The threat of rising sea levels

The threat of rising sea levels

Context:

• The World Meteorological Organisation (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.
• The report, entitled ‘State of the Global Climate 2022’, was published last week.
• Along with accelerating sea­level rise, it focused on a consistent rise in global temperatures, record­breaking increases in the concentration of greenhouse gases as well as glacier loss, sustained drought­like conditions in East Africa, record rainfall in Pakistan, and unprecedented heatwaves that struck Europe and China in 2022.
• Antarctic sea ice fell to its lowest extent on record and the melting of some European glaciers was, literally, off the charts.

How much is the sea rising?

• The rate of global mean sea­level [GSML] rise has doubled between the first decade of the satellite record and the last.
• Since the 1990s, scientists have been measuring sea­level 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 (1993­2022).
• But, while the rate of sea­level rise was 2.27 mm/year in 1993­2002, it shot up to 4.62 mm/year in 2013­2022.

What causes accelerated sea­level rise?

• The WMO report points to the following factors as being responsible for a rising GSML: “ocean warming, ice loss from glaciers and ice sheets, and changes in land water storage”.
• According to the report, in 2005­2019, loss of glaciers and ice sheets contributed 36% to the GSML rise.
• Ocean warming the phenomenon of rising mean ocean temperatures contributed 55%, and changes in the storage of land water contributed less than 10%.
• As increasing concentrations of carbon dioxide and other greenhouse gases drive global warming, 90% of the ‘extra’ heat is stored in the oceans.
• 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.
• The report also says that the earth’s ice cover, known as the cryosphere, has thinned.

What problems will sea­level rise cause?

• Rising seas swallow more of the land cover, particularly in coastal areas, coastal communities will face an “acute shortage of land for human use”.
• It means that those who are better off will be able to cope better than marginalised groups, leading to an increase in social disparities between people living in coastal areas.

• Weather formations such as 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 such as India and South Africa, which have high population densities.
• As the GSML continues to rise, more sea water 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.

• In the Sundarbans 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.

Way forward:

• Focusing more on renewable forms of energy.
• More emphasis on waste to energy technologies.
• Afforestationand reducing deforestation.
• Implementation and binding targets on developed countries.
• Technology transfer and financial transfer from developed countries to Less developed and developing countries.

Syllabus: Mains; GS III – Environment

SOURCE: THE HINDU