Book 2.indb - US Climate Change Science Program

Abrupt Climate Change4. Improved understanding of the dynamiccauses of long-term changes in oceanicconditions, the atmospheric responses tothese ocean conditions, and the role of soilmoisture feedbacks are needed to advancedrought prediction capabilities. Ensembledrought prediction is needed to maximizeforecast skill, and “downscaling” is neededto bring coarse-resolution drought forecastsfrom General Circulation Models down tothe resolution of a watershed.5. Efforts should be made to improve thetheoretical understanding of the processescontrolling the AMOC, including its inherentvariability and stability, especially withrespect to climate change. This will likelybe accomplished through synthesis studiescombining models and observational results.6. Improve long-term monitoring of theAMOC. Parallel efforts should be made tomore confidently predict the future behaviorof the AMOC and the risk of an abruptchange. Such a prediction system shouldinclude advanced computer models, systemsto start model predictions from theobserved climate state, and projections offuture changes in greenhouse gases andother agents that affect the Earth’s energybalance.7. Prioritize the monitoring of atmosphericmethane abundance and its isotopic compositionwith spatial density sufficient toallow detection of any change in net emissionsfrom northern and tropical wetlandregions. The feasibility of monitoring methanein the ocean water column or in theatmosphere to detect emissions from thehydrate reservoir should be investigated.Efforts are needed to reduce uncertaintiesin the size of the global methane hydratereservoir in marine and terrestrial environmentsand to identify the size and locationof hydrate reservoirs that are most vulnerableto climate change.8. Additional modeling efforts should be focusedon (i) processes involved in releasingmethane from the hydrate reservoir and(ii) the current and future climate-drivenacceleration of release of methane fromwetlands and terrestrial hydrate deposits.9. Improve understanding of past abrupt changesthrough the collection and analysis ofthose proxy records that most effectivelydocument past abrupt changes in sea level,ice-sheet and glacier extent, distributionof drought, the AMOC, and methane, andtheir impacts.7