To support states’ technical needs in building and implementing climate action plans — including by developing robust GHG inventories — the U.S. Climate Alliance has convened an “Impact Partnership” of nonprofit organizations with relevant expertise. Through that partnership, a guide for states has been published to develop and improve their GHG inventories with an eye toward one particular sector that has often been shortchanged: natural and working lands (NWL). But to understand why a state-level guide specific to land-based GHG inventories is needed, it’s important to first know what a GHG inventory is, why inventories are produced and how they are created.