20 30J u ly 2 0 0 2 J a n . 2 0 0 3 J u ly 2 0 0 3 J a n . 2 0 0 4 J u ly 2 0 0 4 J a n . 2 0 0 5 J u ly 2 0 0 5 J a n . 2 0 0 6 J u ly 2 0 0 6 J a n . 2 0 0 7 J u ly 2 0 0 7 J a n . is 5.9 cm, compared with 10.3 cm for soil water and 13.8 cm for TWS. These relationships are consistent with those reported in previous studies of soil-water/groundwater covariability 5,14,22 . The soil-water time series reflects rainfall anomalies during the period (discussed below) and exhibits no significant trend. On the other hand, TWS and groundwater decline steadily from 2003 onwards. We calculate the rate of depletion of groundwater to be 4.0 6 1.0 cm yr 21 . Assuming 2 a specific yield of 0.12, the regional mean rate of water As best can be determined from the coarse GRACE observations, maximum rates of groundwater depletion are centred on Haryana. Groundwater levels also appear to be declining quickly in western Uttar Pradesh, to the east of Haryana. If there is groundwater depletion in Pakistan, to the northwest, it seems to be much less severe.Although six years is a short period from which to assess a longterm trend with confidence, two pieces of evidence support our conclusion that severe groundwater depletion is occurring as a result of human consumption rather than natural variability. First, the Indian Ministry of Water Resources reports that groundwater withdrawals exceed recharge in the three states we studied 2 . Irrigation accounts for about 95% of the consumption 2 ; about 28% of the area is irrigated 23 . Second, there was no shortage of rainfall in the region to cause a natural decline in water storage. GLDAS modelled soil-water fields integrate the effects of precipitation, solar radiation, air temperature and other meteorological factors that directly or indirectly influence groundwater storage 4 . The trend in simulated soil-water storage during the period of study was 0.4 cm yr 21 . This supports the notion that groundwater declines were not caused by natural climate variability. It also confirms that the computed groundwater trend is not a mathematical artefact caused by the subtraction of a large positive soil-water trend from the GRACE-derived TWS trend.We conclude that withdrawals for irrigation and other uses are depleting the groundwater reserves of Rajasthan, Punjab and Haryana at a rate of 4.0 6 1.0 cm yr 21 equivalent height of water, or 17.7 6 4.5 km 3 yr 21 . The Indian Ministry of Water Resources reports that the difference between annual available recharge and annual withdrawals in the region is a 13.2 km 3 yr 21 deficit 2 . Our result implies that the portion of irrigated water that replenishes the aquifers is less and/or the rate of withdrawal is more than the Indian government has estimated. Apparently, most of the groundwater withdrawn subsequently is lost from the region as a result of increases in run-off and/or evapotranspiration. Between August 2002 and October 2008, the region lost 109 km 3 of groundwater, which is double the capacity of India's largest reservoir, the Upper Waingang...

Warming and Melting Mass loss from the ice sheets of Greenland and Antarctica account for a large fraction of global sea-level rise. Part of this loss is because of the effects of warmer air temperatures, and another because of the rising ocean temperatures to which they are being exposed. Joughin et al. (p. 1172 ) review how ocean-ice interactions are impacting ice sheets and discuss the possible ways that exposure of floating ice shelves and grounded ice margins are subject to the influences of warming ocean currents. Estimates of the mass balance of the ice sheets of Greenland and Antarctica have differed greatly—in some cases, not even agreeing about whether there is a net loss or a net gain—making it more difficult to project accurately future sea-level change. Shepherd et al. (p. 1183 ) combined data sets produced by satellite altimetry, interferometry, and gravimetry to construct a more robust ice-sheet mass balance for the period between 1992 and 2011. All major regions of the two ice sheets appear to be losing mass, except for East Antarctica. All told, mass loss from the polar ice sheets is contributing about 0.6 millimeters per year (roughly 20% of the total) to the current rate of global sea-level rise.