Again, Ugh...Social Media

While doing some research for a new blog post, I took a break from writing by taking a trip over to Facebook again, and unfortunately found something else to write about:

I've seen this image before and apparently it's making the rounds again. Based on what you see here, with no additional text or context given, is there any way that you can arrive to the same conclusion as the one given? I find that there is an absurd amount of information that is neglected, which prevents me from making any conclusions whatsoever.

But firstly, what is this an image of?

Photograph of Fort Denison, circa 1880s.

(credit: Wikimedia/National Archives of Australia)

This is Fort Denison on delightfully named Pinchgut Island in the Sydney Harbour of Australia. Originally built as a prison, and later converted into a fort to protect the harbor, Fort Denison still stands today well within eyesight of the famous Sydney Opera House and Sydney Harbour Bridge. I was not able to find the exact date the above photograph was taken, nor the year. But, according to Wikimedia Commons, it is circa 1880s.

The second image was taken in 2018, however I was also unable to find the exact day or month:

Fort Denison in 2018 

(credit: Richard F. Ebert)

The exact date the photos were taken are of importance because there is a peculiar phenomenon called tides. They tend to cause the seas to rise or fall, and comparing the sea level in two photos without information about when they were taken is futile unless the change in sea level is noticeably greater than what tides produce. Speaking of tides, Fort Denison conveniently houses a tide gauge and tide measurements have been made there since 1857. Quite the remarkable coincidence! Especially since the data from the tide gauge is used by NOAA and is publicly accessible:

Mean sea level trend (0.65 mm/yr +/-0.10 mm/yr) at Fort Denison, based on data from 1886-2010.

(credit: NOAA)

The data goes back to 1886, which is nearly the time that the original photo was taken. The text below the chart states that on average, the sea level has been rising at Fort Denison at a rate of 0.65 mm per year (+/- 0.10 mm/yr) and "is equivalent to a change of 0.21 feet in 100 years." 

So, there is proof that the sea level has been rising between the years that the photos were taken. But, we must consider whether the rise is due to climate change and/or land uplift/subsidence (relative sea level rise). In geology, we know that the land surface is never absolutely static. There is vertical movement over geologic time and sometimes it is drastic over a human's lifespan. We need to determine if the ground that Fort Denison sits on has moved up or down over the last 140 years. I haven't found any data on this, but no matter, I doubt any exist beyond the last three or four decades. Is it possible that 

According to NOAA, it is thought that there is a 1.7 mm/year rise in sea level globally. While Fort Denison is exhibiting less than half of that, there are areas in Australia and New Zealand that are experiencing more than the global rate. What does this mean? Either the ground around Australia and New Zealand is subsiding and the sea level is constant or there is gradual uplift of the Sydney Harbor but at a lower rate than global sea level rise, while some areas in and around Australia are subsiding or uplifting at a faster rate. Without further data, we are unable to sufficiently reach a conclusion. But, incorporating this data with global data, there is a clear indication that there is a eustatic sea level rise. This leaves us to conclude that while uplift and subsidence rates vary from place to place, Fort Denison appears to be rising, but at a rate outpaced by global sea level rise (appx. 1 mm/yr).

So, while the two slightly blurry photographs in the Facebook image don't prove rising sea levels are due to climate change, they don't disprove it either. In fact, the image doesn't prove or disprove...well....anything, except that the fort has existed for at least 140 years. But, that hasn't stopped this image from being used all over the Internet on various social media platforms, web sites, and blogs attacking the idea of climate change. At this point, I'm honestly not sure why climate change disinformation is still so prevalent or what is to be gained from it. I've considered writing on propaganda/disinformation that attacks geoscientific studies, such as climate change, fossil fuels, and evolution, but someone could probably write an entire book on the topic.