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Over the past 50 years, humans have extracted the Earth’s groundwater stocks at a steep rate, largely to fuel global agro-economic development. Given society’s growing reliance on groundwater, we explore ‘peak water limits’ to investigate whether, when and where humanity might reach peak groundwater extraction. Using an integrated global model of the coupled human–Earth system, we simulate groundwater withdrawals across 235 water basins under 900 future scenarios of global change over the twenty-first century. Here we find that global non-renewable groundwater withdrawals exhibit a distinct peak-and-decline signature, comparable to historical observations of other depletable resources (for example, minerals), in nearly all (98%) scenarios, peaking on average at 625 km3 yr−1 around mid-century, followed by a decline through 2100. The peak and decline occur in about one-third (82) of basins, including 21 that may have already peaked, exposing about half (44%) of the global population to groundwater stress. Most

Une innovation low-tech ? Quel est cet étrange oxymore ? Faut-il retourner à la bougie ou à l’âge des cavernes au lieu de miser sur le progrès technologique ? Certes, le low-tech ne fait pas rêver comme le high-tech et ses applications futuristes. Et pourtant, si c’était là que se situait la vraie modernité et le courage d’innover ?

Emerging ice-sheet modeling suggests once initiated, retreat of the Antarctic Ice Sheet (AIS) can continue for centuries. Unfortunately, the short observational record cannot resolve the tipping points, rate of change, and timescale of responses. Iceberg-rafted debris data from Iceberg Alley identify eight retreat phases after the Last Glacial Maximum that each destabilized the AIS within a decade, contributing to global sea-level rise for centuries to a millennium, which subsequently re-stabilized equally rapidly.

Humans have amazing strengths, but also significant weaknesses. Chief among them, perhaps, is our collective difficulty in grasping the mathematical consequences of exponential growth. Alternative energy technologies have trouble preserving expectations. Human psychology and political/economic institutions turn a technically difficult predicament into a nearly hopeless trap. We are lamentably ill-equipped to appreciate the abnormality of our time and assess a more accurate picture of what long-term “normal” must look like.