Moving toward 1.5°C of warming: implications for climate adaptation strategies

The literature on adaptation to climate change indicates that limiting global warming to 1.5 degrees C or less would reduce damages relative to higher magnitudes of warming, and require less adaptive effort particularly by lessening the risk of extremes and reducing the potential need for transformative adaptation. Smaller climate change nevertheless poses risks of significant impacts, dislocation and adaptation costs in particularly exposed and vulnerable places. Climate change will also vary across space, and smaller, slower average change will likely still result in larger, rapid change for some systems and places (e.g. the Arctic and oceanic islands). Furthermore, non-linearities and power-law relationships among components of the earth's climate system mean that the potential for passing thresholds where parts of the system exhibit extreme behavior cannot be confidently excluded from a 1.5 degrees scenario. The potential for overshoot in a climate that eventually equilibrates at 1.5 degrees C or less above pre-industrial also means that anticipatory adaptation planning efforts should not be relaxed. Yet, taken together, the literature suggests that reactive adaptation has a better chance of keeping pace with the lower range of warming in many places and production systems (although not necessarily all), and could reduce though not eliminate the risk of large damages and adaptation costs in exposed and vulnerable places. Anticipatory adaptation investments, however, can be justified even for low levels of climate change and appear less sensitive to the projected magnitude of change in climate, and driven more by uncertainty in future emission and climate trajectories.