4°c global warming: gg regional patterns and timing · • 4°c global warming (relative to...

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4°C global warming:

© Crown copyright Met Office

g gregional patterns and timing

Richard Betts, Mike Sanderson, Debbie Hemming, Mark New, Jason Lowe, Chris Jones

4°C+ conference, Oxford University, 25.9.09

IPCC SRES emissions scenarios


Van Vuuren and Riahi (2008)

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Model projections of global warming with IPCC SRES emissions scenarios

© Crown copyright Met Office IPCC (2007)

Comparison of SRES scenarios with actual emissions


Van Vuuren and Riahi (2008)

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Using climate model ensembles to assess confidence in projections

• Multi-model ensemble: set of (mostly) different models • IPCC 4th Assessment Report (AR4) – 23 models

• Perturbed physics ensembles: set of variants of one model• ClimatePrediction.net – HadCM3 model (1500+ variants)

• Met Office Hadley Centre (MOHC) “QUMP” project – HadCM3 model (17 variants)

Si l li t d l t d t th b l d l


• Simple climate model tuned to the above complex models• IPCC “likely range of warming” statements

• Combination of the above• UKCP09 – mostly HadCM3, with some input from IPCC AR4 models

A1B scenario


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Global warming with A1B scenario: all IPCC models

“High end”:High-end : simulations with 4°C warming by by 2090s


Pattern of warming by 2090s, A1B Mean of “high-end” IPCC simulations (3 models, mean global warming 4.3°C)

© Crown copyright Met OfficeTemperature change (°C) relative to 1961-1990

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Precipitation changes by 2090s, A1BMean of “high-end” IPCC simulations (3 models, mean global warming 4.3°C)

© Crown copyright Met OfficePrecipitation change (%) relative to 1961-1990

Global warming with A1B scenario: MOHC ensemble


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Pattern of warming by 2090s, A1BMean of “high-end” MOHC simulations (9 simulations, mean global warming 4.6°C)


Precipitation changes by 2090s, A1BMean of “high-end” MOHC simulations (9 simulations, mean global warming 4.6°C)

© Crown copyright Met OfficePrecipitation change (%) relative to 1961-1990

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A1FI scenarioscenario


Pattern of warming by 2090s, A1FIMean of “high-end” MOHC simulations (14 simulations, mean global warming 5.4°C)


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Precipitation changes by 2090s, A1FIMean of “high-end” MOHC simulations (14 simulations, mean global warming 5.4°C)


Global warming with A1FI scenario: MOHC ensemble


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Importance of carbon sinks for slowing CO2 rise

Emissions


Change in atmospheric concentration

IPCC (2007)

The free ecosystem service that has been buying us time may not last…

100

Gt C

) Carbon uptake by plants in 20th

century has buffered the past

–50

0

50

oval

s fr

om a

tmos

pher

e (G y p

CO2 rise

But climate change

© Crown copyright Met Office1850

–150

–100

50

1950 2000 2050 2100

Car

bon

rem

o

vegetation carbonsoil carbon

1900

may put this into reverse

Cox et al (2000)

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Effects of climate-carbon cycle feedbacks on atmospheric CO2 rise

1000 with CO2-climate feedbacks1000

800

600

without CO2-climate feedbacks

cent

ratio

ns (p

pmv) IS92a “business-as-usual” scenario


400

2001900 1950 2000 2050 2100

CO

2co

nc

Cox et al (2000)

Multi-model assessment of carbon cycle feedbacks (C4MIP): A2 emissions scenario


Friedlingstein et al (2006)

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Global mean temperature: SRES A1FI

Range of global warming projections for A1FI (high emissions) scenario, including carbon cycle feedbacks

Simple model tuned to complex models, consistent with IPCC method

3

4

5

6

7

8

ove

pre-

indu

stria

l

90th %ile

10th %ile

median


0

1

2

1980 2000 2020 2040 2060 2080 2100

Year

o C ab

o

Exceedance of global warming thresholds, A1B, no carbon cycle feedbacks: ClimatePrediction.net


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Conclusions

• Current CO2 emissions are near (but not above) upper end of IPCC iscenarios

• 4°C global warming (relative to pre-industrial) is possible by the 2090s, especially under high emissions scenario

• Many areas could warm by 10°C or more

• The Arctic could warm by 15°C or more

• Annual precipitation could decrease by 20% or more in many areas


• Annual precipitation could decrease by 20% or more in many areas

• Carbon cycle feedbacks expected to accelerate warming

• With high emissions, best guess is 4°C in 2070s

• Plausible worst case: 4°C by 2060

4°c global warming: gg regional patterns and timing · • 4°c global warming (relative to...

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