The group Fridays For Future says the current tentative deadline of 2038 is too late and should be brought forward by eight years.
At a news conference in Berlin, leaders of the group said Monday that Germany should also generate all of its energy from renewable sources and cut net greenhouse gas emissions to zero by 2035.
The protests, inspired by Swedish teen activist Greta Thunberg, have grown rapidly in size in Germany and elsewhere since last year.
Some politicians have criticized the fact that they've involved thousands - and sometimes tens of thousands - of students skipping school each Friday.