BERLIN (AP) — Berlin voters were asked Sunday to decide on a proposal that would force the city government to drastically ramp up the German capital’s climate goals.

The referendum calls for Berlin to become climate neutral by 2030. The target means that in less than eight years, the city would no longer be allowed to contribute further 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 recent 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.

While surveys showed Berliners narrowly in favor of the proposal, enthusiasm was muted on Saturday. A rally and concert at the city’s iconic Brandenburg Gate drew far fewer than the 35,000 people organizers had hoped for.

The referendum requires the support of at least 25% of the city’s 2.4 million eligible voters to pass — something that could be harder to achieve on a day when no other voting is taking place.