Advancements in decadal climate predictability: The role of nonoceanic drivers

• Published in: Reviews of geophysics (1985) 2015-06, Vol.53 (2), p.165-202
• Main Authors: Bellucci, A., Haarsma, R., Bellouin, N., Booth, B., Cagnazzo, C., van den Hurk, B., Keenlyside, N., Koenigk, T., Massonnet, F., Materia, S., Weiss, M.
• Format: Article
• Language: English
• Subjects: Aerosols; Climate change; Climate models; climate prediction; Climate system; decadal predictability; decadal variability; Earth system models; Oceans; Sea ice; Stratosphere
• ISSN: 8755-1209; 1944-9208
• DOI: 10.1002/2014RG000473

We review recent progress in understanding the role of sea ice, land surface, stratosphere, and aerosols in decadal‐scale predictability and discuss the perspectives for improving the predictive capabilities of current Earth system models (ESMs). These constituents have received relatively little attention because their contribution to the slow climatic manifold is controversial in comparison to that of the large heat capacity of the oceans. Furthermore, their initialization as well as their representation in state‐of‐the‐art climate models remains a challenge. Numerous extraoceanic processes that could be active over the decadal range are proposed. Potential predictability associated with the aforementioned, poorly represented, and scarcely observed constituents of the climate system has been primarily inspected through numerical simulations performed under idealized experimental settings. The impact, however, on practical decadal predictions, conducted with realistically initialized full‐fledged climate models, is still largely unexploited. Enhancing initial‐value predictability through an improved model initialization appears to be a viable option for land surface, sea ice, and, marginally, the stratosphere. Similarly, capturing future aerosol emission storylines might lead to an improved representation of both global and regional short‐term climatic changes. In addition to these factors, a key role on the overall predictive ability of ESMs is expected to be played by an accurate representation of processes associated with specific components of the climate system. These act as “signal carriers,” transferring across the climatic phase space the information associated with the initial state and boundary forcings, and dynamically bridging different (otherwise unconnected) subsystems. Through this mechanism, Earth system components trigger low‐frequency variability modes, thus extending the predictability beyond the seasonal scale. Key Points Numerous extraoceanic processes active over the decadal scale are established Current ESMs underrepresent processes relevant for decadal predictability Predictive skill assessment is hampered by lack of observations