OECD Workshop on the benefits of climate policy. Paris, 12/13 December 2002 UNCERTAINTIES IN CLIMATE CHANGE PREDICTIONS Geoff Jenkins Hadley Centre MetOffice,UK Hadley Centre for Climate Prediction and Research 1 CLIMATE CHANGE DEPENDS UPON: • How man-made emissions grow – population, GDP, energy use, technology... • How sensitive the climate system is to emissions – how much concentrations change – what forcing effect this has – what climate change this produces – we can estimate this only with climate models Hadley Centre for Climate Prediction and Research 2 Page 1 UNCERTAINTIES IN CLIMATE PREDICTIONS EMISSIONS • Emissions uncertainty • “Science” uncertainty CONCENTRATIONS feedbacks • Natural variability FORCING GLOBAL CLIMATE REGIONAL CLIMATE NATURAL VARIABILITY IMPACTS, COSTS etc Hadley Centre for Climate Prediction and Research 3 CO2 in SRES EMISSIONS SCENARIOS A1FI A2 B1 B2 Hadley Centre for Climate Prediction and Research 4 Page 2 GLOBAL TEMPERATURE RISE IPCC A1FI emissions A2 emissions B2 emissions B1 emissions Start to diverge from mid-century Global temperature rise, degrees C HadCM3 Hadley Centre for Climate Prediction and Research 5 UNCERTAINTY IN CO2 CONCENTRATIONS Hadley 1000 975 coupled GCM ppm 900 850 Bern High 700 620 550 IPCC Bern Low 400 2000 2025 2050 2075 2100 Hadley Centre for Climate Prediction and Research 6 Page 3 CLIMATE FORCING (to 2000) 3 GHG 2.5 2 1.5 1 FF 0.5 sulphate black C indirect direct aerosol 0 -0.5 12345FF -1 org C -1.5 -2 Source: IPCC TAR Hadley Centre for Climate Prediction and Research 7 WINTER ENGLAND & WALES PRECIPITATION observed to 1999; predicted to 2050 Change relative to 61-90 average (mm) Hadley Centre for Climate Prediction and Research 8 Page 4 CHANGE IN DJF PRECIPITATION (%) 2080s - present, SRES A2, 3-member initial condition ensemble Hadley Centre for Climate Prediction and Research 9 GLOBAL PRECIPITATION CHANGE due to A2 emissions, predicted by 9 climate models ±70% Source: IPCC, 2001 Hadley Centre for Climate Prediction and Research 10 Page 5 CHANGE IN GLOBAL PRECIPITATION HadCM3 under a range of emissions scenarios ±25% Change in global precipitation (mm/day) Hadley Centre for Climate Prediction and Research 11 % CHANGE IN WINTER PRECIPITATION 2080s, A2 Hadley Centre for Climate Prediction and Research 12 Page 6 SEA LEVEL RISE REGIONAL VARIATIONS due to thermal expansion and ocean circulation changes only Source: IPCC 0 0.1 0.2 0.3 0.4 0.5 0.6 m Hadley Centre for Climate Prediction and Research 13 GJJ1999 CLOUDS AND CLIMATE Low clouds reflect sunlight but trap little infra-red radiation; They act to cool climate High clouds reflect sunlight but also trap infra-red radiation; They act to warm climate Global warming may change the characteristics of clouds, and thus alter their current net cooling effect; this could exert a powerful feedback on climate change. Hadley Centre for Climate Prediction and Research 14 Page 7 PROBABILISTIC CLIMATE PREDICTIONS current position future position 100% Probability Probability -40% -30% -20% -10% 0% -40% -30% -20% -10% 0% 2050s Paris summer rainfall 2050s Paris summer rainfall Hadley Centre for Climate Prediction and Research 15 PROBABILITY PREDICTIONS • Generate X (50 - 1000) climate models by varying parametrisations within plausible limits • Make simulation (1900-2100) with each model • Assess credibility of each model based on current climatology and 1900-2000 simulation • Weight prediction (2000-2100) according to model credibility • Use X runs to generate pdf of a specific change • pdf can be used direct in risk analyses • next: do this with other climate models Hadley Centre for Climate Prediction and Research 16 Page 8 PROBABILISTIC CLIMATE PREDICTIONS X CLIMATE MODELS ATMOSPHERE + CLOUDS LAND AND Probability VEGETATION CARBON CYCLE OCEAN CIRCULATION ETC. -40% -30% -20% -10% 0% 2050s Paris summer rainfall Hadley Centre for Climate Prediction and Research 17 RESOLUTION OF CLIMATE SCENARIOS 1998: GLOBAL MODEL 2002: REGIONAL MODEL 300km grid 50km grid Hadley Centre for Climate Prediction and Research 18 Page 9 SIMULATION OF A TROPICAL CYCLONE in the PRECIS regional climate model Global climate model Regional climate model Met Office/Hadley Centre Hadley Centre for Climate Prediction and Research 19 REGIONAL MODEL PREDICTIONS OF CHANGE IN WINTER PRECIP BY 2080s Rossby RCM Hadley RCM Both RCMs driven by Hadley Centre HadCM3 GCM Hadley Centre for Climate Prediction and Research 20 Page 10 EMISSIONS AND CONCENTRATIONS OF CO2 from unmitigated and stabilising emission scenarios 20 1000 950 900 15 850 800 750 emissions (GtC/yr) 700 10 2 650 600 2 550 5 CO concentration (ppm) 500 450 Anthropogenic CO 400 0 350 2000 2050 2100 2150 2200 2250 2300 2350 2000 2050 2100 2150 2200 2250 2300 2350 Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation Source: IPCC Hadley Centre for Climate Prediction and Research 21 GLOBAL AVERAGE TEMPERATURE RISE from unmitigated and stabilising emission scenarios Met Office/Hadley Centre 4 3 2 1 Global temperature change (°C) 0 1900 2000 2100 2200 Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation Hadley Centre for Climate Prediction and Research 22 Page 11 CROP YIELD changes from the present day to the 2080s Potential change in cereal yields (%) 10–5 5–2.5 2.5–0 HadCM2 0–-2.5 -2.5–-5 -5–-10 -10–-20 No data Unmitigated emissions Stabilisation of CO2 at 750 ppm Stabilisation of CO2 at 550 ppm University of East Anglia/ IIASA Austria /Universidad Politecnica de Madrid/Goddard Institute for Space Studies Hadley Centre for Climate Prediction and Research 23 ANNUAL NUMBER OF PEOPLE FLOODED with no climate change and under three emissions scenarios 100 University of Middlesex 80 60 HadCM2 40 People flooded20 (millions/year) 0 2020s 2050s 2080s Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation No climate change Hadley Centre for Climate Prediction and Research 24 Page 12 CHANGES IN STORED CARBON 1860-2100 Soil carbon – 10 –5 – 4 –3 –2 – 11 2 3 4510 Change in carbon content (kg C per square metre) Vegetation carbon Hadley Centre coupled climate carbon-cycle model Hadley Centre for Climate Prediction and Research 25 EFFECT ON CO2 CONCENTRATION OF CARBON CYCLE FEEDBACK Met Office / Hadley Centre with carbon cycle 1000 without carbon cycle 800 600 CO2 concentrations (ppmv) 400 200 1900 1950 2000 2050 2100 Hadley Centre for Climate Prediction and Research 26 Page 13 EFFECT ON LAND TEMPERATURES OF CARBON 8 CYCLE FEEDBACK with carbon cycle without carbon cycle 6 4 2 Temperature rise (°C) 0 Met Office / Hadley Centre –2 1850 1900 1950 2000 2050 2100 Hadley Centre for Climate Prediction and Research 27 Impact of carbon cycle feedbacks on CO2 concentrations (WRE550) Hadley Centre for Climate Prediction and Research 28 Page 14 Cumulative emissions consistent with WRE550 CO2 concentration scenario Hadley Centre for Climate Prediction and Research 29 Impact of carbon cycle feedbacks on stabilisation level Hadley Centre for Climate Prediction and Research 30 Page 15 SUMMARY: HANDLING UNCERTAINTIES IN CLIMATE CHANGE PREDICTIONS • Emissions uncertainty – first half C21: uncertainty small∴ ignore – beyond: “scope” using range of SRES scenarios • Science uncertainty – larger than SRES emissions uncertainty – initially: use a range of climate model results (“calibrated” using 1990-2000 simulations) – soon: probability predictions • Natural variability – quantify via initial condition ensemble Hadley Centre for Climate Prediction and Research 31 Page 16.