US President Donald Trump has moved to reverse a foundational scientific determination made during the administration of former president Barack Obama, marking a major shift in federal climate policy and significantly weakening the legal basis for regulating planet-warming greenhouse gas emissions in the US, BBC reported on Friday.
The decision overturns the 2009 “endangerment finding,” a landmark ruling issued by the Environmental Protection Agency that concluded carbon dioxide and other greenhouse gases pose a threat to public health and welfare. That finding has for more than a decade served as the legal cornerstone for a wide range of federal actions aimed at curbing emissions, particularly from vehicles, power plants and industrial sources.
By rescinding the finding, the Trump administration has effectively dismantled the scientific and regulatory justification that obliges federal agencies to control greenhouse gas emissions under the Clean Air Act. Without the endangerment determination in place, the EPA’s authority to impose emissions standards across multiple sectors is sharply curtailed, creating far-reaching implications for US climate regulation.
The original ruling followed extensive scientific assessment and was prompted by a Supreme Court decision that required the EPA to determine whether greenhouse gases endangered public health. Its conclusion enabled successive administrations to introduce vehicle fuel efficiency rules, emissions limits for power plants and broader climate regulations. Environmental groups have long described it as the backbone of US climate law.
Trump’s move aligns with his broader agenda of rolling back environmental regulations, which he has repeatedly criticised as economically damaging and burdensome to industry. The administration has argued that the endangerment finding relied on flawed science and overreached the EPA’s mandate, asserting that climate policy decisions should rest with Congress rather than regulatory agencies.
Critics, however, warn that the reversal represents a fundamental rejection of established climate science and could stall national efforts to address global warming at a time of increasing climate-related risks. Legal experts say the decision is likely to face immediate court challenges, with opponents expected to argue that the EPA cannot discard a science-based determination without providing a robust and legally defensible alternative grounded in evidence.
The rollback also carries international ramifications, potentially weakening US credibility in global climate negotiations and complicating coordination with countries that continue to strengthen emissions controls. Domestically, it is expected to deepen divisions between federal and state authorities, particularly as several US states pursue their own climate policies independent of Washington.
While the administration has framed the move as a correction of regulatory overreach, analysts say the reversal underscores how deeply climate policy in the US remains tied to political leadership. The fate of the endangerment finding, and the regulatory framework built upon it, is now set to become a central battleground in the courts and a defining issue in the country’s ongoing climate debate.