National Greenhouse Gas Emissions Inventory and Registry Act of 2003

National Greenhouse Gas Emissions Inventory and Registry Act of 2003 - Amends the Clean Air Act to require the Administrator of the Environmental Protection Agency to establish and administer: (1) a national greenhouse gas emissions information system to collect annual lists required to be submitted under this Act of an entity's greenhouse gas emissions and their sources; and (2) a national greenhouse gas registry to collect voluntarily reported information on emissions reductions. Specifies factors for adjustment of emissions records by a reporting entity.

Directs the Administrator and the Secretaries of Commerce, Agriculture, and Energy to develop greenhouse gas emissions quantification and verification protocols, electronic reporting methods, and accounting and reporting standards. Requires verification of reported emissions information.

Requires the Administrator to publish an annual national greenhouse gas emissions inventory.