Transportation and greenhouse gas emissions
Transportation plays a crucial role in enabling people and goods to move across distances, influencing both personal and economic activities. It encompasses various modes, including automobiles, public transit, and freight services, which are essential for economic growth and connectivity. However, the transportation sector is a significant contributor to greenhouse gas emissions, primarily through the burning of fossil fuels. In 2021, transportation accounted for approximately 37% of carbon dioxide emissions from end-use sectors globally, with road vehicles being the largest contributor. In the United States, this sector was responsible for 29% of greenhouse gas emissions, predominantly from light-duty vehicles.
The link between transportation and climate change is driven by the reliance on petroleum-based fuels, with nearly 90% of energy used in the U.S. transportation sector sourced from oil. While advancements like electric vehicles (EVs) are emerging, the transition is still heavily reliant on conventional fuel sources. Efforts to mitigate emissions include technological innovations for vehicle efficiency and behavioral changes to promote non-motorized transport options. Governments worldwide are responding with regulations and incentives to encourage EV adoption, aiming to significantly reduce emissions and combat climate change. As the urgency to address environmental concerns grows, the transportation sector's role in greenhouse gas emissions remains a critical area for action and innovation.
Transportation and greenhouse gas emissions
Definition
Transportation is a means to facilitate spatially separated activities: for example, individuals travel to work or for leisure purposes; firms ship raw goods or finished products to clients or distribution centers, and employees travel for business. A small percentage of travel occurs for its own sake, such as walks in parks. The most common modes of personal urban transportation are the automobile, public transportation (buses, rail modes, ferries), motorcycles, bicycles, and walking. Personal intercity travel is commonly associated with intercity rail and buses, airplanes, ships, and the automobile. Freight transportation generally distinguishes between trucks, rail, pipelines, airplanes, ships, and barges.
Individual and freight transportation are the backbone of national and international economic activity and can provide benefits to businesses, individuals, and the nation. Transportation can positively impact employment, product prices, and economic growth. Population growth, increasing incomes, more spread-out land uses, and longer distances between activities have contributed to more than a quadrupling of global car ownership and use since 1950.
In 2020, the United States had the second-highest motor vehicle ownership rate in the world, according to the International Organization of Motor Vehicle Manufacturers: 860 vehicles per 1,000 population, behind only New Zealand with 869 vehicles per 1,000 inhabitants. Wealthy European and Asian countries also had high levels of automobile ownership, but public transportation, walking, and cycling accounted for overall lower rates in most of those countries. The United Kingdom, for example, had 632 cars per 1,000 population, while Japan had 612. Transportation and spatial development patterns are closely connected. Faster motorized modes of transportation allow more spread-out human settlements. Low-density settlements in turn necessitate motorized modes of transportation.
Significance for Climate Change
Automobile emissions have an impact on a global scale, as they are a significant source of greenhouse gases (GHGs). According to the International Energy Agency (IEA), in 2021 transport contributed 37 percent of carbon dioxide emissions from end-use sectors; road automobiles continued to account for the biggest portion of this number. In the United States, the Environmental Protection Agency (EPA) estimated that transportation contributed 29 percent of the nation's greenhouse gas emissions in 2021, with 58 percent of that figure coming from typical light-duty vehicles. Transportation contributes to climate change mainly through the burning of fossil fuels.
Compared to the residential, industrial, and commercial sectors, transportation is uniquely dependent on petroleum, despite the rise of electric vehicles (EVs) during the early twenty-first century. According to the US Department of Energy, in 2021 approximately 90 percent of all energy used in the transportation sector in the United States was petroleum-based. The average passenger vehicle emits some 4.6 metric tons of carbon dioxide annually. Even among developed nations, the United States is uniquely dependent on the automobile and petroleum-based fuels.
The EPA estimates that nearly 60 percent of all US transportation-related GHG emissions come from automobiles, sports utility vehicles (SUVs), and light passenger trucks; only 23 percent of such emissions are attributable to medium and heavy trucks. Airplanes account for 8 percent and rail, water transportation, and pipelines for another 11 percent of transportation-related GHG emissions.
According to the IEA, global carbon dioxide emissions from transportation increased by an average of 1.7 percent per year from 1990 to 2022 (aside from a dip in 2020 due to the COVID-19 pandemic). Transportation-related GHG emissions depend on the level of transportation activity (including number of trips and distance traveled), the mode of transportation (motorized or nonmotorized), and the fuel type and its carbon intensity. Reductions in transportation-related GHG emissions can be achieved through technological and behavioral changes. Technological innovation can improve vehicle efficiency and increase the viability of low-carbon or noncarbon fuels. Changes in behavior can reduce the total amount of travel and increase the share of trips on foot, by bike, or by public transportation.
The rise of electric vehicles was one of the most notable innovations in the early twenty-first century, and the adoption of EVs was increasingly seen as a major way to reduce automobile emissions. As the need to combat climate change became increasingly urgent in the 2020s, the US government implemented new regulations to attempt to tackle the issue. In 2021 President Joe Biden signed an executive order announcing a goal for the country to have 50 percent of its sales of new vehicles consist of electric vehicles by the year 2030. In early 2023, Biden's administration made further efforts to push automakers toward greater production and sales of EVs when the EPA proposed new, more restrictive emissions rules for automobiles. The following year, the EPA unveiled its final rule on the proposed regulation. Under the new rule, cars produced between 2027 and 2032 would be subject to meeting benchmarks requiring 56 percent of new vehicle sales to be electric by 2023 and 13 percent to be partially electric, or hybrid, vehicles. Supporters of the new regulation noted that it would result in a reduction of over 7 billion tons of carbon emissions into the atmosphere, greatly reducing air pollution that contributes to climate change. With many other countries adopting policies to curb climate change by, in part, reducing automobile emissions and transitioning to greater electric transportation, the IEA reported that there were 26 million electric vehicles on the road in 2022 and that EVs made up 14 percent of all new car sales that year.
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