Context: Recent report by Climate Trends has flagged that People living in and near the coastal areas in India may be compelled to stay indoors during working hours for more than half of 2100.

• According to the report Severe heat conditions — and not the novel coronavirus disease (COVID-19) pandemic — would be driving people to do so.

Key Findings

• Millions in India are currently reeling under a severe heat wave. Scientists have warned that the rising climate crisis will make the situation more unbearable in the coming years.
• The report said most parts of India experience 12-66 days of potentially deadly heat and humidity combinations in a year — expressed by ‘wet bulb temperature’. 
• It is an index that measures the impact of heat and humidity on the human body.

The report pointed out that a temperature increase of 4.3 degrees Celsius by 2100 relative to pre-industrial temperatures may happen under RCP (representative concentration pathway) 8.5 scenario.

• The wet bulb temperature will cross the deadly threshold for six months or more by another nine decades.

Climate trends said that “Even fit and acclimatised people can’t work at a wet bulb temperature of 32°C; at 35°C, even fit and acclimatised people sitting in the shade die within six hours. Climate change is making these wet bulb temperatures more likely.”

Heat and humid hotspots to suffer most  

• The report said that “The west coast will be increasingly affected with around 269 days of wet bulb temperature days in Goa (up from 35 currently); 362 days in Kochi (up from 98); and around 349 days in Mangalore (up from 72 currently),”.
• About Heat and humid hotspots: Under this, “Air can hold more moisture with more heat, and the combined impact of heat and humidity becomes critical. With more warming under climate change impact, the combined impact of heat and humidity is set to rise,”.

Heat humidity combination may affect health, productivity

• Journal Weather and Climate Extremes claimed that heat waves caused 17,362 deaths during the last five decades. These accounted for 12 per cent of total deaths due to extreme weather events.
• According to the study, India experienced 73 heat wave spells in 2019 against an average of 17 as measured during 1986-2016.

There are five physiological mechanisms, according to the report, which are triggered by heat exposure: 

1. Ischemia (reduced and restricted blood flow), 
2. heat cytotoxicity (cell death), 
3. inflammatory response (swelling), 
4. disseminated intravascular coagulation (abnormal blood clotting), and 
5. rhabdomyolysis (breakdown of muscle fibres).

These mechanisms affect seven vital organs: Brain, heart, intestines, kidneys, liver, lungs and pancreas. “There are 27 lethal combinations of these mechanisms and organs that have been shown to be caused by heat".

Other Findings

• According to the study, India experienced 73 heat wave spells in 2019 against an average of 17 as measured during 1986-2016.
• It also warned that most of India is presently facing a ‘high’ risk to workability during the hottest months with wet bulb temperature ranging from 30-33°C. It estimated that India currently loses an estimated 21 per cent of effective outdoor working hours due to extreme heat and humidity.
• A McKinsey report, published 2020, stated that under the worst possible climate impact scenario of RCP 8.5, the loss of outdoor working hours may increase to 24 per cent by 2030 and 30 per cent by 2050.