INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE WMO UNEP _______________________________________________________________________________________________________________________ INTERGOVERNMENTAL PANEL IPCC-XXVIII/Doc.13 ON CLIMATE CHANGE (8.IV.2008) TWENTY-EIGHTH SESSION Agenda item: 10 Budapest, 9-10 April 2008 ENGLISH ONLY TECHNICAL PAPER ON CLIMATE CHANGE AND WATER (Finalized at the 37th Session of the IPCC Bureau) _______________________________________________________________________________________________________________________ IPCC Secretariat, c/o WMO, 7bis, Avenue de la Paix, C.P. N° 2300, 1211 Geneva 2, SWITZERLAND Phone: +41 22 730 8208/8254/8284 Fax: +41 22 730 8025/8013 E-mail: [email protected] Website: http://www.ipcc.ch INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE WMO UNEP Climate Change and Water Bryson Bates, Zbigniew W. Kundzewicz, Shaohong Wu, Nigel Arnell, Virginia Burkett, Petra Döll, Daniel Gwary, Clair Hanson, BertJan Heij, Blanca Jiménez, Georg Kaser, Akio Kitoh, Sari Kovats, Pushpam Kumar, Chris Magadza, Daniel Martino, Luis José Mata, Mahmoud Medany, Kathleen Miller, Taikan Oki, Balgis Osman, Jean Palutikof, Terry Prowse, Roger Pulwarty, Jouni Räisänen, Jim Renwick, Francesco Tubiello, Richard Wood, Zong-Ci Zhao, Julie Arblaster, Richard Betts, Aiguo Dai, Christopher Milly, Linda Mortsch, Leonard Nurse, Richard Payne, Iwona Pinskwar, Tom Wilbanks SUBJECT TO FINAL COPY EDIT This is a Technical Paper of the Intergovernmental Panel on Climate Change prepared in response to a decision of the Panel. The material herein has undergone expert and government review, but has not been considered by the Panel for possible acceptance or approval. April 2008 This paper was prepared under the auspices of the IPCC, which is chaired by Dr. Rajendra K. Pachauri, and administered by the IPCC Working Group II Technical Support Unit. IPCC Technical Paper on Climate Change and Water Table of Contents Executive Summary ................................................................................................................ 4 1. Introduction to climate change and water ....................................................................... 7 1.1 Background of this Technical Paper ................................................................................. 7 1.2 Scope of the issues covered................................................................................................. 7 1.3 The context of the Technical Paper: socio-economic and environmental conditions ... 9 1.3.1 Observed changes........................................................................................................................... 9 1.3.2 Projected changes......................................................................................................................... 11 1.4 Outline of the Technical Paper ........................................................................................ 13 2. Observed and projected changes in climate as they relate to water............................ 15 2.1 Observed changes in climate as they relate to water ..................................................... 15 2.1.1 Precipitation (including extremes) and water vapour................................................................... 16 2.1.2 Snow and land ice ........................................................................................................................ 20 2.1.3 Sea level ....................................................................................................................................... 24 2.1.4 Evapotranspiration ....................................................................................................................... 25 2.1.5 Soil moisture ................................................................................................................................ 25 2.1.6 Runoff and river discharge........................................................................................................... 26 2.1.7 Patterns of large scale variability ................................................................................................. 27 2.2 Influences and feedbacks of hydrological changes on climate...................................... 28 2.2.1 Land surface effects ..................................................................................................................... 29 2.2.2 Feedbacks through changes in ocean circulation ......................................................................... 29 2.2.3 Emissions and sinks affected by hydrological processes or biogeochemical feedbacks .............. 30 2.3 Projected changes in climate as they relate to water ..................................................... 31 2.3.1 Precipitation (including extremes) and water vapour................................................................... 32 2.3.2 Snow and land ice ........................................................................................................................ 36 2.3.3 Sea level ....................................................................................................................................... 37 2.3.4 Evapotranspiration ....................................................................................................................... 38 2.3.5 Soil moisture ................................................................................................................................ 38 2.3.6 Runoff and river discharge........................................................................................................... 39 2.3.7 Patterns of large scale variability ................................................................................................. 40 3. Linking climate change and water resources: impacts and responses........................ 42 3.1 Observed climate change impacts ................................................................................... 42 3.1.1 Observed effects due to changes in the cryosphere...................................................................... 42 3.1.2 Hydrology and water resources.................................................................................................... 43 3.2 Future changes in water availability and demand due to climate change ................... 49 3.2.1 Climate-related drivers of freshwater systems in the future......................................................... 49 3.2.2 Non-climatic drivers of freshwater systems in the future............................................................. 54 3.2.3 Impacts of climate change on freshwater availability in the future.............................................. 55 3.2.4 Impacts of climate change on freshwater demand in the future ................................................... 56 3.2.5 Impacts of climate change on water stress in the future............................................................... 56 3.2.6 Impacts of climate change on costs and other socio-economic aspects of freshwater ................. 57 3.2.7 Freshwater areas and sectors highly vulnerable to climate change .............................................. 60 3.2.8 Uncertainties in the projected impacts of climate change on freshwater systems........................ 61 3.3 Water-related adaptation to climate change: an overview ........................................... 62 3.3.1 Integrated Water Resources Management.................................................................................... 66 4. Climate change and water resources in systems and sectors ....................................... 68 4.1 Ecosystems and biodiversity ............................................................................................ 68 4.1.1 Context......................................................................................................................................... 68 4.1.2 Projected changes in hydrology and implications for global biodiversity.................................... 68 4.1.3 Impacts of changes in hydrology on major ecosystem types ....................................................... 69 4.2 Agriculture and food security, land use and forestry .................................................... 74 4.2.1 Context......................................................................................................................................... 74 4.2.2 Observations................................................................................................................................. 76 4.2.3 Projections.................................................................................................................................... 77 4.2.4 Adaptation, vulnerability and sustainable development............................................................... 81 Subject to final copy edit 1 IPCC Technical Paper on Climate Change and Water 4.3 Human health....................................................................................................................87 4.3.1 Context......................................................................................................................................... 87 4.3.2 Observations................................................................................................................................. 90 4.3.3 Projections.................................................................................................................................... 90 4.3.4 Adaptation,