THE IMPORTANCE OF BEING URGENT:
AVIATION, SHIPPING AND THE MITIGATION DEBATE
Alice Bows-Larkin
Tyndall Centre for Climate Change Research & School of Mechanical Aerospace and
Civil Engineering, University of Manchester
Each year global carbon dioxide emissions rise, the chances of avoiding
‘dangerous climate change’ diminish. At the same time, meaningful policy
measures aimed at curbing the CO2 from international shipping and aviation
remain woefully inadequate. Whilst these two sectors are frequently coupled
together, and are to some extent treated with a similar policy approach within
the UN climate negotiations, their strengths and weaknesses within the
carbon debate have important distinctions. This paper will specifically quantify
what avoiding a reasonable probability of a 2°C temperature rise means for
both the international aviation and shipping sectors, presenting the need for
urgency regarding mitigation policy for both. It will go on to discuss the
conflicts and trade-offs between national-scale and global-scale policy
mechanisms, with specific focus on the merits or otherwise of global trading
schemes set against, for instance, the EU’s Emissions Trading Scheme (EU
ETS) or unilateral policy measures by individual nations. Specifically, it will
review recent policy developments regarding the inclusion of only intra-EU
flights within the EU ETS, drawing attention to how this influences policy for
not only aviation, but shipping mitigation, in addition to national-scale climate
change policy in the UK. Finally, the paper will contrast the opportunities for
mitigation technologies and operations for both sectors in the context of
growth in industrialised and industrialising nations alike. The significant
opportunities for technology development in shipping, and the presentation of
technology roadmaps describing potential timelines for sails, Flettner rotors,
kites and biofuels will be set against the very limited technological mitigation
options facing the aviation industry.
1.
Introduction
The analysis within this paper takes as a given that the global community
continues with its ambition to limit global temperature rises to 2°C above preindustrial levels, and that this target represents a meaningful goal, rather than
a political anchor point. This temperature goal is subsequently translated into
emissions budgets and pathways in order to explore the scale of policy
intervention required to remain within the given constraints. There are three
assumptions made in delivering this translation:
(i) The chosen probability of exceeding the 2°C threshold. This constrains the
global carbon budget (Anderson and Bows 2007; Meinshausen et al. 2009)
(ii) The year in which global emissions reach a peak before declining
(iii) The apportionment of responsibility to nations and/or sectors for
remaining within the constrained budget.
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Expressing 2°C through emissions budgets and pathways is a scientifically
robust method for quantifying the scale of the climate challenge for nations,
sectors and regions. However, apportioning responsibility for emissions to
nations is argued by some, particularly those in the aviation and shipping
industries, to overlook the global nature of these activities. It is suggested that
it would be more efficient and less economically damaging to treat
international aviation and shipping like ‘sovereign’ nations, where they can
trade emissions permits in an international global trading scheme.
Apportionment is considered to get in the way of the smooth operation of a
market-based approach aimed at capping and reducing emissions.
There are two issues here that need to be considered in more depth. Firstly,
the assumption by the industry is that emissions trading will lead to a
satisfactory outcome as far as the climate is concerned. Secondly, that no
apportionment provides space for both industries to growth indefinitely, within
carbon constraints. Taking each issue in turn, here it is argued that emissions
trading may have had a role to play if it had been comprehensively
implemented when the problem of rising emissions was first identified. Now,
such pricing mechanisms now have little to offer given the very rapid pace of
emission growth in the meantime and in the face of a need for the urgent and
stringent emission cuts required to remain within budget1. Taking the EU’s
Emissions Trading Scheme (EU ETS) as an example, it has failed to date to
deliver cuts in emissions commensurate with a reasonable chance of avoiding
2°C, and moreover, continues to allow for carbon leakage through off-setting
with mechanisms active in nations with no carbon cap (Anderson 2012).
Regarding emission apportionment, the analysis here, whilst omitting
emissions trading, does not apportion international emissions to nations.
Rather, it assumes international aviation and shipping are treated as
‘sovereign states’ and follow a pathway proportional to the global aggregated
mitigation trajectory commensurate with a reasonable chance of avoiding 2°C.
The paper then quantifies the scale of the challenge for aviation and shipping
in light of current policy debates. Finally, the paper considers the specific
nature of both international aviation and shipping referring to the emission
mitigation barriers and opportunities faced over the coming decades.
2.
Methodology
The three assumptions presented in the introduction underpin the quantitative
framing for delivering emission pathways out to 2050 for international aviation
and shipping. These emission pathways constrain the scale of the challenge
from which emerges the discussion regarding the ability of either the aviation
or shipping sectors to mitigate emissions to the appropriate level.
2.1. Probabilities associated with avoiding 2°C
There is a range of cumulative budgets commensurate with a global
temperature rise of 2°C above pre-industrial levels given the variety of climate
models available coupled with uncertainties, such as climate sensitivity,
therein. A comprehensive scientific analysis of carbon budgets and
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probabilities is provided in the work of Meinshausen et al., (2009). Informed by
their analysis, here the constraining carbon budget is 1578 GtCO2 over the
21st century, ~50% chance of breaching the 2°C threshold.
2.2. Emission peak years
Integrated Assessment Modelling studies (IAMs) provide suites of scenarios
suitable for avoiding a 2°C rise, but the process of a ‘reality check’ on global
peak years often appears absent. Given the proliferation of the outputs of
IAMs in informing the policy process, arguably decision makers are being
informed by highly optimistic, sometimes entirely unrealistic (past) peaking
dates (Hansen et al. 2008; Nordhaus 2010; Raskin et al. 2010) and low
growth to the peak year (Baer and Mastrandrea 2006; Stern et al. 2006;
Ranger et al. 2010; King et al. 2011). This gives the impression that climate
change is a problem of long-term targets not short-term budgets. If instead, a
more realistic appraisal of how soon emissions can peak is taken, a different
quantitative analysis emerges. In one illustration, Anderson and Bows (2008)
show how emission peaking dates of 2015, 2020 and 2025 severely constrain
and change the emission pathways for the same carbon budget.
To remain within budget, the later the emissions peak, the more rapid
reductions are needed post-peak year, increasing by a few percent for each 5
year interval. Thus, the earlier the peak year, the less severe the mitigation
pathway and policies. Choosing to avoid more severe outcomes however
should not be the aim of scientific analysis, rather a realistic appraisal of the
momentum in-built in the emissions trajectories, often underpinned by a
nation’s energy system, should be made. Here it is assumed that an
appropriate peak year is determined by constraining the analysis within a 2°C
budget, whilst considering energy system developments around the world.
Furthermore, the poorer world nations (non-OECD, or ‘non-Annex 1’) are now
the larger share of annual global greenhouse gas emissions both under
territorial and consumption-based accounting approaches (Bows and Barrett
2010). This means that emission trends in non-Annex 1, rather than the richer
Annex 1 nations, dictate the global growth trajectory. In this preliminary
analysis, peak years are therefore taken from Anderson and Bows (2011).
Although within that paper it was assumed viable emissions could reach a
peak by 2015, given four years have passed since that analysis with
emissions continuing to rise unabated, this is no longer considered realistic,
therefore two pathways are chosen with peak years post 2015.
2.3. Apportionment
Stakeholders representative of both aviation and shipping continue to argue
that their emissions should not be apportioned to individual nations, but rather
treated at a global scale, as if sovereign nations (Bows et al. 2009; Gilbert and
Bows 2012). This is partly a legacy of how they are treated within the Kyoto
Protocol, where emissions produced within international waters and airspace
were excluded from national emission inventories and targets. Although the
author has explored apportionment of both aviation and shipping emissions to
nations (Wood et al. 2010; Gilbert and Bows 2012), here a global perspective
more closely aligned with the industry preference is taken. Moreover, the
absence of evidence that emissions trading has something to offer towards
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remaining within the 2°C goal leads to a simplistic assumption here that
aviation and shipping will mitigate no more or less than other sectors. They
will take a path proportionally in line with what is necessary from the global
average rate of mitigation appropriate for the chosen probability (i) and
pathway as determined by (ii). The emission pathway is already so stringent,
that arguably for any sector to do less than the average, places considerable
pressure on other sectors to compensate (Calverley 2012). It is beyond the
scope of this paper to analyse which sectors could, if necessary, deliver
greater emission reductions than the average. However, the feasibility of
international aviation and shipping being able to maintain such stringent
mitigation pathways is the focus of this analysis.
2.4. Shipping and aviation futures
Scenario development and road-mapping are used by academics and
industry/policy stakeholders alike to scope future emissions potential. Some
studies deliver forecasts for levels of emissions underpinned by economic
growth projections, for instance those that build upon the Special Report on
Emission Scenarios (Eyring et al. 2005; Bows 2010). Others take the starting
point as where in the future emissions ‘need’ to be to avoid particular levels of
climate change – known as backcasting (for instance, Bows et al. 2009). This
type of approach articulates potential pathways to change, identifying
necessary milestones that can be technological, operational or related to
changing patterns and levels of demand. For instance, in this case it can be
used to illustrate how a stringent mitigation pathway, such as the 2°C
trajectory, could be achieved. The scale of the challenge is compared with
some of the futures studies in the literature. In addition, research conducted
that has involved industry and policy stakeholders is drawn upon to add
qualitative as well as quantitative grounding to mitigation measures and policy
developments either being implemented or on the horizon. This includes
interviews and workshops hosted by the author and colleagues.
3.
Analysis
3.1. Global trends compared with trends in aviation and shipping
Global emission pathways taken from Anderson and Bows (2011) are indexed
to 1990 and translated for aviation and shipping (Figure 1). Aviation and
shipping emissions data are taken from the International Energy Agency
(IEA), and between 1990 and 2010, global data is based on the Carbon
Dioxide Information Analysis Centre (CDIAC). IEA estimates for the combined
CO2 from both international aviation and shipping (in red) show growth of
approximately 78% by 2010 from 1990, while total global emissions grew by
42%. As cumulative emissions dictate the climate impact, Figure 1 illustrates
that the combined international aviation and shipping industry CO2 emissions
have had a considerably higher climate impact between 1990 and 2010 than if
they had followed the average growth for all sectors. It would not therefore be
unreasonable for other sectors to argue that this historical trend should be
taken into account by removing the additional cumulative emissions already
attributable to aviation and shipping from the remaining 2010-2050 budget.
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However, this has not been done here as it is beyond the scope of this early
analysis.
Carbon Dioxide Emissions (MtCO2)
1200
1000
800
600
400
200
0
1990
C+4 CO2 pathway (50% chance of >2C)
C+5 CO2 pathway (50% chance of >2C)
IEA estimates int aviation + int shipping
2000
2010
2020
2030
2040
2050
Year
Figure 1: International aviation and shipping emissions indexed to 1990 for two 2°C pathways
taken from Anderson and Bows (2011) and Anderson and Bows (2012) and coupled
international aviation and shipping emission estimates for 1990 to 2010 using IEA data.
3.2. Comparison with existing futures studies
From Figure 1, indicators emerge that provide target levels for the aviation
and shipping emissions commensurate with a 50:50 chance of avoiding 2°C:
- By 2030, emissions from international aviation and shipping need to
return to 1990 levels or be higher by less than 25%.
-
Emissions in 2050 need to be between 71 to 76% lower than 1990.
-
The rate of emission reduction from around 2025 onwards needs to be
between 6 and 8% per year.
-
Emissions need to reach a peak by between 2015 or 2020
Comparing these 2°C trajectories with futures studies highlights the gap
between what is necessary to avoid 2°C and what is considered more likely.
For instance, in IMO projections, emissions are expected to increase by 180%
to 305% relative to 1990 levels by 2050 or 102 to 193% if 2000 is the baseline
(Anderson and Bows, 2012) . Similarly for aviation, Gundmundsson and
Anger, (2012) show aviation CO2 emissions are assumed to rise by up to
515% between 2000 and 2050, but more commonly figures of 220% are
projected. This compares with a 75% to 78% cut needed to remain
commensurate with a 50:50 chance of avoiding 2°C. There is little doubt that
the reaction of the international aviation and shipping industries would be that
such reductions are not feasible, and result in economic damage.
3.3. Policy review – international aviation
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At the global scale, the International Civil Aviation Organisation (ICAO) is
charged with mitigating emissions from international aviation in the Kyoto
Protocol. For nearly two decades there has been little progress in establishing
standards or targets for this sectors’ emissions, and the perceived delay has
led to policy measures to be considered at sub-global levels. Nevertheless, as
of 2013, there are indications that the industry’s much sought-after global
trading scheme could finally be within sights. Specifically, ICAO has been
assessing the feasibility of market based measures and will discuss the
implementation of a global trading scheme at its forthcoming General
Assembly in September 2013. ICAO also recommends that revenue derived
from a trading scheme should be applied in the first instance to mitigating the
environmental impact of aircraft engine emissions.
The industry has also progressed in developing a strategy to reduce its
emissions, whereby those airlines represented by the Air Transport
Association (IATA) have set targets for a 1.5% average annual improvement
in fleet fuel efficiency to 2020. ICAO has a somewhat higher target of 2%
efficiency improvement until 2050 and ‘carbon neutral growth from 2020
through technology, operations, alternative fuels and economic instruments’.
Similarly, IATA has a commitment to cap net emissions from 2020 onwards,
as well as net emissions being cut by half in 2050 compared with 2005 levels.
However, it should be borne in mind that net emissions or ‘carbon neutral
growth using…economic instruments’ includes the effect of emissions trading.
In other words, aviation emissions in absolute terms are expected to continue
to rise, with the industry purchasing emissions rights from other sectors in
order that net emissions are flat in terms of growth by 2020. Again, if it is
assumed that existing trading schemes, and the likely range of carbon prices
therein will not be sufficient to mitigate to 2°C, then this amounts to absolute
aviation emissions being outside of the 2°C constraints. Other global
measures include an agreed international CO2 standard for aircraft by 2016
that aims to reward and encourage improvements in technology. It is also
considered that sustainable alternative fuels for aviation offer one of the most
promising (arguably the only) solution to significantly reduce aviation CO 2
emissions. Therefore the UNFCCC agreed ICAO is at the forefront of
facilitating the development and deployment of such fuels on a global basis.
Meanwhile, policymaking at an EU level agreed a comprehensive strategy to
tackle climate change emissions. The two central components of the strategy
are including aviation in the EU ETS and improving EU airspace design
through the Single European Sky programme. Following many years of
debate, in 2012 the EU included some international flights within its emissions
trading scheme. It proposed including aviation within the scheme over a
decade ago to overcome ICAO’s failure to adequately address aviation’s
rising emissions. It also surprised many by setting out a framework to include
not only flights within and between EU nations, but all flights departing or
arriving in EU member states. Nevertheless, much of the analysis conducted
to assess the potential impact of including aviation suggest that it would likely
have little meaningful impact on CO2 emissions, with the costs easily passed
onto the consumer with little impact on demand (Scheelhaase and Grimme
2007; Bows and Anderson 2008; Anger and Köhler 2010).
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However, even before the policy began operation, in November 2012 the EU
suspended plans to include non-EU nations until late in 2013 (European
Commission 2012). Ostensibly this delay is to provide an opportunity for ICAO
to discuss the implementation of a global scheme, as it is the intention of the
EU to work with ICAO to progress a global agreement if meaningful. The EU
describe the suspension as a gesture of goodwill in support of an international
solution yet it has coincided with legal challenges from nations outside the EU,
who expect costs to rise for as a result of this legislation.
Another measure being pursued by the EU is the Single European Sky
initiative, which aims to improve the design, management and regulation of
airspace across the EU, by altering the existing airspace that is divided by
national borders and instead using ‘functional airspace blocks’ (FABs),
designed to maximise the efficiency of airspace.
Scaling down to a national level, whilst international aviation is not considered
within national targets through Kyoto, the UK, for example, has its own
Climate Change Act, within which it makes a commitment to 2°C. In meeting
this objective, the UK has a target to reduce CO2 by 80% by 2050 as well as
short-term carbon budgets that take cumulative emissions into account. Many
in the UK argued strongly that international aviation (and shipping) should be
included quantitatively in these targets. Similarly, the UK’s Committee on
Climate Change (CCC), charged with advising government on how to meet its
commitments, recommended in April 2012 that these international emission
should be formally included, with aviation’s emissions based on the UK’s
share of the EU ETS cap (Committee on Climate Change 2012). However, by
December 2012, the CCC altered its position on the basis of the EU’s decision
to suspend full inclusion of aviation in the EU ETS (Committee on Climate
Change 2012), arguing that the step taken by the EU made it impossible to
make a formal inclusion. The issue will be revisited once uncertainties
surrounding the EU ETS are resolved, with further guidance given when
advice on the fifth carbon budget is presented in 2015.
In addition to pursuing including aviation in the EU ETS, the UK established
an Airports Commission to advise on future need for airport capacity, with
interim advice expected late in 2013. It also launched an aviation policy
framework in March 2013 and remains a strong supporter of the Single
European Sky initiative, having already established the first FAB with Ireland
in 2008. Similarly, it supports the UK’s Civil Aviation Authority’s (CAA’s)
Future Airspace Strategy. The UK Government hopes it will play a significant
role in delivering economic and environmental objectives in relation to
aviation, by improving capacity and enhancing queue management. A
coalition of airlines, airports, aerospace manufactures and air navigation
service providers, ‘Sustainable Aviation’, is also being encouraged by UK
Government, having set out a roadmap for halving net emission from 2005
levels by 2050 through technological improvements and carbon trading,
although it is also being urged to strengthen its targets. Other technologies
such as video-conferencing are mentioned in the UK’s framework, but
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demand-side measures play a very minor role within the document. In
general, there is significant reliance placed on the role of emissions trading.
So, what is clear from the latest UK policy documents is that there is a
preference for global action through ICAO for international emissions, as well
as for supporting the EU in including aviation in the EU ETS given the ‘risk of
putting UK businesses at a competitive disadvantage’ (Secretary of State for
Transport 2013). They consider that while unilateral action can be appropriate
and justified in terms of cost/benefit, this is more difficult to achieve with
international flights due to the risks of market distortions.
3.4. Policy review – international shipping
In the same way as international aviation emissions are subject to the control
of ICAO, the body charged with controlling shipping emissions in the
International Maritime Organisation (IMO). Also similar to international
aviation, progress in devising and implementing mitigation policy has been
slow to materialise, and the industry has come under increasing pressure
from, for instance, the EU to begin meaningful mitigation measures. Different
to aviation though, is one of the core sticking points in gaining a majority vote
to implement policy through the IMO; that is the conflict between the
UNFCCC’s principle of common but differentiated responsibility and the
maritime principle of no more favourable treatment. The first supporting
differentiated mitigation effort depending on a nation’s economic development,
and the other seeking fair and consistent treatment across all shipping
nations. Specifically, important non-Annex 1 maritime nations have sought to
prevent measures that they consider contravene the UNFCCC’s principle.
By July 2011, one measure that had been agreed was a mandate on
minimum efficiency levels for new ships implemented through an Energy
Efficiency Design Index (EEDI). It aims to reduce emissions from new ships
by 30% in 2025, which, when including estimates for fleet turnover, will
increase overall efficiency by 30% by 2050. This amounts to an efficiency
improvement of under 1% per year. Agreeing a market based measure such
as emissions trading or a climate levy has not yet come to fruition.
Policy development at an EU scale had been pointing towards including
shipping within the EU ETS. However, the more complex nature of the
shipping system poses significant challenges towards how to apportion
emissions for the purpose of trading (Gilbert and Bows 2012) leadeing the EU
instead to announce new legislation requiring owners of large ships (over
5,000 gross tonnes) using EU ports to monitor and report the ships’ annual
CO2 emissions (European Commission 2013), to increase transparency
around emissions to create an incentive for the owners to cut them. It is also
considered that robust monitoring, reporting and verification of emissions is an
essential prerequisite for informed discussions on emissions targets globally
and at an EU scale. The proposed rules will apply from January 2018.
Considering a national perspective on these developments, as noted in
Section 3.3, the UK’s CCC had been advising the UK Government to include
both international aviation and shipping emissions within its targets. However
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the developments in relation to aviation have had a subsequent knock-on
impact on decisions around the shipping sector, whereby discussion over the
formal inclusion of shipping emissions into UK budgets and targets is now
suspended until 2015. Thus, whilst there are arguably measures that the UK
could implement unilaterally, or with other EU nations, to influence the
efficiency of shipping around UK nations or of ships calling at UK ports
(Gilbert and Bows 2012), it is the impact of global negotiations around a
trading scheme for aviation that has put UK shipping mitigation on hold.
The current policy landscape, whilst establishing some mitigation goals for
aviation and shipping, relies heavily on the success of emissions trading.
Furthermore, even if trading were considered viable, current plans do not fit
with the 2°C constraints laid out in Figure 1. For instance, even a 50%
reduction in net emissions from aviation by 2050 from 2005 levels, assuming
trading works, falls short of the 78 to 82% necessary to remain commensurate
with 2°C. To more meaningfully address the scope for mitigation across these
two challenging sectors, here an ecological economics framing is taken,
where the physical planetary limits are of paramount importance, with society
and economy residing within those. Using this framework, opportunities from a
technical, operational and demand perspective that could deliver absolute
emission cuts are presented. This paper draws on existing studies to consider
the gap between the necessary mitigation and ‘expected’ development.
4.
Options for decarbonising aviation
Decarbonisation across all sectors tends to consider in the first instance, new
technologies and alternative fuels, and the aviation sector is no exception. Yet
this narrow lens relies on successful technology deployment well before 2050
allowing growth trends in demand and often conventional operational systems
to be maintained. Yet taking a long-term technology-focused view ignores the
science underpinning 2°C – it is curbing cumulative emissions over time not
just cutting emissions significantly in the long-term that is essential. The
absence of meaningful policies that include the demand-side is most acutely
visible in recent emissions growth rates enjoyed by the aviation sector.
Incremental technology change, marginal adjustments to operations, coupled
with very high rates of growth, combine to maintain CO2 growth in
international aviation typically around 3% to 6% per annum. Even if aviation is
considered to be ‘mature’, for instance the USA, CO2 emissions from
international flights have been rising at around 2.5% since 1990, an increase
of 64% in twenty years. The outlook for CO2 growth (or decline) is considered
below by describing available technology, operational and demand-side
measures that could feasibly mitigate rising levels of CO2.
4.1. Technology
Fuel costs are increasingly important, given the very energy-intensive nature
of flight. Even when kerosene could be purchased at a much lower price,
minimising fuel consumption through improving fuel efficiency was a focus. As
a result, engineers have developed extremely efficient high bypass, high
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pressure-ratio gas turbine engines that dominate the fleet (Bows et al. 2008).
Nevertheless, opportunities for ongoing improvements diminish over time, and
reside typically at 1% per year in terms of fuel combusted per passenger-km.
To push efficiency much harder, a fundamental shift in aero-engine design is
needed. Open-rotor engines offer some scope for improvement, but have
limited application given high noise levels. Thus at present, engine
developments are likely to continue to offer marginal efficiency improvements.
Changes to the materials used to construct aircraft can deliver better fuel
efficiency. Composite materials are increasingly incorporated, with newer
designs from both Boeing and Airbus replacing 50% of the aluminium with
composites. Whilst this development plays an important role, it is only as
these newer aircraft renew the existing fleet, when real benefits can be
gained. As suggested by the industry’s own targets in Section 3.3, the
combined technological developments offer a 1 to 2% improvement per year,
with fleet turnover dampening the effect of improvements for new aircraft.
There are some more radical options, such as alternative fuels or completely
different airframe designs, such as the Blended Wing Body aircraft or
hydrogen propulsion. For hydrogen to decarbonise aviation, aircraft need
modifications to incorporate a much larger fuel tank, given hydrogen’s lower
energy density. Compounding the problem of general fleet turnover, any such
radical change also needs alterations to the supporting fuelling and airport
infrastructure. Thus these options are considered viable only in the very longterm. Instead it is more attractive to research technologies that can be
retrofitted into existing aircraft and its infrastructure. Deriving kerosene-grade
fuel from biomass is one option. Research into this is ongoing, and supported
by industry, but needs to address serious concerns over the needs of other
industries for the same biomass and its sustainable production (Bows-Larkin
and Anderson 2013). It is clear why the industry has such conservative goals,
in addition to relying heavily on trading to reduce CO2 levels. To fit with the
challenge posed in Figure 1, non-technical options require consideration.
4.2. Operational change
Measures to improve congestion around airspace to improve its efficient use
continue to be under discussion. Nevertheless, the ‘One European Sky’
initiative, was being put forward around the start of the millennium yet, as of
2013, the initiative is still not comprehensively implemented. Moreover, even if
operational improvements could deliver savings, this would be a one-off
measure. Finally, and arguably more significantly, improving congestion
facilitates increased rates of take-off and landing supporting aviation growth.
So, whilst a more efficient use of airspace reduces the fuel consumed per
passenger-km, these improvements will be soon offset by growth. It is here
arguments around airport expansion revolve. While additional runways can
ease congestion, and lead to less fuel burnt per flight, they facilitate a greater
use of the airport capacity. Therefore, only if the rates of growth are lower
than the improvements to be gained through both operational change and
technology improvement, will CO2 growth be curbed, and ultimately reduce.
Clearly the industry’s objective of having only ‘net’ emissions reaching a
plateau, takes as a given that this will not be the case.
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4.3. Demand management
As absolute emissions are expected to grow, it is helpful to consider what
typical growth rates are ‘allowable’ within constraints of a 2°C target. For the
C+4 scenario, growth rates in terms of passenger-km would need to reduce to
zero from 2020, falling to around a 4% reduction per annum by 2025. For the
C+5 scenario, zero growth is needed by 2025, then reductions of around 6%
per year by 2033. Constraining aviation demand is clearly not a popular policy
measure. There is little reference to it in industry and government literature.
Nevertheless a gradual reduction from the typical 3% per annum growth seen
since 1990 to zero by 2020 to 2025 is more physically feasible than a largescale role out of emerging technologies, or emissions trading being
implemented in a way that is commensurate with 2°C. New research is
needed to consider where passenger-km could be cut in absolute terms
through provision of, for instance, virtual communications, or long-distance,
low-carbon rail travel, so as to allow regions where flying per capita as well as
absolute emissions are still extremely low (such as China), but growth rates
high and anticipated to continue.
5.
Options for decarbonising shipping
Taking the shipping sector in contrast, this section explores the opportunities
in terms of technology, operations and issues of demand relevant for
decarbonising shipping at the same rate as that for aviation. Both sectors
argue they play a pivotal role in economic growth, and should be protected
from cutting emissions severely. Yet these two industries differ substantially.
Aviation is largely driven by leisure travel and passengers, shipping by trade
and freight. One stakeholder suggested that immediately grounding all aircraft
would cause some disgruntlement, while taking similar steps for shipping and
trade would leave supermarket shelves empty within days. Thus, demand
management is likely to be even less politically appealing within shipping than
aviation, but are there other reasons for why demand-side intervention may be
important in shipping mitigation, as discussed in section 5.3.
5.1. Technology
Fuel efficiency has been a weaker driver within shipping than in aviation for a
number of reasons, with ships combusting oil products at the bottom of the
fuel hierarchy – heavy fuel oil. Firstly, the energy required to ship a freighttonne is considerably lower than the equivalent energy required for flight, so
monetary savings gained by improving engines and ship designs are less
pronounced. Secondly, the high number of actors within the shipping system
means the ship operator or charterer may not own the fuel, thus incentivising
fuel-saving measures gets diluted through the system. However, ship engines
are still very efficient, and shipping goods is a very low-carbon method for
moving freight. Thus the range of incremental technologies, many of which
could be retrofitted to existing ships, is yet to be widely exploited.
There are also technologies offering more significant change. Innovative
technological designs for exploiting wind power have emerged with the
potential to offer fuel savings as high as 50% depending on ship type, route
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and speed (Traut et al. 2014). They can also reduce the need for heavy fuel
oil for auxiliary power. Technologies include Flettner Rotors, kites and fixed or
rigid sails. Flettner Rotors harness the Magnus effect for propulsion and can
be retrofitted to existing vessels although the use of deck space for different
ship types is a key consideration. Kites attach to the bow of vessels,
controlled from deck and operate at high altitudes to maximise wind speeds.
Sails have had a demonstrable impact on a bulk carrier run by the Modern
Merchant Sailing Vessel (MMSC), with other examples including sail-assisted
cargo ships (Gilbert et al. 2014). The big advantage of these technologies is
that they can offer short-term emissions savings.
Aside from renewable options, technologies to improve energy storage and
use fuel cells are also feasible. Electric drive using lithium-ion batteries is
being considered, and storage technologies include super-conductors and
flywheels. The electric motor favours ferries and cruise vessels given their
frequent load changes. Fuel cells such as solid oxide fuel cells are appropriate
for application in marine propulsion, while Proton Exchange Membrane
devices are more suitable for auxiliary engines.
Regarding fuels, here too there are a range of feasible options, some already
being exploited. Liquefied natural gas (LNG) delivers CO2 emissions savings
in the short-term, but as a fossil fuel, a fleet-wide switch to LNG is insufficient
to deliver decarbonisation (Gilbert 2013). Biogas, biofuels and micro-algae are
feasible, but suffer the same sustainability concerns as in other sectors.
Nuclear ships are worthy of consideration and are already used in the military.
Opportunities for decarbonising the shipping sector through technological
intervention are manifold, but will require a portfolio of solutions that depend
on a particular end-use. Moreover, many options, particularly wind-propulsion
have more scope for cutting emissions if the ship speed is cut.
5.2. Operations
Many ship operators sought measures to reduce fuel costs following the 2008
global economic downturn, when slow-steaming gained popularity. This is
because fuel consumption has a cubed relationship to ship speed, so slowsteaming offers cuts of up to 80% per voyage (estimated using the ASK-ships
model using data from Buhang et al., (2009)). Depending on the particular
market, ships often wait for many days outside ports, either due to congestion
or waiting for the price of bunker fuel to change. It is not always the case that
the ship arrival time is crucial. However, slow-steaming could impact on flows
of trade, many reliant heavily on ‘just-in-time’ policies. Moreover, slowing
down ships could lead to an incentive to build more ships, to maintain freight
flows. Nevertheless, slow-steaming, and designing ships to be optimised for
slower speeds in future reduces overall propulsive power, providing a greater
incentive to incorporate renewable technologies to further cut CO2.
5.3. Demand management
Shipping has a much more optimistic outlook in terms of technology and
operations than aviation. This, coupled with the ‘need’ for trade, suggests less
relevance for demand management. However, despite very strong potential
for shipping decarbonisation, there are few incentives for it, with only niche
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12
markets at present for some of the more significant interventions. Unlike in
aviation, most ship building occurs in nations without climate targets, and has
a great number of manufacturers, operators, charterers, owners and other
stakeholders serving to maintain the status quo. Influencing change in this
sector is extremely challenging, and arguably most effectively encouraged at
port-state level (Gilbert and Bows 2012; Doudnikoff 2013).
One other key aspect to address is how demand for goods alters over time,
and how this can impact shipping. UK and EU policy on climate change is
implementing measures to decarbonise energy systems. At present, 50% of
tonnes imported and exported to and from the UK are fossil fuels. Depending
on the decarbonisation path chosen, shifts in fossil fuels consumption, and the
potential growth in biomass/biofuels, will significantly alter the landscape
(Mander et al. 2012). This is one area where there will likely be significant
change, but others include the continual strain on global resources of ores
and minerals, as well as climate impacts on food production. This issue of
resource use and the limits to it could feasibly raise the debate around levels
and types of consumption, which again impacts on trade. So, whilst there is
little appetite to manage demand in shipping, there are certainly good reasons
to think that demand will likely shift significantly in future.
6.
Discussion and conclusion
International shipping and aviation are frequently coupled when discussing
climate change mitigation. Like all other sectors, both face a significant
challenge in achieving decarbonisation at a level commensurate with 2°C.
What makes them distinct is that as ‘international’ sectors, global climate
governance arrangements differ from others. Moreover, both have emissions
growing above the global average rate, with further growth expected to 2050.
Yet, when considering the scale of the climate challenge and options for
decarbonisation, clear differences between these sectors are apparent. In
short, the shipping industry has many technological and operational options
that could cut emissions in the short- to medium-term. Aviation does not. This
has led to a strong reliance by the aviation sector on emissions trading to
deliver emission ‘cuts’. The irony is that if it options existed for the aviation
sector, there is a less complicated institutional set-up, with a smaller number
of markets and actors to facilitate change. Yet, as the technologies are not
forthcoming for aviation, demand-management must be seriously considered,
or alternatively, the case made for why aviation takes priority over others for to
use biofuels. With many options on the horizon for shipping, its complex
nature is a significant barrier to change. Nevertheless, energy-system
transitions may well drive change from the demand side.
International shipping and aviation are similar in CO2 growth rates and
decarbonisation efforts to date, but differ significantly in terms of options for
future decarbonisation. To remain commensurate with the scientific
interpretation of 2°C, requiring urgent and rapid decarbonisation, a pragmatic
approach would be to influence, incentivise or set standards around
technology options for shipping and constrain demand for aviation. Combining
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slow-steaming with a range of renewable technologies such as Flettner
Rotors, and encouraging a widespread programme of retrofit through portstate influence, could lead to a significant shift in the emissions associated
with shipping, at least at an EU scale. The issue of paramount importance for
decarbonising shipping is how to influence this complex confluence of varied
markets and ship types. For aviation, the message is simple, nations where
per-capita flying is high, and growth rates maintained, have no option but to
consider constraining growth in the short-term, until fuel efficiency
improvements can off-set rises in passenger-km. Emissions trading is a redherring, but even assuming trading is effective, the industries current goals fall
way short of the emission cuts needed by 2050. Without trading, 2°C needs
international aviation growth rates to be constrained to zero by 2020 to 2025.
7.
Acknowledgements
The research underpinning this paper has been undertaken with funding from
the Tyndall Centre for Climate Change research through EPSRC, NERC and
ESRC grants, and the High Seas project funded under EPSRC’s Energy
Programme. Thanks to the High Seas team for their ongoing quality research
underpinning analysis within the project: Sarah Mander, Paul Gilbert, Conor
Walsh, Michael Traut, Kevin Anderson, Peter Stansby and Antonio Filippone
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Notes
1
A carbon price orders of magnitude higher than the current price would need to be established, but
existing economic models are arguably unable to predict the outcome of such non-incremental
adjustment to the economic system.
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