Current climate change scenarios and risks of extreme events for Northern Europe

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1 Current climate change scenarios and risks of extreme events for Northern Europe Kirsti Jylhä Climate Research Finnish Meteorological Institute (FMI) Network of Climate Change Risks on Forests (FoRisk) SNS Workshop, October 26-28, 29, Tvärminne, Finland

2 FMI: a research and service agency under the Ministry of Transport and Communications Produces high-quality observational data and research knowledge about the past, present and future state of the atmosphere 171 years old: the predecessor of FMI, the Magnetic Observatory of the University of Helsinki, was founded in Marine research Helsinki, Tampere, Kuopio, Rovaniemi, Sodankylä

3 Climate change research unit Climate Research and Applications Socio-economic Impacts of Climate and Weather Greenhouse Gases Fig. Annalea Lohila Aerosols and Climate 5.1. The average date for permanent snow cover in Modelling and Observation of the Atmosphere ~ 55 person years, head prof. Ari Laaksonen Measurements of greenhouse gases and aerosols

4 Daily mean temperature in 22 Sep 21 Oct 29 Helsinki 25 Oct 29 Oulu Number of days with mean temp < ºC Thermal winter September-October th percentile in th percentile in (=median) 2.5th percentile in Thermal autumn

5 Outline Some terminology Uncertainties in climate projections Current climate change scenarios Risks of extreme events Summary

6 Some terminology (1/3) Climate prediction or climate forecast an attempt to produce the most probable estimate of the actual evolution of the climate in the future, e.g., at seasonal, inter-annual or long-term time scales. Climate scenarios or projections descriptions of alternative possible, plausible, internally consistent, but not necessarily equally probable futures. conditional predictions, i.e., conditional on the assumptions made about the future evolution of greenhouse gases and aerosols. help to answer if... then questions Climate change scenario: the difference between a climate scenario and the current climate.

7 Some terminology (2/3) Probabilistic climate scenarios or projections Due to several sources of uncertainty, the prediction of both natural climate variability and the human impact on climate is inherently probabilistic. An ensemble of climate-model simulations: consists of many simulations, performed either by the same model but different initial conditions or by several different models. Probability density (1/ºC) Annual Winter Summer Temperature change (ºC) The probability that T > 3ºC in winter, is proportional to the size of the blue area.

8 Some terminology (3/3) Percentiles The 95th (5th) percentile: a value equal to or below which 95% (5%) of all cases fall. The best estimate The 5th percentile (median), or An ensemble / multi-model mean Probability density (1/ºC) Annual Winter Summer Temperature change (ºC) The probability that T ºC in summer, is proportional to the size of the red area.

9 Why is it not possible to construct accurate predictions of the magnitude of climate change? Inherent sources of uncertainty - future emissions - model formulation - natural climate variability Figures: energyconcepts.tripod.com,

10 Emissions of greenhouse gases and aerosols depend on the future actions of the mankind: changes in population, energy use, energy sources, land use Total emissions (PgC/yr) SRES emission scenarios for CO 2 Atmospheric concentrations of CO 2 A2 A2 A1B B1 B2 Observed Series5 Series2 Series6 Observed Series1 Concentrations (ppm) A2 A1B B2 Observed A2 A1B B1 Series Past and current emissions of CO 2 contribute to future concentrations

11 Progress in the model simulation of the climate system but uncertainties remain /5 29/11? Time Evolution of climate models A computer cluster Some interactions in the climate system may not have been discovered yet Climate models cannot completely simulate all the processes we currently know (e.g., cloud feedback processes).

12 Regional climate projections are more uncertain than global projections Natural climate variability is likely to accelerate changes in climate during some periods, and retard changes during other periods, but these natural fluctuations cannot be predicted. Projected regional signals tend to differ from model to model. Multi-model means for past climate periods generally compare with observations better than single model simulations The approach: to use ensembles of - different models and - different downscaling techniques (e.g. regional climate models) to estimate the possible regional climate change signal.

13 Uncertainties in climate change schematically Observed climate Future climate Natural variability Models Emission scenarios LEVEL OF UNCERTAINTY 2 21 Near future End of the century Natural climate variability + + Climate model sensitivity (+) ++ Emission scenarios ++ Source: J. Räisänen (Univ. of Helsinki)

14 Current climate change scenarios

15 Warming in Finland by ~.4.1 C/1 yr during the next three decades Change in temperature (ºC) Annual mean temperature => Scenario Change (ºC) A2 5.1 (3.1 7.) A1B 4.4 ( ) B1 3.2 ( ) Multi-model mean (19 GCMs) and the 9% uncertainty range The rate of warming deviates little between the different emission scenarios up to by the 24s. The warming by the end of the century would be about one third smaller in the B1 scenario compared to the A2 scenario. (Gt C/year) Emissions

16 Probabilistic forecasts of temperature change in southern Finland ( ) Accounts for natural variability and differences between climate models Probability density (1/ºC) Annual Winter Summer Temperature change (ºC) Winter Summer Annual Best estimate (ºC) % uncertainty range (ºC) Probability of warming (%) 9% 9% 96% Width of the distribution primarily determined by natural temperature variability: larger in winter than in summer. Ref: Räisänen and Ruokolainen (27)

17 Largest warming in winter, smallest in summer 6 Finland => Change in temperature (ºC) Month The best estimate and the 9% uncertainty range, assuming the A1B emissions Differences in climate model formulation (19 GCMs) Internal climate variability (Gt C/year) Emissions A1B

18 Largest warming in northeastern Finland Annual mean temperature change (ºC) => (Gt C/year) Emissions A1B Wintertime changes in the north exceed those in the south Summertime changes are rather uniform across the country.

19 Annual mean temperature in Temperature (ºC) Contour interval two degrees.

20 Annual mean temperature in Temperature (ºC) Contour interval two degrees. (Gt C/year) Emissions A1B

28 Temperatures in central Lapland by the end of the century ~ those in present-day southern Finland A1B Larger emissions => even larger changes

29 Increases in precipitation in Finland in winter by 1 4%, and in summer by 2%, by the 28s Larger precipitation amounts in summer than in winter also in the future DJF => JJA Unit: % A1B

30 Shorter winter season, slightly longer spring season DJF => MAM Change in days Typically no winter season at all to the west of the black curve 19 model mean estimate (Gt C/year) Emissions A1B Ref: ACCLIM project (FMI)

31 Longer summer season, and autumn in SW Finland JJA => SON 4 Change in days (Gt C/year) Emissions A1B 19 model mean estimate Ref: ACCLIM project (FMI)

32 Largest decreases in snow cover in SW Finland Annual mean and max snow water equivalent # of snow cover days -5% -6% -3% -4% -2% -7% -5% -3% -8% -6% -5% -4% Multi-model mean changes (in %) => , SRES A2 Ref: Jylhä et al. (29)

33 Risks of extreme events

34 Very low temperatures will become rarer Hot spells will become more common The highest temperatures will be even higher.

35 Hot summer days* in Finland Observed in Scenario for Turku Joensuu Ivalo *Daily mean temperature > 2ºC Maximum 95% 75% 5% 25% 5% Turku Joensuu Ivalo Ref: ACCLIM project (FMI)

36 More frequent freezing point days* in Dec-Feb (less on annual basis) SON DJF MAM *Tmin < ºC, Tmax > ºC Change (in days) => Ref: Jylhä et al. (28) A2

37 Number of days with precipitation ( 1mm/day) in summer Change (in %) => Two sets of regional climate model simulations (driven by different global models) Disagreement in N Finland, maybe less days with rain in S Finland In winter: the frequency of wet days will increase Ref: Jylhä et al. (29)

38 Longest period without rain in summer Change in length (in %) => Two sets of regional climate model simulations (driven by different global models) Disagreement among model simulations in Finland In winter: decreases in the duration of dry spells Ref: Jylhä et al. (29)

39 Mid-latitude cyclone track density (ERA4) All systems Change by the end of the century Systems per winter (ONDJFM) Blue: decrease Red: increase A largely reduced total number of cyclones in the Northern Hemisphere Leckebusch et al. (28)

40 Mid-latitude cyclones and storms All systems Blue: decrease Red: increase Extreme systems Systems per winter (ONDJFM) An increasing number of extreme cyclones over the Northeast-Atlantic and the British Isles (Gt C/year) Emissions Leckebusch et al. (28)

41 35 Exceptionally strong geostrophic wind* in western Finland 99th, 95th ja 9th percentiles Observations in climate models in Wind speed (m/s) Tuulen nopeus (ms -1 ) % 95 % 9 % LK1v99% LK1v95% LK1v9% 99%C41 95%C41 9%C41 99%METNO 95%METNO 9%METNO 99%CNRM 95%CNRM 9%CNRM 99%KNMI 95%KNMI 9%KNMI 99%MPI 95%MPI 9%MPI LK99mal LK95mal LK9mal Vuosi * Actual wind speed at 1 m is about half of that % 95% 9% Ref: Elina Suvilampi

42 Emissions of greenhouse gases and aerosols depend on the future actions of the mankind Progress in the model simulation of the climate system but uncertainties remain Internal climate variability Summary (1/3) There are inherent uncertainties involved in climate change projections LEVEL OF UNCERTAINTY Near future End of the century Natural climate variability + + Climate model sensitivity (+) ++ Emission scenarios ++

43 Summary (2/3) It is likely that we will never be able to make predictions that are detailed enough and certain enough to make a 'predict and adapt approach to adaptation a viable option. It is important to look at the range of projections from different models rather than just relying on one outcome chosen from many possibilities.

44 Summary (3/3) The probability that in Finland the next full decade (211 22) will be warmer than the baseline period appears to exceed 95%. By the end of this century, the annual mean temperature is projected to increase by 2 6ºC. In winter by 3-9ºC and in summer by 1-5ºC. During the next few decades, changes in precipitation will still be affected more strongly by natural variability than by increasing GHGs conc. By the end of this century, precipitation amounts will increase by 5-25%. In winter by 1-4% and in summer by -2%. Thermal summer and thermal growing season will lengthen by months. Hot summer days and hot spells become more common Decreases in max/mean snow water equivalent and # of snow cover days largest in SW Finland. More frequent freezing point days in Dec-Feb. Possibly less days with rain in summer in southern Finland Minor changes in windiness

45 Effects of a changing climate and hydrology on renewable energy* risks and opportunities for renewable energy* caused by climate change * incl. bioenergy Oslo, Norway, 31 May - 2 June 21 Nordic and Baltic conference on Future Climate and Renewable Energy Impacts, Risks and Adaptation

46 THANK YOU FOR YOUR ATTENTION! Jylhä, K., Ruosteenoja, K., Räisänen, J., Venäläinen, A., Tuomenvirta, H., Ruokolainen, L., Saku, S. and Seitola, T., 29: The changing climate in Finland: estimates for adaptation studies. ACCLIM project report 29. Finnish Meteorological Institute, Reports 29:4, 12 s. (In Finnish, abstract, extended abstract and captions for figures and tables also in English)