Reports:
Transport and climate change - CfIT response to Defra consultation
Section 2: Do you agree with Defra emission projections for the transport sector?
Summary
- Transport (excluding international aviation) accounted for 24% of UK greenhouse gas (GHG) emissions in 2002.
- Defra claims that CO2 emissions from road transport grew by 10% 1990-2000 and they are expected to grow by another 9% or so between 2000 and 2010. Key drivers of road traffic growth include real reductions in fuel prices combined with economic growth.
- DfT, however, believe that emissions grew around 5% between 1990 and 2000 and will grow around 6% in the following decade.
- Transport's share (excluding the UK's share of international aviation) of carbon dioxide emissions by end user could rise from 29% in 2000 to 32% by 2020.
- Data is needed which can be disaggregated to show to what extent the different forms of road transport and the other transport sectors are responsible for the carbon and other greenhouse gas emissions.
- The official forecasts of emissions from the transport sector are characterised by a degree of ambiguity and imprecision. In particular:
- the contribution of transport to the overall emission figures is - to an extent - unclear;
- the contribution of individual transport measures to this sector's emission reduction potential is unclear;
- the considerable range of uncertainty surrounding the assumptions used to derive the transport projections is not acknowledged;
- the underlying assumptions underpinning the forecasts are not transparent;
- within the overall targets for reductions in greenhouse gas emissions, there are no specific targets for transport;
- the consultation document focuses on carbon, to the exclusion of the other 20% of GHG emissions;
- there is insufficient focus on longer term projections - and targets - beyond 2010;
- there is insufficient use of scenario based evidence to underpin emissions' projections.
- Regarding international aviation, carbon dioxide emissions from air travel will amount to some 16-18 MtC by 2030 (97% from international flights).
- The Defra consultation makes no reference to other greenhouse gas emissions from aircraft such as NOx, sulphates, soot, H2O and contrails (which can produce cirrus clouds). This is a significant omission; the overall environmental response from aviation - in terms of climate change - is estimated at between 1.9 and 3.5 times that of the response produced by the CO2 emitted from aircraft alone.
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2.1 Context
2.1.1 Carbon dioxide is the main greenhouse gas responsible for the human contribution to climate change and is projected to account for 70% of radiative forcing of climate over the next century[1]. The Government has both international and domestic commitments to reduce carbon emissions:
- The Government has a commitment under the 1997 Kyoto protocol to reduce the six greenhouse gas emissions by[2] 12.5% below 1990 levels over the period of 2008-2012 (from 168 million tonnes of carbon in 1990).
- In addition, domestically, in 2000, the Government's Climate Change Programme set a goal to cut CO2 emissions by 20% below 1990 levels by 2010.
- Also in 2000, the 10 Year Plan for Transport set out the carbon reductions which were anticipated specifically from the transport sector, breaking down estimates for behavioural and technology change.
- In the 2003 Energy White Paper, the Government recognised that more radical action will be needed over the longer term and aspired to putting the economy on a path to reducing CO2 emissions by 60% to 2050. This followed a recommendation by the Royal Commission on Environmental Pollution[3].
- In 2004, the DfT adopted the PSA target to reduce greenhouse gas emissions to 12% below 1990 levels in line with our Kyoto commitment and move towards a 20% reduction in carbon dioxide emissions below 1990 levels by 2010, through measures including energy efficiency and renewables. This is a joint target with Defra and DTI.
2.1.2 Defra's latest projections of emissions suggest that existing policies will enable the UK to comfortably achieve our Kyoto Protocol commitment but argue that more is needed to achieve the UK national goal of 20% for 2010. It is in this context that the following projections for transport and climate change are assessed.
2.2 Defra projections on transport and CO2 emissions 2000-2010
2.2.1 The Defra Climate Change Review consultation document provides the following projections on transport and greenhouse gas emissions:
- Transport (excluding international aviation) accounted for 24% of UK greenhouse gas (GHG) emissions in 2002, almost the same as the domestic sector on an end-user basis. These are the second largest sources of UK end-user emissions, after the business sector at about 28%[4].
- Carbon Dioxide (CO2) accounts for about 80% of emissions from the transport sector[5].
- CO2 emissions from road transport grew by 10% 1990-2000 and they are expected to grow further by another 9% or so between 2000 and 2010[6].
- The key drivers of change in carbon dioxide emissions from road transport through to 2010 are expected to be real reductions in fuel prices combined with economic growth, which would more than offset the impact of policies to improve the fuel economy of vehicles.
- As emissions from most other sectors are forecast to fall in the same period, transport's share of total emissions is likely to increase. Defra's forecasts of carbon dioxide emissions by end user suggest that transport's share (including domestic aviation) of carbon dioxide emissions by end user could rise from 23% in 2000 to 29% by 2020 (Table 1 below). This amounts to an 19% increase between 2000 and 2020, while total CO2 emissions are forecast to fall by around 6% over this period. With the exception of a small increase (3%) in the business sector, transport is the only sector with rising emissions[7].
2.3 A comparison of Government projections
2.3.1 Projecting CO2 emissions from sector to sector is beset with difficulties and uncertainties. However, this uncertainty is compounded by the fact that figures for energy use and emissions are presented differently according to the publication source (i.e. between government departments) and are not easily comparable.
2.3.2 The following tables are an attempt to compare and contrast emissions data provided by Defra, DfT and DTI in order to provide an idea of the contribution of the transport sector to the climate change targets but also to illustrate the difficulties with the figures.
(a) Projections by sector
2.3.3 Firstly, the most up to date sources of emissions projections by sector are presented. It can be seen from the two tables below that the Defra and DTI figures, whilst not vastly different, are not entirely comparable.
Table 1: Defra emissions projections by sector (from the Climate Change Review Paper) (MtC by end user))
| 2000 | % total | 2010 | % total | 2020 | % total |
|---|
| Business | 49.3 | 32% | 44.5 | 31% | 46.7 | 32% |
| Industrial processes | 7.3 | 5% | 7.3 | 5% | 7.6 | 5% |
| Transport | 41.3 | 27% | 43.3 | 30% | 45.9 | 32% |
| Residential | 39.5 | 26% | 34.9 | 25% | 33.8 | 24% |
| Public | 6.7 | 4% | 5.7 | 4% | 5.2 | 4% |
| Agriculture | 1.2 | 1% | 1.2 | 1% | 1.0 | 1% |
| Land use change | 4.2 | 3% | 2.4 | 2% | 1.7 | 1% |
| Waste management | 0.1 | 0% | 0.1 | 0% | 0.1 | 0% |
| Exports | 3.0 | 2% | 2.6 | 2% | 1.8 | 1% |
| TOTAL | 152.6 |
| 142 |
| 143.8 |
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- These figures are adapted from the table on p 27 of the Climate Change Review (CCR).
- This analysis by 'end user' allocates emissions from power stations to those using the electricity generated.
- These figures assume carbon savings of current policies and measures in all sectors with the exception of transport to continue at the absolute level achieved by 2010 (the assumption in the transport sector is that fuel efficiency standards remain at the same levels achieved in 2010 but the carbon savings will increase with time as older vehicles are replaced).
- Hence, it appears that the CCR expects savings of 10MtC in total from the CCP between 2000 and 2010.
- It is unclear as to whether some or no policies beyond 2010 are included in the projections (p25).
2.3.4 The DTI published projections of carbon dioxide alongside the Climate Change Programme (CCP) in November 2000[8]. These figures also serve to inform the United National Framework Convention on Climate Change and the EU Emissions Trading Scheme (National Allocation Plan). Updates to these figures are published annually, and take into account environmental and other policy developments since the previous exercise and updates the assumptions used[9]. The DTI Energy Model is the basis for these projections.
Table 2: DTI projections of carbon sector emissions (MtC by end user)[10]
| 2000 | % total | 2010 | % total | 2020 | % total |
|---|
| Power stations | 43.1 | 28% | 37.4 | 26% | 35.9 | 25% |
| Refineries | 4.4 | 3% | 5.5 | 4% | 5.5 | 4% |
| Residential | 23.0 | 15% | 20.5 | 15% | 21.8 | 15% |
| Services (incl. agriculture) | 8.1 | 5% | 7.5 | 5% | 7.9 | 6% |
| Industry | 33.8 | 22% | 31.6 | 22% | 30.1 | 21% |
| Road transport | 31.7 | 21% | 34.5 | 24% | 38.2 | 27% |
| Off-road | 1.5 | 1% | 1.5 | 1% | 1.5 | 1% |
| Other transport | 2.8 | 2% | 2.5 | 2% | 2.7 | 2% |
| Sub-total transport | 36.0 | 24% | 38.5 | 27% | 42.4 | 30% |
| Afforestation since 1990 | -0.35 | 0% | -0.65 | 0% | -1.1 | -1% |
| Unallocated measures |
| 0% | -1.34 | -1% | -1.34 | -1% |
| Land use changes | 4.17 | 3% | 2.43 | 2% | 1.9 | -1% |
| TOTAL (all measures baseline) | 152.7 |
| 141.3 |
| 143.1 |
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- Environmental policy measures are included in the baseline beyond 2010 on the basis of savings held constant. The transport projections include impacts of policy measures which are 'firm and funded' (e.g. the current voluntary agreement (VA) with motor manufacturers which runs until 2008.) Projections beyond 2010 do not include improvements expected from a second VA or similar policy agreement as one has yet to be finalised. If so, carbon emissions from the transport sector could be lower than shown.
- Firstly it can be seen that the emissions are presented in different sectors to the CCR.
- The total emissions projections are essentially the same. However, the transport emissions are presented differently. It is not clear but can be assumed that Civil Aviation is included in 'Other Transport'.
- The figures are based on assumption of full impact of Climate Change Programme in 2010.
2.3.5 It is however clear from both sets of figures that the projections show that whilst we shall have made some progress by 2020 in terms of carbon dioxide emissions reduction towards the 60% reduction target, without additional policies, emissions will be about 22% above the linear target path.
(b) Contribution of different modes to transport emissions
2.3.6 Within the transport sector, is very difficult to provide a breakdown of the source of the projected emissions. The DfT provide some indication, but these must also be treated with caution as they appear to be based on figures from the DTI which have now been superceded.
Table 3: DfT breakdown of transport CO2 emissions in the UK[11]
| 2000
(MtC) | As a % of total
transport |
|---|
| Road transport | 38 | 93% |
| Railways | 2 | 5% |
| Civil aircraft | 1 | 2% |
| Shipping | 1 | 2% |
| All transport | 41 |
|
| As a % of all emissions | 28% |
|
| All emissions | 146 |
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2.3.7 It can be seen from this table that the total emissions (146MtC) for 2000 is less than the figure now being provided in the most recent publications from the DTI Table above). It is unclear how this breakdown (i) may change in the light of new figures for 2000 and (ii) are projected into the future as input into the climate change emission projections.
2.3.8 Data is needed which can be disaggregated to show to what extent the different forms of road transport including HGVs and buses for example and the other transport sectors are responsible for the carbon and other greenhouse gas emissions.
(c) Rates of growth in the transport sector beyond 2010
2.3.9 As stated above, Defra states in the review that CO2 emissions from road transport grew by 10% 1990-2000 and they are expected to grow further by another 9% or so between 2000 and 2010.
2.3.10 Firstly, these figures seem to be contradicted by figures in Defra's own report. Figures in the tables on page 27 of the review claim that carbon dioxide (end user) transport emissions have increased by only 5% in the 1990 - 2000 period and are projected to increase by another 5% over the next decade. Corresponding figures for source emissions are 3% and 7% respectively. The only explanation is that the figures in the text correspond to road transport only and those in the tables include the other transport sectors such as aviation, rail and shipping.
2.3.11 Secondly, Defra's stated projections appear to be contradicted by the DfT. A very recent publication by the DfT to the Motorists Forum on Climate Change and Air Quality[12] shows that carbon emissions from road transport grew at about 0.5% per annum between 1990 and 2003[13] (i.e. 5% over the decade) and emissions have levelled off over recent years (Figure 1). This is despite a rise in 20% of road traffic in the 1990s, showing that CO2 emissions from increases in road traffic have been largely offset by improvements in vehicle efficiency.
2.3.12 However, the DfT offered new figures in the revised 10 Year Plan (10YP)[14] indicating that traffic is forecast to rise between 20% and 25% to 2010, while congestion will rise between 11% and 20%. In light of these projections, together with the realisation of lower than originally predicted fuel efficiency savings (discussed in S.3.2 below), carbon emissions from road transport are expected to rise over the next decade - with growth expected at about 0.6% pa from 2000 to 2010 (i.e. about 6% over the decade)[15]. This reflects the expected falling cost of travel per km leading to strong traffic growth.
2.3.13 The trend changes after 2010 as slower traffic growth and continued fuel efficiency improvements are expected to produce a fall in road traffic CO2 emissions of around 5% between 2010 and 2015. This is due to an assumed large fall off in traffic from (i) an ageing population causing average trip lengths to fall and (ii) the fact that the cost per km of travel falls at a lower rate than previously as fuel prices start rising slowly and fuel consumption rates continue to fall but at a lower rate than to 2010[16], with further falls thereafter[17].
Figure 1: Department for Transport projections for CO2 from road transport 1990-2025
Source: DfT Presentation, UKERC Meeting Place Seminar: Transport and Climate Change, December 2004[18]
2.3.14 In its most recent White Paper, the DfT present some figures which differ from those cited above. Essentially, the figures in the White Paper correspond more to Defra's projections in the text of the review (i.e 10% between 2000 and 2010). To quote from the WP:
"Transport is currently responsible for about a quarter of total UK CO2 emissions. This figure excludes international aviation as there is currently no international agreement on ways of allocating such emissions. In the short term, emissions of carbon from road transport are expected to grow by about 10 per cent from 2000 levels by 2010. This is because increased levels of traffic will offset improvements in fuel efficiency. Emissions from other sectors are due to fall in the same time period, so transport's share of total emissions is likely to increase substantially. The trends change after 2010. Slower traffic growth and continued fuel efficiency improvements are expected to produce a fall in road traffic CO2 emissions of around 5 per cent between 2010 and 2015, with further falls thereafter."[19]
2.3.15 These figures in turn contradict earlier DfT figures from the National Transport Model (NTM) which envisage that the level of road transport CO2 emissions will be stable (high forecast = +0.3%) or even fall slightly (-2.7%) by 2010[20]. It can only be assumed that the White Paper has given greater weight to the traffic forecasts vis a vis fuel efficiency savings over this period as the exact source of the White Paper figure is unclear.
Table 4: Summary of the different official transport emissions projections
| Defra
projection in the text of the CCR | Defra
projections in the tables included in the CCR | DfT
2005 paper to the Motorists Forum | DfT 2004 White Paper 2004 | DfT 2003 NTM projections
2003 | DTI
updated projections 2004 |
|---|
| 1990-2000 | 'CO2 from road transport grew 10%' | End user CO2 emissions from 'transport' grew 5% | Carbon emissions from road transport grew 0.5% p.a. (=5%) |
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| Road transport only = 9% or all transport = 7% increase |
| 2000-2010 | '9% or so' increase | End user CO2 emissions from 'transport' to grow 5% | 0.6% growth p.a. (= 6%) | Emissions of carbon from road transport expected to grow 10% | Road transport CO2 emissions will be stable (high forecast = +0.3%) or even fall slightly (-2.7%) by 2010 | Road transport only = 11% or all transport = 10% increase |
| 2010-2020 |
| End user CO2 emissions from 'transport' to grow 11% | Fall in carbon emissions from transport by 5% between 2010-2015 | Fall in road traffic CO2 emissions of around 5% 2010 -2015, with further falls thereafter |
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2.3.16 It may be that there is a simple explanation for the discrepancy in these figures. Most likely is the difference between 'road transport' emissions and 'all transport' sector emissions and the difference between 'tailpipe' and 'end user' emissions. Nevertheless, the figures are confusing and policy advice and design cannot be effective on the basis of these confusing indicators.
2.3.17 Therefore, a main recommendation of this paper is that research is carried out urgently to understand the composition of the official figures, to create a standard breakdown in the various end use sources of transport emissions and to clarify the assumptions used to derive them.
2.4 Confidence in the Defra projections
2.4.1 As explained above, the official forecasts are characterised by a degree of ambiguity and imprecision. A number of factors combine to limit confidence in the emissions figures, and these are considered below.
(a) Transport's contribution to the overall UK emission targets
2.4.2 Defra provides some detail on the updated trends and projections for the different sectors to total UK greenhouse gas and carbon dioxide emissions. However, the contribution of transport to the overall emission figures is still - to some extent - unclear.
2.4.3 For example, it is not clear the extent to which the rising emissions in the transport sector will be responsible for the lack of progress towards the UK domestic target to reduce carbon dioxide emissions by 20% by 2010. Likewise, the figures suggest that the continued increase in emissions from the transport sector could start to raise total emissions again by 2020, but this is not entirely clear from the data.
2.4.4 Although the DfT are predicting a fall in road transport emissions of 5% between 2010 and 2015, projections further than this are unclear. If technological developments are not brought on stream. there is a risk that road transport, but definitely air transport, could begin to erode the projected carbon savings expected from energy efficiency savings and increased renewable electricity use. As a result, the consequence of transport 'not pulling its weight' in the climate change programme could be to jeopardize the achievement of a 60% cut in CO2 emissions by 2050.
2.4.5 It is important that these projections are clarified and the contribution of each sector stated, even if this means 'naming and shaming' policy areas. If we understand the effects of rising transport emissions more clearly, we will be better able to assess whether policies are tough enough.
(b) The contribution of specific transport measures
2.4.6 It is difficult to ascertain from current government policy documents (i) the exact basis of the calculations what is expected to drive the forecasts and (ii) the absolute and relative scale of the emissions savings expected from individual transport policy measures.
2.4.7 We know that the projected savings are expected to come from efficiency gains as well as an assumed large fall off in traffic due to an ageing population and a fall in the rate of decrease in the cost of motoring[21]. However, there are no indications of the extent to which economic growth, motoring taxes, road charging etc will and could contribute to changes in transport sector emissions.
2.4.8 Transport measures are 'lumped' together to give an aggregated assessment of the savings to be expected from the sector. For example, the Climate Change review (p24) and the most recent DTI figures project 4.42MtC from policies including 'voluntary agreements, the 10YP, sustainable distribution and off road programmes'.
(c) Uncertainty in the data - lack of sensitivity analysis
2.4.9 Although Defra admits to some inevitable uncertainly in the forecasts, the considerable range of uncertainly surrounding the assumptions used to derive the transport projections is not acknowledged.
2.4.10 The balance between average fuel efficiency and traffic levels in future years is critical to predictions of future road transport and CO2 emissions. Yet, there are real uncertainties surrounding both of these elements. Indeed, it is notoriously difficult to forecast traffic levels and the transport therefore has a continuing problem even with grounding basic facts. For example, the 10 YP forecasts for congestion used in 2000 were revised in 2002.
2.4.11 The forecast for traffic growth is based on the assumption that car fuel costs will fall by 30% by the end of the decade due to a combination of improvements in fuel efficiency as well as a reduction in real fuel prices. However, the oil price may prove to be higher throughout this decade than forecast. The sensitivity of the forecasts to balances between the price of oil, fuel efficiency, fuel duty and other motoring costs need to be made explicit in order to have confidence in these projections. Where sensitivity tests are carried out, these are not made explicit in the published data.
2.4.12 In addition, some very important policy measures as outlined in the 10 YP are bracketed as an assumption in order to derive forecasts of traffic growth. However, the package of policies set out in the 10YP may not actually materialise (such as local congestion charging schemes and targeted increases in rail travel). In addition, the effect of the policies in the 10YP are combined to provide one overall indication of potential emissions savings (1.6MtC by 2010).
2.4.13 One of the key elements in the forecast for future road transport CO2 emissions concerns the assumptions about future vehicle fuel efficiency. These estimates have also been revised downwards as problems with the Voluntary Agreement (see S.3.2 below) mean that fuel efficiency gains assumed in the forecasts may not materialise. The improvements in fuel efficiency and reduction in CO2 emissions may still prove overoptimistic even though they have been revised downwards. This is because:
- There is not enough understanding of how to motivate consumers and stimulate the purchasing of alternative/ lower carbon vehicles.
- Improvements in fuel efficiency are expressed in terms of test cycle results whereas it is well known that real on-road emissions differ significantly from these because the test cycle poorly reflects real driving conditions. Predicted increases in congestion is one reason to suppose that they may diverge further and that anticipated improvements in average emissions may not fully happen.
- The Voluntary Agreement target only refers to new cars entering the fleet, whereas the overall composition of the car fleet and the rate of replacement of old cars determine the fleet average so that the fleet average is slow to reflect new improvements.
- There are particular reservations about the fuel efficiency projections for goods vehicles. Unlike cars, there is currently no standard measure for quantifying the CO2 emissions from light goods vehicles (LGVs) and heavy goods vehicles (HGVs). This casts doubt on the reliability of the evidence base used to generate fuel efficiency forecasts for good vehicles.
(d) Clarity of the assumptions used
2.4.14 Although this is a complex area, the underlying assumptions underpinning the forecasts are not transparent and can therefore lead to confusion. Linked to point (b) above, the figures give no idea of a range of error or attempt to offer a range of forecasts based on scenario analysis. For example, the projections presented in the Climate Change Review are very different to those in the revised 10YP three years earlier. It should be transparent whether changes to the expected outcomes of the 10 YP are the result of changes to the model or from changes to the inputs and assumptions. The data used and the underlying assumptions made must be clear and well communicated throughout.
(e) No specific targets for transport
2.4.15 Within the overall targets for reductions in greenhouse gas emissions, there are no specific targets for transport. As a result, it is not possible to comment on the degree to which transport is on track to reduce emissions.
(f) Focus on carbon, to the exclusion of the other 20% of GHG emissions
2.4.16 Although carbon dioxide accounts for the majority (80%) of emissions from the transport sector, outputs of other greenhouse gases from transport should be assessed within this review. For example, it should be noted that in respect to the transport industry, the highest GHG increase has been from N2O, which increased 126% but only makes up 3% of all GHG emissions[22]. This is particularly relevant for aviation, as will be discussed below.
(g) Insufficient focus longer term projections beyond 2010
2.4.17 The Climate Change review focuses on the targets and projections for 2010 with some discussion of projections to 2020. However, any discussion on which policies to develop is dependent on the target is being pursued. The more demanding the target, the more substantive the reduction in emissions required. For example, in the period to 2010, technological advances in fuel efficiency may be enough to secure savings from the transport sector with little behavioural adaptation. However, if the 60% reduction target by 2050 is being evaluated, it may be less likely that technology can be relied upon on its own (discussed in S.6.2).
2.4.18 This is especially important given the time that it takes to change policies and affect outcomes. In addition, the more targeted the reduction, the more defined, costly and time consuming the transport policy changes will need to be.
2.4.19 There is a need to develop long term thinking on transport and to establish appropriate CO2 targets for the UK transport sector - not just to 2010 but right up to 2050.
(h) Insufficient use of scenarios- based evidence
2.4.20 Various studies have used future scenarios for the UK with a focus on carbon emissions. The role that transport was expected to play in achieving the 60% reduction varied amongst the various studies and scenarios evaluated[23]. There were differences in both the magnitude of the expected role and the combination of the different measures used to achieve the reduction.
2.4.21 Very little work appears to have been done within government departments to include a range of scenarios of future policies and where they may be introduced. Given the instability in the projections, policy development may benefit from being able to draw upon official scenario analysis.
(i) Conflicting objectives
2.4.22 The 10 YP emphasised government targets/ projections for the reduction of congestion. It is not yet clear what the relationship is between emissions projections and those for congestion.
2.4.23 In addition, the government should clarify how important the CO2 targets are in relation to other environmental priorities and in relation to other policy objectives such as safety and accessibility. For example, industry is faced with conflicting objectives such as measures to clean exhaust emissions which work against measures to improve CO2, as do vehicle design standards (eg safety enhancements) which add to vehicle weight and emissions. There is little evidence as to the implications of such changes for public transport operating costs and fares. In addition, reductions in average HGV loadings, whilst potentially negative in terms of congestion and air quality, are potentially positive in terms of road maintenance.
2.4.24 Hence, there could be some counterproductive policies at work here which are in need of further evaluation.
2.5 Emissions from (international) aviation
2.5.1 Including international aviation, carbon dioxide emissions from air travel will amount to some 16-18 MtC by 2030 (97% from international flights) and this could amount to a quarter of the UK's total contribution to global warming by this date.
2.5.2 The 16-18 MtC figure is consistent with the projections in the Air Transport White Paper, although DfT use a slightly longer time horizon - stressing the potential problem posed by aviation - to predict that aviation's proportion of total UK climate change impacts could be as much as 33-35% by 2050.
2.5.3 This 33-35% figure does represent something of a 'worst case' scenario for aviation, however. The projection includes international flights departing from the UK, and assumes that three new runways are constructed in the South East; no economic instruments are introduced to manage demand for aviation; and that other sectors will meet the Energy White Paper goal of 60% reductions in CO2 by 2050.
2.5.4 The Defra consultation makes no reference to other emissions from aircraft which also contribute to global warming. As well as CO2, aircraft produce a range of emissions including NOx, sulphates, soot, H2O and contrails, which can produce cirrus clouds. These emissions produce a net warming effect over and above emissions of carbon dioxide, although their affect on chemistry of the atmosphere varies with altitude.
2.5.4 Aviation's impact on climate change is complex and - with the exception of CO2 - relatively poorly understood. The overall environmental response from aviation - in terms of climate change - is estimated at between 1.9 and 3.5 times that of the response produced by the CO2 emitted from aircraft alone (see Figure 2).
Figure 2: Radiative forcing of climate from aircraft emissions and effects in 1992 (IPCC, 1999[24])
(The limit of the bars shows the best estimate, whilst the 'whiskers' represent the two thirds uncertainty range. The evaluations below represent a relative appraisal associated with each component.)
2.5.5 The impact of the various emissions are difficult to compare, however. NOx and contrails are produced in relatively potent - but short-lived - pulses, compared to CO2 which remains in the atmosphere for up to 100 years. Aircraft emissions also have a differential impact depending on the altitude and latitude of their flight path. A long haul flight which spends much of its time cruising at 10,000m will have a disproportionately adverse environmental impact than an aircraft on a domestic route flying at 5000m. The emissions from long haul flights will also have differential impacts depending on whether they are flying in the mid northern latitudes or in the tropics.
2.5.6 Whereas emissions from road vehicles can be measured, and externalities costed and allocated, with relative ease, pollution from cars and lorries does not vary with journey destination, the height of the road or weather conditions.
2.5.7 Such scientific complexity - and uncertainty - presents a considerable barrier for policy makers. Nevertheless, failure to take account of all emissions from aviation, as will be discussed below, could dilute the effectiveness of policy instruments designed to tackling CO2 emissions alone.
1: Foley,J and Fergusson,M 2003 Putting the Brakes on Climate Change: A policy report on road transport and climate change. IPPR, London.
2: The six greenhouse gas emissions are carbon dioxide, methane, nitrous oxide, hydroflurocarbons, perflurocarbons and sulphur hexaflouride.
3: Royal Commission on Environmental Pollution (RCEP) 1994 Transport and the Environment, 18th Report. Cm 2674. London, HMSO.
4: p56 although slightly contradicted by the figures presented on page 21 showing transport's share as closer to 22%.
5: p56.
6: p56.
7: Derived from Table 6, p27.
8: Energy Paper 68: Energy Projections for the UK November 2000 The Stationary Office.
9: DTI 2004 Updated Emissions Projections - Final Projections to inform the National Allocation Plan 11 November 2004 and UEP November 2004 Addendum (Projections beyond 2010).
10: DTI 2004.
11: DfT 2004 Transport Statistics UK.
12: DfT (Cleaner Fuels and Vehicles Division) 2005 Climate Change and Air Quality paper to Motorists Forum (January 2005) MF(22)5.
13: DfT 2005.
14: DfT 2002 Delivering better transport: progress report.
15: DfT 2005.
16: DfT 2005.
17: DfT 2004 The Future of Transport (White Paper) DfT available at www.dft.gov.uk/pgr/strategy/whitepapers/fot/.
18: Note that this graph is slightly different to the one included in the 2005 DfT paper to the Motorists Forum. In addition to including projections to 2025 as opposed to only 2015, it may be that some of the figures are also different. This is testimony once again to the need for greater clarity on this issue.
19: DfT 2004 The Future of Transport (White Paper) DfT p 107.
20: DfT (2003) Modelling and Forecasting using the National Transport Model DfT.
21: DfT 2005.
22: European Environment Agency (2003) Greenhouse Gas Emission Trends in Europe 1990 - 2001; Copenhagen.
23: Foley,J and Fergusson,M 2003 Putting the Brakes on Climate Change: A policy report on road transport and climate change. IPPR, London; Pridmore,A,, Bristow,A, May,T and Tight,M 2003 Climate Change, Impacts, Future Scenarios and the Role of Transport. Tyndell Centre for Climate Change Research Working Paper 33.
24: IPCC (1999) Aviation and the Global Atmosphere. A Special Report of IPCC Working Groups.
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