A movement of climate activists wants the world to respond to the growing wave of extreme weather and climate disasters the way they would to a mass shooting — like it’s an emergency. On Tuesday, they got three prominent progressive allies in the United States to publicly join their cause: Sen. Bernie Sanders (I-VT) and Reps. Alexandria Ocasio Cortez (D-NY) and Earl Blumenauer (D-OR).

The lawmakers introduced a joint resolution calling for the US to join 16 other countries and hundreds of local governments in declaring a “climate emergency.” New York City declared a climate emergency last month.

“This is a moral imperative. There is no choice. We are going to have to take on the greed of the fossil fuel industry and the ignorance of Donald Trump,” Sanders said Tuesday.

A concurrent resolution is nonbinding and does not have the force of law. But Blumenauer said this is the first step toward a Green New Deal, an ambitious progressive resolution Ocasio-Cortez and Sen. Ed Markey (D-MA) proposed earlier this year to address climate change and growing inequality.

It also sends a stark political message about the two parties’ priorities. This week, President Trump held an event about his environmental record, repeating a series of misleading statements about his administration’s policies without acknowledging climate change. The backdrop to the event: flooding in Washington, DC, a historic heat wave in Alaska, and a $19 billion disaster aid package passed by Congress last month for hurricane, wildfire, tornado, and storm relief around the country.

The resolution declares global warming “a climate emergency that severely and urgently impacts the economic and social well-being, health and safety, and national security of the United States,” and calls for “a national, social, industrial, and economic mobilization of the resources and labor of the United States at a massive-scale to halt, reverse, mitigate, and prepare for the consequences of the climate emergency and to restore the climate for future generations.”

Why there’s a movement to declare climate change a national emergency

Sanders’s presidential campaign has yet to unveil its own climate plan. The senator has supported the Green New Deal framework and said Tuesday that he will be coming out with the “strongest” plan in the current Democratic field. He said specifics were an “ongoing proposal” but cited investments in sustainable energy and public transportation.

But this proposed emergency declaration fits in with Sanders’s most central message: a need for political revolution. On climate change, Ocasio-Cortez says the United States is in a “political crisis of inaction.”

This is well established. Climate policy has become a zero-sum game in Washington, where Republican leaders have made it their political platform to block any climate policy, incremental or bold.

It’s created immense headwind to address what is unmistakably a growing global crisis, which if left unaddressed threatens civilization altogether. Vox’s Dave Roberts puts the magnitude of this hurdle in this context:

The only way Democrats can hope to pass any legislation — not big legislation, any legislation — is by radically shaking up the status quo balance of powers. That would mean getting rid of the filibuster, possibly granting statehood to Washington, DC, and Puerto Rico, reforming the Electoral College and voting laws, and possibly expanding the Supreme Court.

So the response from climate activists and progressive lawmakers has been to create a people’s movement — largely in line with how Sanders frames every policy fight. Here’s Roberts explaining this approach:

Here’s the only way any of this works: You develop a vision of politics that puts ordinary people at the center and gives them a tangible stake in the country’s future, a share in its enormous wealth, and a role to play in its greater purpose. Then organize people around that vision and demand it from elected representatives. If elected representatives don’t push for it, make sure they get primaried or defeated. If you want bipartisanship, get it because politicians in purple districts and states are scared to cross you, not because you led them to the sweet light of reason.

Blumenauer said Trump’s decision to declare a national emergency on the southern border to get his wall inspired him to draft this climate emergency resolution. But he’s not the first to think that using the language of national crises is the way to get countries to act — that’s part of a global activist movement to view climate change more urgently.