The case for a shorter workweek usually centers on worker well-being. If you’re working four days a week or six hours a day, you’ll probably be happier, and companies benefit if happy workers are more likely to stick with a job. But there’s also an argument that working fewer hours could help fight climate change.

The reasoning is simple: If companies produced less each week, and ran their offices for fewer hours, they would also emit less CO2. Other studies have looked at different ways that reducing work benefits emissions, starting with the fact that commuters can spend less time in cars. With more free time, workers may also end up consuming less–they might have time to walk or bike to run an errand instead of driving, for example, or might be more likely to spend time socializing rather than shopping.

A new paper calculates how much work needs to shrink in some economies to get on track to stay under 2 degrees of global warming, the upper limit to avoid some of the worst impacts of climate change. In the U.K., it would mean moving to a nine-hour workweek. In Sweden, the week would be around 12 hours. The U.S. was not part of the paper, but might have to cut hours even more.

“The conclusions were pretty radical and stark,” says Will Stronge, director of Autonomy, a British think tank that focuses on the future of work. The report looks at the carbon budget for the U.K., Sweden, and Germany–how much each country can emit before exceeding its share of safe limits for the planet–and then compares that number to emissions from industry. “You can actually trace how much CO2 is being pumped into the atmosphere per hour worked, because the OECD [Organisation for Economic Co-operation and Development] has data on how much greenhouse gas is being pumped out by each industry, and then also how GDP power relates to greenhouse gas emissions,” he says.

The new report is intended as a provocation, not a recommendation–and it’s hard to see how the economy in the U.K. could survive a sudden shift to nine-hour weeks. Still, even smaller changes could help. A 2006 study suggests that if U.S. companies moved to working hours that were more similar to Europe, that could cut energy consumption by 20%. A 2015 study found that each 1% decrease in working hours could lead to a 0.8% decrease in emissions. A four-day week, then, might cut emissions by 16%.

Obviously, the amount of time people spend working is not the only thing that needs to change. But as we move to renewable energy and other pieces of a zero-carbon society, the time we spend working could play a role. “Ultimately, we want the shorter working week to be at the core of any kind of Green New Deal or economy that is sustainable,” Stronge says. “We think this should be part of it.”