HAI reports the Obama administration plans to propose a first-time federal endangerment finding on Thursday, April 16, citing climate change as posing a risk to public health and welfare, with plans to finalize it by the end of June.

This long-awaited finding by the Environmental Protection Agency (EPA) is intended to give a scientific justification for labeling climate change as a public risk. President Obama has pushed for a requirement that companies limit their greenhouse gas emissions.

The announcement due tomorrow is an important symbolic step as Congress plans to get down to business on climate change talks this year. Supporters of climate change legislation, or what is more commonly known as ‘cap and trade’ legislation, see this step as necessary to ensure that federal greenhouse gas regulations hold legal water.

It is unclear whether the proposed endangerment finding will include simply a scientific finding or a broader discussion of how the finding would trigger action required by EPA under the Clean Air Act.

By the end of June, the Obama administration will determine whether to grant California’s request to set its own limits for greenhouse gas emissions from tailpipes or whether a national approach is needed. Auto companies have lobbied the Obama administration to set up a national tailpipe standard to give them more flexibility in reducing tailpipe emissions instead of allowing California and about 17 other states the opportunity to have a different standard than other states. There is growing speculation in Washington that EPA will deny California’s waiver request and instead propose a national standard. The White House has cited a growing need for the federal government to establish a unified national policy for clean vehicles.

The recently introduced House draft legislation on climate change/cap and trade requires the president to “harmonize” federal fuel efficiency standards with any future tailpipe standards from EPA or from California if the state is granted a waiver.