Sea level rise is certain 

Source: This post is based on the article “Sea level rise is certain” published in The Hindu on 23rd Sep 2021. 

What is the news? 

Recently, Intergovernmental Panel on Climate Change (IPCC) published a report, ‘Climate Change 2021: The Physical Science Basis’.

This report provides scientific reviews on the science and impacts of climate change. It also discusses different shared socio-economic pathways for the future with varying levels of greenhouse gas (GHG) emissions. 

What are the scenarios illustrated by the report? 

The scenarios illustrated are the following:  

First, very low and low GHG emissions, where emissions decline to net zero around or after the middle of the century, beyond which emissions are net negative;  

Second, intermediate GHG emissions; it is extremely likely that average warming will exceed 2 °C near midcentury. 

Third, high and very high emissions where they are double the current levels by 2100 and 2050, respectively.  

Today, the average global temperature is already 1.09 °C higher than preindustrial levels and CO2 concentration in the atmosphere is currently 410 ppm compared to 285 ppm in 1850. 

What are the findings of the report? 

First, sea level rise occurs mainly due to the expansion of warm ocean waters, melting of glaciers on land, and the melting of ice sheets in Greenland and Antarctica. Sea level rise will continue after emissions no longer increase, because oceans respond slowly to warming.  

Second, Global mean sea level (GMSL) rose by 0.2m between 1901 and 2018. Sea level rise in the last century was mainly due to thermal expansion. But glacier and ice sheet melt are now big contributors. Sea level can rise as high as 1.61 m by 2100.  

Third, ice sheets can destabilise rapidly as the water gets warm (marine ice sheet instability or MISI) and ice cliffs can collapse swiftly in a related process, leading to rapid sea level rise; this is marine ice cliff instability (MICI).  

Fourthly, there is uncertainty regarding when high-end scenario will occur. 

What is the situation in India regarding sea level rise? 

Communities along the coast in India are vulnerable to sea level rise and storms. They will be accompanied by storm surges, heavy rain and flooding in case of further increase in sea level.  

What are the recommendations? 

Adaptation to sea level rise must include a range of strict measures, along with coastal regulation. 

The government should not insure or bail out speculators, coastal communities should be alerted in advance and protected during severe weather events.

Natural and other barriers should be considered in a limited manner to protect certain vulnerable areas.

Retreat should be part of the adaptation strategies for some very lowlying areas.