Cars evaluated against climate targets: analysis and app

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1. Background

Holding back global warming likely demands that greenhouse gas emissions from the transportation sector -- accounting for one-third of all U.S. emissions -- peak, then start to fall, within the next twenty years. Several vehicle technologies and fuels that can reduce emissions are already commercially available, such as battery electric and fuel cell powertrains. The question is: what are the best options, and are any sufficient to meet climate policy goals? To date, most studies have addressed this question abstractly, modeling emissions - and not costs - from generic, usually compact, cars. More consumer-oriented information is needed.

2. Methods

Most U.S. transportation emissions come from light-duty vehicles -- cars and light trucks. Our study asks: How do the costs and carbon intensities of vehicle models compare across the full diversity of today’s light-duty vehicle market, and what is the potential for vehicle technologies to close the gap between the current fleet and future emission targets?

We began by calculating vehicle emission targets for the years 2030, 2040, and 2050 consistent with holding global warming below the 2°C guardrail. This allows us to evaluate the performance of each vehicle against climate policy goals.

We then evaluated the lifecycle emissions and costs to the consumer of more than 100 models currently on the market. We did so by constructing parametrized emission and cost models that allow us to assess any given vehicle model based on a small set of publicly available parameters. This also enables us to look long term: to investigate how vehicle improvements and energy-market developments could enable 2040 and 2050 targets to be met.

Finally, we built and launched an interactive website, This puts information in the hands of consumers, allowing them to explore and compare the emissions and costs of today’s most popular cars.

3. Results

Although the average carbon intensity of vehicles sold in 2014 exceeds the climate target for 2030 by more than 50%, we find that most hybrids and electric vehicles available today meet this target, emitting 25-40% less than comparable internal combustion engine vehicles. They often even get close to the 2040 target. Emissions from hybrid and electric vehicles are lower still under certain conditions, such as California’s relatively clean electricity mix, or predominantly urban driving.

Crucially, our results show that consumers are not required to pay more for a low-carbon-emitting vehicle. Across the diverse set of vehicle models and powertrain technologies examined, a clean vehicle is usually a low-cost vehicle. This is a result of two factors: vehicles with advanced powertrains have substantially lower operating (fuel and maintenance) costs; and current federal tax incentives.

We find that by 2050, only electric vehicles supplied with almost completely carbon-free electric power meet climate-policy targets.

In less than a year, the interactive version of our results, published online at, has been visited more than 100,000 times. According to consumer feedback we have received, the tool is helping to inform car purchasing decisions.

4. Conclusions

We have presented an approach to quantifying the diversity of carbon emissions across the U.S. light-duty vehicle market and comparing it against climate change mitigation targets, with the goal of better informing three categories of decision-makers: car owners, car manufacturers, and transportation policymakers. Our analysis identifies choices available to consumers, and insights that can inform directed innovation efforts by policymakers and car manufacturers. Together, these stakeholders will dictate progress in decarbonizing the transportation sector and whether a transition occurs at a speed and scale commensurate with climate policy goals.

In the near term, we have found that although the average carbon intensity of vehicles sold in 2014 exceeds the 2030 climate target by more than 50%, most available (plug-in) hybrids and electric vehicles meet this goal. It turns out that the least-emitting cars also tend to be the most affordable ones.

Longer term, electrification of the vehicle fleet and a large and rapid decarbonization of the electricity generation sector -- roughly 80% by 2050 -- must go hand-in-hand.

By building an online, interactive app,, we have translated scientific results into actionable consumer information. User feedback has indicated that this engaging approach has helped inform real-world vehicle purchasing decisions.

5. Future ideas/collaborators needed to further research?

We are currently working to advance two aspects of our analysis:

  1. Better modeling of region-specific driving patterns and traffic conditions. This will allow us to tailor information more precisely to consumers’ needs. 
  2. Reliable survey information on how is impacting consumer purchasing decisions of different car models and technologies. 

In addition, promising avenues for future refinements and collaborations include:

  1. Developing a refined vehicle cost model that makes our information as helpful as possible to on-the-ground consumer decision-making. For instance, we would like to improve how we account for depreciation rates of cars: how does vehicle depreciation depend on vehicle type, technology, total miles driven, and vehicle age? We would also like to improve our maintenance cost estimates.
  2. Expanding our vehicle database multinationally, so that it applies to consumers outside of the United States. 


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6 months ago

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