The art of climate modeling

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The art of climate modeling
David Noone, Phil Rasch, Natalie Mahowald
NCAR ASP Colloquium, June 2006
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This talk

• Motivation for the colloquium
• Overview of the next two weeks
• Few details on tutorials and projects
• Things you must do by the end of today
• Project group and topic
• Computer ready for todays tutorial
• your laptop works (X-windows/ssh)
• your accounts work (cryptocards)

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Many thanks to

• Folks at NCAR Advanced Study Program
  (ASP)Kathleen Barney, Scott Briggs, Paula
  Fisher, Maura Hagen
• TutorsChristine Shields, Dani Coleman, Keith
  Lindsay, Dave Bailey, Sam Levis
• HelpersMatt Rothstein, Rich Neale, and Tutors
• Lecturers for donating their time and effort to
  visit Boulder

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Welcome to Boulder
Boulder is at 5430 feet a.s.l. (1655 m) (NCAR
Mesa Lab is 280 m higher) Sunny and dry drink
lots of water, use lots of sunscreen (especially
if going on hikes)

• Climate 4 June
• Ave High 75 F Ave Low 50 F
• Record High 94 F (1990)
• Record Low 38 F (1951)
• May hotter than 57 year mean (76 F vs 72F, 8th
  hottest)
• May drier than 57 year mean (29 mm vs 77 mm, 5th
  driest)
• Is this climate change?

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Observed temperature(Instrumental record)
Greenhouse gases, aerosols, solar variability,
volcanoes, ocean circulation patterns
Climate is not just temperature
IPCC, TAR
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Climate signals in proxy records
Etheridge et al.
CO2 in bubbles from Law Dome ice core
Climate signals seen in even the smallest parts
of the climate system
Temperature based on rings
Mann et al. Hockey Stick
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Correlation is not causality! Not necessarily
understanding. Quantify and demonstrate
knowledge by modeling.
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Not just global warming, but understanding the
coupled system
Expected 2100 (ppm)
Today (365 ppm)
Forcing response External and internal
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What is a model?(Key ingredients)

• State variables what quantifies climate
• Rules that govern changes
• Conservation rules(energy, momentum, mass
  often define state)
• Diagnostics (output)
• Choices what processes are important, which
  aspects can be ignored, how much
  complexity/detail. This choice is art.
• Ideally, measure of error or uncertainty
• Also, method for validation. Is there a model
  prediction that can be tested with observations?

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Climate system models
Atmosphere (momentum, temperature, mass, humidity)
Atmospheric chemistry
Terrestrial biology
Sea ice
Land surface
Ocean biology
Ocean chemistry
Ocean(momentum, temperature, salinity, mass)
CCSM is structured more-or-less like this.
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• "Several sciences are often necessary to form the
  groundwork of a single art" - Mills, 1843
• "Science is knowledge which we understand so well
  that we can teach it to a computer and if we
  don't fully understand something it is an art to
  deal with it" - Knuth, 1974

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Models vs. data
Both anthropogenic and natural forcing (e.g.,
solar and volcanic aerosol) are required to
explain historical changes
Model allows hypothesis testing.
But does the match mean the model is correct?
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Projecting climate change
Temperature
Emissions

• Uncertainty about human decisions
• Uncertainty in physical feedbacks and coupled
  behavior
• Uncoupled response may be simple, but coupled
  response may not.
• Processes that couple often non-linear, and can
  be subtle.

CO2
IPCC, TAR
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Objectives for the colloquium

• Explore coupled climate problems
• Develop sense of what models can do to help
• Have a working knowledge of parts of a climate
  model and the theoretical basis for those parts
• Understand limitations of models, and how
  construct a research methodology that exploits
  model strengths
• Understand limitations, and what would be needed
  to improve models
• At end of 2 weeks, you should be able to use and
  modify CCSM for your own research thesis and
  beyond.
• No exams, no grades. Just the science and
  learning. The more you put in the more you get
  out.
• Ask lots of questions

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Notes on agenda

• Lectures - 2 or 3 per dayThis week Intro to
  coupled models, atmosphere, ocean, land and sea
  iceNext week more focused on climate system.
• Tutorials one each day this weekAimed to
  develop skills needed to run CCSM.Today
  Building and running CCSM, navigating
  supercomputers. Then atmosphere, ocean, sea ice,
  land focus.
• Projects start today! (And will be the focus
  of lab time next week)

Each day has combinations of the three.
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Projects

• This is the primary task for the two weeks, and
  should be given you fullest attention.
• Projects are your (groups) work
• Open ended, unlikely to be an known answer(How
  will you know if model experiments work?)
• Mentors are there to be a resource and will help
  guide scope of projects, but definition and
  refinement of project topics and tasks are yours
• Presentation of project outcome next Friday.
• PlanningToday, 5 minutes presentation by
  mentors.
• By the end of lunch, you need to submit your top
  3 preferences for projects.
• At 4 pm we will meet in project groups to discuss
  details of
• a) project title and aim (report back to
  group)b) type of experiments to runc) ideally,
  an outline plan for how to proceed
• Note scope of projects limited to experiments
  that can be done with the order of 10 year model
  simulations.
• Meet daily with mentors during office hours, plus
  some longer discussions in the agenda

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Tutorials

• Build, run, analyze, modify the model
  input/output, modify the model Fortran code.
• Develop skills to help with project work, and
  for your thesis work!
• Today Intro to CCSM (3 hours, Christine
  Shields)
• Tuesday Atmosphere focus (2 hours, Dani
  Coleman)
• Wednesday Ocean focus (1 hour, Keith Lindsay)
• Thursday Sea ice focus (1 hour, Dave Bailey)
• Friday Land focus (1 hour, Sam Levis)

Tutorial assignments and some NCL scripts are on
the wiki.
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Lectures

• Range of topics on climate system modeling by
  experts gathered from around the US.
• This week, aimed to introduce coupled models by
  focusing on each part of the CCSM, and science
  problems typical with each component.
• Next week, broader climate system
• Plenty of time after lectures for discussion.
• Lecturers will be around for at least a few days
  feel free to quiz them on any related topics.
  They may have useful suggestions on your project!
• Typically in the morning and after lunch.

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Community Climate System Model(CCSM)

• Atmosphere (CAM)
• Ocean (POP)
• Land (CLM)
• Sea ice (CSIM)
• As users of CCSM, please be considerate of the
  science others have invested/are investing in
  code
• Also, when using computers, be mindful of
  resource use and other users (this group, and all
  other users)

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Notes on logistics

• Challenging workshop
• Hopefully all important resources on wiki
  (notes, tutorials, ) http//atoc.colorado.edu/d
  cn/ACM
• Any logistical problems ask David, Natalie or
  Phil (who will probably direct you to Scott
  Briggs or Kathleen Barney)
• Computer problems ask tutors, tutorial/project
  helpers, or Scott. Mentors may also know.
• Meals in NCAR cafeteria (just downstairs), and
  coffee breaks in Damon room.
• Lots of details on ASP web sitehttp//www.asp.uc
  ar.edu/colloquium/2006/climate-model/logistics.jsp

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All work no play?

• Dinner together tonight
• Movie night tomorrow
• B.B.Q. at Phils house Saturday(transportation
  details to come)
• Weekend to explore Boulder area
• Plenty great science can be done on hikes around
  NCAR at lunchtime!

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• Reminder 1If you using your laptop, please check
  that it works before the tutorial. i.e., during
  lunchtime or at 1 pm.
• Reminder 2Be sure you can log on to the
  supercomputers using your cryptocard