Global Change: Enough Water for all?

Water is of vital importance: Without water no life would exist and our planet would be a huge desert. Water plays a dominant role in the climate system as well. Atmospheric water vapour is the most important greenhouse gas; over 60% of the greenhouse effect of the atmosphere is due to water vapour. Without greenhouse gases the mean surface temperature of our planet would be around -18 C. Water is the basic condition for the high biodiversity on Earth. Plants, animals and humans are composed of 50--80% water. They are stressed, fall ill or die from water scarcity or polluted water. Therefore, our common future is endangered when water is not available in sufficient amount and quality. Water traverses an endless cycle (the water cycle), enabling a self-purification on its long way through the soil and rock layers. Water is a heritage of nature and it belongs to all living beings. The right of access to sufficient and clean water is a universal law and it is therefore anchored in important international treaties. The uneven distribution of precipitation and water on Earth leads to water scarcity in many regions. Already today 1.2 billion people (20% of the world population) have no secure access to clean drinking water and 2.4 billion people do not dispose of access to sanitary installations. Millions of children die every year due to polluted water. While Europeans use 130--150 litres water per capita and day (in the USA this amount is even at around 300 litres), many people south of the Sahara Desert have less than 20 litres per day at their disposal. Global climate change will intensify the water crisis. This is mainly caused by the emission of anthropogenic greenhouse gases, mostly from the industrialised countries. Glaciers in particular are sensitive to climate change. Most glaciers on Earth are shrinking. Global warming intensifies the water cycle and exacerbates the water problems on our planet. In humid regions (e.g. Scandinavia) the precipitation increases