15% of GHG emissions worldwide originate from human transport-related activities, including, but not limited to, automotive vehicles such as light-weight cars, freight trucks, airplanes, and maritime shipping vessels. Of this, 6% originate from the United States alone, where transportation-related emissions account for an estimated 1/3 of total GHG emissions domestically. Further, transportation-generated CO2 emissions represent 48% of the total increase in the United States’ domestic GHG emissions since 1990 according to the U.S. Department of Transportation.
During this period, inter-state, city, and long distance by single-passenger cars increased, ride-share in public transport options including rail and bus decreased, and reliance on container shipping increased. Similar trends have occurred in rapidly developing economies like China and India, with China most likely to emulate the United States’ pattern of growth. With a growing 1.3 billion population, inefficient transport planning could not only pose a public health risk locally to Chinese citizens in high-traffic areas like Beijing, but also on global CO2 emissions.
In Wake of the IPCC’s 5th Assessment Report
In late September of 2013, the Intergovernmental Panel on Climate Change (IPCC) released the first installment of its 5th Assessment Report. An immediate catalyst for discussion rested in the report’s reevaluation of the viability of the 2° Celsius goal set by international agreement as mitigating the worst effects of climate change in the next century. The report indicates that global temperatures could rise by as much as 4.8 degrees Celsius by 2100 unless the strictest of emissions reduction measures are adopted simultaneously, globally.
The 2013 IPCC report also indicates with a 90% confidence level that the significant rise in GHG emissions since the middle of the 20th century, particularly CO2, correlates with human activity. Among the most robust evidence for this relationship is that within the past five years, and particularly in 2011, human activity has “burn” through more than half of the GHG emissions credits allowed in order to stay within the 2° Celsius goal. In terms of total CO2 emitted, China, the United States, India, Russia, and Japan ranked as the highest five emitters of CO2, respectively, emitting a combined 20,160,000 kilo tonnes of CO2 in 2011 according the EDGAR database, with international transport following close behind Japan at a close 1,040,000 kilo tonnes of CO2.
However, among the five highest emitters, it may be more useful to look at a ratio of population to per-capita tonnage of CO2 emissions as an indicator of transportation efficiency and use, rather than net CO2 emissions in isolation. Domestically, transportation-related activity simultaneously ranks as one of the greatest current contributors to and fastest growing shares of both China and the United States’ GHG emissions, with 28% of all CO2 emissions within the United States coming from transportation activities as of 2004.
Linking GDP Growth, GHG Emission Increase and Transport in China
Less publicly-accessible information exists on dis-aggregated figures for Chinese emissions figures, but an interesting trend emerges regarding the increase in per-capita CO2 emissions in China vs. the United States. In China, per-capita CO2 emission grew 1.6 percent in one year, or 6.2 in 2010 and 7.8 in 2011, whereas per capita emissions only increased .3 percent in the United States, or 17.3 in 2010 to 17.6 in 2011. We can infer some support for the role of transportation-related activities contributing to Chinese increase in GHG emissions from this large increase in CO2 per capita, as GDP growth in China saw a record growth rates of 10.4% in the same year (2010). Though CO2 emissions in China largely relate to the energy demands of industry, where 50% more energy is needed to produce the same 1 billion in GDP as the United States, there was a 35% increase in vehicles on the road globally in 2011, the second-largest increase ever. A huge factor in this increase was the “success of the motor vehicle in Asian mega-cities” (as reported by the Guardian in April 2011).
Solutions and Alternatives: Taking the Road Less Traveled
The most visible strategies for reducing GHG from transportation relate to motorized vehicles that run on fossil-fuels like petroleum, one of the biggest sources for CO2 world-wide. There are many mid-range and long-term solutions for reducing the number of vehicular miles traveled, and most of them rely on changing consumer preferences. Offering benefits and incentives for using public transport will be important, as long as systems engineers are able to balance equity with efficiency and include all sectors of an urban or semi-urban population within budget. Finding a way to move workers closer to the centers of production, and increase the viability and appeal of telecommuting where feasible will also be important.
In terms of reducing the CO2 component of fuel and improving vehicular efficiency, alternative fuels such as natural gas and electric power are becoming increasingly viable options, especially within the United States, which is seeking to become the largest producer of natural gas in the years to come. Making fuel economy standards on engines has enjoyed success in the past, especially within the context of U.S. markets, where fuel efficiency increased after plateauing from 1990-2004.
Essentially, making human-driven transportation greener involves two strategies: reducing the number of vehicle miles traveled, and increasing vehicle efficiency. Approaches to achieving the above two goals rest in improving urban and land-use policy and design, and decreasing vehicular use of fossil fuels, which compose some of the highest fuels emitting CO2. Challenges to making the above two methods actionable rest in simultaneously incorporating more efficient strategies in long-term urban transport, and land use planning with limited information, and finding short-term solutions that will immediately alleviate the load transportation activity places on GHG emissions.