The Netherlands approach for generating climate change scenarios

Transcription

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

2 Projections mean precipitation (2050/1990) with the MPI model A1B A2 +25% Winter Summer -50%

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

4 The production of the KNMI 06 scenarios

5 The production of the KNMI 06 scenarios

6 Global mean climate change scenarios Start with projections with Global Circulation Models (GCM s): Multiple emission scenarios Multiple models

7 But there s more than global mean temperature Sea level pressure difference from 2 different GCMs Van Ulden and Van Oldenborgh, 2006

8 G-west in West-Europe for present-day climate Approx 10 GCM-runs for the upcoming IPCC report (2007) Observations Models Van Ulden et al, 2005

9 G-west end of 21 st century with doubled CO 2 -levels Changes relative to present climate

10 G-west end of 21 st century with doubled CO 2 -levels Changes relative to present climate

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

12 Winter temperature and wind direction Eastern winds give low winter temperatures A2 scenario Control simulation Observed

13 Rationale of the scenarios The steering variables 1. Global temperature 2. Strength of seasonal mean west-circulation (not for z sea ) Circulatie verandering niet wel Gematigd+ verandering Warm+ verandering + 1 C + 2 C Gematigd Warm Wereld Temperatuur Strength of west-circulation month

14 The production of the KNMI 06 scenarios

15 Precipitation extremes in summer (difference A2 CTL) Purpose of downscaling: extra spatial and temporal detail Mean; 90%; 95%; 99%; 99.5%; 99.9% more Danish Met. Institute less

16 Precipitation extremes in summer (difference A2 CTL) Mean; 90%; 95%; 99%; 99.5%; 99.9% more less Danish Met. Institute

17 Precipitation extremes in summer (difference A2 CTL) Mean; 90%; 95%; 99%; 99.5%; 99.9% ~10 times per summer more less Danish Met. Institute

18 Precipitation extremes in summer (difference A2 CTL) Mean; 90%; 95%; 99%; 99.5%; 99.9% ~5 times per summer more less Danish Met. Institute

19 Precipitation extremes in summer (difference A2 CTL) Mean; 90%; 95%; 99%; 99.5%; 99.9% ~annual wettest summer day more less Danish Met. Institute

20 Precipitation extremes in summer (difference A2 CTL) Mean; 90%; 95%; 99%; 99.5%; 99.9% ~shower exceeded once per 5 yrs more less Danish Met. Institute

21 Precipitation extremes in summer (difference A2 CTL) Mean; 90%; 95%; 99%; 99.5%; 99.9% ~shower exceeded once per 10 yrs more less Danish Met. Institute

22 Model predictions in number of wet days Difference A2 CTL winter summer About equal Reduced by 25-35%

23 Result: change in 2050 relative to 1990

24 Result: change in 2050 relative to 1990 mean temperature yearly coldest day With circulation change the coldest temperature changes more than mean

25 Result: change in 2050 relative to 1990 Nr of wet days strongly dependent on circulation change wet day frequency

26 Result: change in 2050 relative to 1990 Wet day mean precipitation dependent on global temperature rise mean precipitation

27 Result: change in 2050 relative to 1990 Extreme precipitation is more likely in a wetter climate daily precipitation exceeded 1/10yrs

28 Result: change in 2050 relative to 1990 annual maximum daily mean wind Windscenarios hardly show a significant change

29 Result: change in 2050 relative to 1990 Sea level scenario s after 2050 show acceleration: For 2100 the range is between 35 and 85 cm sea level rise

30 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)

31 Tailored climate scenarios Specific use in water management requires tailoring Dutch Programme Climate Changes Spatial Planning co-funded a tailoring project Examples (not all from this project) High resolution time series of precipitation Ground water tables in the Netherlands Rhine discharge Closure of Maasland barrier

32 The production of the KNMI 06 scenarios

33 Generation of high resolution time series Climate scenarios provide general key numbers (change of mean, change of 1/10yr return value) Change an existing (obs) time series of precipitation linearly (using only mean change) non-linearly (changing also shape of distribution and # wet days)

34 precipitation (mm/day) Generation of high resolution time series obs W W+ W+ linear 15 and different changes for 10 different intensities n-lin > obs lin < obs non-linear transformation introduces dry day Julian Days n-lin < obs lin < obs

35 Effect on groundwater table (example) groundwater level to NAP (cm) Oirschot (906) obs W W_linear W+ W+_linear non-linear transformation has tendency to be wetter in wet episodes and drier in dry spells Julian Days

36 Groundwater tables in the Netherlands Current practice: detailed hydrological model is used to calculate high resolution ground water balance Climate change assessment needs long records: expensive! To enable affordable climate change assessment: can one construct a single reference year that reproduces proper reference climatological ground water product?

37 Groundwater tables in the Netherlands Result: a spatially and temporally varying factor is needed to relate a single year to a climatological mean Not all features of variability can be captured in a single year! 30yr mean optimally corrected single year (e.g. 1967) residual difference

38 Change in ground water table the Netherlands Aim: first assessment of effect of W+ scenario on ground water table in various stages of the growing season Tailoring: production of location specific meteo (applied linearly in this example) running high resolution ground water model Start of growing season: generally wetter Lowest water table during growing season: generally drier courtesy Timo Kroon, Franziska Keller ea

39 Assessment of impact of KNMI 06 scenarios on Rhine discharge Old WB21 scenarios New KNMI 06 scenarios

40 Assessment of impact of KNMI 06 scenarios on Rhine discharge old +1 and +2 new +1 and +2 (no circ)

41 Assessment of impact of KNMI 06 scenarios on Rhine discharge old +1 and +2 new +1 and +2 (no circ) new +1 and +2 (with circ)

42 Closure of Maasland-barrier: costly! Dependent on (simultaneous) high water level due to surge and Rhine discharge Sea level at Hoek v Holland (m) H vd Brink ea Rhine discharge ( 1000 m 3 /s)

43 Closure of Maasland-barrier: costly! Dependent on (simultaneous) high water level due to surge and Rhine discharge Sea level at Hoek v Holland (m) Closure return time (years) Rhine discharge ( 1000 m 3 /s) Sea level rise (m) H vd Brink ea

44 Final remarks Generic scenarios Designed to span a wide range of possible climate change, suitable for many applications Tailoring Process of tailoring is important for application in practice. Close multi-disciplinary cooperation is required Dry summers Particularly dry summer conditions gain additional attention in Dutch climate adaptation policy