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Can	  we	  detect	  long-­‐term,	  global	  change	  from	  sparse,	  135-­‐year-­‐old	  ocean	  data?	  Will	  Hobbs:	  U...
Ar#st:	  John	  Steven	  Dews	  1.  Does	  the	  HMS	  Challenger	  data	  provide	  a	  reasonable	  esNmate	  of	  globa...
SpaNal	  sampling	  error	  Trend	  implies	  bias	  in	  ΔT	  st.	  deviaNon	  indicates	  random	  error	  	  Total	  un...
Sounding	  line	  error	  StaNons	  prone	  to	  bias	  are	  clustered	  in	  the	  Pacific	  Equatorial	  Counter	  Curre...
Summary	  of	  uncertainNes	  StaNons	  prone	  to	  bias	  are	  clustered	  in	  the	  Pacific	  Equatorial	  Counter	  C...
Significance	  of	  temperature	  change	  –	  natural	  variability	  PDFs	  are	  based	  on	  1000	  random	  temperatur...
Temperature	  change	  over	  Nme	  ’historical’	  simulaNons	  show	  ΔT	  consistent	  with	  Argo-­‐Challenger	  esNmat...
3)	  Thermosteric	  sea	  level	  rise	  0.54	  mmyr-­‐1	  (Levitus	  et	  al,	  2012)	  0.50	  mmyr-­‐1	  0.74	  ±	  0.3	...
3)	  Thermosteric	  sea	  level	  rise	  0.74	  ±	  0.3	  mmyr-­‐1	  Component	   Early	  20th	  Century	  	  Source	  Sub...
Conclusions	  •  The	  HMS	  Challenger	  observaNons	  provide	  a	  reasonable	  proxy	  of	  global-­‐mean	  ocean	  te...
Profile	  of	  temperature	  change	  
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New Analysis of Old Ship Temperature Data Finds Ocean Warming Signature

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Here's the paper abstract: http://onlinelibrary.wiley.com/doi/10.1002/grl.50370/abstract

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New Analysis of Old Ship Temperature Data Finds Ocean Warming Signature

  1. 1. Can  we  detect  long-­‐term,  global  change  from  sparse,  135-­‐year-­‐old  ocean  data?  Will  Hobbs:  University  of  Tasmania,  IMAS  Josh  Willis  :Caltech/NASA  Jet  Propulsion  Laboratory  
  2. 2. Ar#st:  John  Steven  Dews  1.  Does  the  HMS  Challenger  data  provide  a  reasonable  esNmate  of  global  ocean  temperature?  2.  Is  the  esNmated  change  significantly  different  from  natural  variability,  parNcularly  prior  to  IGY?  3.  ImplicaNons  for  historical  esNmates  of  sea-­‐level  rise  
  3. 3. SpaNal  sampling  error  Trend  implies  bias  in  ΔT  st.  deviaNon  indicates  random  error    Total  uncertainty=  bias  +  √  (2  x  rand.  error2)    ±0.17oC  ±0.13oC  
  4. 4. Sounding  line  error  StaNons  prone  to  bias  are  clustered  in  the  Pacific  Equatorial  Counter  Current,  and  tend  to  show  cooling.    EliminaNon  of  these  staNons  increases  0-­‐730m  ΔT  by  0.06oC  (~  17  %)  
  5. 5. Summary  of  uncertainNes  StaNons  prone  to  bias  are  clustered  in  the  Pacific  Equatorial  Counter  Current,  and  tend  to  show  cooling.    EliminaNon  of  these  staNons  increases  0-­‐730m  ΔT  by  0.06oC  (~  17  %)  0-­‐730m  (0-­‐400  fm)   0-­‐1822m  (0-­‐1000  fm)    Precision    ±  0.014  oC   ±  0.014  oC  Sampling  error    ±  0.17  oC   ±  0.13  oC  Total    ±  0.17  oC   ±  0.13  oC  Sounding  line  bias    -­‐  0.06  oC  ?   -­‐  0.03  oC  ?  
  6. 6. Significance  of  temperature  change  –  natural  variability  PDFs  are  based  on  1000  random  temperature  differences  for  each  model,  between  Challenger  staNon  sub-­‐sampled  four  year  esNmates    99%  confidence  level  shown  by  red  line  Global  AtlanNc  Pacific  
  7. 7. Temperature  change  over  Nme  ’historical’  simulaNons  show  ΔT  consistent  with  Argo-­‐Challenger  esNmates  No  simulated  warming  in  ’historicalNat’  experiments  ’historical’  –  ‘historicalNat’  improves  agreement  between  models,  and  with  obs.  Argo-­‐Challenger  Levitus  et  al,2012  
  8. 8. 3)  Thermosteric  sea  level  rise  0.54  mmyr-­‐1  (Levitus  et  al,  2012)  0.50  mmyr-­‐1  0.74  ±  0.3  mmyr-­‐1  1.3  mmyr-­‐1  
  9. 9. 3)  Thermosteric  sea  level  rise  0.74  ±  0.3  mmyr-­‐1  Component   Early  20th  Century    Source  Sub-­‐2000m  thermosteric   O(10-­‐10  mmyr-­‐1)   CMIP5  historical    Glaciers  &  ice  caps   0.59-­‐0.68  mmyr-­‐1   Gregory  et  al,  2013  (1900-­‐1970)  Ice  sheets  -­‐  Greenland   -­‐0.33  to  0.31mmyr-­‐1    Gregory  et  al,  2013  (1900-­‐1970)  Terrestrial  storage   -­‐0.16  to  -­‐0.11  mmyr-­‐1  Gregory  et  al,  2013  (1900-­‐1970)  Total   0.49  (±  0.3)  mmyr-­‐1   Big  pinch  of  salt!  ‘Missing’  component   0.25  ±  0.4  mmyr-­‐1  
  10. 10. Conclusions  •  The  HMS  Challenger  observaNons  provide  a  reasonable  proxy  of  global-­‐mean  ocean  temperature,  albeit  with  large  uncertainty  •  Even  accounNng  for  this  uncertainty,  the  implied  early  20th  century  warming  is  highly  likely  to  due  to  an  anthropogenic  forcing  •  The  Challenger-­‐1955  ΔT  esNmate  implies  a  non-­‐thermosteric  contribuNon  of  0.50  ±  0.3  mmyr-­‐1  for  the  early  20th  century  
  11. 11. Profile  of  temperature  change  

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