Berlin voters were asked Sunday to vote on a proposal that would force the city government to ramp up the German capital's climate goals.
By the year 2030, Berlin will become climate neutral. In less than eight years, the city would no longer be allowed to contribute to global warming.
An existing law sets the deadline for achieving that goal at 2045, which is also Germany's national target.
The center-right Christian Democratic Union, which won a local election in the capital and is likely to lead its new government, opposes the earlier target but would be bound to implement it if the referendum passes.
Although Berliners were overwhelmingly in favor of the proposal, enthusiasm was muted on Saturday. A rally and concert at the city's iconic Brandenburg Gate drew fewer than the 35,000 people organizers had hoped for.
At least 25% of the city's 2.4 million eligible voters must pass to pass the referendum, something that could be harder to achieve on a day when no other voting takes place.