Poster layout by Louise Bell, CSIRO Marine and Atmospheric Research

Catia.Domingues@csiro.au Ph: +61-3-6232 5038

CSIRO Marine and Atmospheric ResearchGPO Box 1538, Hobart, Tasmania, 7004, Australia

Conclusions Our estimates show that the rate of ocean warming and thermosteric rise from 1961 to 2003 is about 50% larger than previously reported.

The closure of the sea level budget over multi-decadal periods, and the agreement of the observed and simulated ocean heat content decadal variability, increase confidence in the present results and represent progress since the last two IPCC reports1,17.

There is an ongoing need for careful quality control of ocean data and continuous monitoring of the oceans using diverse observations that can be checked against each other.

Our ocean warming (black) trends for 1961–2003 are about 50% larger than earlier estimates but about 40% smaller for 1993–2003. The large rise in the early 1970s and the subsequent fall, which dominate previous estimates, are mainly the result of instrumental biases7.

Comparison with previous upper-ocean (0–700 m) estimates

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The multi-decadal sea level budget

The sum of all contributions is consistent with the observed sea-level rise from 1961 to 2003.

The different decadal variability is probably an indication of the uncertainty in the estimates and the (unknown) variability in the cryospheric and deep-ocean contributions.

Satellite altimeter sea level diverges after 1999, implying a higher rate of rise. It is unclear why the in situ and satellite estimates diverge, and careful comparison is urgently needed.

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Deep Thermosteric Sea Level11,12

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Terrestrial Storage15

Sum of Above ContributionsSea Level (Tide Gauge)8

Sea Level (Tide Gauge)16

Sea Level 8 (Satellite Altimeter)

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Acknowledgements This paper is a contribution to the Commonwealth Scientific Industrial Research Organization (CSIRO) Climate Change Research Program and Wealth from Oceans Flagship and was supported by the Australian Government’s Cooperative Research Centres Programme through the Antarctic Climate and Ecosystems Cooperative Research Centre. C.M.D., J.A.C., N.J.W. and S.E.W. were partly funded by the Australian Climate Change Science Program. We acknowledge the modelling groups, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) and the WCRP’s Working Group on Coupled Modelling (WGCM) for their roles in making available the WCRP CMIP-3 multi-model data set. Support for P.J.G. and this data set at the Lawrence Livermore National Laboratory was provided by the Office of Science, US Department of Energy. The Centre for Australian Weather and Climate Research is a partnership between CSIRO and the Australian Bureau of Meteorology.

1 Centre for Australian Weather and Climate Research – A partnership between CSIRO and the Australian Bureau of Meteorology, CSIRO Marine and Atmospheric Research: GPO Box 1538, Hobart, Tasmania, 7004, Australia 2 Antarctic Climate and Ecosystems Cooperative Research Centre: Hobart, Tasmania, Australia

3 Program for Climate Model Diagnosis and Intercomparison: Lawrence Livermore National Laboratory, Livermore, CA, USA

Improved estimates of upper-ocean warming: implications for climate models and sea-level rise

Puzzles about ocean warming and sea-level riseTwo key uncertainties in the 2007 Intergovernmental Panel on Climate Change Report1,2 (IPCC AR4) are:

(1) Global mean sea-level rise from 1961 to 2003 is larger than the sum of all known contributions.

(2) The large decadal variability in global mean ocean heat content (thermosteric sea level) observed during the 1970-1980s is not reproduced by climate models.

What are the difficulties? Incomplete global coverage could result in inaccurate (possibly biased) estimates of global ocean heat content.

Systematic biases have been discovered3 in temperature data from eXpendable Bathy-Thermographs (XBTs), associated with errors in the estimated depth. XBT data comprise more than 50% of the ocean observing system.

ObjectiveTo estimate quasi-global (65ºS to 65ºN) ocean heat content and thermosteric sea level for the upper 700 m of the oceans, from 1950 to 2003.

MethodWe use a reduced-space optimal interpolation technique4,5,6 to recover the large-scale robust climate signals that can be derived from sparse ocean data. To minimise the XBT biases, we apply a recent time-variable fall-rate correction7.

Comparison with climate model simulations including anthropogenic and other forcings

Models without volcanic forcing

The decadal variability in models without volcanic forcing is not in good agreement with the observations. The simulated multi-decadal trends overestimate the observed ocean warming.

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GISS−AOMGISS−AOMFGOALS−g1.0FGOALS−g1.0FGOALS−g1.0UKMO−HadCM3UKMO−HadCM3

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References 1. Bindoff, N.L. et al., Chapter 5, IPCC (2007).

2. Solomon. et al., Technical Summary, IPCC (2007).

3. Gouretski, V. & Koltermann, K.P., Geophys. Res. Lett. 34: L01610, doi:10.1029/2006GL027834 (2007).

4. Kaplan, A. et al., J. Clim., 13, 2987-3002 (2000).

5. Church, J.A. et al., J. Clim. 17, 2609-2625 (2004).

6. Church, J.A., & White, N. J., Geophys. Res. Lett. 33, L01602, doi:10.1029/2005GL024826 (2006).

7. Wijffels S.E. et al., J. Clim., in press, doi: 10.1175/2008JCLI2290.1 (2008).

8. Domingues, C. M. et al., Nature 453, 1090-1093, doi:10.1038/nature07080.

9. Levitus S. et al., Geophys. Res. Lett., 32, L02604, doi:10.1029/2004GL021592 (2005).

10. Ishii, M. et al., J. Oceanogr. 62, 155-170 (2006).

11. Antonov, J. I. et al., Geophys. Res. Lett. 32, L12602, doi:10.1029/2005GL023112 (2005).

12. Köhl, A. et al., J. Phys.Oceanogr. 37, 313-337 (2007).

13. Lemke, P. et al., Chapter 4, IPCC (2007).

14. Dyurgerov, M.B. & Meier, M.F., Institute of Arctic and Alpine Research, University of Colorado, Occasional paper number 58, 177pp (2005).

15. Ngo-Duc, T. et al., Geophys. Res. Lett. 32, 9704-9707 (2005).

16. Jevrejeva, S. et al., J. Geophys. Res. 111: C09012, doi:10.1029/2005JC003229 (2006).

17. Church, J. A. et al. Changes in Sea Level, IPCC (2001).

The decadal variability in models that include volcanic forcing is in good agreement with the observations. The simulated multi-decadal trends tend to underestimate the observed ocean warming (30% smaller in the upper 300 m and 10% smaller in the upper 700 m).

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Agung Chichon Pinatubo Agung Chichon Pinatubo| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

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MIROC3.2 (hires)MIROC3.2 (medres)MIROC3.2 (medres)MIROC3.2 (medres)MRI−CGCM2.3.2MRI−CGCM2.3.2MRI−CGCM2.3.2MRI−CGCM2.3.2MRI−CGCM2.3.2

CCSM3CCSM3

Models with volcanic forcing

• Catia M. Domingues1 • John A. Church1,2 • Neil J. White1,2 • Peter J. Gleckler3

• Susan E. Wijffels1 • Paul M. Barker1 • Jeff R. Dunn1