Global sea level rise
The Intergovernmental Panel on Climate Change has found that warming of the climate system is unequivocal and that anthropogenic greenhouse gases are very likely responsible.
Predictive work indicates that this warming will accelerate into the future due to continued anthropogenic greenhouse gas emissions and this will influence sea level.
Global average sea level has risen at a rate of 1.8 mm per year from 1961 to 2003. From 1993 to 2003 this rate increased to approximately 3.1 mm per year (Fig. 1).
Whether the acceleration between 1993 and 2003 is the result of decadal variability or a longer term trend is unclear .
There is however a high degree of confidence that sea level will continue to rise, and possibly accelerate, over the next century and beyond, through a combination of mechanisms including:
- thermal expansion of the oceans;
- melting of glaciers and ice caps;
- melting of the Greenland and Antarctic ice sheets; and
- changes in terrestrial storage.
Figure 1. Observed changes in a) global surface temperature, b) global average sea-level from tide guage (blue) and satellite (red) data, and c) Northern Hemisphere snow cover for March to April. From the IPCC 2007 Fourth Assessment Report .
Issues arising from sea level rise
Changes in sea level will be felt through :
- increases in intensity and frequency of storm surges and coastal flooding;
- increased salinity of rivers, bays and coastal
aquifers resulting from saline
- increased coastal erosion;
- inundation of low-lying coastal communities and critical infrastructure;
- loss of important mangroves and other
wetlands (the exact response will
depend on the balance between sedimentation
and sea level change ); and
- impacts on marine ecosystems i.e. coral reefs.
Any or all of these changes may have a severe impact on urban communities if unmitigated.
- IPCC (2007). The Fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC). Climate Change 2007: The Physical Science Basis. (Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller, Editors). Contribution of the Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, 944pp
- Scavia, D., Field, J.C., Boesch, D.F., Buddemeier, R.W., Burkett, V., Cayan, D.R., Fogarty, M., Harwell, M.A.,
Howarth, R.W., Mason, C., Reed, D.J., Royer, T.C., Sallenger, A.H., and J.G. Titus. 2002. Climate change impacts on
U.S. coastal and marine ecosystems. Estuaries 25(2), 149-164.
- Woodroffe, C.D. 1995. Response of tide-dominated mangrove shorelines in northern Australia to anticipated
sea-level rise. Earth Surface Processes and Landforms 20, 65-85.
- A Post-IPCC AR4 Update on Sea-Level Rise
- Polar Ice Sheets and Climate Change