LAST WEEK, a bipartisan climate bill passed with overwhelming majorities in the Massachusetts House and Senate. Gov. Charlie Baker now has to choose – by Thursday at midnight – between cementing his and the Commonwealth’s position as climate leaders, or withholding the tools needed for Massachusetts to comply with its own climate law.

A broad coalition of business, health, environmental, and environmental justice groups supports the bill. It includes key efforts that the Baker administration and the Legislature alike have deemed essential: offshore wind, better appliance efficiency standards, natural gas safety measures, and much more. Critically, the bill updates the state’s Global Warming Solutions Act by including a mandate to reduce state emissions to net zero by 2050, and centers environmental justice in policy-making. This bill sets the course for decarbonizing our economy and society over the next 30 years.

If Baker does not sign by midnight on Thursday, the bill dies. Lawmakers, advocates, and the Baker Administration, all of whom have been working toward this bill for more than two years, must start over.

If he signs, Massachusetts will continue to lead the nation in demonstrating pragmatic and effective climate policy. The governor will have a capstone climate achievement and build on his administration’s record of first-in-the-nation initiatives.

In a time of division in our country, Baker has the opportunity to model bipartisan climate leadership to 49 other governors. Across the US, leaders are reckoning with the ways climate change and pollution sharpen inequality. They are fighting wildfires, reeling from record heat, battling drought, and keeping a wary eye on rising seas.  Each governor is leading their piece of this fragmented nation and seeking proven policy solutions to unite their residents for a brighter future. Many states are watching closely to see what Baker does. Some will follow if he leads.

Indeed, Baker himself reinforced the need for this bill when, just this past Earth Day, he raised the stakes under the Commonwealth’s climate law by establishing the net-zero emissions mandate, replacing the previous goal of an 80 percent reduction in greenhouse emissions by 2050. This bill is the natural and necessary continuation of these efforts and the administration’s strong climate planning work, like the 2030 clean energy plan and 2050 roadmap.

Baker may understandably be frustrated by receiving this bill in the final days of the legislative session. While the bill is exceptional, Baker was not given time to formally propose amendments. Nevertheless, he should embrace all that is great about the bill and focus on the many measures his administration will now have the ability to shape in implementing the law.

We urge the governor to sign. This bill is essential for Massachusetts – and equally important for the nation.

Bradley Campbell is the president of Conservation Law Foundation and Elizabeth Henry is the president of the Environmental League of Massachusetts.