A key part of the federal government’s legal authority to regulate emissions from vehicles, power plants, and other sources could soon disappear. Sept. 22 is the deadline for public comment on the U.S. Environmental Protection Agency (EPA) proposal to do away with the endangerment finding. Research by Stanford environmental scientist Chris Field and colleagues shows evidence for climate change’s damaging impacts – such as food insecurity, mass migration, and health problems – has only grown since the finding was established.

“The endangerment finding is the foundation for regulation of greenhouse gases at the federal level,” Field said. “It is not the government’s only tool for tackling climate change, but it is key to a balanced program with both carrots and sticks.”

Here are five things to know about the endangerment finding: 

1. The endangerment finding identifies six greenhouse gases as a danger under the Clean Air Act.

In 2009, the EPA issued the Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act – otherwise known as the endangerment finding. Citing a massive body of scientific evidence, the finding singled out six greenhouse gases for the danger they pose to public health and welfare:

·      Carbon dioxide
·      Methane
·      Nitrous oxide
·      Hydrofluorocarbons
·      Perfluorocarbons
·      Sulfur hexafluoride

2. Courts have upheld the finding, which underpins federal limits on climate pollution.

The finding has its origins in a 2007 case, Massachusetts v. EPA, in which the U.S. Supreme Court ruled that greenhouse gases qualify as pollutants under the Clean Air Act. Because the EPA is required to set limits for damaging pollutants, the court directed the agency to determine whether these gases endanger public health and welfare. The EPA conclusion that six greenhouse gases meet this endangerment criteria unlocked the agency’s authority to regulate emissions from cars, trucks, and power plants. Although industry groups challenged the finding, a district court upheld it, and the U.S. Supreme Court declined to review it. Since then, the finding has provided the legal foundation for federal climate action.

3. Regulatory signals influence consumer choices and corporate investment.

The endangerment finding not only enables regulations but makes clear that the U.S. government is serious about cutting emissions, according to Field.

“It provides an indication that dealing with climate change is important for individuals when they think about a vehicle purchase or home heating system,” Field said. “It also sends a clear market signal. When companies know the government is serious about cutting emissions, they invest in innovation – better vehicles, cleaner fuels, more efficient appliances. That kind of policy certainty drives progress.” 

4. Evidence of climate-related health and welfare risks in the United States has strengthened since 2009.

Since 2009, the scientific evidence for endangerment has only strengthened, according to Stanford research that finds climate change is driving more severe heat waves, larger wildfires and more wildfire smoke-related deaths, rising seas, growing food insecurity, and a range of health problems.

Together with Stanford climate scientist Noah Diffenbaugh and Woods Hole Research Center president Philip Duffy, Field led a 2018 study showing that since the endangerment finding was established, scientific evidence has increased “dramatically” for each climate change impact noted in the endangerment finding. Those areas ranged from increased disease rates to coastal flooding in the original report. The 2018 study added to the list of understood negative impacts in the U.S. to include increased dangers from ocean acidification, effects on national security and economic well-being, and threats from violence.

A 2019 study Field co-authored estimated climate change had influenced as much as 20% of armed conflict risk over the previous last century, and that the influence would likely increase significantly.

Most recently, the National Academies of Sciences, Engineering, and Medicine put out a report on Sept. 17 revisiting evidence for health threats from greenhouse gases, and declaring that the basis for the endangerment finding has “stood the test of time.” Michele Barry, the senior associate dean of global health in the Stanford School of Medicine, was on the committee that issued the report (read related Q&A with Barry).

5. Higher emissions raise risks in the U.S. and abroad.

Without the endangerment finding, the U.S. would have fewer tools to curb emissions, leaving Americans more exposed to climate damages, according to Field. That could mean more cases of asthma and heart disease linked to poor air quality, higher food prices from climate-stressed crops, and economic losses as U.S. companies fall behind in global clean-tech markets.

Among other economic impacts of eliminating the endangerment finding, U.S. automakers could lose their edge, Field said. “Taking the foot off the accelerator on developing compelling electric vehicle options means the best ones will be Chinese vehicles, and American carmakers will struggle to compete,” he said. “In the long run, it’s clear what direction the world is headed, and it’s clear that U.S. companies are already falling behind.”

The impacts would not stop at America’s borders, according to Field: Climate instability abroad could lead to a host of impacts in the U.S., including increased conflict and disruptions in trade with other countries. “A world with massive amounts of climate change is going to have millions of climate migrants. It’s going to have regional conflicts driven by climate change, terrible conditions for markets for U.S. goods or suppliers of raw materials, and conflicts that eventually reach our shores or involve our forces. We ignore global impacts at our peril.”