The spatially distributed scenarios of random and systematic errors described in the Mission Products section have been integrated into an atmospheric inversion simulator that converts uncertainties in XCH₄ into uncertainties on surface emissions using an inversion system. This simulator has the originality to carry both, random and systematic error. Although relatively marginal at sounding level (±3.7 ppb on global scale), the systematic errors have a larger influence than the random errors on the regional CH₄ emission estimates, because they are not reduced by data averaging accounting for both types of errors.

Expected uncertainty reductions on CH₄  emissions are found on average to be

• 59% for the continental tropics (30°S–30°N)
• 84% for continental mid-latitudes (30°N–50°N)
• 53% for continental high latitudes (above 50°N).

The largest uncertainty reductions are achieved for temperate regions. Uncertainty reductions obtained for the aggregated boreal regions is 53% on average, indicating that MERLIN still brings constraints for high northern latitudes, contrary to most passive SWIR missions. For tropical regions, the score for uncertainty reduction is mostly influenced by desert regions and the choice to distribute systematic errors partly on albedo to represent potential driver of nonlinearity effect of the MERLIN detector. More details and regional analyses can be found in Bousquet et al.