Fort Denison pics no indicator of sea level rise
Explanation
AAP Fact Check Viewed a Facebook post shared by AUSTRALIA-The Land Down-Under on 11 October 2019, showing two photos of Fort Denison on Sydney Harbour.
The post claims these are proof that there has been no sea level rise in Sydney Harbor for 140 years.
The post shows two photos side by side, one in black and white, with the text at the top: “unprecedented climate change has caused sea level in Sydney Harbor to rise by approximately 0.0cm over the last 140 years.”
The post sparked more than 2,100 shares, more than 1,600 reactions and 180 comments. Similar versions of the post appeared on other Australian pages here and here.
Analysis
The first photograph of Fort Denison was taken before 1885, according to the State Library of NSW, whose original image is in its archives. The distinctive tower structure on the island was completed in 1857. The Bureau of Meteorology has records of sea level readings for Fort Denison dating back to 1914.
AAP Fact Check He could not find the origin of the second photo, but the military ship in the background bears the number 304, the identifier of the Australian navy HMAS Success. HMAS Success was in service from 1984 until June 2019.
AAP Fact Check could not confirm whether the images were taken 140 years apart. However, according to the timelines of the construction of Fort Denison and the launch of HMAS Success, the photo was taken between 99 and 162 years apart.
An Australian Bureau of Meteorology (BOM) spokesman said between 1914 and 2007, sea levels in Sydney Harbor rose by approximately 68mm to 105mm.
“Global rates of change range from 1.4 mm/yr (between 1901 and 1990) to 3.2 mm/yr (between 1970 and 2015), while estimates of sea level rise in Sydney Harbor range from 0.73 to 1.13 mm/yr (between 1914 and 2007), which is slightly below the global average,” the spokesperson said.
The data referenced by the BOM spokesperson was taken from a 2009 study commissioned by the NSW Department of Environment.
Regarding the photos used in the post, a BOM spokesperson said it would be impossible to use the images to determine a change in sea level.
“Sea level varies throughout the day and year, influenced by tides and seasonal changes in weather systems,” the spokesman said.
“Just as two single photographs of equivalent sea level at a particular location do not tell us whether the tide is coming in, two single photographs from a location taken years apart do not tell us whether sea level is rising at that time.
“A good analogy for this is that we can find an image of a hot summer day in 1950 and an image of a cold winter day in 2010 and infer that there was no warming trend during this time.”
Decision
Based on the above evidence, AAP Fact Check It found that the post claiming that there has been no rise in sea level in Sydney Harbor in the last 140 years was false.
WRONG – The main claim of the content is factually false.
* AAP Fact Check It is an accredited member of the International Verification Network. Follow us on Facebook, Twitter and Instagram to keep up with our latest fact checks.
First published 25 October 2019, 15:25 AEST
