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Working Group III: Mitigation


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3.4.7 Conclusions

Over the past 25 years, transport activity has grown at approximately twice the rate of energy efficiency improvements. Because the world’s transportation system continued to rely overwhelmingly on petroleum as an energy source, transport energy use and GHG emissions grew in excess of 2% per year. Projections to 2010 and beyond reviewed above reflect the belief that transport growth will continue to outpace efficiency improvements and that without significant policy interventions, global transport GHG emissions will be 50%–100% greater in 2020 than in 1995. Largely as a result of this anticipated growth, studies of the technical and economic potential for reducing GHG emissions from transport generally conclude that while significant reductions from business-as-usual projections are attainable, it is probably not practical to reduce transport emissions below 1990 levels by the 2010–2015 time period. On the other hand, the studies reviewed generally indicate that cost-effective reductions on the order of 10%–20% versus baseline appear to be achievable. In addition, more rapid than expected advances in key technologies such as hybrid and fuel cell vehicles, should they continue, hold out the prospect of dramatic reductions in GHG emission from road passenger vehicles beyond 2020. Most analyses project slower rates of GHG reductions for freight and air passenger modes, to a large extent reflecting expectations of faster rates of growth in activity.

Assessing the total global potential for reducing GHG emissions from transportation is hindered by the relatively small number of studies (especially for non-OECD countries) and by the lack of consistency in methods and conventions across studies. Not all studies shown in Table 3.16 cover the entire transportation sector, even of the countries included in the study. Most consider a limited set of policy options, (e.g., only motor vehicle fuel economy improvement). In general, the studies do not report marginal costs of GHG mitigation, but rather average costs versus a base case. Keeping all of these limitations in mind, Table 3.16 summarizes the findings of several major studies. For 2010, the average low GHG reduction estimate is just under 7% of baseline total transport sector emissions in 2010, with the higher estimates averaging a 17% reduction. There is, however, considerable dispersion around both numbers, indicative both of uncertainty and differences in methodology and assumptions. For studies looking ahead to 2020, the average low estimate is 15% and the average high estimate is 34% of baseline 2020 transport sector emissions. Estimated (average rather than marginal) costs are generally negative (as much as -US$200/tC), indicating that fuel savings are expected to outweigh incremental costs. There are some positive cost estimates as high as US$200/tC, however. The majority of the studies cited in Table 3.16 are based on engineering-economic analyses. Some argue that this method tends to underestimate welfare costs because trade-offs between CO2 mitigation and non-price attributes (e.g., performance, comfort, reliability) are rarely explicitly considered (Sierra Research, Inc., 1999).

Table 3.16: Estimates of the costs of reducing carbon emissions from transport based on various studies, 2010-2030
(
Brown et al., 1998; ECMT, 1997; US DOE/EIA, 1998; DeCicco and Mark, 1998; Worrell et al., 1997b; Michaelis, 1997; Denis and Koopman, 1998)
Study Year of publication Application Year of scenario Years in future Country Low
(MtC)
High
(MtC)
Low
(%)
High
(%)
Low High
OECD Working Paper 1 1997 Light-duty road vehicle efficiency 2010 13 OECD 50 150 2.5 7.5 US$0 US$0
US National Academy of Sciences 1992

1992
Vehicle efficiency
System efficiency
2010

2010
18

18
USA

USA
20

3
79

13
3.2

0.5
12.7

2.1
-US$275

-US$183
-US$77

US$18
US DOE 5-Lab Study 1997 Transport sector 2010 13 USA 82 103 13.2 16.6 -US$157 US$6
US Energy Information Administration 1998 Transportation sector 2010 12 USA 41 55 6.6 8.9 -US$121 US$163
Tellus Institute 1997

1997
Transportation efficiency
Transportation demand reduction
2010

2010
13

13
USA

USA
90

61
90

61
14.5

9.8
14.5

9.8
-US$465

US$0
-US$465

US$0
ACEEE 1998 Transport sector 2010 12 USA   125   22.6 -US$139  
US DOE, Clean Energy Futures 2000 Transport sector 2010 10 USA 20 66 3.2 10.5 -US$280 -US$144
European Council of Ministers of Transport 1997

1997

1997

1997

1997

1997

1997

1997
Transport sector
Transport sector
Transport sector
Transport sector
Transport sector
Transport sector
Transport sector
Transport sector
2010

2010

2010

2010

2010

2010

2010

2010
13

13

13

13

13

13

13

13
Austria

Belgium

Czech R.

Netherl.

Poland

Slovakia

Sweden

UK
2

4

6

11

5

1

4

22
    8.3

13.3

57.1

37.2

12.8

16.3

23.2

14.3
   
Summary for 2010     Minimum/maximum
average
0.5
6.7
57.1
16.9
-US$465
-US$153
US$163
-US$62
Denis and Koopman 1998
1998
1998
Road pricing
CO2 tax
Purchase subsidy + CO2 tax
2015
2015
2015
17
17
17
EU
EU
EU
      25.0
13.0
14.0


US$0


US$0
US Congress OTA 1991 Transportation efficiency 2015 24 USA   195   29.2 -US$180 US$195
Summary for 2015     Minimum/maximum
average
13.0 29.2
20.3
-US$180 US$195
US DOE, Clean Energy Futures 2000 Transport sector 2020 20 USA 58 163 8.3 23.4 -US$234 -US$153
ACEEE 1998 Transport sector 2020 22 USA   260   42.4 -US$164  
United Nations 1997

1997

1997
Transport sector
Transport sector
Transport sector
2020

2020

2020
23

23

23
Industrialized

Transitional

Developing
153

72

297
423

126

450
14.9

18.2

28.4
41.2

31.8

43.1
   
OECD Working Paper 1 1997 Light-duty road vehicle efficiency 2020 23 OECD 100 500 4.3 21.7 US$0 US$0
Summary for 2020     Minimum/maximum
average
4.3
14.8
43.1
34.0
-US$234  
ACEEE 1998   2030 32 USA   401   58.8 -US$192  


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