Global Change: a challenge for climate modeling

1
Global Change a challenge for climate modeling

• Arnaud.Caubel_at_cea.fr
• DSM/LSCE

2
Some clues of the global warming
Water vapor with respect to 1975-1995 average
3
Some clues of the global warming
Global Temperature 200-2000 AD
4
Some clues of the global warming
5
International Context IPCC

• International Panel on Climate Change (IPCC)
  writes an assessment report every 5 years.
• Next report is due for January 2007.
• The report is based on published scientific
  results, from Earth observation and from
  numerical modeling.

6
IPCC Assessment report 2007, back plan

• 2003/09 - 1st IPCC lead authors meeting, draft 0
  of IPCC report. Groups commits on simulations,
  and discuss preliminary results.
• 2004/10- 2nd lead authors meeting.
• 2005/05 - 3nd lead authors meeting. Discussion
  only of published results. All simulations are
  done, analysed, and published.
• 2006/09 - Final report ready.
• 2007/01 - Plenary session of working group 1.
  Report approved.
• IPCC 2012 Discussions, models developments
  already started

7
Different Steps

• Develop a model different time scales
• Perform simulations 
• Do some science
• Missing links, next steps

8
Different time scales from seconds to days
9
Different time scales from days to weeks
Phytoplancton
Relative vorticity
Biological pump of CO2
10
Different time scales from centuries to
milleniums
11
Develop a model different time scales
12
IPSL Earth Climate Model
Energy, water cycle
Circulation, precip ..
SST, ice extent
Evap., rivers 
Vegetation, soil carbon
Biogeochemistry
CO2
Carbon cycle
NOx, O3
DMS
Iron
CH4, VOCs, Aerosols
Chemistry, aerosols
Chemistry
Sea salt
Aerosols
Polluant emissions
CO2 emissions
Deforestation, land use
Human activities
13
IPSL Earth Climate Model
LIM
ORCHIDEE
Sea-ice
Land surface Soil and Vegetation
ORCA
OASIS
LMDZ
Ocean
Coupler
Atmosphere
Atmospheric fields Solar Heat Flux (on ice and
ocean) Non Solar Heat Flux (on ice, ocean and
derivative) Evaporation (ice and
water) Precipitation (solid and liquid) Runoff
(direct and river) Iceberg calving Wind stress
Oceanic fields Sea ice fraction Sea ice albedo
(weighted) Sea ice surface temperature
(weighted) Sea surface temperature (weighted)
14
Development and validation
Surface temperature, difference with climatology.
Simulated Precipitation Observations
15
Development and validation
2001 results from 3 models
White observations, colors models
16
Scenarios
IPCC simulations
17
Simulations

• Control simulations (mandatory) long
  simulations
• Pre-industrial gases 
• Present gase.
• IPPC simulations IPCC (given economic scenarios)
• XXth century simulations 
• XXIth century simulations 
• Other simulations to participate to international
  model intercomparison projects.
• Simulations for our own studies of climate change
• Water cycle modeling 
• Climate-carbon coupling 
• Land-use 
• Coupling between climate, aerosols and chemistry.

16000 hours CPU
32000 hours CPU
32600 hours CPU
80 000 Hours
18
Simulations - Machines

• Two singulars points
• ?x 0 numerical stability (CFL criterion).
• Two classical solutions 
• High latitudes filter
• Spectral model
• Problems for massive parallelism
• Small grid size
• A lot of exchanges

Each IPCC simulation spent 3 months on vector
machine reduced resolutions (92x76x19) for
IPSL.
19
Results 1860-2000
Without sulfates
Observations
With sulfates Direct effect and 1st indirect
effect.
20
Results
21
Missing links

• Coupling climate and carbon cycle 
• Aerosols (sulfate), chemistry (CH4, O3) 
• Land use

22
Whats next ?
23
Paysage d'hiver, Pieter Brueghel le Jeune
(1564-1637/8)