Do your greenhouse gas emissions depend only on location, location, location? – Blog of the Institute of Energy
New research examines the role of people in relation to places in determining household carbon emissions.
Source: Smiley N. Pool / Chronicle of Houston, Shutterstock
The average household in San Francisco emits 36% less CO2 of residential and transportation energy use than the average Houston household. In the San Francisco Bay Area, the top 10 census tracts with the highest household carbon emissions emit, on average, 5.6 times more per capita than the 10 lowest-emitting census tracts. Researchers and policymakers have recently highlighted the enormous spatial variation in household carbon emissions, both within and between cities. See for example here and here.
Some of these differences can be explained by household characteristics, such as household size and income; some can be explained by gas heating versus electric heating or the type of automobile. The remaining variation has historically been attributed to the characteristics of the places themselves and the correlation between various amenities (e.g. climate, density, public transportation, ability to walk) with average carbon footprints.
Average Household Carbon Emissions in the San Francisco Bay Area
The figure shows the average household carbon emissions from residential energy and transportation by census tract in the San Francisco Bay Area. Units are tonnes of CO2 annually per household. Data source Green and Knittel, 2020.
This spatial variability could present an opportunity – perhaps we can learn from these low-carbon places to better design and implement similar policies and practices nationwide in an effort to decarbonize the U.S. economy.
A new article from the Energy Institute Eva lyubich, available here as a new Energy Institute working paper, explores these issues in detail. The starting point of her article is to recognize that people make choices about where to live, so different types of people live in different types of cities. Some people want to live in cities where they can drive to work, others prefer to travel by public transport, bicycle or on foot. Some people want to live in a 3 bedroom house with a yard and others prefer an apartment building close to lots of other people and restaurants. Through this lens, one quickly begins to realize that much of the differences we see in household carbon emissions in the United States come from a mixture of the characteristics of a particular place and the characteristics and preferences. people who choose to live there.
This distinction between people and places is fundamental, because if policy makers adopted some of the low carbon ‘best practices’ of green cities and applied them elsewhere, we could receive much less carbon benefits than the differences. observation may suggest. In other words, someone from Houston, TX who enjoys driving their SUV may not be as inclined to use a new extension of public transportation as someone from New York.
Eva explores these questions using restricted US Census data. Using this data, Eva can track millions of (anonymized) people who moved between 2000 and 2019. She can also see how much households reported spending on residential energy last year, how long the typical commute lasted. of each individual and whether they commuted by car, public transport, on foot or by bicycle. She combines this with information on energy prices and carbon intensity by location, allowing her to quantify individual and household carbon emissions for each respondent.
Eva can then ask, “How much do household carbon emissions change for a person moving from Houston to San Francisco?” And “How does this change compare to the average differences between these cities?” By repeating this exercise millions of times, she can begin to distinguish the role of people versus places in contributing to the overall change in household carbon emissions.
Learn from movers
Another way to phrase the same question is to ask how much a person’s location determines their GHG emissions. If I move from San Francisco to Houston, will my carbon emissions increase?
The figure below, taken from Eva’s article, shows the result. The figure shows that when a person moves to a higher-emission metropolitan area, their own emissions increase by almost the entire gap between their home city and their destination city. This change in household emissions is not entirely surprising given what we know about differences in climate and electricity sources between cities, but the magnitude of the effect is surprising for two reasons: (1) differences in household characteristics such as income and household size account for a lot of variation in CO2 footprints, and it may be that these characteristics are more important than the places themselves, and (2) there is a lot of neighborhood variation within a metropolitan area, and mobile households could selectively sort the neighborhoods in their new city that most closely resemble their places of origin.
Moves through cities
The figure shows the average changes in household carbon emissions for movers by differences in the average origin-destination emissions for cities (CBSA).
So to go deeper into it, Eva takes advantage of the detailed geographic information in her survey data and repeats this exercise with the people who move through neighborhoods. This result is shown in a similar figure below. She finds that when households move from one neighborhood to another, their emissions change by around 60% of the average origin-destination differences. In other words, more than half of the differences between neighborhoods can be explained by the place itself. The remaining share is due to people with different preferences living in different neighborhoods, and if you simply compared the average differences in household carbon emissions between places, you would overestimate the potential carbon reductions.
Moves through neighborhoods
The figure shows the average changes in household carbon emissions for movers as a function of the average origin-destination emissions differences for neighborhoods (census tracts).
So what? How important is location in determining carbon emissions relative to other household factors, such as Income? Eva finds that locations account for 25% of the overall variation in carbon emissions between households. About 10 percentage points of this effect comes from climatic differences, grid carbon intensity and local energy prices; the remaining 15 percentage points are due to other characteristics of the place (eg, walkability, transit, density).
Eva uses her estimates to better understand the potential carbon reductions resulting from investment-based investments or regulatory changes. For example, by how much would Bay Area household carbon emissions drop if Oakland, Hayward, and other parts of the East Bay were more like San Francisco? She does this brainstorming exercise for nearly 1,000 cities in the United States. On average, she finds that household carbon emissions would decrease by 15% (although, on average, central cities emit around 27% less than their surrounding suburbs).
Taken together, Eva’s findings provide new evidence on the importance of cities and neighborhoods in driving household carbon emissions. The answer is nuanced. The characteristics of cities and neighborhoods play a key role in a household’s carbon footprint, although their importance will be overestimated if one simply compares the differences in carbon emissions between locations. Localized investments in public goods that reduce carbon emissions, such as public transit, could still lead to carbon footprint reductions for many households at once. Work like Eva’s is essential to identify public investments that can reduce emissions at the lowest cost.
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For more details, see Eva Lyubich, “The Role of People vs. Places in Individual Carbon Emissions“ Working document of the Energy Institute, UC Berkeley, December 2021.
Suggested citation: Walker, Reed. “Do your greenhouse gas emissions just depend on location, location, location?, UC Berkeley, December 6, 2021, https://energyathaas.wordpress.com/2021/12/06/are-your-greenhouse-gas-emissions-all-about-location-location-location/