The rate of Sea Level Rise has NOT remained constant during the past century!

Climate change has become a hot topic these days, with policymakers, scientists, and several other stakeholders expressing different ideas and opinions on climate change and its consequences. Unfortunately, within all this noise, some statements related to climate change get shared with a misleading narrative. This is a fact check on the recurring misconception associated with global sea level rise.

CLAIM:

The rising sea level is a natural process. Global warming has not contributed to it. Sea level rise rates have remained unchanged for over 100 years.

The above often is debated get shared by many climate deniers as a social narration. Moreover, several web articles and social media posts often highlight this point. Related web articles can be read here and here. Archived & Archived

Below is a Tweet that tries to imply that sea level rise rates have remained unchanged over the last century.

Archived

However, in this particular Tweet only the data for Victoria, Canada was considered, we decided to look into the facts regarding the global sea level rise.

Global mean sea level has risen approximately 210–240 millimeters (mm) since 1880, with about a third coming in just the last two and a half decades. Currently, the annual rise is approximately 3mm per year. And this rate has further increased in recent times as in the year 2021, the global sea level set a new record high of 97 mm (3.8 inches) above 1993 levels. More details about the sea level rise can be referred to here, Archived.

The graph related to sea level rise over the last century, taken from the United States government agency, EPA (Environment Protection Agency). The diagram is pasted below.

Especially around the turn of the twenty-first century, the global average sea level rise has seen a significant increase. Here is another graphical representation of this data.

When averaged over all of the world’s oceans, the absolute sea level has risen at an average rate of 0.06 inches per year from 1880 to 2013. However, since 1993, the average sea level has risen at a rate of 0.12 to 0.14 inches per year—roughly twice as fast as the long-term trend. Details about this can be referred to here. Archived.

In other words, the rate of sea level rise has almost doubled from 0.06 inches (1.4 millimeters) per year throughout most of the twentieth century to 0.14 inches (3.6 millimeters) per year from 2006–2015 as shown here.

According to the data of the National Ocean Service, USA, from 1900 to 1990 (90 years) the mean value of the sea level rise was 4 to five inches. However, from 1990 to 2015, (25 years) time, the rise was 3 inches. There is a clear acceleration of the rate. The current rate of acceleration is one-eighth inch per year. Details about this can be read here. Archived.

So, it`s clear that the rate of the sea level rising has been accelerating, and it has not been at the same level for the last 100 years

We found some evidence supporting the theory that “human-induced global warming accelerates the sea level rising.” Those reasons can be mainly categorized into three main aspects.

1. Short term
2. Seasonal to decadal
3. Longer term

Short Term: Some of the processes that pave the way to short-term (hours to days) changes in sea level are tides, surface waves, and storm surges, as well as other events like tsunamis.

Seasonal to Decadal: Seasonal to decadal changes include the change in the water level of sea bodies due to seasonal changes like summer, autumn, and winter. And also, decadal changes like El Nino belong to this category.

Long Term: Incidents like thermal expansion, polar-non-polar glaciers, and other incidents belong to this category.

More details about the above-discussed points can be read here. Archived

Now, it`s evident that there are multiple causes for the rise in sea level. But how does human-induced global warming/climate change contribute to it?

The systematic warming of the planet is directly causing global mean sea level to rise in two main ways:

(1) mountain glaciers and polar ice sheets are increasingly melting and adding water to the ocean.

(2) The warming of the ocean water leads to an expansion and, thus, increased volume.

As there are a number of reasons contributing to sea level changes, it`s difficult to predict which percentage, of human-induced actions contribute to this dilemma as studies in this regard are also limited. However, there is a lot of evidence that suggests human-induced global warming contributes to the current global sea level rising significantly.

The National Aeronautics and Space Administration (NASA) of the USA, stated that according to their observations, global sea levels are rising as a result of human-caused global warming, with recent rates being unprecedented over the past 2,500-plus years. According to their observations, two major factors contribute to ongoing sea level rise; those two factors are connected with human-induced global warming. here. Archived

According to the above-mentioned data, we can say that the sea level rise is clearly influenced by human-induced global warming and also the rate of the average global sea level rise being accelerated annually, more so in the last few decades, and the rate of change has not been same over the last century. However, the sea level rise rate can be different in various parts of the world as multiple factors contribute to this.