Earlier this month, a broad coalition of groups, representing millions of Americans, filed amici curiae – or “friend of the court” – briefs with the U.S. Court of Appeals for the District of Columbia Circuit in support of the Environmental Protection Agency’s Clean Power Plan.

Businesses, members of Congress, major tech companies, public health organizations, faith leaders, government officials, utilities, attorneys general, environmental groups and mayors from all over America are so interested in these legal proceedings because they know what’s at stake. By setting the first ever federal limits on carbon pollution from power plants and encouraging the development of cleaner, safer energy, the EPA’s plan will help protect our economy and public health from the dangerous impacts of climate change. That’s why I was one of those amicus brief signers.

The modern Clean Air Act is set forth in major amendments that were enacted in 1970 and 1990. My predecessor in the Senate, Ed Muskie, was the principal author of the 1970 amendments, and I was deeply involved in the 1990 amendments.

Each change reflected the growing body of scientific knowledge about the number and nature of the many pollutants that exist in an industrialized society. The combination of changes demonstrate a clear intention by Congress to establish a comprehensive program to deal with known pollutants and to grant to the EPA the authority to regulate others as they became known.

To accomplish this objective, the act mandates the promulgation of national air quality standards, and the development by the states to implement those standards, for those pollutants determined to be harmful to the public health and welfare (these pollutants are described as “criteria pollutants”). It also authorizes the EPA to establish more strict regulation for more hazardous air pollutants. And it authorizes the EPA to regulate all other harmful air pollutants that are not criteria pollutants or hazardous air pollutants.

In light of these provisions, the argument of opponents to the EPA’s action – that the EPA lacks authority for its plan – appears to be unsustainable.

Climate change directly affects our way of life, the global economy and the well-being and safety of disadvantaged communities. Twenty-five years ago, I was serving as majority leader of the U.S. Senate, and I headed the Senate’s Environmental Pollution Subcommittee. I wrote a book about the potentially devastating effects of climate change if we failed to act. To a disturbing degree, what I feared would happen has happened.

On Friday, heads of state will gather at the United Nations headquarters in New York to sign the Paris agreement, a groundbreaking plan that will encourage every member of the U.N. to work together to address the hazards of climate change.

It’s essential that they do so, for their citizens’ health and safety.

Climate change causes more frequent and more extreme severe weather events, asthma attacks, disruptions in food and supplies, more vector-borne diseases and sea-level rise that, if allowed to continue unchecked, will displace millions of people. Nearly all of the world’s countries have agreed to take action that will help us meet our obligation to safeguard all our children and grandchildren and leave them a better future. The Paris agreement commits all countries to do their part.

This international coordination was led by the U.S., and the example we set with the Clean Power Plan. The EPA’s plan will encourage American innovation, thereby helping our economy transition to cleaner and safer sources of energy that protect healthy communities. It’s our country’s best available tool to address climate change and will help us meet our commitments. Hopefully, the Paris agreement will give confidence to Americans that other countries will be held to the same standards as we are – and that we won’t be acting alone.

As Senate majority leader, I worked with Republicans and Democrats to hammer out bipartisan improvements to the Clean Air Act that have kept millions of Americans safe from dirty air. The vast majority of Americans support the Clean Power Plan, which makes it easy for our leaders to represent public opinion and the public interest.

The recent legal filings remind me of what empowers our democracy – diverse Americans coming together to drive policy that makes us stronger, healthier and better as a nation. That’s why I call on everyone to remain engaged in this process. Help your community transition to healthier energy, and tell your representative to support the Clean Power Plan and the Paris agreement.

We all know what’s at stake.