A popular example of the type of meme I’m talking about.

It is an indisputable scientific fact that the average global sea level is increasing. Nevertheless, numerous memes and posts on the internet claim to have photographic proof that sea level rise (and by extension, global climate change) is a hoax. These posts generally contain an old photograph of a shoreline next to a recent photo of the same shoreline, with similar water levels in both photos. Therefore, according to the purveyors of this misinformation, the sea level has not changed and global warming is not real. Checkmate, science nerds, right? Not so much.

There are many versions of this argument (particularly popular ones include the Plymouth Stone, Palm Beach Florida, and various bridges), but they all suffer the same fundamental problem, so there is no need to harp on specifics (with one exception discussed later).

The core problem here is that the photos don’t take into account several critical factors, such as tides. The sea level is not static. It goes up and down twice every day, in some places quite dramatically. Further, the timing of peak high and peak low tides shifts from one day to the next, and the magnitude of the tides changes throughout the year. This means that the sea level at any one location is constantly changing. As a result, two photos of the same spot at two different time points are completely meaningless. If, for example, the old photo was at high tide and the recent photo was at low tide, it is going to look like there was no change in sea level, but that’s clearly a bad comparison because the tides were different! You can’t just ignore the existence of tides.

Another example of the type of meme I’m talking about. Once again, tides were ignored.

Beyond tides, there are factors like storm surges and the ground itself raising or subsiding. Further, because of a wide range of factors, sea level rise is happening faster in some places than in others. All of these things have to be taken into account to actually measure long-term patterns in sea level change. So, just like for temperature, scientists use a massive array of recording stations and satellites and carefully factor in tides, storms, etc. so that they can see the long-term trends.

When scientists account for these factors, they find that on average, the global sea level is rising, and that rise is caused by anthropogenic climate change. Indeed, the most recent IPCC report (IPCC 2022) made the following conclusion (their emphasis):

“Global mean sea level (GMSL) rose faster in the 20th century than in any prior century over the last three millennia (high confidence), with a 0.20 [0.15 to 0.25] m rise over the period 1901–2018 (high confidence). GMSL rise has accelerated since the late 1960s, with an average rate of 2.3 [1.6 to 3.1] mm yr –1 over the period 1971–2018 increasing to 3.7 [3.2 to 4.2] mm yr –1 over the period 2006–2018 (high confidence).”

There are four important things to note from that:

1. Scientists are highly confident. Scientists are a cautious bunch, and we reserve that terminology for cases where the evidence is extremely clear and compelling.
2. Over the past 100 years, the sea level rose faster than at any comparable period in the past three millennia. So, to those who try to attribute all of this to natural cycles, no, this isn’t normal. We’ve looked at the natural cycles and they don’t explain what we are seeing now (details here).
3. The change so far has been relatively small, about 20 cm (7.9 inches). That’s small enough that you might not notice it on an occasional trip to the beach (or when looking at old photos of shorelines and structures), but it is enough that it is already having impacts on coastal properties (McAlpine and Porter 2018; Moftakhari et al. 2015).
4. The rate of rise is increasing. This is the really concerning part. Things are going to get really bad if we don’t act immediately and drastically, and old photos don’t change that fact.

“but the predictions have all been wrong!”

IPCC predictions compared to our actual observations. Figure from the Copenhagen Diagnosis 2009See Skeptical Science for more information.

At this point, I can hear the people shooting, “but the models have all been wrong! What about all those doomsday predictions!? I thought New York was supposed to be under water by now?” This misinformation comes from a range of sources, none of which are the actual scientific studies. The actual predictions made in the peer-reviewed literature have been very accurate (more details here). Studies have compared the IPCC model predictions with subsequent observations and, guess what, the predictions were correct (Wang et al. 2021; The Copenhagen Diagnosis 2009).

You don’t even need to understand complex modelling or scientific jargon to see that the actual predictions by scientists do not match climate change deniers’ caricatures but do match our observations. Just read the executive summary (written in plain English) from the first IPCC report (the report was in 1990 and the summary was released in 1992).

“Under the IPCC Business-as-Usual emissions scenario, an average rate of global mean sea-level rise of about 6 cm per decade over the next century (with an uncertainty range of 3—10 cm per decade), mainly due to thermal expansion of the oceans and the melting of some land ice. The predicted rise is about 20 cm in global-mean sea level by 2030, and 65 cm by the end of the next century.”

Notice that they did not predict that all of Florida would be under water by now, nor did they forecast meters of sea level rise by 2020. They predicted 20 cm of rise by 2030 with 3–6 mm per year, which, you’ll notice, matches the observations I reported earlier, and before you baselessly accuse the IPCC of trickery, you can look at their work and read the studies they cited. The data are unequivocal. It is a simple fact that sea levels are rising and coastal flooding risk is increasing (Church and White 2011; Sweet et al. 2019).

So if scientists weren’t the ones making those inaccurate doomsday predictions, where did they come from? In some cases, the media is to blame, and honestly, I’m surprised that I have to say this because if there was one thing that I thought climate change deniers and I could agree on, it was that the media is often sensational and doesn’t report things accurately. News outlets are notoriously bad at getting the science right and love to latch onto unlikely worst-case scenarios and present them as if they are what most scientists are claiming is likely. This then provides fodder for idealogues who deliberately misrepresent the science for personal gain, and before you know it, the misinformation has been repeated so many times that people take it for granted that scientists predicted the complete demise of Florida by 2020 even though they actually predicted nothing of the kind.

An additional factor is that people simply fail to grasp the timescale of the predictions (and this can again get distorted). There certainly are models that predict that large parts of New York, Florida, etc. will be submerged by 2100 (if we don’t change our actions), but you can’t take a prediction for 80 years from now and say, “well it hasn’t happened yet, so the scientists are wrong.”

Likewise, I’m sure that if you dig around you can find one off statements made by various scientists, that turned out to be wrong. but don’t confuse those off the cuff remarks or the predictions of a few outliers for the actual predictions being made by the actual models in the scientific literature. Again, the actual IPCC predictions have been accurate (in some cases erring on the side of caution).

Please read this post before claiming that scientists predicted an ice age in the 70s (they didn’t)

“but when floating ice melts, the water level doesn’t increase”

It is usually around this point that I encounter a particularly comical counterargument. This one is generally stated as a simple experiment that you can do yourself to prove that climate change isn’t causing the sea level to rise. All you have to do is take a cup of water, put some ice cubes in it, mark the water level, then wait for them to melt. Once they have melted you will find that, lo and behold, the water level is unchanged. Therefore, according to those with degrees from Google University, climate change is a myth and the sea level isn’t rising.

It is true that as floating ice melts the water level is unchanged (but see note), but it is also a straw man fallacy.  Melting icebergs (floating ice) are not the cause of sea level rise. Rather, sea level rise is being caused by the thermal expansion of water as it heats up (i.e., warm water expands and takes up more space compared to cold water) and the melting of land-based ice (Frederkikse et al. 2020).

Note: Although the melting of floating ice does not change the water levels in freshwater, it can have an effect in salt water because of the difference in the density of salt and freshwater (sea ice is predominantly fresh). So melting sea ice does technically have an impact on sea levels, but that impact is quite small compared to the impact of melting glaciers on land and thermal expansion (Noerdlinger and Brower 2007).

Scientists aren’t stupid

As I’ve explained before, if you think that you have found something extremely obvious and simple that every scientist in the world has missed, you are almost certainly wrong and, honestly, are being extremely arrogant. I don’t say that to attack or belittle anyone. Rather, I am trying to get you to think rationally and engage in some basic plausibility checks.

Which one of the following actually seems more likely to you?

1. Despite years of training and a lifetime spent doing research and studying the factors that affect sea level, all of the world’s scientists (tens of thousands of people from hundreds of universities, government institutions, etc. from all over the world) completely missed an extremely basic fact of physics, and you have completely overthrown decades of research with an elementary school science experiment involving nothing more than a cup, water, and ice cubes, or
2. Your understanding of the topic is incomplete and scientists know more about their areas of expertise than you do

Believing option A is the very epitome of hubris. If you are intellectually honest, you have to acknowledge that option A is wildly implausible, and that should, at the very least, make you spend a few seconds googling the causes of sea level rise rather than going around pretending that all scientists are absolute idiots. It should make you ask questions like, “if the problem with climate change is this obvious, why aren’t scientists aware of it?”

Likewise, it is absurd to completely ignore a mountain of data collected by thousands of scientists from all over the world using cutting edge technology and sophisticated statistical methods simply because you found a black and white photo online. Really think about this. Does it honestly seem rational that all of that research is so hopelessly wrong that a simple photo will discredit it? Do you seriously think that all of the world’s scientists are that utterly incompetent? Do you really think that none of them bothered to go down to the shore and check? Really ask yourself, which is more likely, that essentially all of the world’s experts are hopelessly wrong, or the situation is more complicated than you realize?

Again, the answer to that question should be obvious, and it should make you do some basic fact checking. As I’ve said repeatedly on this blog, I’m not advocating for blind faith in authority (fact check everything), but you need to have some extremely good evidence before claiming that all of the world’s experts are wrong, and in cases like this, mere minutes on Google would be sufficient to explain why the experts are right and the memes of old photos are wrong.

Indeed, in a particularly laughable display of wilful ignorance, the Plymouth Rock photo has been among the more popular memes I’ve seen floating around, but that rock has, in fact, been moved multiple times! You don’t even need to know anything about tides to know that the claim being made in the meme is bogus, and that fact is easily discoverable to anyone who checks.

This is, in many ways, the most frustrating thing about the anti-science movement, in my experience. The arguments used against science are generally so laughably naive and childish that anyone could easily find and comprehend information explaining why they are wrong if they would only bother to look, but most people don’t bother to look. They see something that conforms to their preconceptions, so they blindly believe and repeated it without ever testing its veracity, thus forcing people like me to spend our days explaining that tides exist and that scientists are in fact aware of how ice melts.

Don’t go through life blindly believing things you agree with and dismissing things you disagree with. Be curious. Be intellectually honest and rigorous. Take the time to check the facts and look at the evidence before you decide what to accept and reject.

Recommended reading:

• NOAA: Climate Change: Global Sea Level
• Skeptical Science (various posts on sea levels)

Related posts

• 25 myths and bad arguments about climate change
• Global warming isn’t natural, and here’s how we know
• Extreme weather: The effects of climate change are already here
• The overwhelming consensus on climate change
• Facts: Why they matter and how to check them
• Scientists aren’t stupid, and science deniers are arrogant

Literature cited

• Church and White 2011. Sea-Level Rise from the Late 19th to the Early 21st Century. Surveys in Geophysics 32:585–602
• Frederkikse et al. 2020. The causes of sea-level rise since 1900. Nature 584: 393–397
• IPCC 1992. First Assessment Report Overview and Policymaker Summaries and 1992 IPCC Supplement.
• IPCC 2022. Fox-Kemper et al. Ocean, Cryosphere and Sea Level Change. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate
• McAlpine and Porter 2018. Estimating Recent Local Impacts of Sea-Level Rise on Current Real-Estate Losses: A Housing Market Case Study in Miami-Dade, Florida. Population Research and Policy Review 37: 871-895
• Moftakhari et al. 2015. Increased nuisance flooding along the coasts of the United States due to sea level rise: Past and future. Geophysical Research Letters 9846-9852
• Noerdlinger and Brower 2007. The melting of floating ice raises the ocean level. Geophysical Journal International 170:145–150
• Sweet et al. 2019. 2019 State of U.S. High Tide Flooding with a 2020 Outlook. NOAA Technical Report NOS CO-OPS 092
• The Copenhagen Diagnosis 2009. Updating the world on the Latest Climate Science. Allison, et al. The University of New South Wales Climate Change Research Centre (CCRC), Sydney, Australia, 60pp.
• Wang et al. 2021. Reconciling global mean and regional sea level change in projections and observations. Nature Communications 12