Date: 12/10/2022

Relevance: GS-3: Conservation, environmental pollution and degradation, environmental impact assessment.

Key Phrases: UN climate, Storms and tidal surges, Rising sea level, Warmer temperatures, Indian Ocean, Coastal flooding, Low-lying island nations, Global sea level, Relocation, Building Sea Wall, Building Enclosures, Natural Infrastructure.

Context:

• According to UN climate experts, sea levels have already risen 15 to 25 cm (six to 10 inches) since 1900, and the pace of rise is accelerating, especially in some tropical areas.
• If warming trends continue, the oceans could rise by nearly one additional meter (39 inches) around the Pacific and Indian Ocean islands by the end of the century.
• This is still below the highest point of the smallest, flattest island states, but rising seas will be accompanied by an increase in storms and tidal surges: Salt contamination to water and land will make many atolls uninhabitable long before they are covered over by the sea.
• According to a study cited by the UN's Intergovernmental Panel on Climate Change, five nations (the Maldives, Tuvalu, the Marshall Islands, Nauru and Kiribati) may become uninhabitable by 2100, creating 600,000 stateless climate refugees.

Sea level rise

• Over the past century, the average height of the sea has risen more consistently—less than a centimeter every year, but those small additions add up.
• Today, sea level is 6 to 10 inches (6-25 centimeters) higher on average than it was in 1900. That's a pretty big change: for the previous 2,000 years, sea level hadn't changed much at all.
• The rate of sea level rise has also increased over time. Between 1900 and 1990 studies show that sea level rose between 1.2 millimeters and 1.7 millimeters per year on average.
• By 2000, that rate had increased to about 3.2 millimeters per year and the rate in 2016 is estimated at 3.4 millimeters per year.

Causes for rising sea level:

• Scientists agree that the changes in climate evident today are largely caused by human activity, and it's climate change that drives sea level rise.
• Sea level started rising in the late 1800s, soon after we started burning coal, gas and other fossil fuels for energy. When burned, these high-energy fuel sources send carbon dioxide up into the atmosphere. Carbon dioxide absorbs heat from the sun and traps it, warming the atmosphere and the planet.
• As the planet gets warmer, sea level rises for two reasons.
  • First, warmer temperatures cause ice on land like glaciers and ice sheets to melt, and the meltwater flows into the ocean to increase sea level.
  • Second, warm water expands and takes up more space than colder water, increasing the volume of water in the sea.

Vulnerability to Island Nations:

• The IPCC report pointed that the global mean sea level in the Indian Ocean is rising at 3.7 meters annually, adding that extreme sea level events that previously occurred once every 100 years, will now be seen nearly every year, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion.
• This seriously comes up as a major threat to the low-lying island nations of the Indian Ocean like the Maldives etc.
• Even the coastal areas of the nations like India and Africa are under serious threat from the sea level rise.
• Sea level rise will hit the coasts the hardest. Over the coming centuries, land that is today home to between 470 and 760 million coastal residents will be inundated by sea level rise associated with a 4 degree Celsius warming that will occur if we fail to curb the amount of carbon dioxide in the atmosphere. Much of this population lives in cities.
• Sea level rise already makes storms more dangerous, causing more flooding and damage in areas crowded with people. And it will affect different parts of the world differently, with some parts of the planet being particularly hard hit.

What's the difference between global and local sea levels?

• Global sea level trends and relative sea level trends are different measurements. Just as the surface of the Earth is not flat, the surface of the ocean is also not flat—in other words, the sea surface is not changing at the same rate globally.
• Sea level rise at specific locations may be more or less than the global average due to many local factors: subsidence, upstream flood control, erosion, regional ocean currents, variations in land height, and whether the land is still rebounding from the compressive weight of Ice Age glaciers.
• Sea level is primarily measured using tide stations and satellite laser altimeters. Tide stations around the globe tell us what is happening at a local level—the height of the water as measured along the coast relative to a specific point on land.
• Satellite measurements provide us with the average height of the entire ocean. Taken together, these tools tell us how our ocean sea levels are changing over time.

Various steps taken to tackle sea level rise:

• Relocation:
  • Many coastal cities have planned to adopt relocation as a mitigation strategy. For example, Kiribati Island has planned to shift to Fiji, while the Capital of Indonesia is being relocated from Jakarta to Borneo.
• Building Sea Wall:
  • Indonesia’s government launched a coastal development project called a Giant Sea Wall or “Giant Garuda” in 2014 meant to protect the city from floods.
• Using Beaches as Barriers:
  • Similar to seawalls, beaches and dunes can act as a natural wall and reduce the impact of storm surges.
  • The bigger the beach or larger the dune, the more water can be stopped from reaching homes and roads. Towns can add sand to make beaches bigger or to prevent them from eroding.
  • Using this type of natural infrastructure can protect against flooding while maintaining beaches for the community to enjoy.
• Building Enclosures:
  • Researchers have proposed Northern European Enclosure Dam (NEED), enclosing all of the North Sea to protect 15 Northern European countries from rising seas.
  • The Persian Gulf, the Mediterranean Sea, the Baltic Sea, the Irish Sea, and the Red Sea were also identified as areas that could benefit from similar mega enclosures.
• Creating Natural Infrastructure
  • Coastal communities can restore natural infrastructure, which can act as a buffer against storms and coastal flooding.
  • Natural structures such as barrier islands, oyster and coral reefs, mangroves, seagrass, and salt marshes can work alone or in unison with built infrastructure, like seawalls, to absorb storm surges.
• Architecture to Steer Flow of Water:
  • Dutch City Rotterdam built barriers, drainage, and innovative architectural features such as a "water square" with temporary ponds.

Way Forward:

• Across the globe, we can see innovative and resourceful solutions from communities that are coming together to combat sea level rise. Such solutions can become the guiding path for other cities to follow.

Source: The Hindu

Mains Question:

Q. Discuss the factors that contribute to sea level rise in the world. Suggest measures to tackle the problem of sea level rise?