Climate change and water resources in Europe Professor Nigel Arnell EU Water Directors Meeting London, 28-29th November 2005 Climate change and water resources in Europe Professor Nigel Arnell School of Geography University of Southampton

Outline Climate change: trends and projections Implications for river flows and water resources Implications for adaptation and water policy

Temperature change The last 150 years

The future Future climate change depends on (i) future emissions (ii) what happens to gases (iii) sensitivity of climate to change

Change in temperature 2020s: 0.8 to 0.94oC higher than 1961-1990

Change in precipitation Shift in regional patterns Change in seasonality

Effects on runoff and recharge Annual runoff Change by 2020s A2 emissions The pattern is very similar for drought runoff

Trajectories of change Dotted lines indicate decadal variability: this can be added to or subtracted from climate change trend

Changes in timing of flows Higher temperatures result in changes in the seasonal distribution of flows in some regions where winter precipitation currently falls as snow

Pressures on water resources Resources per capita by 2021 Increases in demand place resources under pressure in many basins

What effect does climate change have? Basins with < 1700 m3/capita/year Net increase in stress Abstract measure of water resources stress

What effect does climate change have? 2021, no climate change, A2 world: 365.6 million people living in watersheds with < 1700 m3/capita/year

Specific water resources impacts… Severn-Trent 6.5% reduction by 2025 Thames / London 11-13% reduction by 2025

Certainties and uncertainties “Climate change is uncertain: we don’t know what will happen over the next few decades” “We can’t predict future energy use” “We can’t predict future weather or climate” but…. We KNOW climate will change We KNOW we cannot rely on past climatic data We KNOW to expect surprises

Implications for adaptation Capacity-building and specific actions Capacity-building - conceptual change - development of procedures / tools - development of intellectual capacity Specific actions - measures to meet adaptation target (e.g. maintain supply-demand balance) - supply-side / demand-side

What are the limits to adaptation? Physical limits - change is so great that the impacted system is destroyed - change is so great that it is physically impossible to reduce loss Financial limits - it is too expensive to respond to the impact Feasibility limits - social and political constraints on options ADAPTATION iv. Capacity limits - limited institutional capacity to make adaptation decisions

Enhancing the knowledge base Enhanced climate scenarios (extremes/variability) Moving beyond water quantity: water quality and land use effects Developing “best practice” assessment methodologies (and incorporating into water policy) Developing flexible adaptation measures - understanding consumer behaviour

Conclusions Climate change is happening Climate policy will have little effect over the next few decades We will see significant changes in water resources We need now to incorporate climate change into strategies and plans