• climate change;
  • climate variability

Climate, as experienced over time in a particular locality or region, exhibits a wide spectrum of variability, ranging from daily weather to century-scale trends and beyond. As a result, climate-related risks will tend to vary as well, with slower variations modulating the likelihood of adverse or beneficial events that play out on shorter time scales. For example, the risk of crop loss due to insufficient seasonal rainfall will generally be increased during decades that themselves are drier than normal, and vice versa. Short-term planning for such risk might involve securing adequate supplies of a drought-resistant cultivar, while on longer time scales such infrastructure decisions as the design of irrigation systems or reservoirs may be at issue. An understanding of how variations on different time scales have combined to produce observed climate histories can inform adaptation or risk mitigation strategies in light of such multi-time-scale risk variability.