2000 Years of Drought Variability in the Central United States

TLDR

Droughts are among the most devastating natural hazards in the United States, with twentieth‑century events profoundly affecting economies, society, and the environment, yet the limited instrumental record and uncertain links to low‑frequency Pacific and Atlantic variations constrain our understanding of their full range. The study aims to use paleoclimatic records to capture the full spectrum of past drought magnitude and duration, thereby improving societal preparedness for future droughts. Paleoclimatic evidence indicates that 20th‑century droughts were eclipsed by several earlier, longer‑lasting, and more widespread events over the past 2000 years, and that future droughts could be even more severe than the 1930s and 1950s, especially under projected greenhouse warming.

Abstract

Droughts are one of the most devastating natural hazards faced by the United States today. Severe droughts of the twentieth century have had large impacts on economies, society, and the environment, especially in the Great Plains. However, the instrumental record of the last 100 years contains only a limited subset of drought realizations. One must turn to the paleoclimatic record to examine the full range of past drought variability, including the range of magnitude and duration, and thus gain the improved understanding needed for society to anticipate and plan for droughts of the future. Historical documents, tree rings, archaeological remains, lake sediment, and geomorphic data make it clear that the droughts of the twentieth century, including those of the 1930s and 1950s, were eclipsed several times by droughts earlier in the last 2000 years, and as recently as the late sixteenth century. In general, some droughts prior to 1600 appear to be characterized by longer duration (i.e., multidecadal) and greater spatial extent than those of the twentieth century. The authors' assessment of the full range of past natural drought variability, deduced from a comprehensive review of the paleoclimatic literature, suggests that droughts more severe than those of the 1930s and 1950s are likely to occur in the future, a likelihood that might be exacerbated by greenhouse warming in the next century. Persistence conditions that lead to decadal-scale drought may be related to low-frequency variations, or base-state shifts, in both the Pacific and Atlantic Oceans, although more research is needed to understand the mechanisms of severe drought.