Real climate evidence requires precautionary action

Contrary to Cr Peter Freewater's claim of "no real evidence" that sea level is rising in Brisbane Water, there is strong evidence for sea level rise and other climate change impacts and a real need to plan for this now.

Noting that sea level rises are not uniform or consistent year by year, CSIRO and the Bureau of Meteorology's State of the Climate Report (2012) states global average mean sea level since 1880 is now 210 mm higher (Church and White 2011).

Closer to home tidal, records at Fort Denison show a "clearly apparent" long term sea level rise trend of 0.94 mm per year over 40 years (NSW Ocean Water Levels Manly Hydraulics Laboratory Report, March 2011).

This is even with slight rises in the Australian continent of around 0.3 to 0.4mm a year around Sydney which partially offset increases in sea levels.

When barometric pressure is included, Bureau of Meteorological tidal gauge records such as those for Port Kembla show a sea level rise of around 3mm which is comparable to global averages according to CSIRO scientist Dr John Church.

These rises are consistent with the IPCC modelling and if anything since 1990 we have been near the upper end of predicted levels.

The data support the adopted NSW benchmark of 0.9m by 2100.

Added to this is that sea level rise appears to be accelerating.

Data from satellite observations indicate average mean sea levels have risen faster between 1993 and 2011 than during the whole 20th century.

Of greater significance for coastal and near coastal areas like Brisbane Water will be the impacts of extreme weather events such as storm surges and associated coastal erosion.

Dr Church has said the NSW coast was likely to experience sea-level rises greater than global estimates due to changes in the wind stress patterns in the Pacific Ocean, which will strengthen the East Australian Current.

Data for these increasing events is also emerging.

For example, analysis of records from Fort Denison reveal periods of extreme sea-level rises occurred three times as frequently as in the first half of the 20th century.

So an extreme that used to occur, say, every three years now occurs every year (CSIRO).

As oceans continue to warm and expand and glaciers, land ice and the Antarctic and Greenland ice sheets melt, there will be further rise.

The legacy of carbon dioxide and other greenhouse gases in the atmosphere will continue to impact on global ocean and atmospheric temperatures so we are only at the beginning of the sea level rise trend.

While this will be very difficult for property owners in vulnerable areas, the risks should not be down played or planning and management actions put into the "too hard basket".

Good environmental adaptive management is based on sound science and involves making decisions and taking action based on a precautionary approach.

It should not be dictated by political opportunities or vested interests but rather be carried out for the community as a whole and with future generations in mind.

Email, 14 Aug 2012

Rachel Lonie, Pearl Beach