Transportation and Climate Change

Source: U.S. Department of Transportation, Center for Climate Change and Environmental Forecasting

I. Introduction

Carbon dioxide (CO2) is a major greenhouse gas emitted from the burning of fossil fuels and is considered to be a major determinant of climate variability. CO2 is not one of the air pollutants specified in the Clean Air Acts, although it is a target pollutant in the air pollution legislation of many other countries.

Some potential effects of climate change include 1) ocean warming and ice cap melting leading to a rise of sea levels, flooding low-lying areas and coastal communities; 2)more droughts, monsoons and other extreme weather events; 3) extinctions of species and other biological changes; 4) changes in crop yields, agricultural productivity, and lumber supplies; 5) increases in infectious diseases (e.g. malaria, dengue, and yellow fever); 6) impacts on water supply; and soil fertility.

In the United States, the transportation sector surpassed the industrial sector’s carbon dioxide emissions for the first time in 1998.

Current U.S. trends in transportation’s contribution to CO2:

Source: http://www.bts.gov/transtu/indicators/Environment/html/US_Carbon_Dioxide_Emissions.html

The current automobile fleet produces 1.15 lbs. of CO2 per mile, or 19.5 lbs. per gallon.

Other greenhouse gases also from motor vehicles:

• N2O from catalytic converters and from reformulated gasolines
• CFCs and the shorter-lived HFCs in air-conditioning systems
• CH4 from the incomplete combustion of petroleum during production.

In addition to carbon dioxide (CO2), the following greenhouse gases are major contributors to global warming:

• methane [CH4],
• nitrous oxide [N2O],
• ozone [O3],
• water vapor,
• manmade chlorofluorocarbons [CFCs],
• hydrochlorofluorocarbons [HCFCs],
• hydrofluorocarbons [HFCs]

The transportation sector emitted an estimated 450-500 million metric tonnes of carbon (MtC) as carbon dioxide. Based on the latest energy use projections by the Department of Energy's Energy Information Administration (EIA), total transportation emissions could grow to 704 MtC by 2020.

Source: http://www.ott.doe.gov/facts/archives/fotw126.shtml

In future, aircraft emissions are expected to grow at the fastest rate, increasing nearly 170% from 1996 to 2020. Although the share of transportation emissions due to aircraft is expected to grow from 9% to 16%, light vehicles will still account for the largest portion in 2020 at 57%.

II. Current trends

The U.S. accounts for 23% of CO2 produced globally by fossil fuel combustion, and U.S. transportation accounts for 7.4% of global CO2 production. The latest emission figures reflect the predominant position of transportation as the largest sector of the economy responsible for CO2 production in the U.S. Transportation activities accounted for 31 percent of CO2 emissions from fossil fuel combustion in 1999. The lion’s share of all of the energy consumed in the transportation sector came from petroleum products.

Carbon Dioxide Emissions by Economic Sector

Source: U.S. Department of Energy, Energy Information Administration, Emissions of Greenhouse Gases in the United States, 1990-1999.
Available at: http://www.eia.doe.gov/oiaf/1605/ggrpt/index.html.
For 2000 numbers: U.S. Department of Energy, Energy, Information Administration, Energy-CO2 Flash estimate, available at: http://www.eia.doe.gov/oiaf/1605/flash/sld001.htm

The transportation sector's emissions have grown considerably faster than those of other sectors, which averaged about 1.25 percent annually during the same period. CO2 emissions from motor vehicles are projected, in the absence of change, to be one-third higher in the next 20 years and will double by 2050.

Almost two thirds of the emissions resulted from gasoline consumption in cars when compared with other vehicle types.

U.S. Greenhouse Gas Emissions by Vehicle Type

Source: EPA Inventory Report 2001

The Btu/person per mile consumed for different transportation modes has been calculated and indicates the efficiency of public transportation in terms of energy use on a per capita basis.

Source: Rocky Mountain Institute (RMI)

CH4 and N2O emissions also result from fuel combustion. HFC emissions are associated with motor vehicle air conditioners.

III. Proposed solutions

Four major sets of policy options exist for reducing CO2 emissions from the transportation sector:

A) Reducing VMT

B) Increasing the fuel economy of vehicles

C) Raising the price of gasoline and other carbon fuels

D) Encouraging alternative technologies and technological advances

A. Reducing VMT

• Reviews of regional and metropolitan plans by US-DOT suggest that controls on travel demand in large metro areas could potentially reduce VMT growth forecasts by 10% p.a.
• Doubts exist about whether sufficient controls (e.g. road pricing, parking surcharges, higher vehicle taxes, land use controls that might impact on travel) could be implemented by state and local governments to achieve this result.
• A scenario that assumes a gradual reduction in the growth of VMT from 1.5% to 1.0% p.a. over the next 40 years would reduce VMT (and presumably CO2) by 5 percent by 2020 and 10-15% by 2040.

Regardless of feasibility, VMT-reduction measures raise a wide range of issues relating to costs and benefits, politics and institutions. They would require major changes in incentives, preferences and even lifestyles.

B. Increasing the fuel economy of vehicles

The improvement of fuel economy includes a number of solutions.

1) Traffic flow and highway capacity improvements

2) ITS (Intelligent Transportation Systems)

3) Mandates for fuel-saving vehicles

1) Simple traffic flow measures include: synchronized signals, reversible traffic lanes, left-turn signals, peak on-street parking restrictions, and ramp metering. More expensive measures include road building, road expansions, and road widening.

2) ITS is a general term to cover the application of advanced computer, electronics, and communications technologies as a means of improving traffic efficiency. They range from computer-controlled traffic signal systems and centralized traffic monitoring and control centers to in-vehicle navigation systems (with real-time routing information) and automatic vehicle control systems (e.g. “platoons” traveling at full speed one-foot apart).

3) The impact on fuel economy is unclear because they would also increase travel as well as making smaller vehicles safer and more efficient. They are also very costly, and their likelihood of adoption even in the medium term is doubtful.

• The most important mandate to improve fuel economy is the 1975 Federal CAFÉ (Corporate Average Fuel Economy) program that sets minimum mpg requirements for automobile manufacturers based on total vehicle sales.
• The impact on fuel economy is unclear; the gains were greatest in years when gas prices were higher but were dissipated when gas prices fell.
• The impact has been diluted because the requirements for the popular SUVs (Sports Utility Vehicles), minivans and pick-ups are different.
• Also, there is a “rebound” effect; more fuel efficient vehicles may induce people to drive more (an average estimate of 20% in fuel savings offset).

C. Raising the price of gasoline and other carbon fuels

• Some European countries (e.g. Denmark, Norway, Austria) impose taxes that penalize fuel-inefficient vehicles.
• Freight and service trucks account for 7% of VMT and 20% of highway petroleum use. Mpg (diesel) about ¼ that of cars.
• One strategy would be to shift traffic from truck to rail which consumes only 1/9 of fuel per ton-mile (but most truck traffic is short-haul). Truck size and weight restrictions would shift freight to smaller trucks with more rather than less aggregate fuel consumption. Logistics (e.g. service, delivery times, inventory management, etc.) make modal shifts from trucks highly problematic.

What about higher fuel prices? The effects are:

1) in the short run, to forgo or shorten trips

2) to alter commuting patterns and promote HOV use

3) to substitute more fuel-efficient vehicles

4) to induce manufacturers to invest more in R & D

5) to influence household location decisions (where to live, work, shop and socialize).

• Short-term price elasticities are estimated to be in the –0.05 to –0.5 range; long- term elasticities in the –0.2 to –1.0 range (averaging –0.53 over 40+ studies).
• In the long run, is it likely that a 50% increase in the price of gasoline would result in a 26.5% reduction in gasoline consumption? Only if we assume significant new fuel-efficient car substitutions.
• Gasoline taxes are much lower in the U.S. than abroad (see Figure 3-4, p.130), and taxes are by far the largest component of price in most countries.
• A more sophisticated kind of tax targeting CO2 emissions is a carbon tax, where the tax is proportional to fossil carbon content. Diesel fuel, natural gas, and alcohol/gasoline blends might become more attractive, and the search for low- or zero-carbon fuels would intensify.
• A scenario involving a gasoline price increase of 3% p.a. and a long-run price elasticity of –0.04 (with its effects split between reduced VMT and increased fleet fuel economy) would reduce petroleum consumption by 15% after 20 years and by 35% after 40 years. Fleet fuel economy would rise by 25% and VMT would drop by 20% (compared with their baselines).
• Other incentives to consumers include: “gas-guzzler” taxes, fee and rebate programs, vehicle registration taxes based on vehicle weight, engine size, and other characteristics of fuel efficiency, such as “clunker” scrapping schemes.

D. Technological measures to save fuel

• Development of vehicles with low CO2 emissions:

1) Electric and hybrid vehicles
2) Hydrogen and fuel cell vehicles
3) Biomass fuel vehicles

• About 400,000 alternative-fuel vehicles already in use. 60% of them are LPG, most of the rest are CNG, LNG, with a much smaller number of alcohol (i.e. methanol and ethanol) vehicles.
• The alternatives to gasoline all have disadvantages, e.g. emission trade-offs (e.g. if methanol was produced from coal, or ethanol was produced from energy-intensive corn production), heavier on-board fuel storage (natural gas), safety and toxicity, etc.
• Electric vehicles (if recharged from low-emission sources, more likely in the Pacific Northwest with hydro-power than in the Midwest with its high reliance on coal) have considerable potential for reducing CO2 emissions, but hitherto they have problems:

  1) power-weight problems, giving them feeble acceleration and/or too light for safety;
  2) restricted driving range;
  3) insufficient progress with new battery technology.

• A potentially more attractive short-term alternative is the electric-gas hybrid (to be introduced soon by Honda and Toyota). They offer significant improvements in fuel economy and longer range (the small-engined Honda will get 70 mpg with a range of 600 miles), but they are likely to be much more expensive.
• Hydrogen can be used to fuel an internal combustion engine or to power fuel cells. Fuel cells (based on transforming oxygen and hydrogen into water via electrochemical reactions) are virtually pollution free, although much depends on how the hydrogen is produced. Also, there are technical problems, e.g. the need for systems that transmit and deliver hydrogen safely, safe on-board, leak-free storage. These options are unlikely to be applied in the short run.
• Biomass-fuel vehicles (i.e. producing ethanol or methanol from cellulosic biomass, e.g. wood, grass and other waste) are another option. Also, this can often be done on marginal farmland.

IV. Conclusions

The U.S. share in global CO2 emissions has been falling, and is expected to decline from 23% to 18% in the next 20 years, reflecting the rising CO2 contribution of other developed countries, such as Japan, France and Italy.

1) Despite uncertainty and controversy, the long-term repercussions from CO2 buildup could be severe and permanent.

2) CO2 contributes more than ½ of the increased warming resulting from greenhouse gas buildup.

3) The U.S. transportation sector, via petroleum consumption, is the source of 5% of global annual CO2.

4) Policy makers are not yet prepared to take strong, decisive action.

5) Many of the possibly more effective actions (affecting changes in land use patterns, infrastructure systems, and lifestyles) would take decades to work themselves out.

6) Options for reducing auto-related CO2 emissions include measures to slow VMT growth, improve vehicle fuel efficiency, increase fuel prices, and promote new technologies.

7) Of these alternatives, measures to restrain VMT may generate some early but modest gains, fuel economy strategies are appealing only in an environment of higher fuel prices, and technological solutions, while potentially the most effective, may be a long way from substantial implementation.

V. Information sources

A. General

For a quick read on the basics of climate change science from the huge international effort by climate scientists, see www.ipcc.ch/pub/spm22-01.pdf

For a comprehensive list of climate change links, see http://www.pacinst.org/ccresource.html

B. EPA

http://www.epa.gov/globalwarming/

http://www.epa.gov/otaq/climate.htm

Office of Transportation and Air Quality
http://www.epa.gov/otaq/

C. DOE

For an overall U.S. Department of Energy, Energy Information Administration, Emissions of Greenhouse Gases in the United States, 1990-1999. It is available at http://www.eia.doe.gov/oiaf/1605/ggrpt/index.html.

D. DOT

http://www.ott.doe.gov/ott.shtml

http://climate.volpe.dot.gov/trans.html

Bureau of Transportation Statistics
http://www.bts.gov/transtu/indicators/Environment/html/US_Carbon_Dioxide_Emissions.html

E. Other

Rocky Mountain Institute
http://www.rmi.org/sitepages/pid342.php

Prepared by Christine Bae and Nathaniel Trumbull