Book 2.indb - US Climate Change Science Program

The U.S. Climate Change Science Program Chapter 5CHAPTER 5. RECOMMENDATIONS• Monitoring of the abundance of atmospheric methane and its isotopic composition sufficient toallow detection of change in emissions from northern and tropical wetland regions should beprioritized. Specifically, systematic measurements of CH 4 from tall towers and aircraft in theArctic and subarctic regions and expanded surface flux measurements and continued observationof CH 4 abundance in the tropics and subtropics would allow detection of changes in emissionsfrom sparsely monitored but important regions.• The feasibility of monitoring methane in the ocean water column near marine hydrate deposits,or in the atmosphere near terrestrial hydrate deposits, to detect changes in emissions from thosesources, should be investigated, and if feasible, this monitoring should be implemented.• Efforts should be made to increase certainty in the size of the global methane hydrate reservoirs.The level of concern about catastrophic release of methane to the atmosphere is directly linkedto the size of these reservoirs.• The size and location of hydrate reservoirs that are most vulnerable to climate change (forexample, shallow-water deposits, shallow subsurface deposits on land, or regions of potentiallarge submarine landslides) should be identified accurately and their potential impact on futuremethane concentrations should be evaluated.• Improvement in process-based modeling of methane release from marine hydrates is needed. Thetransport of bubbles is particularly important, as are the migration of gas through the stabilityzone and the mechanisms controlling methane release from submarine landslides.• Modeling efforts should establish the current and future climate-driven acceleration of chronicrelease of methane from wetlands and terrestrial hydrate deposits. These efforts should includedevelopment of improved representations of wetland hydrology and biogeochemistry, andpermafrost dynamics, in earth system and global climate models.• Further work on the ice core record of atmospheric methane is needed to fully understand theimplications of past abrupt changes in atmospheric methane. This work should include highresolutionand high-precision measurements of methane mixing ratios and isotopic ratios, andbiogeochemical modeling of past methane emissions and relevant atmospheric chemical cycles.Further understanding of the history of wetland regions is also needed.164