The Beltway is abuzz about a Green New Deal, and the House of Representatives recently held its first serious climate change hearings in years. But the most important upcoming vote on climate policy will not be in Washington. It will be right here in Pennsylvania.

This month, lawmakers introduced a bill to rework the state’s “alternative energy portfolio standard,” adding a requirement that 50 percent of the electricity sold to Pennsylvania consumers come from carbon-free resources like nuclear, wind, and solar by 2021. To understand the potential impacts, just look at some of its loudest opponents — the state’s fossil fuel industry. Major natural gas producers are trying to crush this legislation, knowing that if it fails, two of Pennsylvania’s nuclear power plants will shut down, and the remaining three could follow. They would be more than happy to replace nuclear power on the grid, even if it means more emissions and higher costs to Pennsylvanians.

Because Pennsylvania is among the nation’s largest producers and consumers of electricity, this legislation could have a more sweeping impact on America’s carbon emissions than any other state or federal action this year. When you’re that big, any steps you take toward cleaner power are going to make an impact.

Passing this bill would not only help to keep Pennsylvania’s five nuclear plants online and producing emissions-free electricity but also increase power from renewable sources. While it isn’t the intention of the bill, this could lay the groundwork for Pennsylvania to generate all of its power from clean, carbon-free energy sources by 2050 — the benchmark scientists say we must hit to stave off climate change’s most devastating impacts.

If the legislation fails, Pennsylvania will instead take a massive step backward — enough to hinder the entire country’s emissions-reduction goals. Nuclear energy currently accounts for 42 percent of the state’s total electric power generation, and more than 90 percent of its carbon-free power. For perspective, per our analysis, closing Pennsylvania’s nuclear plants would have the same emissions impact as eliminating one-third of the entire country’s wind power.

According to a recent analysis from The Brattle Group, closing these nuclear plants would require increased use of natural gas and coal-fired plants in the region to keep the lights on. The resulting increase in emissions would be equivalent to 50 percent of the current carbon footprint of Pennsylvania’s power sector.

The economic impact would also be severe. If Pennsylvania were to abandon its nuclear power it would be sacrificing nearly 16,000 jobs. The Three Mile Island facility alone employs more than 675 full-time employees and another 1,500 local union workers who are contracted to help refuel the plant. Two billion dollars in state GDP and $69 million in state tax revenues also would be swept away.

Opponents of the bill, including the state’s powerful natural gas industry, are decrying it as a nuclear “bailout” and an unnecessary increase in cost for power. In reality, The Brattle Group analysis shows that closing the nuclear plants could raise consumers’ energy costs by $788 million each year.

Fortunately, it’s not too late for lawmakers to prevent unnecessary environmental and economic damages. The first nuclear plant on the chopping block will need to make a decision about refueling by June. Without a viable path forward, they’ll choose not to refuel, and the plant will permanently close. Its clean energy will be replaced by dirtier, more expensive power.

If, on the other hand, Harrisburg moves quickly, legislators can preserve a source of reliable, affordable, and carbon-free energy. In the process, they will send a powerful message to the country and future generations that Pennsylvania is ready to lead in the fight against climate change.

Josh Freed is the senior vice president of the Clean Energy Program at Third Way, a center-left think tank.