The first step in addressing the challenge of climate change is to define a consistent way to measure its causes. In April 2007, thirty-four U.S. states formed the Climate Registry to measure, track, verify, and publicly report GHG emissions accurately, transparently, and consistently across borders and industry sectors. The Registry will support voluntary, market-based, and regulatory GHG emissions reporting programs. The states joining represent 78% of the U.S. population, with impressive geographic, economic, and political diversity. WRI played a pivotal role in helping to convene this initiative and by providing technical consulting. Ideally, these standards and strategies will help support and provide a common template for federal climate change policies and programs.