about sea-level rise

A major effect of climate change is a present and continuing increase in sea level (Sea-Level Rise), caused mainly by thermal expansion of seawater (in a similar way to the expansion of liquid in a thermometer) and the addition of water to the oceans from melted land ice (such as mountain glaciers, and the Greenland and Antarctic ice sheets).

Over the last century, global-average sea level rose about 16 cm (i.e. at an average rate of 1.6 mm/year) and the present rate of rise is about 3 mm/year (Rate of Sea-Level Rise). The most recent report of the Intergovernmental Panel on Climate Change indicated that, during this century, sea level is expected to rise about 0.2-0.8 m over the 21st century, in the absence of significant mitigation of greenhouse-gas emissions (Sea-Level Rise Projections). There is, however, considerable uncertainty in these projections and recent, but controversial, research has suggested that they may be underestimates (Recent Projections).

Sea-level rise will be experienced mainly as an increase in the frequency or likelihood of flooding events, rather than simply as a steady increase in an otherwise constant level. The figure shows the rate of increase of frequency of flooding events for Australia for a 0.5 m rise in mean sea level, which will almost certainly be attained during this century. On average, Australia will experience a roughly 300-fold increase in flooding events, meaning that infrastructure that is presently flooded once in 100 years will be flooded several times per year after a sea-level rise of 0.5 m.

Reference: ACE CRC (2012) Report Card: Sea-Level Rise 2012