The impacts of increased concentration of greenhouse gases in the earth’s atmosphere such as average temperature rise and changes in precipitation dynamics that pose an existential threat to millions in the global south are frequently discussed. A range of different actors are leading efforts to identify and scale adaptation measures. But the increase in accumulated heat at local levels is less discussed and systematically studied, though this accumulation poses equally serious challenges.

Extreme heat is already becoming a regular problem in many parts of the world, including in South Asia. High temperature and humidity in the air raise the heat index or apparent temperature, and further increases risks for people. As the apparent temperature approaches the average human body temperature of 37 degrees C, it is harder for the body to function. If temperatures exceed this threshold for more than three days and nights in a row, it may result in a heat stroke. The body must cool down to recover. Without cooling down, our capacity to function effectively decreases quickly. In the Ganga plains, temperatures are likely to approach 37 degrees C for a higher number of days, and the elderly, children and pregnant women will face increased risks of heat strokes.

A 2014 study by the National Centre for Atmospheric Research (NCAR) and the Institute for Social and Environmental Transition (ISET) found that in the Ganga plains, temperature hovered around 37 degrees C for a total of 50 days between May and August in 1950. These hot spells usually lasted for two or three days, with lower temperatures in between. This historical data combined with climate change projections and models suggest that in 2050 the apparent temperature would increase by 5 to 7 degrees C. These models show that in 2050, about 152 out of 200 days between April and October would experience a heat index higher than 37 degrees C.

Heat island effects

Local heat island effects caused by human activities in rapidly growing urban areas add to the heat stress from a warming climate. This is evident across the cities of South Asia and even in hill cities like Kathmandu. Anecdotal evidence suggests that the summer temperature in urban Kathmandu’s built-up area is about 1 degree C higher than in the outskirts. Kathmandu’s built-up area is almost four times the size it was in the mid-1980s. This expansion is associated with decimation of natural heat sinks like ponds, wetlands, trees and green spaces.

A simple back of the envelope calculation combining humidity and temperature shows that in May 2016, Kathmandu’s air had 20 percent more heat than the corresponding month 30 years ago. However, good time series data about historical temperature records across different areas of Kathmandu is hard to come by to accurately assess changes in heat trends in the Valley. Given this limitation, the sale of air conditioners can be a proxy to understand the trend.

A study in 2015 estimated that, of the 25,000 to 28,000 air conditioners sold in Nepal, Kathmandu Valley’s share was 30 percent and the Tarai’s 70 percent. Currently about 18,000 to 20,000 individual units are sold in the Valley with an annual market growth of 15 percent. Compared to this, much fewer units were sold in Kathmandu in the early 1980s and it can be inferred that preference for active cooling has gone up as the city’s summer afternoons are hotter than before. Of course, this increase is also a result of higher incomes and purchasing capacity over the years.

Health risks

Millions of lower-income families in South Asia who are dependent on livelihoods that expose their bodies to extreme heat don’t have access to active cooling systems. For them increased heat means heightened health risks, lower productivity and even heat strokes. Particularly at risk are manual labourers and small farmers whose livelihoods are exposed to the external environment. Extreme heat harms livestock, crop growth and stored food— the very livelihood assets of the poor. Heat worsens the ills that emanate from low quality of drinking water supply, sanitation and solid waste management services. Heat exacerbates health risks from air pollution in cities.

Nepal will likely suffer from increased heat in the future. Temperature trend analyses show that both minimum and maximum temperature levels are increasing in some seasons in Nepal’s Tarai, and increasing in almost all seasons in the hills and the mountains. Model studies show that by 2060s, across Nepal, average temperature would increase by 2.8 degrees C compared to the mean of the 1970-1999 records. The Tarai will face increasing heat stress. Settlements in tar lands and lower river valleys in the hills will also face stress albeit lower than the Tarai, whereas hill settlements and cities like Kathmandu will face somewhat milder and episodic stresses.

Dealing with stress

Efforts to contain increasing heat stress will require significant improvements in the access to active and passive cooling techniques as well as delivery of basic services such as drinking water, sanitation and health, which help individuals to deal with heat. Providing cooling solutions across South Asia at the scale required presents massive technological and energy challenges. First, cooling technology needs to be affordable. Second, active cooling through air conditioners and other technologies will require the generation of additional reliable energy. If this increased energy demand is met from burning fossil fuel based sources, global greenhouse gas mitigation objectives will be seriously jeopardised.

Given the pace and scale of urbanisation in the global south and South Asia, it is likely that heat related challenges from the impacts of climate change as well as from urban heat island effects will increase. City governments need to be well prepared to deal with increasing heat stress. They should begin working with each other and also build partnership with their counterparts in the global north to minimise heat stress as well as adapt to other climate change impacts.

They must develop and implement urban development strategies that foster fundamental innovations in building design and construction, working behaviour, and regulations to minimise these impacts. Insulation, reflective and radiant barriers, and rooftop gardens can help concrete buildings retain low temperatures from overnight cooling for longer periods of time. The NCAR/ISET study found that in hot regions of Pakistan, average night time temperature in the rooms immediately below flat concrete roofs that didn’t have passive cooling measures was about 3 degrees C higher than outside.

Other necessary policy measures call for creating and maintaining open spaces and parks, developing and using climate-friendly affordable materials for constructing houses, providing clean energy solutions for both households and public transportation systems, and leveraging the capacities of local natural ecosystems to help absorb and adapt to the impacts of changes related to the climate and urbanisation. If emissions of greenhouse gases continue unabated and rise of global average temperature exceeds 2 degrees C by 2100, extreme heat conditions could severely increase, causing major challenges to the people across South Asia.

Dixit is Executive Director at ISET-Nepal