New frontiers on climate predictions

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Sea-ice, land surface, stratosphere and aerosols have received relatively little attention on how they can contribute to decadal scale predictability and to new perspectives for improving the predictive capabilities of current Earth system models (ESM). In a paper published by Reviews of Geophysics, a quarterly peer-reviewed scientific journal that belongs to the publications series of the AGU – American Geophysical Union, a team of scientists addresses recent progress in the understanding the role of these constituents and their impacts on practical decadal predictions.

Alessio Bellucci (corresponding author) and Stefano Materia, CMCC scientists at CSP – Climate Simulation and Prediction Division, contributed to the paper Advancements in decadal climate predictability: the role of non-oceanic drivers.

“Recent research on decadal-scale predictability has mostly focused on the impact exerted by the oceans – Alessio Bellucci explains – This stems from the ocean’s large heat capacity that results in a slow manifold of the climate system. Other constituents of the climate system have received relatively less attention because their contribution to the low-frequency climate variability is less obvious and the initialization as well as the representation of these components in current climate models are still very challenging. This is further exacerbated by a lack of adequate observations. Here we present an overview of the most recent progress in understanding the potential role of sea-ice, land surface, stratosphere and aerosols in decadal-scale climate predictability. Numerous extra-oceanic processes that could be active over the decadal range are proposed. Prospects for improving the predictive capabilities of current decadal prediction systems are discussed”.

Abstract
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 (ESM). 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 extra-oceanic processes that could be active over the decadal range are proposed. Potential predictability associated with the afore-mentioned, 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) sub-systems. Through this mechanism, Earth-system components trigger low-frequency variability modes, thus extending the predictability beyond the seasonal scale.

The paper at Reviews of Geophysics’ web site:
A. Bellucci, R. Haarsma, N. Bellouin, B. Booth, C. Cagnazzo, B. van den Hurk, N. Keenlyside, T. Koenigk, F. Massonnet, S. Materia, and M. Weiss – Advancements in decadal climate predictability: the role of non-oceanic drivers2015, Reviews of Geophysics, DOI: 10.1002/2014RG000473

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