ALBERT

Description: The dominant variability modes in the Tropics are investigated and contrasted with the anomalous situation observed during the last few years. The prime quantity analyzed is anomalous sea surface temperature (SST) in the region 30°S–60°N. Additionally, observed tropical surface wind stress fields were investigated. Further tropical atmospheric information was derived from a multidecadal run with an atmospheric general circulation model that was forced by the same SSTs. The tropical SST variability can be characterized by three modes: an interannual mode [the El Niño–Southern Oscillation (ENSO)], a decadal mode, and a trend or unresolved ultra-low-frequency variability. The dominant mode of SST variability is the ENSO mode. It is strongest in the eastern equatorial Pacific, but influences also the SSTs in other regions through atmospheric teleconnections, such as the Indian and North Pacific Oceans. The ENSO mode was strong during the 1980s, but it existed with very weak amplitude and short period after 1991. The second most energetic mode is characterized by considerable decadal variability. This decadal mode is connected with SST anomalies of the same sign in all three tropical oceans. The tropical Pacific signature of the decadal mode resembles closely that observed during the last few years and can be characterized by a horseshoe pattern, with strongest SST anomalies in the western equatorial Pacific, extending to the northeast and southeast into the subtropics. It is distinct from the ENSO mode, since it is not connected with any significant SST anomalies in the eastern equatorial Pacific, which is the ENSO key region. However, the impact of the decadal mode on the tropical climate resembles in many respects that of ENSO. In particular, the decadal mode is strongly linked to decadal rainfall fluctuations over northeastern Australia in the observations. It is shown that the anomalous 1990s were dominated by the decadal mode. Considerable SST variability can be attributed also to a linear trend or unresolved ultra-low-frequency variability. This trend that might be related to greenhouse warming is rather strong and positive in the Indian Ocean and western equatorial Pacific where it accounts for up to 30% of the total SST variability. Consistent with the increase of SST in the warm pool region, the trends over the tropical Pacific derived from both the observations and the model indicate a strengthening of the trade winds. This is inconsistent with the conditions observed during the 1990s. If the wind trends reflect greenhouse warming, it must be concluded that the anomalous 1990s are not caused by greenhouse warming. Finally, hybrid coupled ocean–atmosphere model experiments were conducted in order to investigate the sensistivity of ENSO to the low-frequency changes induced by the decadal mode and the trend. The results indicate that ENSO is rather sensitive to these changes in the background conditions.

Description: Crises like climate change, the recent pandemic and the war in Ukraine have a profound effect on all of us. Crises are growing in number, severity and complexity, and at an accelerating pace. The connectedness of European societies increases their vulnerability, and today’s crises have multiple cascading and rippling effects that can extend to all parts of society, the economy and environment. The need for effective strategic crisis management is evident and, given the increasingly transboundary nature of crises, the EU has emerged as an important player. Crisis management can be highly sectoral and not always geared to effective performance over the long term, especially when crises become protracted. The consequences of failed or ineffective crisis management can be severe, with rising inequalities and negative impacts such as political fragmentation, societal polarisation and economic disruption. Recent crises have illustrated starkly the need for preparation, improved capacity and resources. This Evidence Review Report is designed to address issues described in the scoping paper,1 which sets out the formal request for advice from the European College of Commissioners to the Group of Chief Scientific Advisors to the European Commission. This report synthesises the evidence in response to the main question from the scoping paper: Based on a broad and multidisciplinary understanding, how can the EU improve its strategic crisis management? This report focuses on the strategic level, involving those decision-makers and policymakers who are responsible and accountable for the outcome of a crisis. During the response phase in particular, strategic issues are often neglected because of the urgent need to act and react. For a response to be effective, it is essential to develop rapid decision-making capabilities and appropriate resources. Although crises are all different in terms of their type, duration and governance arrangements, there are underlying principles that are common to their management. This report identifies fundamental generic principles and frameworks that relate to the roles played by the EU in strategic crisis management. It provides concrete examples of past and ongoing crises, reflecting on trends and developments in the field. Importantly, it embeds strategic crisis management within the context of risk and resilience.