Climate Change and Water: "An overview from the World Water Development Report 3: Water in a Changing World"

An overview from the World Water Development Report 3: Water in a Changing World

Water is an integral component of climate change and the primary medium through which it exhibits its impacts.
With the world facing growing water challenges in many regions, how climate change will affect future societies
cannot be understood without looking at its impact on this most vital of our planet’s resources.
This World Water Assessment Programme Special Report brings together messages on water and climate change
from the World Water Development Report 3: Water in a Changing World. A joint effort of the 26 United Nations
agencies that make up UN-Water, the triennial World Water Development Report is the United Nations’
foremost and most comprehensive review of the state of the world’s freshwater resources.
Water in a Changing World shows that changes in our water resources are shaped to a great extent by a number of
key externalities, among them climate change, and that decisions taken far from the conventionally defined water
sector have a tremendous influence on water resources and how they are used or misused. These two principle
messages of the report could not be timelier, with the challenges of climate change currently being squarely
addressed and innovative responses sought with such enthusiasm. Water in a Changing World describes the
dynamic linkages that interconnect changes in climate, the state of our water resources, demographic expansion
and migration issues, food and energy shortages, and the continuing challenge of poverty. Rather than addressing
these issues in isolation, it argues that a holistic approach is crucial if we are to solve the crises we face today
and avoid worse crises tomorrow.
Climate change directly affects the water cycle and, through it, the quantity and quality of water resources
available to meet human and environmental demands. It can lead to both floods and drought. Rising sea levels
have a serious effect on coastal aquifers, a major source of urban and regional water supply systems, and higher
water temperatures and changes in extremes can exacerbate many forms of water pollution. Water supply
reliability, health, agriculture, energy and aquatic ecosystems – all will feel the impact of these changes to the
water cycle. The demand for water to meet these needs is also affected by climate change. The importance of
water to sustainable social and economic development cannot be underestimated, yet many countries are already
facing multiple water challenges, all of them compounded by climate change.
While mitigation of anthropogenic climate change is vital, the blunt reality is that all countries must also adapt
to climate change – particularly developing countries, which are often especially vulnerable to climate change
and many of which will be hit hardest and earliest. Even if greenhouse gas concentrations stabilize in the coming
years, some impacts from climate change are unavoidable. These include increasing water stress in many regions,
more extreme weather events and the potential for large population migration.
Adaptation to climate change will demand a firm commitment from leaders in government, private sector and
civil society worldwide. Public policy on key water services and functions must prioritize a strengthening of
competencies and institutions, and ensuring the infrastructure investment necessary for long-term water security.
But policy choices and other decisions made outside the water domain are also crucial if we are to change and
improve how water is allocated and used, as well as making the adaptation to new, more efficient management
systems more effective and less costly. The international community will have to balance investments to reduce
risks and to prepare for increasingly severe climate events against investments to improve responses to the crises
already being experienced today. Both are vital, and focusing on today’s problems can also create greater resilience
for dealing with the problems of tomorrow.
Carbon is a measure of the anthropogenic causes of climate change; water is a measure of its impacts. We must
act now, and act together, if we are to rise to the challenges of climate change to ensure long-term economic,
environmental and social sustainability and avert a global water crisis.

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Published by the United Nations World Water Assessment Programme