If the Mediterranean Sea continues to increase in salinity, shifting climatic patterns throughout the world may cause high-latitude areas in Canada to glaciate within the next century. The Mediterranean is starved of freshwater by human activities: most of the annual flow of the Nile River is now used for irrigation and no longer enters the sea. The sea surface evaporation losses are also increasing as the surface warms due to rising CO2 concentrations in the atmosphere. Consequently, the Mediterranean hydrologic deficit is steadily increasing. The deficit is the difference between the larger amount of water lost by evaporation and the smaller amount received from rainfall and river inputs. The difference is made up by a two-way exchange of water with the Atlantic at Gibraltar. Barring a significant change in regional atmospheric circulation, these two human modifications of the environment will cause the salinity of the Mediterranean to increase for some time as fossil fuels are consumed.