President Donald Trump's administration has proposed revoking a foundational scientific finding that underpins United States regulations on greenhouse gas emissions, a move that could drastically weaken federal efforts to combat climate change. The Environmental Protection Agency's proposal would rescind the 2009 declaration that carbon dioxide and other greenhouse gases endanger public health and welfare, a key legal basis for many climate rules. Environmental groups and former agency leaders have sharply criticized the plan, warning it would endanger millions and undermine protections against climate pollution. The proposal is expected to face a lengthy review process and likely court challenges before it could be finalized.