EURANDOM & KNMI, May 2009 Analysis of extremes in a changing climate in support of informed decisions for adaptation

EURANDOM & KNMI, May 2009 Agenda Changing climate extremes Traditional practices WMO guidance document Analyses of extremes Take home message

EURANDOM & KNMI, May 2009

Changing climate extremes IPCC-AR4: ‘confidence has increased that some extremes will become more frequent, more widespread and/or more intense during the 21st century’

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Changing climate extremes Definitions? –High impact events –Exceedence of a relatively low threshold (e.g., 95th percentile of daily precipitation amounts) –Rare events (long return periods) –Unprecedented events (in the available record)

EURANDOM & KNMI, May 2009 Changing climate extremes Definitions? –High impact events –Exceedence of a relatively low threshold (e.g., 95th percentile of daily precipitation amounts) –Rare events (long return periods) –Unprecedented events (in the available record) Wide range of space and time scales –From very small scale (tornadoes) to large scale (drought)

EURANDOM & KNMI, May 2009 Extremes table IPCC-AR4, WG1 report

EURANDOM & KNMI, May 2009 Traditional practices Design criteria for safety of infrastructure are typically based on historical observations of extremes, assuming a stationary climate

EURANDOM & KNMI, May 2009 Traditional practices Design criteria for safety of infrastructure are typically based on historical observations of extremes, assuming a stationary climate Methods fit extreme value distributions to selected observations of extremes

EURANDOM & KNMI, May 2009 Annual maxima of daily precipitation amounts Station De Bilt, the Netherlands,

EURANDOM & KNMI, May 2009 EVT estimates:  70 mm: once in 50yr  50 mm : once in 5yr Map of daily rainfall, 31 July 2002

EURANDOM & KNMI, May July August 2002

EURANDOM & KNMI, May July August August 2002

EURANDOM & KNMI, May 2009 Climate change makes it likely that there will be change in some extremes that lies outside the envelope of constant variability assumed under stationary climate conditions Traditional practices

EURANDOM & KNMI, May 2009 Climate change makes it likely that there will be change in some extremes that lies outside the envelope of constant variability assumed under stationary climate conditions Adaptation strategies should begin to take into account the observed and projected changes in extremes Traditional practices

EURANDOM & KNMI, May 2009 A new WMO/WCRP guidance document on this topic is now in press: –Albert M.G. Klein Tank, Francis W. Zwiers and Xuebin Zhang, 2009: Analysis of climate and weather extremes in a changing climate in support of informed decisions for adaptation. WMO/TD-No ???? WMO Guidance document

EURANDOM & KNMI, May 2009 Targeted at National Meteorological and Hydrological Services (NMHSs) around the world Aim is: –to help build capacity to identify and describe changes in extremes, and –to improve the information services on extremes under climate change conditions WMO Guidance document

EURANDOM & KNMI, May 2009 The focus is on climate extremes defined as rare events within the statistical reference distribution of particular weather elements that are monitored daily at a particular place, such as temperature and precipitation More complicated weather elements that involve compound factors, such as tropical cyclones or storm surges, fall outside the scope WMO Guidance document

EURANDOM & KNMI, May 2009 Need long and quality controlled observational series with high time resolution Analysis of extremes TN, Amos (Canada)

EURANDOM & KNMI, May 2009 Tests for nonclimatic jumps and/or gradual shifts due to changes in station location, environment (exposure), instrumentation or observing practices Analysis of extremes

EURANDOM & KNMI, May 2009 For analyzing moderate extremes an internationally coordinated set of descriptive indices can be used, which describe frequency, amplitude, persistence User-friendly R-based software (RClimDex) for their calculation is available from Analysis of extremes

EURANDOM & KNMI, May 2009 For analyzing moderate extremes an internationally coordinated set of descriptive indices can be used, which describe frequency, amplitude, persistence User-friendly R-based software (RClimDex) for their calculation is available from One key approach involves counting the number of days in a season or a year that exceed specific thresholds Analysis of extremes

EURANDOM & KNMI, May 2009 upper 10-ptile the year 1996 lower 10-ptile Analysis of extremes

EURANDOM & KNMI, May 2009 upper 10-ptile the year 1996 lower 10-ptile “cold nights” Analysis of extremes

EURANDOM & KNMI, May 2009 upper 10-ptile the year 1996 lower 10-ptile “warm nights” “cold nights” Analysis of extremes

EURANDOM & KNMI, May 2009 De Bilt, the Netherlands Analysis of extremes

EURANDOM & KNMI, May 2009 AR4 map of observed trends (days per decade) for 1951 to 2003 (Alexander et al., JGR, 2006) Analysis of extremes The results (in a series of journal papers) contributed to IPCC-AR4, Ch3

EURANDOM & KNMI, May 2009 The results (in a series of journal papers) contributed to IPCC-AR4, Ch3 –Workshops held post-AR4 –New workshops organized in 2009 AR4 map of observed trends (days per decade) for 1951 to 2003 (Alexander et al., JGR, 2006) Analysis of extremes

EURANDOM & KNMI, May 2009 Analysis of extremes Linking the trends in extremes indices to regional circulation changes Example for Europe (van den Besselaar et al., Theor. Appl. Climatol, in press)

EURANDOM & KNMI, May 2009 Classic EVT provides a framework for analyzing extremes further in the tails of the statistical distributions Analysis of extremes

EURANDOM & KNMI, May 2009 Classic EVT provides a framework for analyzing extremes further in the tails of the statistical distributions Possible to account for “non-stationarity”, but the best way to do this is still under debate Analysis of extremes

EURANDOM & KNMI, May 2009 Classic EVT provides a framework for analyzing extremes further in the tails of the statistical distributions Possible to account for “non-stationarity”, but the best way to do this is still under debate One option is making the parameters of the GEV models time-dependent Analysis of extremes

EURANDOM & KNMI, May 2009

Among others, a user-friendly R-based toolkit (extRemes) is available from (Stephenson and Gilleland, 2006; Gilleland and Katz, 2005) Analysis of extremes

EURANDOM & KNMI, May 2009

Kharin et al., J.Climate, 2007

EURANDOM & KNMI, May 2009 For providing information services on changing climate extremes the combined use of different techniques is recommended, as this will also provide information on the uncertainties Take home message

EURANDOM & KNMI, May 2009 For providing information services on changing climate extremes the combined use of different techniques is recommended, as this will also provide information on the uncertainties New infrastructural works should be designed on the basis of both historical information on changes in extremes and projected future changes Take home message

EURANDOM & KNMI, May 2009 the end

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EURANDOM & KNMI, May 2009 Alexander et al.,2006; in IPCC-AR4