chemical feedbacks that can lead to changes in the atmospheric lifetime of methane also need to be identified and quantified.
Improve model projections of future climate change. Numerous decisions about climate change, including setting emissions targets and developing and implementing adaptation plans, require information that is underpinned by models of the physical climate system. There are a number of scientific and technological advances needed to improve model projections of future changes in the Earth system, especially changes over the next several decades and at the local and regional levels where many climate-related decisions occur. While this research should not be expected to eliminate uncertainties, especially given the inherent uncertainty in projections of future climate forcing, efforts to expand and improve model simulations of future climate changes can be expected to yield more, more robust, and more relevant information for decision making, including the effectiveness of various actions that can be taken to respond to climate change. It should also be noted that improvements in modeling go hand-in-hand with improvements in understanding and observation.
The core of the nation’s climate modeling enterprise is the development and testing of global Earth system models, many of which already or are now beginning to incorporate some of the key forcing and feedback processes noted above, including an explicit carbon cycle, certain biogeochemical and ecological processes, and improved parameterizations for clouds, aerosols, and ocean mixing. While these important activities should continue, the nation should also initiate a strategy for developing the next generation of ultra-high-resolution global models; models that can explicitly resolve clouds and other small-scale processes, include explicit representations of ice sheets and terrestrial and marine ecosystems, and allow for integrated exploration of forcing and feedback processes from local to global scales (Shapiro et al., in press). It may be valuable to consider the merits of coordinating the development of climate models with the development of weather models through “seamless prediction” paradigms that could potentially improve the simulation of extreme events as well as lower development costs (Tebaldi and Knutti, 2007). Expanded computing resources and human capital are needed to support all of these activities.
Climate modelers in the United States and around the world have also begun to devise strategies for improving the utility of climate models. Decadal-scale climate prediction, in which climate models are initialized with present-day observations and run forward in time at fairly high resolution for three to four decades, is another emerging strategy to provide decision makers with information to support near-term decision making (Meehl et al., 2009b). Extending or coupling current models to models of human and environmental systems, including both ecosystems models and models