Extremes Events in Climate Change Projections Jana Sillmann

Transcription

1 Extremes Events in Climate Change Projections Jana Sillmann Max Planck Institute for Meteorology International Max Planck Research School on Earth System Modeling

2 Temperature distribution IPCC (2001)

3 Outline What are Extreme Climate Events? Definitions How can we assess Extreme Climate Events? Climate Change Indices for extreme events What can we learn from the present? Observations What might happen in the future? Changes of climate extremes in future scenarios

4 What is an EXTREME Climate Event? Extreme climate events are very severe, rare and intense and determined by their Spatial scale (thunderstorm, River flooding, heat wave) temporal scale (hours, days, weeks, ) Complexity (1 or more variables) Economic and societal losses due to extreme events have increased in the last decades (Munich Re-Insurance)

5 How can we assess Extreme Climate Events? A ) Extreme Value Theory (Statistical Modeling) B) Development of a set of Climate Change Indices with focus on extremes: based on daily maximum and minimum temperature and precipitation data applied to global data to make data comparison easier describe moderate extremes, but robust easily understandable and manageable for impact studies

6 INDICES for Extreme Climate Events 5 categories: Percentile-based indices: sample the extreme end of a reference period distribution e.g. 10th or 90th percentile of min./max. temperature 1 st 10 th 50 th 90 th 99 th percentiles Absolute indices: represent maximum or minimum values within a season/year e.g. maximum 5 day precipitation

7 INDICES for Extreme Climate Events Threshold indices: number of days on which temperature/precipitation falls above or below a fixed threshold e.g. Frost days (min. Temperature <0 C), days with preciptiation > 10mm Duration indices: define periods of excessive warmth, cold, wetness or dryness e.g. heat wave duration, growing season length, number of consecutive dry days Other which have significant societal impacts e.g. diurnal or inter-annual temperature range, intensity of daily rainfall

8 Assessing Extreme Climate Events Various studies of observed station-based temperature and precipitation data have been achieved to asses changes of extreme events in the past century ( ) Problems: data availability and inhomogeneities global daily temperature and precipitation data from General Circulation Models

9 Coupled Atmosphere-Ocean General Circulation Model ECHAM5/MPI-OM (T63/L31) A1B: a world of rapid economic growth and introduction of new technologies, mix of fossil fuels and renewable energies B1: a world of dematerialization and introduction of clean technologies

10 What has been observed in EUROPE? Most observed trends in recent decades are not significant, but in general there is: a shift in the temperature distribution, where minimum temperature increase faster than maximum temperatures less frost days, more warm nights, more heat waves, longer growing season a shift in the precipitation distribution towards generally wetter conditions with an increase in dry days and an increase in intense precipitation events there are less rain days, but when it rains it is more intense

11 What might happen in the future? Difference between A1B scenario ( ) 2100) and 20 th Century ( ) Maximum Tmax [ºC] Minimum Tmin [ºC] Tropical Nights [days]

12 Regional changes of the indices in Europe from Maximum Tmax [ C] Minimum Tmin [ C] A1B ensmean B1 ensmean

13 What might happen in the future? Heat wave duration (ANNUAL)

14 Difference between A1B scenario ( ) 2100) and 20 th Century ( ) max. 5-day precipitation [mm] precipitation >95 th percentile [mm] max. consecutive dry days [days]

15 Regional changes of the indices in Europe from max. 5-day precipitation [mm] max. consecutive dry days [days] A1B ensmean B1 ensmean

16 What might happen in the future? Max. number of consecutive dry days (ANNUAL) movie

17 What might happen in the future? Max. 5 Day precipitation (ANNUAL)

18 SUMMARY We have seen: Trends that have been observed in the last decades will continue and intensify in the future scenarios What we can expect: More heat waves and longer drought periods water stress for agriculture, forest fires, higher energy demand for cooling systems, health risks

19 What we can expect: Increase in warm nights changes in energy demand for heating, less night cooling during heat waves Increase in intense precipitation events Risk of flooding, especially after long dry periods in summer, and in winter when soil is already over-saturated with water

20 What makes the analysis of extreme events so difficult: Definition of extreme events regional dependency, validity in the future Rareness of extreme events statistical significance Indices for Extreme Climate events are one way to assess changes in Extremes