 Abstract, blue hydrogen is often touted as a solution to reducing greenhouse gas emissions associated with hydrogen production. However, this study found that when fugitive methane emissions from natural gas are taken into consideration, blue hydrogen has a larger carbon footprint than grey hydrogen. Furthermore, even under optimistic assumptions about carbon capture and storage, blue hydrogen's carbon footprint is still worse than burning natural gas directly. This article was offered by Robert W. Hoeth and Mark Z. Jacobson.