RISING SEA LEVEL – ENVIRONMENT
News: Explained
| How rising sea levels threaten agriculture, rainfall, and the social fabric
What's in the news?
● The
World Meteorological Organization (WMO)
has found in a new report that the world’s
sea level is rising at an unprecedented rate, portending potentially disastrous
consequences for the weather, agriculture, the extant groundwater crisis, and
social disparities.
About the report:
● The report, entitled
‘State of the Global Climate 2022’, was published last week. Along with
accelerating sea-level rise, it focused on a consistent rise in global temperatures,
record-breaking increases in the concentration of greenhouse gases as well as
glacier loss, sustained drought-like conditions in East Africa, record rainfall
in Pakistan, and unprecedented heat waves that struck Europe and China in 2022.
● Droughts, floods and heat
waves affected communities on every continent
and cost many billions of dollars.
● Antarctic sea ice fell to
its lowest extent on record and the melting of some
European glaciers was, literally, off the charts.
Sea level rise:
● The
rate of global mean sea-level [GSML] rise has doubled between the first decade of the satellite record and the
last.
● Satellite altimeter: Since
the 1990s, scientists have been measuring sea-level rise using satellite
altimeters. These instruments send radar
pulses to the sea surface and measure the time they take to get back and
the change in their intensity. The higher the sea level, the faster and
stronger the return signal.
● According
to the WMO report, the sea level has been rising in the three decades for which
satellite altimeter data is available (1993-2022). But while the rate of sea-level rise was 2.27 mm/year in 1993-2002, it
shot up to 4.62 mm/year in 2013-2022.
Major contribution to the
sea level rise:
1. Three primary reasons:
● The
WMO report points to the following factors as being responsible for a rising
GSML:
○ Ocean
warming
○ Ice
loss from glaciers and ice sheets
○ Changes
in land water storage.
2. GSML budget:
● The
report also quantifies the individual
contribution of the above three factors to yield what researchers call the
“GSML budget”.
● According
to the report, in 2005-2019, loss of
glaciers and ice sheets contributed 36% to the GSML rise.
● Ocean warming –
the phenomenon of rising mean ocean temperatures – contributed 55%.
● Changes in the storage of
land water contributed less than 10%.
3. Ocean thermal expansion:
● As
increasing concentrations of carbon
dioxide and other greenhouse gases drive global warming, 90% of the ‘extra’
heat is stored in the oceans. This leads to ocean warming.
● As
the ocean heats up, it undergoes thermal expansion, which in turn leads to a
rise in the GSML.
● One
measure of ocean warming is the ocean
heat content (OHC). As per the report, OHC measures in 2022 touched a new
record.
4. Cryosphere:
● The
report also says that the earth’s ice
cover, known as the cryosphere, has thinned.
● The
cryosphere includes the Arctic and Antarctic regions (called “sea ice”), glaciers,
the ice sheets of Greenland and Antarctica (area of ice on land covering more
than 50,000 km), seasonal snow cover, and permafrost (mass of land that remains
below 0º C for at least two straight years).
Major Impacts:
1. Land crunch:
● Rising
seas swallow more of the land cover, particularly in coastal areas, coastal
communities will face an “acute shortage
of land for human use”.
● This
land crunch will mean that those who are better off will be able to cope better
than marginalized groups, leading to an increase in social disparities between
people living in coastal areas.
2. Natural disasters or Extreme events:
● Weather
formations like cyclones are known
to typically originate in the open seas.
● As
the GSML continues to rise, along with a rise in ocean temperatures, the
chances of cyclones could increase, affecting coastal communities and leading
to large economic liabilities for
tropical countries like India and South Africa, which have high population
densities.
3. Saltwater intrusion:
● As
the GSML continues to rise, more seawater could seep into the ground, leading
to the groundwater – which is usually freshwater – turning more and more
saline.
● This
in turn can exacerbate water crises in
coastal areas as well as agriculture in adjacent regions.
4. Affect Coastal ecosystem:
● Coastal
ecosystems could be “completely changed”.
● For
example, in the Sunderbans delta in West
Bengal, the world’s largest mangrove area, rising sea levels and coastal
erosion, due to loss of land and sediment from coastal areas, has left more
islands submerged under water, and that in turn has forced members of local communities to migrate. Indeed, a combination of
these forces having increased child trafficking in the Sundarbans area has
already been documented.
5. Affect local coastal communities:
● Since the lives of coastal communities, including their economic activities, is tied intricately with the coastal ecosystem, changes in the coastal ecosystem as a result of GSML rise – especially when it happens faster than rehabilitative policies and laws can catch up – will further endanger the socio-economic stability of these communities.
6. Food insecurity:
● Climate
change will increasingly put pressure on food production and access, especially
in vulnerable regions, undermining food
security and nutrition and increases in frequency, intensity and severity of
droughts, floods and heatwaves, and continued sea level rise will increase
risks to food security in vulnerable regions.
7. Health impacts:
● Reduction
of freshwater in coastal regions can cause water-related
diseases like diarrhoea.
● Decrease
in food production can contribute to malnutrition
among coastal populations.
● Flooding
in coastal areas can increase outbreaks of water-borne diseases like cholera.
8. Submergence:
● Although
the sea-level rise is not uniform globally and differs locally, the report
warns that prolonged and increasing sea-level rise would encroach on coastal
infrastructure and settlements and expose low-lying coastal ecosystems to
submersion and destruction.
Solutions to mitigate the impacts:
1. Reducing greenhouse gas emissions:
● The
primary cause of sea level rise is global warming caused by the burning of
fossil fuels.
● To
address this, it is essential to reduce greenhouse gas emissions through
actions such as shifting to renewable
energy sources, increasing energy efficiency, and improving public
transportation.
2. Adaptation measures:
● Coastal
communities can also implement adaptation measures such as building sea walls, relocating vulnerable communities, and improving
coastal land-use planning to reduce the impacts of sea level rise.
3. Natural Infrastructure:
● Restoration
of natural infrastructure by coastal towns can serve as a safeguard against
storms and coastal flooding.
● Barrier islands, oyster
and coral reefs, mangroves, seagrass beds, and salt marshes
are examples of natural structures that can absorb storm surges on their own or
in conjunction with man-made structures like seawalls.
4. Developing sustainable infrastructure:
● Infrastructure
such as buildings and roads can be designed to be more resilient to the impacts
of sea level rise.
● This
includes elevating buildings, designing roads to withstand flooding, and
improving drainage systems.