Since around 2000, there has been a revolution in our ability to observe and record almost all components of the sea level budget via new satellite and in-situ approaches. For example:
• The Gravity Recovery and Climate Experiment (GRACE), launched in 2002, has allowed us, for the first time, to measure the exchange of mass between the land and ocean at a global scale [1].
• The network of Argo buoys, dating from about 2004 and now exceeding 3,000 sites, is providing unprecedented information about changes in ocean heat content [2] [3].
• Satellite radar altimetry, since 1993, has provided monthly, high accuracy, estimates of absolute sea level between ±65° latitude.
• GRACE and the ICESat satellite laser altimeter mission, in operation between 2002 and 2009, provide comprehensive estimates of ice mass loss for glaciers and ice sheets worldwide [4] [5].

These new observational capabilities supplement and complement older, longer and more “traditional” time series from, for example, the long-term tide gauge network [6], shipborne ocean temperature data, geodetic and glaciological field measurements of individual glacier mass balance [7] and the global network of GPS stations measuring vertical land motion [8].

The different observational approaches and associated datasets are, however, generally not consistent with each other or with the average long-term sea level signal. Few scientists have been in a position to tackle the complete sea level budget problem because of (i) the volume and complexity of the observations, (ii) the multidisciplinary nature of the challenge and (iii) the extremely demanding nature of the statistical techniques and computational resources needed for a problem of this scale.

[1] Riva, R. E. M., J. L. Bamber, D. A. Lavallée, and B. Wouters (2010), Sea-level fingerprint of continental water and ice mass change from GRACE, Geophys. Res. Lett., 37, L19605, doi:10.1029/2010GL044770.
[2] Leuliette, E. W., and L. Miller (2009), Closing the sea level rise budget with altimetry, Argo, and GRACE, Geophys. Res. Lett., 36, L04608, doi:10.1029/2008GL036010.
[3] Willis, J. K., D. P. Chambers, and R. S. Nerem (2008), Assessing the globally averaged sea level budget on seasonal to interannual timescales, J. Geophys. Res., 113, C06015, doi:10.1029/2007JC004517.
[4] Jacob, T., J. Wahr, W. T. Pfeffer and S. Swenson (2012). “Recent contributions of glaciers and ice caps to sea level rise.” Nature 482(7386): 514-518.
[5] Kaab, A., E. Berthier, C. Nuth, J. Gardelle and Y. Arnaud (2012). “Contrasting patterns of early twenty-first-century glacier mass change in the Himalayas.” Nature 488(7412): 495-498.
[6] Holgate, S. J., A. Matthews, P. L. Woodworth, L. J. Rickards, M. E. Tamisiea, E. Bradshaw, P. R. Foden, K. M. Gordon, S. Jevrejeva and J. Pugh (2013). “New Data Systems and Products at the Permanent Service for Mean Sea Level.” J. Coastal Res. 29(3): 493-504.
[7] Zemp, M., M. Hoelzle and W. Haeberli (2009). “Six decades of glacier mass-balance observations: a review of the worldwide monitoring network.” Annals of Glaciology 50(50): 101-111.