IN THE WANING hours of the 2019–2020 legislative session, the Massachusetts House and Senate passed a climate bill that would have taken important steps toward a cleaner, healthier, safer future. This bill would have set efficiency standards for appliances, required at least 40 percent of our electricity to come from renewable sources by 2030, and increased our offshore wind capacity by 2,400 megawatts.

Faced with a decision between signing the bill and letting it die, Gov. Charlie Baker chose the latter, explaining his pocket veto in a message filled with dubious claims about the cost of climate action.

Now, with the start of the new session, legislators get a chance at a do-over. A bill identical to last session’s climate bill has been introduced, and House Speaker Ron Mariano and Senate President Karen Spilka have said they will get it onto the governor’s desk “in the coming days.” That may happen as soon as Thursday. I applaud the speaker and Senate resident for this commitment.

I’m nervous about what comes next, though. Baker may veto the bill again or return it with amendments, requiring further action from the Legislature to turn the bill into a law.

Without a public push to get this bill over the finish line, days may well turn into weeks, and weeks into months. In the seven years I’ve worked as an environmental advocate in the State House, I’ve seen this “time warp” all too often. Some lawmakers have already suggested to me that the bill may not become law until March or April — a timeline that could easily slip later into the year.

We can’t tolerate any delay. The Legislature needs to pass last session’s climate bill into law as soon as possible, so we can move onto the next climate bill.

For all that last session’s bill would accomplish, a lot has been left on the table. The Legislature will need to take further action in 2021 to protect our health from fossil fuel pollution and ensure a safe future for us and our children.

Last session’s climate bill won’t put Massachusetts on track to 100 percent clean electricity, a commitment already passed into law in seven other states. It won’t do much to increase the number of electric vehicles on the road or encourage people to travel by public transit, walking, or biking instead of driving. It won’t prohibit oil or gas heating in new buildings, meaning that we’ll likely have to spend millions of dollars retrofitting those buildings with efficient electric heating over the coming decades.

We need to pass last session’s bill into law as quickly as possible so legislators can turn their attention to the other important climate policies awaiting action. One policy that’s at the top of the to-do list for 2021: a bill championed by Rep. Marjorie Decker to transition our electricity, buildings, and transportation system to 100 percent clean energy.

The longer this process is delayed and drawn out, the greater the risk that last session’s climate bill will come to be seen as this session’s climate bill. If that happens, we might not make any further progress on climate action in the 2021–2022 session. Delay also gives special interests more time to try to weaken the bill.

The costs of inaction are high. By the year 2100, if global warming pollution continues at a high rate, sea levels in Boston Harbor could be up to 10 feet higher than they are today. That may seem like a long way off, but it’s within the lifetime of a child born today.

What kind of future are we creating for ourselves and for our children? The choice is in our hands. More precisely, it’s in the hands of the 200 people who represent us on Beacon Hill.

So we are setting a deadline: Friday, February 19.

By February 19, we’re expecting last session’s climate bill to be the law of the land. That includes passing it through the House and Senate without any weakening amendments, getting it to Baker’s desk, and — if necessary — overriding another veto from the governor.

February 19 also happens to be the deadline for legislators to file new bills for the current session. It’s the perfect day to clear the decks of last session’s business.

Once that’s accomplished, all of us can take a few moments to celebrate — and then we should turn our attention to all of the other laws we need to pass to ensure a safe, healthy future.

Ben Hellerstein is the state director of Environment Massachusetts, the statewide environmental advocacy organization working to protect clean air, clean water, and open space.