Transferability and uncertainty of landfill methane models in hot arid and hyper-arid environments: a critical review with an Arabian Gulf evidence-gap analysis.

Landfills are a major and, in several settings, growing source of methane, and many widely used operational- and inventory-scale estimates rely on first-order decay (FOD) models whose default parameterizations are largely underpinned by North American and European datasets. Whether these models transfer reliably to hot arid and hyper-arid systems-and specifically to the Arabian Gulf-remains unresolved. This critical review examines that question through a structured descriptive synthesis and an evidence-gap analysis for the six Gulf Cooperation Council (GCC) states. The provenance analysis shows that major frameworks represent aridity through broad climate or moisture categories, with limited direct calibration evidence from hot hyper-arid systems. The synthesis finds that the decay constant is climate-sensitive, with lower fitted values in drier settings; that realized methane yield can fall below nominal potential under persistent moisture limitation; that site-specific parameterization frequently departs materially from defaults; and that the direction of model-measurement disagreement is site-, method- and parameter-specific, so no systematic over- or under-estimation can be attributed to any framework. Screening the regional evidence, including geographic screening of a global satellite survey against GCC boundaries, identified no peer-reviewed site-level measured-versus-modeled landfill methane flux comparison for any GCC state in the present search; local, unindexed or grey studies beyond its reach cannot be excluded. Transferability to Gulf conditions is therefore conditional and not yet locally validated; the review converts this gap into a staged, uncertainty-explicit validation program to establish it by measurement.