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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Profile of temperature change