© Crown copyright Met Office AR5 Proposed runs for CMIP5 John Mitchell, after Karl Taylor, Ron Stouffer and others ENES, arch 2009

© Crown copyright Met Office

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

ENES, arch 2009


Change in IPCC philosophy

Short and long term predictions

Runs and analysis


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


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.


Strategy for AR5


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


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



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


Basic runs (ctd)

• 1%/increase CO2 (140 years)

• Abrupt 4xCO2 (150 years)

• Fixed SST with 1x and 4x CO2


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


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.


Control, model evaluation



20th Century temperature change – CMIP3 ensemble

Philip Brohan

Diagnose radiative forcing –especially that due to aerosols!



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




Questions

Documents

© Crown copyright Met Office AR5 Proposed runs for CMIP5 John Mitchell, after Karl Taylor, Ron Stouffer and others ENES, arch 2009