Trump To Undo Legal Basis For US Climate Rules

President Donald Trump is poised Thursday to revoke a landmark scientific finding that greenhouse gases endanger public health by driving climate change -- a determination that underpins US regulations aimed at curbing planet-warming pollution.

White House Press Secretary Karoline Leavitt billed it as a "largest deregulatory action in American history," with Trump to appear alongside Environmental Protection Agency Administrator Lee Zeldin for the announcement.

Ordered by court, implemented by Obama

The 2009 "endangerment finding" was a determination under then-president Barack Obama that six greenhouse gases threaten public health and welfare by fueling climate change.

It came about as a result of prolonged legal battle ending in a 2007 Supreme Court decision, Massachusetts v. EPA, which ruled that greenhouse gases qualify as pollutants under the Clean Air Act and directed the EPA to determine whether they pose a danger to public health and welfare.

While it initially applied only to vehicle emissions, it later became the legal foundation for a broader suite of climate regulations.

Thursday's repeal will thus be accompanied by scrapping federal greenhouse gas standards for automobiles.

But the consequences could ripple further, placing a host of climate rules in jeopardy -- including limits on carbon dioxide from power plants and methane from oil and gas operations.

Trump administration convened climate skeptics

The administration's draft proposal, which elicited more than half a million public comments, asserts that greenhouse gases should not be treated as pollutants in the traditional sense because their effects on human health are indirect and global rather than local.  

Regulating them within US borders, it contends, cannot meaningfully resolve a worldwide problem. 

The proposal also sought to downplay the scale and impacts of human-caused climate change, citing a study commissioned by an Energy Department working group comprised of skeptics to produce a report challenging the scientific consensus. 

The report was quickly panned by researchers, who said it was riddled with errors and, in some cases, misrepresented the very studies it cited.

Environmental groups sued, alleging the panel was convened behind closed doors in violation of federal rules, and Energy Secretary Chris Wright later disbanded the group.

Legal challenges, disputed math

The administration has claimed repealing the endangerment finding would generate more than $1 trillion in regulatory savings, without detailing how the figure was calculated. It has also said it would lower new car costs.

Environmental advocates counter ignoring the other side of the ledger, including lives saved from reduced pollution and fuel savings from more efficient vehicles.

They also warn the rollback would further skew the market toward more gas-guzzling cars, undermining the American autor industry's ability to compete in the global race toward electric vehicles.

Critics are awaiting the final text but say they are confident it will not survive in court.