Global stratospheric methane loss from satellite observations.

Area of Science:

• Atmospheric Chemistry
• Climate Science
• Earth System Science

Background:

• Stratospheric methane (CH4) oxidation influences global climate and ozone chemistry.
• Previous estimates of stratospheric CH4 loss rely heavily on models, leading to uncertainties.

Purpose of the Study:

• To provide an observationally based estimate of stratospheric CH4 loss (LSTR).
• To reconcile the global CH4 budget by improving estimates of stratospheric loss.

Main Methods:

• Utilized satellite measurements of CH4 concentration, temperature, and radiative heating rates (2007-2010).
• Calculated CH4 diabatic flux across the isentropic surface fitted to the tropical tropopause.

Main Results:

• Estimated LSTR at 49.8 ± 7.8 Tg/y, significantly higher than reanalysis (38.1 Tg/y) and CCMs (25.7 Tg/y).
• Reanalysis and CCMs systematically underestimate stratospheric CH4 loss due to biases in CH4 concentrations, temperature, and radiative heating.
• Incorporating observational LSTR reduced the global CH4 budget imbalance from 23 to 3 Tg/y.

Conclusions:

• Observational constraints on stratospheric CH4 loss are critical for reconciling the global CH4 budget.
• Findings have significant implications for understanding stratospheric water vapor and ozone chemistry.
• Highlights the need to improve models using observational data for accurate climate and atmospheric chemistry assessments.