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.
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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
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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
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RESOLUTION OF CLIMATE SCENARIOS 1998: GLOBAL MODEL 2002: REGIONAL MODEL 300km grid 50km grid
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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
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