M. Lautenschlager (M&D/MPIM) Changing Weather Patterns Weather: Yesterday - Today - Tomorrow Michael Lautenschlager Modelle und Daten / Max-Planck-Institut für Meteorologie, Hamburg AON - Seminar: "Catastrophe Modelling, Techniques and Applications" in Amsterdam

M. Lautenschlager (M&D/MPIM) Weather: Yesterday - Today - Tomorrow Content: 1) Introduction / Overview Low pressure systems and storms Definition of weather and climate 2) Climate Development on Different Time Scales Ice Ages (100,000 years) Little Ice Age (500 years) Industrialisation (100 years) 3) Climate Modelling Principles Phenomena within climate models Limits of resolution 4) IPCC Third Assessment Report Definition of climate modelling experiments Global temperature increase Global sea level rise Regional temperature response Regional precipitation response 5) Outlook North Atlantic deep water formation Storm frequency over North-western Europe

M. Lautenschlager (M&D/MPIM) Hurricane Georges (Sept in the Caribbean) Strongest hurricane since 20 years Wind speed: 200 km/h Peaks: 250 km/h Trajectory: Florida was not hidden For comparison gale (Orkan): Wind strength 12 bft with Wind speed > 120 km/h 1946 WMO increases the Beaufort-Scale up to 17 bft Tropical phenomenon: Water temperature > 27°C

M. Lautenschlager (M&D/MPIM) Northern Hemisphere Low Pressure System Core pressure: Surface low hPa Gale low hPa High hPa Pressure gradient determines the wind strength: Storm 4 hPa / 100 km

M. Lautenschlager (M&D/MPIM) Definition of Weather and Climate Weather "Weather is concerned with detailed instantaneous states of the atmosphere and with the day-to-day evolution of individual synoptic systems. The atmosphere is characterised by relatively rapid random fluctuations in time and space so that weather, identified as the complete state of the atmosphere at a given instant, is continuously changing." (Peixoto and Oort, 1993) Climate The climate, on the other hand, can be considered as the "averaged weather", completed with some measures of variability of its elements and with information on the occurrence of extreme events. Thus we may note that the same variables that are relevant in the weather and in other branches of meteorology are also those that are important in the characterisation of climate." (Peixoto and Oort, 1993)

M. Lautenschlager (M&D/MPIM) Weather: Yesterday - Today - Tomorrow Content: 1) Introduction / Overview 2) Climate Development on Different Time Scales Ice Ages (100,000 years) Little Ice Age (500 years) Industrialisation (100 years) 3) Climate Modelling Principles 4) IPCC Third Assessment Report 5) Outlook

M. Lautenschlager (M&D/MPIM) Global temperature reduction of approx. 5°C Sea level reduction of approx. 180 m (Comp. expected global warming)

M. Lautenschlager (M&D/MPIM) Last Interglacial Temperature increase in Central-Greenland: + 20°C in 5000 years Younger Dryas (rapid climate change)

M. Lautenschlager (M&D/MPIM) IPCC TAR (2001) Industrialisation Future development?

M. Lautenschlager (M&D/MPIM) Weather: Yesterday - Today - Tomorrow Content: 1) Introduction / Overview 2) Climate Development on Different Time Scales 3) Climate Modelling Principles Phenomena within climate models Limits of resolution 4) IPCC Third Assessment Report 5) Outlook

M. Lautenschlager (M&D/MPIM) Phenomena and Processes in Climate Models Noreiks (MPIM), 2001

M. Lautenschlager (M&D/MPIM) Radiation Transfer and Greenhouse Effect Greenhouse effect: Intensification by Means of CO 2 increase Noreiks (MPIM), 2002

M. Lautenschlager (M&D/MPIM) Limits of model resolution ECHAM4(T42) Grid resolution: 2.8° Time step: 40 min ECHAM4(T106) Grid resolution: 1.1° Time step: 20 min Standard resolution for IPCC TAR The climate model calculates: "averaged weather" and variability Noreiks (MPIM), 2001

M. Lautenschlager (M&D/MPIM) See Slides from Jena DKRZ Computing Environment

M. Lautenschlager (M&D/MPIM) DKRZ Computing Environment February 2002 Compute server: 64 CPUs NEC-SX6, 0.5 TB memory, 200 GFlops sustained performance (appr. 40 * C916) Data server: 720 TB tape capacity, 30 TB disk capacity, 240 MB/sec LAN band width August 2002 Compute and data server increase by a factor of 2

M. Lautenschlager (M&D/MPIM) Weather: Yesterday - Today - Tomorrow Content: 1) Introduction / Overview 2) Climate Development on Different Time Scales 3) Climate Modelling Principles 4) IPCC Third Assessment Report Definition of climate modelling experiments Global temperature increase Global sea level rise Regional temperature response Regional precipitation response 5) Outlook

M. Lautenschlager (M&D/MPIM) Climate change in IPCC usage refers to any change in climate over time, whether due to natural variability or as a result of human activity. This usage differs from that in the Framework Convention on Climate Change, where climate change refers to a change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods. 2 In total 122 Co-ordinating Lead Authors and Lead Authors, 515 Contributing Authors, 21 Review Editors and 337 Expert Reviewers. 3 Delegations of 99 IPCC member countries participated in the Eighth Session of Working Group I in Shanghai on 17 to 20 January IPCC Third Assessment Report (TAR) Druck: Cambridge University Press Internet:

M. Lautenschlager (M&D/MPIM) IPCC TAR (2001) Extrapolation of the CO 2 -Development Used as Climate Model Forcing Method: Different assumptions of energy consumption and economic development are expressed in CO 2 concentrations of the atmosphere. A2: Scenario family describes a very heterogeneous world with slow and fragmented technological change. B2: Scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. B2: 80 ppm in 100 years (Interglacial: 80 ppm in 10,000 years) A2: 400 ppm in 100 years

M. Lautenschlager (M&D/MPIM) IPCC TAR (2001) Development of Global Surface Temperature ÇT(2100) = °C (comp. glacial reduction and time scale)

M. Lautenschlager (M&D/MPIM) IPCC TAR (2001) Sea Level Rise due to Thermal Expansion Çz(2100) = cm (comp. glacial reduction)

M. Lautenschlager (M&D/MPIM) At least 7 of 9 models are considered. IPCC TAR (2001) Regional Temperature Response

M. Lautenschlager (M&D/MPIM) Regional Precipitation Response At least 7 of 9 models are considered. IPCC TAR (2001)

M. Lautenschlager (M&D/MPIM) Weather: Yesterday - Today - Tomorrow Content: 1) Introduction / Overview 2) Climate Development on Different Time Scales 3) Climate Modelling Principles 4) IPCC Third Assessment Report 5) Outlook North Atlantic deep water formation Storm frequency over North-western Europe

M. Lautenschlager (M&D/MPIM) North-Atlantic Deep Water Formation North-Atlantic energy sources: 1/3 thermohaline circulation, 2/3 solar radiation Noreiks (MPIM), 2002

M. Lautenschlager (M&D/MPIM) Model response in deep water formation is an prevailing topic in climate research.

M. Lautenschlager (M&D/MPIM) Storm Activity over North-Western Europe Low pressure activity (geopotential metres) in 500 hPa over north-western Europe ( ° N, 6° W - 20° E) Data: Climate simulation IS92a with ECHAM4(T42) Quelle: Ulbrich, U. and M. Christoph (1999) Basic message: Storm activity in winter will increase. Reduction between 1920 und 1950 corresponds with observed index. Separation between storm strength and frequency is a prevailing topic in climate research. Winter

M. Lautenschlager (M&D/MPIM) Summary Statements inferred from the "Third Assessment Report": a) Weather tomorrow will change. b) Summer and winter in Europe will be warmer. c) Winter in Europe will become wetter, summer drier. d) Winter storm activity will increase in winter. Questions for the "Fourth Assessment Report": a) Climate response in North-Atlantic deep water formation? b) Increase of storm frequency and/or strength in the Tropics and Europe? c) Are weather extremes increasing?

M. Lautenschlager (M&D/MPIM) ENDE