One of the most significant direct effects of global warming is an alteration of the hydrological cycle, which affects the world's water supplies, floods, and droughts. Most studies assume that if human-induced temperature changes were reversed, the hydrological cycle would revert to its prewarming state.

A new study, however, reveals that climate change mitigation will not quickly return the hydrological cycle to its previous state. Wu et al. used climate model simulations to show how the hydrological cycle could react to changes in future amounts of carbon dioxide (CO2) in the atmosphere. They simulated the effects of a steady rise in CO2 levels to more than 1000 parts per million (ppm), followed by a decrease to preindustrial levels of around 280 ppm.