A new assessment has estimated that there are 1,650 gigatonnes of carbon stored in the northern circumpolar permafrost region4, more than twice the amount of carbon in the atmosphere.

Consistent with the rapid retreat of sea ice, the surface waters of the Arctic Ocean have been warming in recent years, because declining sea-ice cover allows the water to absorb more heat from the sun.

Atmosphere-ocean exchanges of carbon.

MOC strength in a suite of coupled climate models.

Sea-level rise is accelerating.

Reduced sea ice amplifies warming.

At the regional, ocean basin scale, the area between the insulating sea-ice cover and the open ocean (known as the ice margin) is characterized by particularly strong temperature gradients during winter, favoring the development of low pressure systems along the edge of the ice, as well as smaller, intense features known as polar lows that present hazards to shipping.

Satellite altimetry data has revealed that sea level is not rising uniformly.

The significance of wastewater and contents of wastewater vary greatly between and even within regions. In Africa for example, it is the impact on people’s health that is the major factor, in Europe, the input of nutrients into the coastal waters reducing productivity and creating anoxic dead zones.

The contaminants in waste- water come from many different sources and can have cumulative and synergistic effects requiring a multi-pronged response.

Regional variation in water withdrawal per capita and its use by sector.

Desalination is an increasingly important practice to secure clean water in a number of countries. Monitoring is key to minimize negative impacts on the ecosystem.

What one litre of wastewater might contain in terms of pathogens.

Increasing water scarcity with population increase.

Population by region was calculated averaging the results forecasted by the scenarios of the GEO-4 report using the WaterGAP modeling.

Is reuse of wastewater a benefit or a threat for agri- culture?

Case study to compare two urban centres.

Access to improved sanitation remains a pressing issue in many regions.

As water is extracted and used along the supply chain, both the quality and quantity of water is reduced.

Distribution of causes of death among children un- der five years and within the neonatal period, 2004 (Figure from WHO, 2008).