In its first major assessment since 2013, the United Nations Intergovernmental Panel on Climate Change recently delivered a comprehensive report on the state of the global climate. The news isn't good: The last decade was hotter than any period in the last 125,000 years and atmospheric CO2 is now at a two-million-year peak, resulting in more extreme weather events.
The report certainly lends credence to the idea that we need to embrace transformational change—and soon—in order to quickly curtail emissions and slow the planet's warming. We agree. As we cut emissions as never before, how do we simultaneously bolster efforts to cope with the impacts that we will encounter? In this article, we explore the opportunities and constraints of the adaptation pathways approach, one that ramps up as climate change hits new triggers rather than going for the biggest and most expensive solutions right out of the gate.
Adaptation pathways 101
Adapting to climate change poses challenges to decision-makers who need to decide now whether and how to adapt for the future impacts of a changing climate. The adaptation pathways approach escalates in scale and scope the measures we take to address climate change as the severity of climate impacts intensify. They’re relevant for a wide range of stakeholders—such as state and local governments, national governments, and businesses like utility companies—that are investing in climate resilience.
Adaptation to the impacts of climate change is at once both a critical long-term need and a short-term imperative. Flexible adaptation pathways address short- and long-term adaptation priorities together, in contrast to traditional techniques that often force a false choice: choosing to enhance resilience to rapidly emerging climate impacts today or choosing to address the impacts predicted in decades to come. The approach also accounts for the fact that the social and economic context for adaptation will inevitably change over time, rather than assuming that the best solutions for today will necessarily be the best solutions for tomorrow.
Pathways aim to meet defined adaptation objectives and explore the conditions under which an implementation strategy would succeed or fail in meeting that objective. If the strategy or policy becomes ineffective (i.e., a tipping point is reached), then an alternative strategy is required. Signposts, triggers, and tipping points are used to help determine the best time to switch measures and can be based on asset or community-set thresholds.
Benefits of pathways
Adaptation pathways provide a multitude of benefits. Here are three of the most important:
- Flexibility: Adaptation pathways embrace uncertainty and change. We know that climate change is often a hot-button issue within contested political environments. As a result, any policy implemented today faces an uncertain future. Adaptation pathways provide a way of considering political uncertainty alongside other societal, economic, environmental, and technological change. In doing so, adaptation pathways provide an opportunity for sustainable policy implementation over time. Pathways also include early warnings that signal when decision-makers may want to switch to another pathway, allowing for flexibility and decisions tailored to local conditions.
- Cost-effectiveness: Because the pathways approach considers multiple strategies, it helps reduce the risk of over- or underinvesting in adaptation. The ability to assess various strategies over a long period also allows practitioners to spread or defer large capital costs for future projects over time and allow efficient planning and funding of projects.
- Transparency in decision-making: Because triggers and thresholds are set ahead of time, pathways allow for transparently integrating climate adaptation considerations into existing decision-making processes, which can support implementation. They create a long-term, programmatic approach for adaptation planning that encourages continuity of investment and allows for evaluation over time. Furthermore, pathways accommodate the possibility of collaborating with local communities to find the most effective adaptation solutions and respond to a community’s changing needs.
Adaptation pathways in practice
Despite their widespread use in Europe, adaptation pathways are not widely used in the U.S. outside of California, where they are routinely used in sea-level rise impact assessments to comply with state coastal policy and in adaptation assessments by energy utilities and other infrastructure providers. California’s Climate-Safe Infrastructure Working Group 2018 report also advocated for adoption of pathways-based approaches.
For example, the Los Angeles County Metropolitan Transportation Authority (LA Metro) was concerned with ensuring the continued operation of their subway elevator system in the face of increasing extreme heat events (see Figure 1). LA Metro staff identified an immediate adaptation measure of transporting passengers by bus to and from a station where the elevators are failing.
Over time, if new projections show that extreme heat will exceed a specific threshold (e.g., the number of extreme heat days per year or number of elevator outages per year), LA Metro will invest in another adaptation measure, such as adding cooling equipment or building new heat-resistant elevators. If temperatures continue to rise past a further threshold—or confidence in future estimates increases—the redesign and replacement of elevators with a heat-resilient design may be warranted. The exact degree of change in extreme heat over time is uncertain, so pathways allow users to factor that uncertainty into adaptation planning in a transparent manner.