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World Meteorological Organization’s Report on Water Resources – Climate Change

Water Resources

What is the World Meteorological Organization?
The World Meteorological Organization (WMO) is a specialized agency of the United Nations dedicated to meteorology (weather and climate), operational hydrology (water) and other related geophysical sciences such as oceanography and atmospheric chemistry.

Hydrology and Water Resources Program
As the world enters the 21st Century, it faces many challenges, above all that of establishing a sustainable way of life that would not threaten future generations. One of the essential elements of life on this planet is freshwater. Sustainable development therefore demands sustainable management of the world’s limited resources of freshwater. Water resources cannot be managed, however, unless we know where they are, in what quantity and quality, and how variable they are likely to be in the foreseeable future.

The challenge is to provide such hydrologic information on a regular basis.   For over 70 years, the World Meteorological Organization (WMO) and its predecessor, the International Meteorological Organization, have supported National Hydrological Services, River Basin Authorities and other institutions responsible for water management in a wide range of activities. Presently, the Hydrology and Water Resources Programme (HWRP) is concerned with the assessment of the quantity and quality of water resources, both surface and groundwater, in order to meet the needs of society, to permit mitigation of water-related hazards, and to maintain or enhance the condition of the global environment. It includes standardization of various aspects of hydrological observations and the organized transfer of technologies for enabling Hydrological Services to provide the hydrological data and information required for the sustainable development of their countries. It provides advice to Members on flood management policy and assists them in their effort to adopt Integrated Water Resources Management (IWRM) with an emphasis on practical applications.

  1. Is our climate changing?
    Experts generally agree that the Earth is warming up. How much this has been directly attributed to or caused by human activity—the effects of which are extremely difficult to assess—is not clear, though increases in greenhouse gases such as carbon dioxide are more than likely taking their toll. What is clear is that, globally, 1998 was the warmest year ever recorded and eight of the 10 other top annual mean temperatures have occurred during the last decade. The upturn has likely been responsible for melting ice sheets in both polar regions. Mountain glaciers around the world have been on the wane as well. A rise in global mean sea level of between 0.09 and 0.88 metres by 2100 has been projected, mainly due to the thermal expansion of sea-water and loss of mass from ice caps and glaciers.
  2. How will this affect our climate over the coming century?
    The Intergovernmental Panel for Climate Change (IPCC) Fourth Assessment Report (2007) projects an increase of globally averaged surface temperatures of 2.1 to 6.1 degrees Celsius, compared to the middle of the 20th century, by 2100. Nearly all land areas are projected to experience more hot days and heat waves and fewer cold days and cold waves. In a warmer world, the hydrological cycle becomes more intense, with heavier and more frequent precipitation and flooding in many areas. Increased summer drying and associated risk of drought over most mid-latitude continental interiors are also predicted. Climate change is expected to decrease water availability in arid and semi-arid regions, which could lead to a doubling of the population living with water scarcity in the next 30 years. Areas affected by diseases such as malaria (and waterborne illnesses) could well expand, while crop models indicate a decrease in yields for tropical and sub-tropical areas. It has also been calculated that a rise of more than a few degrees would trigger a fall in plant productivity throughout most regions of the world. IPCC has started work on its Fifth Assessment Report, aimed at refining a number of the previous conclusions, but the whole report, which requires the coordinated work of about 2000 scientists, will not be completed before 2014.
  3. What is the hydrological cycle?
    Around 98 per cent of the water on Earth lies in the seas and is therefore saline. Powered by solar energy, seawater and other surface waters evaporate and form clouds. These clouds condense and provide freshwater in the form of precipitation. Under the force of gravity, freshwater makes its way back towards the seas in rivers and as groundwater, serving the needs of living organisms on the way. From the sea it again evaporates and the process repeats itself.
  4. Are the world’s water resources decreasing?
    Only 2 per cent of the total water available at any given time on Earth is freshwater, approximately 70 per cent of which is located in the ice caps. Globally, over a short period of time (a few centuries in this case), total freshwater delivered through the world’s hydrological cycle remains constant. However, water is not distributed evenly around the world. In any given river basin, freshwater delivery through rain differs from year-to-year. Many of the planet’s largest river basins run through thinly populated regions, while numerous densely populated zones possess inadequate water supplies, a problem which has been worsened by increasing pollution. Freshwater supplies have been further stretched by demands from irrigation, industry, urbanization and rising living standards.
  5. How is climate change likely to affect the availability of water resources?
    Rising temperatures will accelerate the hydrological cycle, changing the temporal and spatial distribution of freshwater, though total planetary water availability is likely to remain constant. The shrinkage of glaciers will probably result in reduced flows to areas which rely on such supplies in lean seasons. Should sea levels rise, coastal aquifers could suffer reductions in water quality. Demand from human consumption, agriculture and natural vegetation are expected to alter as well. All these factors are likely to have an impact on our water management practices.