Climate scenarios for the Netherlands The Netherlands approach for generating climate change scenarios Bart van den Hurk, KNMI and many others

Climate scenarios for the Netherlands Climate change in observations Temperature rise since 1956 accelerating to 0.13  0.03 K/10yrs Sea level rise since 1993 accelerating to 3.1  0.7 mm/yr Snow cover/glacier length decreasing IPCC, 2007

Climate scenarios for the Netherlands Model reconstructions IPCC, 2007 Antropogenic contribution needed to explain observed changes

Climate scenarios for the Netherlands Scenarios and predictions Scenario: –Assessment of consequenses of certain assumed developments (“what-if”) Projection: –Model simulation forced by a scenario Prediction/forecast: –Best estimate of future developments Probabilistic forecast: –Best estimate of probability distribution of all possible future developments value (eg T glob ) prob

Climate scenarios for the Netherlands Construction of model projections Starting points: –multiple scenarios for socio-economic developments –multiple climate models use set scenarios Emission-scenarios Concentration-scenarios –chemistry-transportmodels Climate Projections –AR4: Large number (~25) GCMs available for 1900 – 2200 ( )

Climate scenarios for the Netherlands Emission scenario’s (SRES) CO 2 CH 4 N2ON2O SO 2

Climate scenarios for the Netherlands Model projections (global mean temperature) IPCC, 2007

Climate scenarios for the Netherlands Projections mean precipitation (2050/1990) with the ECHAM model Winter Summer A1B A2 +25% -50%

Climate scenarios for the Netherlands Projections mean precipitation (2050/1990) with the ECHAM model Winter Summer A1B A2 +25% -50% Gradient N-S gradient in winter SE-NW gradient in summer Mean change Winter change  +5 – +10% Summer change  -10 – -15% Difference scenarios A2 a bit stronger in winter A1B a bit stronger in summer Resolution Resolution very coarse (>150 km) Extremes Only seasonal mean! No info on extremes or nr of wet days.

Climate scenarios for the Netherlands Climate change involves many aspects Future temperature change not uniform Mean wind patterns may also change! Mean temperature change SRES A2 scenario IPCC, 2007

Climate scenarios for the Netherlands Atmospheric circulation change Sea level pressure difference from 2 different GCMs Van Ulden and Van Oldenborgh, 2006

Climate scenarios for the Netherlands The influence from circulation change Change of precipitation annual cycle in Rhine area from multiple regional climate model simulations Two different GCM’s HadAM3H (small changes in circulation statistics) ECHAM4/OPYC (more Atlantic advection in winter, less in summer)

Climate scenarios for the Netherlands Climate change in the Netherlands Climate change in the Netherlands depends on –global temperature rise –change in local wind regime

Climate scenarios for the Netherlands Regional climate change: downscaling GCM-grid box too coarse Regional model Global model

Climate scenarios for the Netherlands Regional Climate Modelling (RCM) High resolution GCM (50 – 20 km) Lateral boundary conditions from reanalysis (present-day climate conditions) or GCM runs (scenario runs) –multi-level –temporal frequency dependent on domain Inner domain free evolving

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less Purpose of downscaling: extra spatial and temporal detail Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less ~10 times per summer Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less ~5 times per summer Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less ~annual wettest summer day Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less ~shower exceeded once per 5 yrs Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands Mean; 90%; 95%; 99%; 99.5%; 99.9% Danish Met. Institute more less ~shower exceeded once per 10 yrs Precipitation extremes in summer (A2 – CTL)

Climate scenarios for the Netherlands The KNMI’06 climate scenarios: change in 2050 relative to 1990

Climate scenarios for the Netherlands Some examples With circulation change the coldest and warmest temperature change more than mean average temperature warmest summer day per year average temperature coldest winter day per year Winter Summer

Climate scenarios for the Netherlands Some examples Nr of wet days strongly dependent on circulation change number of wet days Summer

Climate scenarios for the Netherlands Some examples Extreme precipitation more likely in a wet climate daily precipitaiton exceeded once in 10 years Summer

Climate scenarios for the Netherlands Return time of 2003 drought GG+WW+ Precipitation deficit (mm) Return time of 2003-drought (yrs) 9,77,94,16,52,0

Climate scenarios for the Netherlands General picture Extreme temperature change is stronger than mean, especially when circulation also changes When circulation changes number of precipitation days is strongly reduced in summer, causing a reduction of mean summertime precipitation In winter mean precipitation increases (dependent on circulation) Extreme precipitation increases both in summer and winter Sea level rise is slightly smaller than in TAR 1/yr Wind slightly increases (but not significantly)

Climate scenarios for the Netherlands Relevant issues Sea level rise Extreme precipitation Water availability and droughts Cumulative precipitation

Climate scenarios for the Netherlands Closure of Maasland-kering Dependent on (simultaneous) high water level due to surge and Rhine discharge H vd Brink ea Sea level at Hoek v Holland (m) Rhine discharge (  1000 m 3 /s)

Climate scenarios for the Netherlands Closure of Maasland-kering Dependent on (simultaneous) high water level due to surge and Rhine discharge H vd Brink ea Closure return time (years) Sea level rise (m) Sea level at Hoek v Holland (m) Rhine discharge (  1000 m 3 /s)

Climate scenarios for the Netherlands New science: Hourly precipitation intensity Scenarios give change in daily precipitation. Extreme precipitation comes in short time events. 14%/degree 7%/degree (Clausius Clapeyron) 3.5%/degree Hourly precipitation in De Bilt G+/W+ scenarios give much lower changes (5%/degree), probably on the low side

Climate scenarios for the Netherlands And the real world: The summer of 2006 July was anomalously warm and dry (W+)? Precipitation August 2006 (W?) courtesy Geert Lenderink Erik van Meijgaard Sea surface temperature normal Aug 2006

Climate scenarios for the Netherlands Precipitation gradient Heavy precipitation limited to coastal zone run with normal SST run with true Aug’06 SST courtesy Geert Lenderink Erik van Meijgaard

Climate scenarios for the Netherlands Spring and summer 2007 April was extremely dry and warm Summer (June-July-August) very wet and cool Potential evaporation minus precipitation 5% driest years record (1976) median 2007

Climate scenarios for the Netherlands Conclusions Regional climate change scenarios span wide range of conditions …but science evolves …and nature doesn’t know about (fixed) scenarios Scenarios should be used to feed imagination, not as a quantitative forecast!

Climate scenarios for the Netherlands EC-Earth: effect of high resolution