On February 18, 2010, the White House Council on Environmental Quality (CEQ) released a draft guidance document describing how and when climate change considerations should factor into environmental impact assessments by federal agencies under the National Environmental Policy Act (NEPA). The draft guidance is important for anyone proposing to build infrastructure, such as power plants, pipelines, roads, and large industrial and commercial facilities, since the document (once finalized) will influence whether and under what conditions federal agencies will issue permits and other approvals. Most federal approvals for large projects are subject to NEPA, which is the law mandating environmental impact assessments as an aid to federal decision-making.

The proposed guidance recommends that federal agencies consider climate change if the proposed action (such as a federal permit) would lead to the release of at least 25,000 tons of greenhouse gases. However, the guidance intentionally does not define any standard – quantitative or qualitative – by which to measure the significance of a climate impact for purposes of NEPA. "Significant" effects on the environment must be avoided or mitigated before an agency will approve a project. Agencies must still be guided by a "rule of reason" when making a case-by-case assessment of the potential effects of their actions on the environment via climate change.

In considering climate change, agencies are cautioned to "be realistic" and to "ensure the scientific and professional integrity of their assessment," as well as to "recognize the scientific limits of their ability." Throughout the draft guidance, CEQ takes notable steps to emphasize that all climate-related impact assessments should be proportional to the importance of climate change to the decision-making process.

The energy sector, the transportation sector, and Tribal and Native Alaskan communities are singled out for attention in the draft guidance. Likewise, the document highlights the importance of comparing the proposed action against alternatives on the basis of expected climate-change effects. In doing so, agencies are invited to consider not just federal but also state and local goals for energy conservation and reductions in greenhouse gas emissions, especially as associated with energy production. Furthermore, the proposed action is to be assessed against a "no action" alternative that is based on a projection of the reasonably foreseeable future condition of the affected environment subject to climate change.

CEQ identifies specific resources for agencies to consult in assessing the likely effects of climate change and the relevance to the proposed action (and its alternatives). The draft guidance refers to the U.S. Global Change Research Program website as a source of peer-reviewed information. CEQ also emphasizes the need to consider and disclose the uncertainties, limitations and variability of any studies being relied upon.

The draft guidance is not effective until it is finalized. In the interim, CEQ has requested public comments on the proposal.