Decadal Climate Variability and Predictability: Challenges and Opportunities

Abstract

The study of Decadal Climate Variability (DCV) and Predictability is the interdisciplinary endeavor to characterize, understand, attribute, simulate, and predict the slow, multiyear variations of climate at global (e.g., the recent slowdown of global mean temperature rise in the early 2000s) and regional (e.g., decadal modulation of hurricane activity in the Atlantic, ongoing drought in California or in the Sahel in the 1970s–80s, etc.) scales. This study remains very challenging despite decades of research, extensive progress in climate system modeling, and improvements in the availability and coverage of a wide variety of observations. Considerable obstacles in applying this knowledge to actual predictions remain. This short article is a succint review paper about DCV and predictability. Based on listed issues and priorities, it also proposes a unifying theme referred to as “drivers of teleconnectivity” as a backbone to address and structure the core DCV research challenge. This framework goes beyond a preoccupation with changes in the global mean temperature and directly addresses the regional impacts of external (natural and anthropogenic) climate forcing and internal climate interactions; it thus explicitly deals with the societal needs for region-specific climate information. Such a framework also enables the integration of efforts in a large international research community toward advancing the observation, characterization, understanding, and prediction of DCV. Recommendations to make progress are provided as part of the contribution of the CLIVAR “DCVP Research Focus” group.

Science Directions in a Post COP21 World of Transient Climate Change: Enabling Regional to Local Predictions in Support of Reliable Climate Information

“…Many severe consequences for populations surrounding the Pacific emerge from those climate fluctuations, including those associated with water availability, wildfires, or food supply from the ocean and land. More recent research has expanded to other parts of the world and to longer (decadal) time scales (Cassou et al, 2017;Smith et al, 2013). Similar progress has been made for the onset of monsoons (Pradhan et al, 2017), which are critical for the water and food supply of many nations in Asia, the Americas, and Africa.…”

“…For both ENSO and monsoons, however, there remain fundamental questions regarding their underlying mechanisms, flavors, and present and future predictability (Kumar et al, 2017;Polson et al, 2014). More recent research has expanded to other parts of the world and to longer (decadal) time scales (Cassou et al, 2017;Smith et al, 2013).…”

Dynamics and Predictability of Hemispheric-Scale Multidecadal Climate Variability in an Observationally Constrained Mechanistic Model

“…Finally, initialized near-term prediction systems [see Cassou et al (2018) for a recent summary] show a larger skill of predicting AMO compared to PDO/IPO, although the skill for the former seems to be confined to the Atlantic Ocean region due, tentatively, to underestimated magnitude of multidecadal variability in AMOC (Yan et al 2018) combined, as discussed above, with misrepresentation, in climate models, of air-sea feedbacks that shape and energize the observed basin-scale AMO signature. The resulting weaker-than-observed basin-scale multidecadal AMO signals in coupled climate GCMs (Kravtsov and Callicutt 2017;Kravtsov 2017;Kim et al 2018;Yan et al 2019) are consistent with weak interbasin coupling in free runs of these models (despite an apparent teleconnectivity demonstrated via pacemaker experiments), the loss of potential AMOrelated skill in predicting the PDO/IPO, as well as with the lack, in these models, of the global-scale multidecadal variability matching the magnitude and spatiotemporal structure of such variability diagnosed in the reanalysis data (Kravtsov et al 2018).…”

“…Decadal climate variability (DCV) generated internally within the climate system can give rise to significant modulations of regional-to-global warming trends and may be associated with useful near-term climate predictability (Latif et al 2006;Smith et al 2012;Kirtman et al 2013;Meehl et al 2014;Yeager and Robson 2017;Cassou et al 2018). At longer, multidecadal time scales, a tantalizing property of both observed DCV (Kravtsov and Spannagle 2008;Wyatt et al 2012;Deser and Phillips 2017) and DCV simulated by the state-of-the-art climate models (Dommenget and Latif 2008;Barcikowska et al 2017;Ghil et al 2019) is its tendency to exhibit a truly global character, forming a ''network of teleconnections, linking neighboring ocean basins, the tropics and extratropics, and the oceans and land regions'' (Cassou et al 2018, p. 479), although the overall magnitude and spatiotemporal structure of these teleconnections in models versus observations appears to be different (Kravtsov et al 2014;Kravtsov 2017;Kravtsov et al 2018).…”

Influence of the Atlantic Meridional Overturning Circulation on the Tropical Climate Response to CO2 Forcing

“…Physical mechanisms have also been proposed to explain the considerable spread among the models' projections (Long et al, 2016;Ma & Xie, 2013;Oueslati et al, 2016;Xie et al, 2015). On the other hand, few studies so far have evaluated the importance of the decadal-to-multidecadal internal variability in modulating the long-term response of regional rainfall to anthropogenic forcing (Cassou et al, 2018;Xie et al, 2015), despite the dominant contribution of natural climate variability to uncertainties in regional precipitation projections (Hawkins & Sutton, 2011).…”