Environmentalists rallying in Annapolis Thursday called on lawmakers to pass toughest-in-the-nation legislation requiring a 90-percent reduction in carbon emissions by 2050.

With snow falling, advocates called for passage of a bill that would require a 25 percent reduction in greenhouse gas emissions in Maryland by 2020 and a 90 percent reduction by 2050. The plan calls for a carbon cap that could force expensive investments in solar and wind power and eco-friendly buildings, but advocates said they are necessary to halt the potentially disastrous effects of global warming.