© crown copyright met office ar5 proposed runs for cmip5 john mitchell, after karl taylor, ron...

© Crown copyright Met Office

AR5 Proposed runs for CMIP5John Mitchell, after Karl Taylor, Ron Stouffer and others

ENES, arch 2009

© Crown copyright Met Office

Change in IPCC philosophy

Short and long term predictions

Runs and analysis

© Crown copyright Met Office

Socio-economic variables EmissionsSurface temperature

Socio-economic variables ConcentrationsSurface temperature

Forward approach: start with socio-economic variables

Reverse approach: start with stabilization scenario concentrations

Concentrations

Emissions

Pre AR4 used forward approachAR5 will use reverse approach

mitigation costs implied emissions concentrations sensitivity impacts

Requires interpolating and scaling

© Crown copyright Met Office

DEFINING SCENARIOS LONG-TERM 2005-2100

Reference concentration profiles

• High reference—~8.5 W/m2 in 2100 but rising RCP8.5

• High stabilization level—~6 W/m2 RCP6

• Median stabilization level—~4.5 W/m2 RCP4.5

• Low stabilization level—~2~3 W/m2 RCP2.X

ONLY the 2.x W/m2 scenario is at its stabilization level before 2100.

© Crown copyright Met Office

Strategy for AR5

© Crown copyright Met Office

Two classes of models to address two time frames and two sets of science questions:

1. Near-Term (2005-2030)high resolution (perhaps 0.5°), no carbon

cycle, some chemistry and aerosols, single scenario,

science question: e.g. regional extremes

2. Longer term (to 2100 and beyond)lower resolution (roughly 1.5°), carbon cycle,

specified or simple chemistry and aerosols, benchmark stabilization

concentration scenariosScience question: e.g. feedbacks

© Crown copyright Met Office

Groups of experiments (long term)

•Control, historical and AMIP simulations

•Future projections ( prescribed concentrations)

•Past and future (prescribed emissions)

•Runs to diagnose feedbacks, increase understanding

•Historical and AMIP runs

•Detection and attribution

© Crown copyright Met Office

© Crown copyright Met Office

Basic runs

Coupled AO models

• Control, AMIP & 20C

• RCP 4.5, 8.5

Carbon cycle models

• Emissions driven control and 20C

• Emissions driven RCP8.5

© Crown copyright Met Office

Basic runs (ctd)

• 1%/increase CO2 (140 years)

• Abrupt 4xCO2 (150 years)

• Fixed SST with 1x and 4x CO2

© Crown copyright Met Office

Carbon cycle feedbacks:• AOGCM and ESM experiment 1 (specified concentrations)

-give CO2 and climate vegetation feedback

• ESM experiment 2 (specified concentrations, radiation sees 1XCO2

- no climate change)

-with (1) gives climate vegetation feedback

• ESM experiment 3 (fully coupled CC, driven by emissions)

- check on full carbon cycle feedback

• ESM experiment additional ( specified concentrations, vegetation sees 1XCO2)

- With (1), check on CO2 vegetation feedback

© Crown copyright Met Office

Simulations to diagnose “fast” and “slow” climate system responses

4.1* Idealized 1%/yr run to 4xCO2 in coupled model. 4.3a* Control for Hansen-style experiment (4.3b) to diagnose “fast” climate

system responses (i.e. “forcing”) 4.3b* Hansen-style expt. to diagnose “fast” climate system responses, CO2

quadrupled, otherwise as in 4.3a. 4.3c** Hansen-style expt. to isolate the model’s “fast” response to CO2’s

greenhouse effect alone. As 4.3b but carbon cycle “seeing” 1xCO2 (rather than 4xCO2)

4.4* Diagnose “slow” climate system responses to an instantaneous quadrupling of CO2 in coupled model. Perform a Gregory-style analysis to diagnose the “slow” responses and estimate climate sensitivity.

4.5† Gregory-method estimate of the “fast” climate response with a 12? member

ensemble of 5-year runs in which CO2 is instantaneously quadrupled.

© Crown copyright Met Office

Control, model evaluation

© Crown copyright Met Office

© Crown copyright Met Office

20th Century temperature change – CMIP3 ensemble

Philip Brohan

Diagnose radiative forcing –especially that due to aerosols!

© Crown copyright Met Office

© Crown copyright Met Office

More Information

• WGCM Report

http://eprints.soton.ac.uk/65383

• Taylor, Stouffer et al

http://www.clivar.org/organization/wgcm/wgcm-12/reports/Taylor_CMIP5_expts7.pdf

© Crown copyright Met Office

Questions