NATURE CLIMATE CHANGE | VOL 4 | JUNE 2014 | www.nature.com/natureclimatechange 407 opinion & comment COMMENTARY: Changing the resilience paradigm Igor Linkov, Todd Bridges, Felix Creutzig, Jennifer Decker, Cate Fox-Lent, Wolfgang Kröger, James H. Lambert, Anders Levermann, Benoit Montreuil, Jatin Nathwani, Raymond Nyer, Ortwin Renn, Benjamin Scharte, Alexander Schefer, Miranda Schreurs and Thomas Thiel-Clemen Resilience management goes beyond risk management to address the complexities of large integrated systems and the uncertainty of future threats, especially those associated with climate change. T he human body is resilient in its ability to persevere through infections or trauma. Even through severe disease, critical life functions are sustained and the body recovers, ofen adapting by developing immunity to further attacks of the same type. Our society’s critical infrastructure  — cyber, energy, water, transportation and communication — lacks the same degree of resilience, typically losing essential functionality following adverse events. Although the number of climatic extremes may intensify or become more frequent 1 , there is currently no scientifc method available to precisely predict the long-term evolution and spatial distribution of tropical cyclones, atmospheric blockages and extra- tropical storm surges; nor are the impacts on society’s infrastructure in any way quantifed 2 . In the face of these unknowns, building resilience becomes the optimal course of action for large complex systems. Resilience, as a property of a system, must transition from just a buzzword to an operational paradigm for system management, especially under future climate change. Current risk analysis methods identify the vulnerabilities of specifc system components to an expected adverse event and quantify the loss in functionality of the system as a consequence of the event occurring 3 . Subsequent risk management has focused on hardening these specifc system components to withstand the identifed threats to an acceptable level and to prevent overall system failure. Two factors make this form of protection unrealistic for many systems. First, increasingly interconnected social, technical and economic networks create large complex systems and the risk analysis of many individual components becomes cost and time prohibitive. Second, the uncertainties associated with the vulnerabilities of these systems, combined with the unpredictability of climatic extremes, challenges our ability to understand and manage them. To address these challenges, risk analysis should be used where possible to help prepare for and prevent consequences of foreseeable events, but resilience must be built into systems to help them quickly recover and adapt when adverse events do occur. A roadmap for enabling the development of such capability should include: (1) specifc methods to defne and measure resilience; (2) new modelling and simulation techniques for highly complex systems; (3) development of resilience engineering; (4) approaches for communication with stakeholders. Strategies for communicating with policy makers are needed to support the shif to resilience management by legislative, regulatory and other means. Te National Academy of Sciences (NAS) defnes resilience as “the ability to prepare and plan for, absorb, recover from, and more successfully adapt to adverse events” 4 . Conceptually, risk analysis quantifes the probability that the system will reach the lowest point of the critical functionality profle. Risk management helps the system prepare and plan for adverse events, whereas resilience management goes further by integrating the temporal capacity of a system to absorb and recover from adverse events, and then adapt (Fig. 1). Resilience is not a substitute for principled system design or risk management 5 . Rather, resilience is a complementary attribute that uses strategies of adaptation and mitigation to improve traditional risk management. Strategies to build resilience can take the form of fexible response, distributed decision making, modularity, redundancy, ensuring the independence of component interactions or a combination of adaptive strategies to Plan Adapt Absorb Recover Time Critical functionality Risk Consequence Threat Vulnerability System resilience Figure 1 | A resilience management framework includes risk analysis as a central component. Risk analysis depends on characterization of the threats, vulnerabilities and consequences of adverse events to determine the expected loss of critical functionality. The National Academy of Sciences defnition of resilience places risk in the broader context of a system’s ability to plan for, recover from and adapt to adverse events over time. In the system functionality profle, risk in a system is interpreted as the total reduction in critical functionality and the resilience of the system is related to the slope of the absorption curve and the shape of the recovery curve — indicating the temporal efect of the adverse event on the system. The dashed line suggests that highly resilient systems can adapt in such a way that the functionality of the system may improve with respect to the initial performance, enhancing the system’s resilience to future adverse events. © 2014 Macmillan Publishers Limited. All rights reserved