Millions of people across the globe are already affected by natural variability in the water cycle. A multidisciplinary team of experts from the University of East Anglia and the University of Nottingham, led by Timothy Osborn, Professor of Climate Science at the world-renowned Climatic Research Unit, set out the empirical evidence-and argue the need for implementation of measured adaptation mechanisms that take into account uncertainties in the projection of future precipitation patterns. Earth's freshwater is distributed unevenly – spatially, day by day, through the changing seasons, and between dry and wet periods lasting years to decades. Climate change, though still very uncertain in its regional details, will have a tendency to exacerbate this unevenness, drying some already arid regions, wetting some humid regions, enhancing seasonality in many areas, and concentrating rainfall into shorter but more intense spells. As a result, projections of future changes in climate and the hydrological cycle indicate that the population exposed to hydrological risks will increase significantly during the 21st century, though slowing climate change through reductions in greenhouse gas emissions could reduce this risk.