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Transcript of Climate v Weather: Climate Climate v Weather: Climate Services Simon Mason simon@iri. The

  • Climate v Weather: Climate Services

    Simon Mason simon@iri.columbia.edu

    The Climate-Weather Connection

    New York, NY, U. S. A., 24 September 2014

  • 2   The  Climate-­‐Weather  Connec2on  

    Date:  Friday  24  September  1993   Request:  forecasts  for  Saturday  23  and  30  April  1994  

    Climate  Services  

    The  academic   The  sleazy  salesman   The  equivocator   The  voice  of  authority  

  • 3   The  Climate-­‐Weather  Connec2on  

    Climate  v  Weather   “Climate  is  what  you  expect;   weather  is  what  you  get.”  

    Ed  Lorenz  

    What  if  you  do  not  know  what  to  expect?  

    What  if  you  expect  almost  anything  can  happen?   The  Bri2sh,  he  thought,  must  be  gluSons  for   sa2re:  even  the  weather  forecast  seemed  to  be   some  kind  of  spoof,  predic2ng  every  possible   combina2on  of  weather  for  the  next  twenty-­‐ four  hours  without  actually  commiTng  itself  to   anything  specific.  

     David  John  Lodge,    Changing   Places  

  • 4   The  Climate-­‐Weather  Connec2on  

    Spot  the  Ball  Compe33on   Where  is  the  ball  now?  

    Where  will  it  be  in  20  seconds?   Who  will  win  the  match?  

    What  is  the  current  weather?  

    What  will  it  be  on  Saturday?   Will  winter  be  unusually  wet?  

  • 5   The  Climate-­‐Weather  Connec2on  

    Sources  of  Predictability  

    •  We  can  make  forecasts  at  different  2mescales  because  there   are  different  reasons  why  the  predic2ons  can  work:  

    –  days:  current  weather   – months:  sea-­‐surface  temperatures   –  years:  sub-­‐surface  ocean  temperatures   –  decades:  atmospheric  composi2on  

  • 6   The  Climate-­‐Weather  Connec2on  

    Making  seasonal  forecasts   I:  Models  of  past  sta3s3cs  -­‐  correla3ons  

    How  have  past  El  Niño  events  affected  the  weather?  

     Typical  El  Niño  impacts  during  December  -­‐  February  

  • 7   The  Climate-­‐Weather  Connec2on  

    Making  seasonal  forecasts   II:  Models  of  the  physics  –  causa3on  

    How  might  this  El   Niño  affect  weather?  

    Run  lots  of  forecasts,   ideally  using  a   selec2on  of  models.   Do  many  of  the   forecasts  agree?  

  • 8   The  Climate-­‐Weather  Connec2on  

    Do  seasonal  forecasts  work?  

    How  well  can  we  predict  seasonal  rainfall  totals?  

  • 9   The  Climate-­‐Weather  Connec2on  

    Climate  Services  

    It  is  in  the  very  nature  of  probability   that  improbable  things  will  happen.  

     Aristotle,  Rhetoric  

    Climate  services  involve  specifying  precisely  how   improbable  the  improbable  is,  by:   •  understanding  the  past;   •  analyzing  the  present;   •  predic2ng  the  future.  

  • Simon J. Mason simon@iri.columbia.edu

    web: iri.columbia.edu

    @climatesociety  

    …/climatesociety