Causes
Global sea level
is rising. It has been rising since the peak of the last Ice Age in general,
with some pullbacks in cooler periods. It is mainly the loss of continental ice
sheet volume to the sea, thermal expansion of seawater, and changes in
land-water storage that cause sea level rise. Sea level rise has likely been
accelerated by global warming, but it is difficult to quantify the share of sea
level rise attributable to anthropogenic climate change. Global warming
influences both the loss of continental ice and thermal expansion. Thus, it is
likely there is anthropogenic acceleration, but we don’t really know how much.
Global sea level has risen by about 24
cm since 1880. It averaged an annual rate of 1.4 mm per year until the
mid-2000s, when the rate of sea level rise increased significantly. It has
since dropped back a bit. Global sea level is projected to rise by 0.7 m in a
low emissions scenario, but could be much higher than that in a high emissions
scenario.
More of the water on land is
also making its way to the oceans due to human activity. As we extract water
for use from wetlands, water bodies, and groundwater, there is less land
storage of water and more water making it to the oceans. However, this is a
very minor contributing source of sea level rise.
High tide flooding is
becoming more and more common as time goes on. A 2024 episode of Energy Switch,
hosted by geologist Scott Tinker, was about sea level rise. It featured Dr.
Rachel Cleetus, an economist at the Union of Concerned Scientists, and Susmita
Dasgupta, a lead environmental economist for the Development Research Group at
the World Bank.
Expectations of sea level rise
include land loss, coastal erosion, salination of freshwater aquifers and soil,
loss of mangrove forests, and much more. Dasgupta calls it the elephant in the
room. Sea levels have risen 8 to 9 inches since the Industrial Revolution
began. One-third of sea level rise has occurred since 1993, according to some
analyses. We know that in the geological past, when glaciers melted, the global
mean sea level rose by hundreds of feet. NOAA estimated that 10-12 inches of
new sea level rise by 2050 and 2 to 7 feet of sea level rise by the end of the
century, which would be massive. Loss of ice sheet mass is supporting these
estimates. East Asia, North Africa, and the north coast of South America are at
high risk. Existing infrastructure is not flood-resistant enough. In places
like Florida, the substrate is porous, and saltwater is encroaching into
agricultural soils and into groundwater used for drinking and irrigating crops.
These are very challenging problems. The delta regions – Nile Delta,
Bangladesh, etc. are seeing these problems now. Desalination plants are now
needed where they weren’t before.
Dangers of Sea Level Rise
Sea level rise can have some
dangerous impacts. Some are already occurring with the current sea level rise.
Coastal freshwater aquifers have been inundated with saltwater in many places.
Heavy groundwater withdrawal in some cities, including Houston, has led to
sinking ground levels, enough to seriously exacerbate flooding when it occurs.
This can also affect buildings and foundations. Storm surges have increased in
magnitude, and king tides are more frequent. At some point, these issues must
be addressed. Storm damage and shoreline erosion are more damaging effects of
sea level rise. Insurance costs and availability are likely to become issues in
vulnerable areas.
Of course, the biggest
potential problem with sea level rise is coastal flooding, often in the form of
storm surges, higher tides, and big rain events. The risk includes thousands of
hazardous waste sites that could be inundated in the future. A new study seeks
to identify and quantify the potential for flooding hazardous sites.
“Researchers pinpointed 5,500 locations that store,
emit, or handle sewage, trash, oil, gas, and other dangerous materials, all
vulnerable to coastal flooding by 2100. A substantial portion of this risk is
already unavoidable due to historical emissions. Worryingly, over half of these
sites are projected to face flood risks much sooner, potentially by 2050.”
In many places along the
coastal U.S., sea level rise is accelerating faster than the global average due
to erosion and land sinking from groundwater pumping, as the National Oceanic
and Atmospheric Administration (NOAA) notes.
“The 5,500 at-risk sites includes 44% that are fossil
fuel ports and terminals, 30% power plants, 24% refineries and 22% coastal
sewage treatment facilities. Most of the sites — nearly 80% — are in Louisiana,
Florida, New Jersey, Texas, California, New York and Massachusetts.”
Flood waters near industrial
animal farms or sewage treatment plants could expose people to bacteria like E.
coli, which can cause bloody or watery diarrhea, severe stomach cramps or
vomiting and fever. Chemical exposures can come from flooding of industrial
sites, refineries, and other fossil fuel sites. Risks need to be assessed, and
resilience planning needs to be conducted.
Sea Level Rise Must Be Addressed: Adaptation, Delaying the
Inevitable, and Retreat
Perhaps an important first
step in addressing the likely impacts of sea level rise would be to restrict
development in vulnerable areas. Unfortunately, many populated cities are
located along coasts and at low elevations, vulnerable to flooding from rising
sea levels. Also, unfortunately, the population is growing in many of these
cities, setting the stage for future problems coping with encroaching seas.
Populated regions of China, Bangladesh and India are particularly susceptible.
Some low-lying islands like the Maldives are suffering from rising seas and are likely to need to evacuate people soon.
Better flood protection
through engineered solutions like flood walls is important, but may not last
long enough if the seas keep rising, which is likely. The ability to adapt
depends on adaptation investment, either by companies that own buildings and
infrastructure or by communities and governments.
People are already moving out
of coastal areas due to the dangers of flooding. People are attached to places
and often don’t want to leave. Training programs can help people move out and
into new jobs and careers. 311,000 homes and properties are at risk in the
U.S., according to Dr. Cleetus in the Energy Switch episode. Unfortunately,
there is still new building and development going on in these areas. Power
plants, wastewater treatment plants, military installations, and industry all
present problems. Land use and development patterns are exacerbating exposure
to risk. Land subsidence in the Gulf Coast of the U.S. is another important
factor that suggests forced displacement is coming. Insurance companies are
beginning to make insurance unavailable to high-risk areas. Flood protection
and storm protection need to be incorporated into development and existing
facilities. Disruption of sedimentation patterns by coastal infrastructure is
another issue. Massive pumps will help mitigate sea level rise, but they won’t
last if sea level keeps rising. Mangrove forests are very helpful for
mitigating coastal flooding and are considered to be a nature-based solution.
It also keeps overall adaptation costs lower. Dasgupta notes that higher
salinity crops like sunflowers can grow in salinized soil areas. Cleetus notes
that a better assessment is needed to prioritize adaptation measures. She
emphasizes that low-lying islands and places that did not contribute much to
global warming are suffering its biggest impacts, and this is an environmental
justice issue, and rather a climate justice issue. Dasgupta makes three final
points: 1) adaptation is necessary and ecosystem and community vulnerabilities
must be understood with good comparisons with baseline data, 2) adaptation
measures must be location-specific and will need community and government
support, and 3) a very difficult cost-benefit analysis must be done. Whether
subsidized mitigation or subsidized retreat will be the preferred measure needs
to be determined.
Energy Switch’s Tinker notes:
“A combination of engineered, natural, and social
adaptation strategies will likely be most effective.”
References:
Warning:
thousands of hazardous sites could flood and release chemicals. Dorany Pineda.
The Independent. November 20, 2025. Warning
thousands of hazardous sites could flood and release chemicals
Explainer:
What Is Causing Sea Level to Rise? Martina Igini. Earth.org. September 25, 2023.
Explainer: What Causes the Sea Level
to Rise? | Earth.Org
Sea
Level Rise. Energy Switch. Season 4, Episode 7. PBS. April 7, 2024. Energy Switch | Sea
Level Rise | Season 4 | Episode 7 | PBS
No comments:
Post a Comment