The SANTA FE project

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The SANTA FE project

• Jean-François Lamarque

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Brief history

• 1st Chemistry-Climate Interactions workshop in
  February 2003, Santa Fe
• Variety of speakers to discuss potential
  feedbacks between chemistry (gas-phase, aerosols,
  clouds) and climate
• Define a project to look at nitrogen deposition
  (Sequential analysis of nitrogen

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     Scientific     Analysis (of)     Nitrogen
(Cycle)     Towards     Atmospheric    
Forcing     Estimation
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Goal of the project

• Look at the evolution of nitrogen deposition on
  the terrestrial biosphere during the 21st century
• Look at the impact on the carbon uptake
• Force the climate model with the updated CO2
  forcing

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Approach (1)

• Run climate models (GISS, NCAR, UKMO) with A2
  scenario to construct a separate SSTs and
  climates
• Use a variety of online and offline chemistry
  models (GISS, Harvard, IPSL, LLNL, MPI-Hamburg,
  MPI-Mainz, NCAR, UKMO) to calculate nitrogen
  deposition (emissions are specific to each group)

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Approach (2)

• Look at the impact of climate change only and of
  emissions change only
• Force CLM at T31 using each nitrogen deposition
  field
• Look at the spread of results as a lower bound on
  the uncertainty on the results

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Status (simulations available)
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Status (simulations in progress)
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Time table

• Compile all nitrogen deposition estimates and
  write paper by summer 2004
• Perform the CLM simulations and write paper by
  fall 2004
• The goal is to be available for the next IPCC
  assessment

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Normalized Ndep
Dry deposition
Wet deposition
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(No Transcript)
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(No Transcript)
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Global NOx emissions (lightning)
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Comparison with observations (EMEP)
Plots by J. Sulzman
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Comparison with observations (NADP)
Plots by J. Sulzman
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Comparison with observations

• Poor skill over European stations (on average
  models tend to be lower)
• Good skill over US stations, with a tendency to
  overestimate nitrogen deposition (10) at large
  values

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Analysis of Ndep totals
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Analysis of Ndep
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Normalized Ndep
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Conclusions

• Global increase in Ndep tends to closely follow
  the increase in emissions, especially in the NCAR
  model. Unclear if the increase in other models
  from climate change is statistically significant
• What is happening to GISS_2100?
• The hydrological cycle (as identified by
  lightning and wet deposition) in the GISS model
  seems to have a stronger response to climate
  change than other models, except with the NCAR
  SSTs