GREAT BARRIER REEF
// Outlook Report 2014
Ocean uptake of carbon dioxide will increase ocean acidification, continuing the observed trends of past decades and reducing pH within the Region’s waters (see Section 3.3.2). 30,51 Global ocean surface pH is currently 8.1 and there is high confidence that it has decreased by 0.1 since 1750. 30 Projections based on RCP 4.5 and RCP 8.5 are for further reductions in pH of around 0.05 to 0.2 by 2030, and around 0.05 to 0.3 by 2080.40 Currents There is increasing evidence of changes in the East Australian Current adjacent to the Region’s southern coast (see Section 3.2.1). Its flow is expected to increase off southeast Australia with a compensating decrease off north-east Australia. 52 There is little information about the Hiri Current, another of the Region’s prominent currents. Both tropical cyclones and east coast lows can produce extreme wind speeds and heavy rainfall. 53 Over the last decade, particularly between 2005 and 2012, there have been a Figure 6.6 Rates of sea level rise in Australia, 1993–2013 Rates of sea level rise are highest in northern Australia. The map shows the rate of sea number of severe tropical cyclones in the Region surface height rise measured by satellite observations. Note: satellite observations have (see Section 3.2.2). Most of the Region has been had the seasonal signal removed and small corrections applied for changes in atmospheric pressure. Source: Australian Baseline Sea Level Monitoring Project and CSIRO, map adapted exposed to severe cyclonic winds during that from Bureau of Meteorology 2014 49 time; with the area between Cairns and Townsville particularly affected (Figure 6.7). There is low confidence in determining changes in cyclones over a century scale 39, but the frequency of eastern Australian land-falling cyclones has possibly declined since the late nineteenth century. 39,53 The frequency of tropical cyclones is likely to decrease or remain unchanged, though there is a possible trend towards more intense storms 39,54; however, confidence is low in regional projections 55,56. An increase in intensity would increase the proportion of severe tropical cyclones (categories three, four and five). A small poleward shift in storm tracks is likely. 55 North-east tropical rainfall is concentrated during the summer and is variable from year to year. Indicators of flood events, dating back to late seventeenth century show that wet and dry extremes have become more frequent since the late nineteenth century.60 Between late 2010 and early 2011, one of the strongest La Niña events on record since the late 1800s was observed 61 resulting in record high rainfall and widespread flooding in many areas (see Section 3.2.3).
The global average sea level has risen about 19 centimetres since 1901