To cut emissions, could you give up living in a large house?

A house with a white picket fence in the verdant suburbs has long been an American dream. It could also be a major hurdle for the United States' chances of cutting climate-warming emissions, researchers at the University of Michigan said in a study on Monday.

U.S. households account for one-fifth of the country's total greenhouse gas emissions, thanks partly to Americans' general preference for bigger houses and spacious suburbs. Those preferences also translated into an emissions divide between the rich and the poor, with wealthier households in recent years emitting around 25% more than their lower-income counterparts in smaller homes, the researchers said.

To bring down the country's future emissions, Americans may need to rethink how they live, said Benjamin Goldstein, a co-author on the study published in the journal Proceedings of the National Academy of Sciences.

"Structural change is going to be important and necessary," said Mr. Goldstein, a professor at the University of Michigan. Developers might need to look for more options in already dense settlements. Builders can consider reducing floor spaces. And residential buildings might reconsider using natural gas, a fossil fuel, for heating and cooking, he said.

Such measures may be especially important, given that more than 100 million new homes are expected to be built in the next 30 years, while the country's 328 million population is projected to grow by more than a third in that time.

Because the average lifespan of an American house is around 40 years, the U.S. risks a "carbon lock-in" unless it commits to more energy-efficient homes and neighborhoods, the researchers said.

"We need to have denser and smaller homes," said Mr. Goldstein, who said home sizes in the U.S. and Canada are abnormally large compared with other rich nations.

Policies should also tackle emissions from existing buildings, with measures like tax incentives to spur retrofits, he said.

The study estimated energy use by 93 million U.S. homes, based on details from tax assessor records for 2015 including a house's size, age, location, and construction date.

Through analyzing ZIP codes, the study revealed a correlation between higher wealth and higher-per-capita energy use and emissions.

And poorer neighborhoods are more at risk to climate change, according to AP:

Even though richer Americans produce more heat-trapping gases, “the poor are more exposed to the dangers of the climate crisis, like heat waves, more likely to have chronic medical problems that make them more at risk to be hospitalized or die once exposed to heat, and often lack the resources to protect themselves or access health care,” said Dr. Renee Salas, a Boston emergency room physician and Harvard climate health researcher who wasn’t part of the study.

However, there were also big differences depending on the U.S. state: Household emissions on both the East and West coasts were far lower than in states in the middle of the country, with North Dakota, Oklahoma, and Missouri having among the highest average household emissions.

There is a growing movement by U.S. municipalities to tackle emissions from residential and commercial buildings, starting with banning the use of natural gas in new construction. San Francisco is the latest city to propose such a measure.

At the federal level, congressional Democrats unveiled a climate policy blueprint earlier this month that calls for an update of building codes to eliminate greenhouse gas emissions.

Builders say, however, that home sizes have been trending downward since 2015, the year of focus in the study.

"Our surveys consistently show that consumers want homes that are more energy efficient," said Liz Thompson, spokeswoman for the National Association of Home Builders, the lobby group for the home construction industry.

The group said, however, that the four-year trend toward smaller houses may end this year, as people have spent more time at home during the COVID-19 pandemic and may again seek bigger spaces.

At the international level, Swedish teen activist Greta Thunberg said on Monday she would donate $1.14 million from a new prize she has won to groups tackling climate change and defending nature.

She said in a video posted on Instagram that the award was "more money than I can even begin to imagine" and she hoped it would help her "do more good in the world."

This story was reported by Reuters. Reuters writer Thin Lei Win in Rome contributed to this report.

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