AP Photo / Jae C. Hong

A new study compares the range of possible actions.

You may recall that a couple months ago the nations of the world met in Paris and agreed on a plan to fight climate change. The complex international treaty resulting from those talks includes targets for the governments to meet. But what about people?

Individuals can take tons of actions with the aim of trimming carbon footprints. But in order to prioritize these behaviors, we need some basis of comparison. How does replacing incandescent light bulbs compare to cutting the number of miles you drive?

A new study by Michael Sivak and Brandon Schoettle of the University of Michigan’s Transportation Research Institute sets out to answer that question by putting an assortment of attainable actions over the same denominator.

Sivak and Schoettle break down U.S. emissions by sector (industry, transportation, residential, commercial, and agriculture) and then calculate the total reductions that would be possible if everyone tweaked their habits. For the purposes of this study, they set aside government actions and outline selected changes individual Americans could make that would have “the least impact on their current lifestyle”; things like switching from driving to public transit or putting solar panels on your roof aren’t included.

As it turns out, adjustments to driving behavior carry far and away the most bang for your buck. Transportation accounts for 27 percent of U.S. emissions, the largest of the sectors that an individual can directly modulate (industry generates 29 percent, but regular folks can’t do much about that). Light-duty vehicles—cars, pickups, SUVs, and the like—produce 60 percent of transportation emissions, which comes out to 16.2 percent of total emissions. That’s the center of gravity where countrywide action by individuals can have the largest effect.

The calculations affirm the principle that you get out what you put in. Incremental-but-easy changes, like eliminating aggressive and very high-speed driving, yield small cuts to greenhouse gases. To make a real dent, you have to up the ante by reducing overall driving—a 10 percent cut would save 1.6 percent of total emissions—or buying cars with substantially better fuel efficiency. Substantially, as in, bump average fuel economy from the current level of 21.4 mpg to 56.0 mpg, which would chop off 10 percent of the country’s emissions.

If Americans aren’t interested in buying dramatically more efficient vehicles, they could instead try an across-the-board approach, piling up little actions in different sectors. For instance, you could reduce driving by 6 percent, buy a car that’s 22.8 mpg instead of 21.4, replace any remaining incandescent bulbs with LEDS, eat 35 percent less meat, and cut 67 percent of personal food waste. Each of those piecemeal choices makes a 1 percent cut in overall emissions.

If you want to do things on several fronts and combine the benefits that way because it’s easier for you, you would have to do a lot of different small things to equal the benefit of a large increase in fuel economy,” Sivak tells CityLab.

The danger with that approach is that limited progress will amount to failure. As the authors point out, the population is growing by 0.8 percent per year. Assuming emissions grow proportionally to the size of population, they calculate that the country will need compounded reductions of 8.3 percent over 10 years just to keep the carbon footprint steady.

Sivak draws hope from his analysis, because it gives regular people the information to make choices that, collectively, could have a major impact. “Every little thing will count,” he tells CityLab.

Of course, it’s hard to get 320 million people to all act toward the same goal, especially if many of them don’t share it. If some people go out and buy super-efficient cars and the rest chug around in Hummers, the potential benefits won’t accrue.

Also, the best-case savings from individual actions don’t come close to meeting the national goal of cutting emissions by 2025 to 28 percent below 2005 levels. Even if the entire population did rally and double the efficiency of the cars they buy, those greenhouse gas reductions couldn’t even keep pace with population rise 10 years down the road.

That gap affirms the crucial role of government and industry action in making the goal achievable. Cleaning up the electric grid, as President Obama hopes to do with his Clean Power Plan, will drive substantial CO2 savings across the industrial, commercial, and residential sectors. Market forces are already pushing power plants in that direction. Higher fuel efficiency standards can lift the national average. Technological innovation can drive down the energy usage of appliances and manufacturing processes. And more user-friendly urban design can help people live their lives without hopping in a car for every trip.

Individuals’ actions help, but they’re not enough to solve the problem of America’s massive carbon emissions. Perhaps advocacy for macro-level solutions is the most effective commitment a sustainability-minded person can make.

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