Climate change and regional water cycle – www.knmi.nl/climatescenarios
Prof. Bart van den Hurk, KNMI
Projected changes in the climate
system affecting the regional
water cycle
Climate change and regional water cycle – www.knmi.nl/climatescenarios
• IPCC published 4th Assessment report
– GHG-emission and temperature rise continues
– Precipitation variability increases
– Many (varying) projections for the future
• KNMI produced new Climate Change scenarios
– Addressing regional changes
• Some example episodes in the recent past
– july/august 2006
– spring/summer 2007
• Conclusions
– Regional variability increases at many time scales
– Climate change scenarios will continue to develop
Overview
IPCC, 2007
Climate change and regional water cycle – www.knmi.nl/climatescenarios
Snow cover/glacier
length decreasing
Sea level rise
since 1993
accelerating to
3.1 ± 0.7 mm/yr
Temperature rise
since 1956
accelerating to
0.13 ± 0.03 K/10yrs
Climate change in observations
IPCC, 2007
Climate change and regional water cycle – www.knmi.nl/climatescenarios
Antropogenic contribution
needed to explain
observed changes
Model reconstructions
IPCC, 2007
Climate change and regional water cycle – www.knmi.nl/climatescenarios
Model projections (global
mean temperature)
IPCC, 2007
2100
Climate change and regional water cycle – www.knmi.nl/climatescenarios
2025
Mean temperature change SRES A2 scenario
• Future temperature change varies between regions
• Mean wind patterns may also change!
Climate change involves
many aspects
Climate change and regional water cycle – www.knmi.nl/climatescenarios
Van Ulden and Van Oldenborgh, 2006
Sea level pressure difference
from 2 different GCMs
Atmospheric circulation change
Climate change and regional water cycle – www.knmi.nl/climatescenarios
HadAM3H (small
changes in circulation
statistics)
ECHAM4/OPYC (more
Atlantic advection in winter,
less in summer)
• Change of precipitation annual cycle in Rhine area
from multiple regional climate model simulations
• Two different GCM’s
The influence from
circulation change
Climate change and regional water cycle – www.knmi.nl/climatescenarios
• Climate change in the Netherlands depends on
– global temperature rise
– change in local wind regime
Climate change in the
Netherlands
Climate change and regional water cycle – www.knmi.nl/climatescenarios
The KNMI’06 climate scenarios:
change in 2050 relative to 1990
coldest winter day per year
average temperature
Summer
Climate change and regional water cycle – www.knmi.nl/climatescenarios
warmest summer day per year
average temperature
With circulation change the coldest and warmest
temperature change more than mean
Winter
Some examples
Summer
Climate change and regional water cycle – www.knmi.nl/climatescenarios
number of wet days
Nr of wet days strongly dependent on
circulation change
Some examples
144
9,7
Precipitation deficit
(mm)
Return time of
2003-drought
(yrs)
7,9
151
G
4,1
179
G+
6,5
158
W
2,0
220
W+
Climate change and regional water cycle – www.knmi.nl/climatescenarios
19062000
Return time of 2003 drought
courtesy Geert Lenderink
Erik van Meijgaard
Climate change and regional water cycle – www.knmi.nl/climatescenarios
Sea surface temperature
normal
Aug 2006
• July was anomalously warm and dry
• Precipitation August 2006
The summer of 2006
courtesy Geert Lenderink
Erik van Meijgaard
Climate change and regional water cycle – www.knmi.nl/climatescenarios
may lead to refined
climate scenarios
run with normal SST run with true Aug’06 SST
• Heavy precipitation limited to coastal zone
Precipitation gradient
Climate change and regional water cycle – www.knmi.nl/climatescenarios
5% driest years
record (1976)
median
2007
Potential evaporation minus precipitation
• April was extremely dry and warm
• Summer (June-July-August) very wet and cool
Spring and summer 2007
eca.knmi.nl
R95p (nr of
very wet
days > 95%)
RR1 (nr of
wet days)
JJA
Climate change and regional water cycle – www.knmi.nl/climatescenarios
DJF
Observed trends in extreme
precipitation (1946 – 2006)
Climate change and regional water cycle – www.knmi.nl/climatescenarios
• Regional variability increases
– at daily time scale (changes of extremes are
stronger than changes of means)
– within a season (nr of wet days changes,
evidence for rapid transition of persistent
anomalous episodes)
– between years (scenarios differ widely but none
can be excluded)
• Climate change scenarios will continue to develop
– present state of the art is different from
yesterday’s
Conclusions