Trump has scrapped the long-standing legal basis for tackling climate emissions

Regulating climate emissions just became more difficult. US President Donald Trump announced on Thursday the Environmental Protection Agency (EPA) has repealed its own 2009 legal finding that greenhouse gas emissions endanger human health.

Vindicated by a Supreme Court ruling in 2007, and based on scientific evidence, this so-called endangerment finding by the EPA provided the legal warrant for the regulation of greenhouse gases by the federal government. It underpinned the Obama administration’s Clean Power Plan, which regulated emissions from power plants. In his first term, Trump had tried to weaken it but a new version was introduced by the Biden administration.

Without the endangerment finding, and in the absence of new laws passed by both Houses of Congress, the federal government lacks the legal mandate for direct regulation of greenhouse emissions. The science hasn’t changed, but the obligation to act on it has been scrubbed out.

If you imagine the United States as a collection of big greenhouse gas pots with lids, the Trump administration has been lifting the lids off one by one, releasing more emissions by stepping up fossil fuel extraction, production and consumption. This legal finding held down the biggest lid on climate emissions — and Trump has pulled it right off. This will have a structural effect globally.

What is the endangerment finding, and how was it developed?

In 1970, when the US environment movement was at its most influential, Congress passed an important piece of legislation called the Clean Air Act. It empowered the new Environmental Protection Agency (EPA) to declare something a pollutant if it endangered public health. Initially, it was used to regulate pollutants such as smog or coal ash, the byproducts of industry.

During the George W. Bush presidency, the EPA made a ruling that greenhouse gases were also a pollutant within the meaning of the Clean Air Act. This ruling was challenged in 2007 by fossil fuel interests in the case of Massachusetts v EPA, but the court ruled (five judges to four) that carbon dioxide and other greenhouse gases were “air pollutants” that endangered human health and welfare. It directed the EPA to assess their impact on human welfare — allowing the agency to regulate them.

However, the Bush administration did not push the EPA to implement the ruling.

How was the endangerment finding used for climate action?

President Barack Obama promised to act on climate during his election campaign but faced a hostile Senate when he came to power. His efforts to enact an emission trading bill failed.

However, the endangerment finding allowed him to use his executive power to direct the EPA to regulate emissions. In his first term, the EPA issued new vehicle emissions regulations for cars and light trucks, and some power plants and refineries.

In his second term, Obama extended those regulations to all power plants. These moves represented the US’s first significant steps towards emissions reductions. They enhanced Obama’s diplomatic credibility in the negotiations for the Paris Agreement in 2015. This provided a footing for bilateral cooperation with China on clean energy, helping to build diplomatic trust between the world’s two biggest emitters. Their lead negotiators worked together in the final days of the negotiations to get the Paris Agreement over the line.

Why has Trump overturned it?

On February 12, Trump announced the EPA would rescind the legal finding it has relied on for nearly 20 years. Among all the wrecking balls he has swung at efforts to decarbonise the US economy, this is the biggest. He claims the legal finding hurts Americans. The EPA’s director, Trump-appointed Lee Zeldin, called the rule the “holy grail of climate change religion”.