Source Found for Missing Water in Sea-Level Rise: Human use of water contributes markedly to rising tides
Climate change, with its associated melting ice caps and shrinking glaciers, is the usual suspect when it comes to explaining rising sea levels. But a recent study now shows that human water use has a major impact on sea-level change that has been overlooked.
During the latter half of the twentieth century, global sea level rose by about 1.8 millimetres per year, according to data from tide gauges. The combined contribution from heating of the oceans, which makes the water expand, along with melting of ice caps and glaciers, is estimated to be 1.1 millimetres per year, which leaves some 0.7 millimetres per year unaccounted for. This gap has been considered an important missing piece of the puzzle in estimates for past and current sea-level changes and for projections of future rises.
It now seems that the effects of human water use on land could fill that gap. A team of researchers reports in Nature Geoscience that land-based water storage could account for 0.77 millimetres per year, or 42%, of the observed sea-level rise between 1961 and 2003. Of that amount, the extraction of groundwater for irrigation and home and industrial use, with subsequent run-off to rivers and eventually to the oceans, represents the bulk of the contribution.