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In 2050: 600m people can be impacted by raising sea level

Guest Author: Marta Brighenti

Knowledge is not enough

Before diving into what sea-level rise is - and how we can address it- it could be helpful to take a moment to think about how we frame environmental issues. The first steps to further a debate around the consequences of human actions on the environment were advanced over the '80s; back at that time, scientists coined the term "inadvertent climate modification" to refer to how human beings could negatively interfere with nature. Instead, the expressions we now generally use, like climate change or global warming, have become common during the '90s and the '00s, symbolizing a different perception and approach to environmental issues.

June 23, 1988 marked the date on which climate change became a US national issue and a headline in the New York times. In landmark testimony before the U.S. Senate Energy and Natural Resources Committee, Dr. James Hansen, then director of NASA’s Institute for Space Studies, stated that “Global warming has reached a level such that we can ascribe with a high degree of confidence a cause-and-effect relationship between the greenhouse effect and observed warming…In my opinion, the greenhouse effect has been detected, and it is changing our climate now.”

Yet despite decades of public education on climate change and international negotiations to address it, progress continues to stall.

One reason for the political inaction is the gaping divide in public opinion that resulted from a deliberate misinformation campaign to redirect the public discussion on climate change.

On the other side, if we decide to frame environmental distresses as "inadvertent", it becomes possible to excuse every behavior before the shield of unintentionality. On the contrary, by recognizing the complexity and the interconnection of different phenomena here at play, it becomes possible to identify causes and consequences, effects and implications of human actions.

That is why this premise is more than necessary: to better understand the sea-level rise phenomenon and consequently redirect our actions and behavior, we need to be able to see the invisible causes-consequences nexus behind it. So, before going into details about how sea-level rising is reshaping our geographies and threatening cities, let us take a moment to unveil these connections and better understand what sea-level rise is.

Sea level rise: what are we talking about

Metaphors and images aside, sea-level rise could be defined as a long-term rise of the ocean surfaces on a global level. The advancement of the marine surface is no news for the Earth: according to different studies, the sea level has risen about 21-24 cm, around 8-9 inches, from 1880.

It is not the first time in the history of the Earth that the sea levels are so high. For example, by looking at the numbers of the Eemian interglacial period - approximately 120 thousand years ago - we discover how sea levels were at least 5 meters higher than now. Some studies also suggest that, before the Eemian interglacial, there had been other times with even higher peaks. So, as you may have understood, the problem does not lie in sea levels rising per se.

Data shows how sea-level has always been rising during the Earth’s long history.

IPCC, 2014

The real troubles begin when we look at the time and velocity rate sea level is rising. According to the IPCC, sea-level indicators did not show significant changes until the late 19th century. On the contrary, estimation concerning the 20th century suggests that the level rose about 1.7 mm every year. Moreover, looking at the projections for this century, scientists suggest that the global average sea level will grow at a greater rate than what it had from 1963 to 2003. But what do these numbers mean?

Put it shortly, data reveal that the rising of sea levels is going through what seems to be an acceleration. As often happens with projections, precise numbers are uncertain. Yet, there is one thing the scientific community agrees on: such acceleration cannot be explained only by the natural thermal cycles of the Earth. Human actions are playing a part too.

The real problem, when it comes to sea-level rise, is the peak of acceleration we’re witnessing in the last decades.

IPCC, 2014

Sea level rise: the causes

As anticipated, explaining such complex phenomena requires the ability to identify more or less hidden causes that lead to the rising of sea levels. Simplifying, two layers can be distinguished: a first, made of more direct and intuitive cause-consequences links, and a second, which, on the contrary, requires the capacity of widening the framework.

Globally, there are two direct causes behind sea-level rise: the expansion of oceans and the melting of glaciers and ice sheets. There is a common denominator that links together these two phenomena: heat. When the temperature rises, water expands due to what is known as thermal expansion. It means that, when it's hotter, oceans tend to extend their surfaces. At the same time, heat influences the rate of formation and melting of ice. The hotter it is, the faster ice melts and the slower snowfalls can turn into new ice.

Source: Nasa

It is no news that the temperature is rising yearly. Studies show how Earth's temperature has become hotter by 0.08° per decade in the last century. There has been an acceleration in the past 40 years: the rate has doubled, touching the peak of 0.18° per decade. All of this, as shown before, is highly influencing the level of oceans and seas. Since it becomes hotter each year, the sea level increases.

However, the red line doesn't stop here. What do human beings have to do with all of this? As we have said before, the Earth has a long history of alternating between warmer and colder eras. Yet, scholars have pointed out how, in the past century, our planet has warmed quicker than ever. You certainly have heard of the greenhouse gas effect: Earth's atmosphere traps some greenhouse gasses, like CO2, to create a protective layer. This layer is indispensable for life since it traps heat on the surface, warming the planet. When the level of greenhouse gasses increases, the greenhouse effect on the Earth becomes stronger. It means that too much heat gets trapped by these gasses, and the planet slowly becomes too warm.

Here is why - and when - human beings play a big part in the sea-level rising phenomenon. The greenhouse gasses have been released at an unusual and dangerous rate into the atmosphere since we have started burning fossil fuels. Everything on the Earth is interconnected, and each action always fosters a reaction: how we live partly shapes how our oceans expand.

Sea level rise: the consequences

The most immediate consequence of sea-level rising is intuitive: the higher the level, the more water invades coastal areas. We may think about the peaceful image of high tides waves on the shores. Well, forget that. When the water level rises, it erodes soils and damages farmlands. Water threatens cities and houses, affecting at the same time biodiversity and causing species loss by disrupting their habitats.

For the sake of shortness, it would be impossible here to deeply explore how serious the impacts of sea-level rise on the flora and fauna all over the world are. Yet, to give a sense, it could be relevant to keep in mind that, according to the Center for Biodiversity, the rising sea levels is already threatening 17% of the federally protected species in the US only. Among these species, there are, for example, the Hawaiian monk seal and the loggerhead sea turtle. Looking outside the US, data show a similar situation: for example, being for many parts of coastal areas, the European continent proves to be as vulnerable as other areas. The threat of disappearing habitats is especially true for protected species of birds such as the marbled teal. Its natural environment is, in fact, mainly composed of wetlands: panoramas put at high risk by the rising of waters.

Focusing on the consequences rising seas will have on human life, it's clear how these will be no joke either. When waters expand on the coastlines, they can infiltrate underground freshwater reservoirs, increasing their salinity level. It would cause immense damage to our lives since freshwater availability is already a complicated issue: only 0.5% of the total water on Earth is currently fresh and available. It does not only threaten water availability for human purposes, like drinking or showering, but also for farming ones. Crops, if watered with saline water, would die. It, therefore, goes without saying that if aquifers were to increase their salinity, it would also reflect on our eating habits.

Sea rising will also accelerate the impact of extreme water events: flooding would become more frequent and devastating. At the same time, according to the current projections, a big part of coastlines areas seems to be due to extinction. The rising water levels threaten to reshape our geographies, obliging us to rethink our societies and even our States. Over the past years, it has become an increasingly common point of discussion has been that of sinking islands: small islands nations in the oceans, where sea levels rise is threatening their existence. The numbers are scary: up to 25 main cities may be underwater by 2050. In 2100 the number of people affected could rise to 600 million, mainly composed of inhabitants of nearby coastal areas.

The good news is that not everything is lost. We can still do something. The question is: what?

Sea level rise: how can we save our cities?

As you can imagine, such complex problems require many different levels of solutions. On a global level, various solutions are being tested far and wide. The Netherlands, which is 90% below sea level, is implementing different strategies to cope with the problem. The city of Rotterdam, in particular, offers an example to think and design solutions for the future to come. On one side, the Dutch are starting to put in place a series of small actions, like educating citizens, or installing retention fountains in each neighborhood. On the other hand, they built a storm surge barrier to prevent the city from flooding. It's called Maeslantkering, and it took six years to be constructed.

The Maeslantkering, here displayed both with the barriers open and closed. When the water rises, the barriers prevent lands from flooding.

Quite the same scheme is being applied to the city of Venice. For the first time, on the 10th of July of 2020, the mobile gates of MOSE lifted, enclosing the city and ensuring that - hopefully - it won't ever flood again.

MOSE (Modulo sperimentale elettromeccanico) is a system of integrated rows of mobile gates able to isolate the lagoon when the tide rises.

Venezia Today; PANDAPHOTO 2012

These represent only some examples of how engineering solutions can prevent cities from facing floods and the terrible consequences they imply. However, such works have a series of negative implications, both for the natural and eventually for the human environment. Other kinds of solutions are being studied: some imply the elevation of roads and territories, others the use of mangroves as natural defenses. Many recently born startups are bringing innovative solutions to the table. Some of them, like Green Stream or Jupiter Intel, focus on the prediction of tidal tendencies through the development of innovative eco-friendly technologies. Thanks to such projections, it is possible for communities and scientists to better have a sense of sea-level rising trends, as well as to better plan for the near and far future. Other companies, such as Coastal Innovations, offer ad hoc mitigation solutions to protect and prevent coastline damages through new eco-friendly resistant materials. Moreover, another valuable example is the work made by the French company Tenaka, which uses nature-based solutions to restore coral reefs and regenerate the oceans, therefore increasing sea-level rise resilience. As you can see, there are many different possible roads to cross. However, even if they differ in costs, approach and adaptation to a geographical area, these solutions share a common trait: they're just palliative.

To stop sea-level rising, in fact, a wall, a bridge or a barrier simply isn't enough. It may buy us some time, but such solutions only act on the consequences without touching the causes. To solve sea-level rise, we need to cut down greenhouse gasses emissions. It's the only way in which we can stop this vicious cycle. Even if it may sound terrible, it is actually good news. It means that each of us can be part of the solution in its small way. Riding or walking instead of driving, eating less meat or avoiding plastics as much as possible are all ways to prevent our coastlines and islands from disappearing. While complex engineering solutions will still be necessary to mitigate damages, we all should cooperate to cut down our carbon footprint. Every day, we get the chance to save a piece of our Earth.


IPCC, [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)], Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, 2014, chapter 3.

WCRP Global Sea Level Budget Group, Earth System Science Data, Global sea-level budget 1993–present, 2018, 10 (3), 1551–1590, pp. 1560-1570. Bibcode:2018ESSD...10.1551W. doi:10.5194/essd-10-1551-2018.

Kulp, S.A., Strauss, B.H., Nat Commun, New elevation data triple estimates of global vulnerability to sea-level rise and coastal flooding, 2019, 10, 4844, p. 50

About the author:

Marta is an Italian environmental humanist scholar, with a strong passion for foreign languages and cultures. Highly interested in social issues, Marta firmly believes that to successfully address environmental issues it is necessary to unveil the interconnections between social, economic, and environmental spheres. She's currently working on her master's degree thesis on ecofeminism while specializing in environmental communication.



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