase of greenhouse gases.

“We have to encourage both the switch to renewables and pilot projects for carbon sequestration technologies.”


Dr Shaun Fitzgerald of Girton College, Cambridge University, said:

“The report states, ‘Cutting emissions from electricity production to near zero is a common feature of ambitious mitigation scenarios. But using energy efficiently is also important.’ What is intriguing is that the energy efficiency argument is often the second point, perhaps the after-thought. The world of energy is a set of scales – demand and supply. It is obvious that by cutting demand, or at least stemming the growth in demand, the issue of how to supply CO2 friendly power is made easier.

“The true cost of reducing CO2 emissions is generally lower by using energy efficiency measures than by installing green power schemes. It is bewildering why governments use tax break schemes on specific technology initiatives such as feed in tariffs for solar to force behaviour, when in fact the market can figure out which is the most cost effective means of reducing CO2 emissions.

“Take a building for example – who is best placed to determine whether a builder should use more insulation, install an energy efficient ventilation system or PV panels? The contractor and their expert team of designers and procurement team, or the government who oversees feed-in-tariffs? In this case, ‘the government would do more by trying to do less!’ The government should set targets on CO2 emissions for buildings but then let the market sort out the detail to get the lowest cost solution. If government really let the market work, we’d have more energy efficient systems being adopted everywhere.”


Prof Tim Benton, UK Champion for Global Food Security & Professor of Population Ecology at the University of Leeds, said:

“The three IPCC reports highlight the extent to which climate change is caused by our emissions, the impacts that they are likely to have and how we can change our consumption behaviour to mitigate the effects.  We are currently on course for a world that may average 4 degrees hotter by 2100, with the frightening implications this may have for food security as outline in the WGII report. 

“The WGIII report emphasises if we are to act to keep to about 2 degrees of warming, we have to do it over the next decade or so, or the costs will be prohibitive, and we have to reduce GHG emissions by 40-70% in the next 3-4 decades.  Agriculture and forestry are responsible for about a quarter of all GHG emissions and there is significant scope to reduce this.  Perhaps the most important route is via reducing deforestation – which is occurring widely for production of palm oil and soy – and increasing afforestation. 

“Farming can become more ‘climate smart’ by, for example, increasing carbon storage in soils and this may have a range of other benefits for sustainability and resilience.  Changing our diets, especially eating less meat, may have significant impacts, as will reducing our wastage of food. 

“There are many ways that individuals can contribute, but the report also emphasises that collective action is necessary: if individuals and institutions at local, national or super-national level put their own interests first, mitigation at the necessary scale will not come about.”


Dr Hannah Chalmers, Lecturer in Power Plant Engineering and Carbon Capture at the University of Edinburgh, said:

“The scientists of the IPCC have produced an excellent overview of the importance of developing and deploying a broad range of low carbon technologies. The UK has well-advanced plans to accelerate the deployment of carbon capture and storage (CCS) as part of its wide-ranging reforms of the UK electricity market. This report confirms that this support is timely and has an important role to play in global CO2 emissions mitigation efforts.

“The increased emphasis given to the likely role of ‘negative’ emissions technologies that draw CO2 from the atmosphere is important.  They could be essential to allow climate change mitigation to be delivered in ways that are acceptable to society. Some technologies are available today, but there is scope for improvement and also scientific breakthroughs in this area.  Members of the UK CCS Research Centre are among the scientists currently working hard to ensure that priority technologies and effective strategies for using them are rapidly developed and implemented.”


Prof John Shepherd FRS, Professor of Ocean and Earth Science at the University of Southampton, said:

“Cutting CO2 emissions enough to reduce climate change and ocean acidification significantly is going to be difficult, but the alternatives are not easy either. Adapting to climate change is also going to be expensive, and will not always be possible. None of the proposals for geo-engineering the climate looks like being sufficiently safe or effective either. If we just carry on burning fossil fuels, and suffer the consequences, the impacts will be very serious, especially for people who are poor and vulnerable, and least able to adapt. In practice we shall most likely need to use some mixture of these four possible responses.

“It is not for scientists to determine policy, but in my opinion cutting CO2 emissions is the safest and most predictable way to respond to man-made climate change. There is no magic bullet for achieving a sustainable and low-carbon economy, and we are likely to need to use many of the available and possible new technologies, as well as new fiscal measures and regulations, and changes of behaviour and lifestyles.”


Dr Konstantinos Chalvatzis of UEA’s Norwich Business School and a reviewer of chapters on industry and energy for IPCC WGIII, said:

“The IPCC WGIII report outlines the options available to mitigate the effects of climate change. It is the consensus reached by hundreds of scientists after careful consideration of all the available evidence which has emerged since the publication of the last report in 2007.

“The artificially maintained debate on climate change distracts our attention from the major risks that businesses are facing in nearly all aspects of their operations. The climate is changing and we need to do more to manage supply chain and operational vulnerabilities.

“The energy sector, both demand and supply, will have to be entirely transformed in the following decades. If climate change mitigation is not enough to convince us, then energy supply security and rising energy prices should.”


Prof Jason Lowe, Head of Mitigation Advice at the Met Office, said:

The earlier parts of the IPCC 5th assessment have already shown that cumulative carbon budgets need to be constrained in order to limit peak warming. This new report highlights how society might actually reduce emissions of greenhouse gases to achieve this. To avoid the most dangerous changes in future climate requires greenhouse emissions to peak in the near future and then decline. The remaining scientific and economic uncertainties mean it’s not possible to provide a single precise date when emissions need to peak, but peaking later means more rapid emissions reductions or reliance on untested technologies in the future.

“A major unknown surrounds artificial greenhouse gas removal, which, in theory, would allow more flexibility in the timing of fossil fuel emission reductions. However, there is great uncertainty around the potential size of the removal and its side effects are poorly understood. Although simple metrics, such as global average warming, are a useful short hand when discussing future climate change, it is vital to remember that the consequences of a changing climate happen locally and often involve extreme weather and climate events. More work is required to better understand these.”


Prof Stuart Haszeldine, Professor of Carbon Capture and Storage at the University of Edinburgh, said:

“Climate change is happening; as predicted, ‘weird weather’ and harvest shortages are already having an impact. It’s clear beyond doubt that much, much, stronger and faster action is needed to reduce these global effects. 

“The UK talks positively about what must be done, and has achieved a great deal in analysis and regulation, but lags behind in practical action.  Being prosecuted for air quality, halting the carbon price escalator, extending the life of polluting coal power plants, failing to improve energy efficiency for the poorest households, and allowing new gas power plant to be built without carbon capture – these are all signs that the UK evades long-term decisions and has yet to take a firm grip on the solutions. 

“Energy is not the problem; there are many ways to generate energy.  The problem is an overdosing on fossil carbon. There is a global carbon budget – that is the amount we can emit before sliding into dangerous climate change – and humans are halfway through their carbon party.

“Politicians need a big visionary project in order to provide leadership; climate change is it.

“Extraction and combustion of fossil carbon can only continue if that easy energy is matched, tonne for tonne, by the recapture and storage of carbon. It doesn’t matter if that is by Carbon Capture and Storage (CCS), by Bio Energy Capture and Storage (BECCS), by direct air capture, or by enhanced mineral weathering – all of these will be needed.

“The important things are to make a start – and sooner than 2030 – embedding carbon budgeting into every business and every behaviour, and make these actions sustainable without destroying natural ecosystems or diversity with biomass farms.”


David Symons, director in consultancy WSP’s environment business said:

“The largest opportunity to cut emissions by far lies in energy efficiency.  Since UK electricity prices are forecast to be 30% higher by 2020 than today, largely due to higher fossil fuel prices, this is the obvious place to start.

“What’s more, action doesn’t need to be complicated.  At international level, Brussels needs to zero rate VAT on insulation products.  National Governments should set high building and product standards, and enforce them.  And business can get much better at tracking energy use.”


Dr Charlie Wilson, of the school of Environmental Sciences at the University of East Anglia (UEA) and the UEA-based Tyndall Centre for Climate Change Research, said:

“Analysing different future scenarios gives us a robust insight into how we can reduce emissions now and into the future to avoid dangerous climate change.

“If we delay a concerted global effort to reduce climate change, it will lead to increased future costs, reduced flexibility, and an increased reliance on commercially unproven technologies.

“By contrast, taking immediate action to improve energy efficiency and reduce energy demand would be cost-effective, feasible, and it would provide multiple benefits to the economy, public health, and the environment.

“This sends a very clear message to policymakers meeting in Paris next year to negotiate a global climate change agreement.”


Roberto Palacin, Senior Research Associate at Newcastle University leading the Railway Systems Research Group at NewRail, said:

“The well-known socio-economic and demographic challenges that 9bn world population will bring by 2050 mean we cannot afford to ignore the clear warning of climate change.

“This is particularly relevant when 75% of the world population is expected to inhabit urban areas by 2050.  So any efforts to reduce or prevent emission of greenhouse gases (GHG) must involve the way we move people and goods.  

“Mobility is a key driver for the world’s economy as well as allowing access to jobs, education and health care.  But in order to mitigate the effects of GHG emissions, we must radically change our transport.  We must rebalance transport in urban areas by shifting away from private vehicles and towards high quality public transport.  Mass transit systems are key to achieving these goals. 

“These are by no means the only aspects to be considered of course; clean technology and energy, customer service, use of smart devices and above all, a radical change in behaviour are required if we want to have a chance to mitigate the effects of climate change.”


Prof Sir Brian Hoskins, Director of the Grantham Institute for Climate Change, Imperial College London, said:

“The science shows us that we need substantial and sustained reductions in greenhouse gas emissions if we are to limit the risks posed by climate change.  This is not that difficult – we already have the technologies that are required and they will get better and cheaper in the years to come. Potential competitiveness issues, affecting a small number of very energy intensive industries, can be handled.  We should stop wringing our hands and just get on with it.” 


Dr Simon Buckle, Policy Director at the Grantham Institute for Climate Change, Imperial College London, said:

“We can achieve a reduction in emissions without damaging the economy if countries act together and have the right policies in place.  Indeed, tackling climate change is vital to support continued economic development. 

“Most of the reductions in emissions to 2020 needed to limit climate risks could come from action on energy efficiency, limits on the construction and use of inefficient coal plants, dealing with fugitive methane emissions and reducing subsidies for fossil fuels without harming growth.  These measures can save companies money and, in the case of methane emissions, have significant health and agricultural benefits. “


Ajay Gambhir, Research Fellow at the Grantham Institute for Climate Change, Imperial College London, said:

“Low-carbon technologies are becoming cheaper and some are already competitive with fossil fuels in many locations. Renewable technologies such as solar photovoltaics have tremendous potential to address cost-effectively the needs of the 1.3 billion people in the world who do not have access to electricity. 

Various analyses, including a study from Imperial College London, suggest that halving the world’s emissions by 2050 might be achievable at a cost of a few percent of GDP or less depending on the future price of fossil fuels.”

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