Sweltering heat wave hits Sri Lanka; climate change will likely bring more

COLOMBO — The month of April is typically the warmest in Sri Lanka as the sun is positioned directly over the Indian Ocean island. Coupled with high humidity, the high temperatures make people uncomfortable and sweaty. This year, the Department of Meteorology went so far as to issue heat warnings for several districts, cautioning residents against exposure to high heat that can have harmful health implications.

As neighboring South Asian countries are scorched by a severe heat wave, the unusually high temperature rise is impacting people and their daily lives, a change that causes worry among locals about climate risk.

“As the temperature has risen to about 36 degrees Celsius [96.8 degrees Fahrenheit], Sri Lanka has experienced about 3 degrees Celsius [5.4 degrees Fahrenheit] increase of the daily maximum temperature during the recent heat stress period,” says Shiromani Jayawardena, the deputy director of the Department of Meteorology. Exposure to excessive heat along with high humidity may prove stressful to the body and in extreme cases can even kill, so the department assesses the situation and issues warnings to the public to remain cautious, Jayawardena said.

This year, an unusual heat wave with high temperatures over 40 degrees Celsius impacted South and Central Asia. As Sri Lanka is an island, it did not have the same impacts as neighboring countries, but climate models project risks of similar heat waves after 2030 under emission projections, Jayawardena told Mongabay.

Increased heat stress is an indication of climate change, and a recent study found that deadly heat stress is becoming a common occurrence across South Asia even with 1.5 degrees Celsius (2.7 degrees Fahrenheit) global warming. Lareef Zubair, a scientist at the Foundation for Environment, Climate, and Technology (FECT) said heat stress in Sri Lanka is rising to dangerous levels for a larger share of the population due to climate change.

Sri Lankans are now experiencing more warm nights compared with cold nights. A study found that annually averaged mean minimum temperatures are increasing, reducing the gap between maximum and minimum temperatures. Temperatures in Sri Lanka have been rising faster than the global average at about 1.8 degrees Celsius (3.24 degrees Fahrenheit) per decade, Zubair said.

“By 2019, 2020 and 2022, The heat stress reached risk levels particularly in low elevation parts of Sri Lanka from April to June and this is a clear indication of the role of warming temperatures,” Zubair said. The data also indicate that the number of days the heat index reaches “extreme caution” levels is on the rise, the climate scientist said.

Urban areas more impacted

Urbanized areas are more prone to excessive heat due to the heat island effect in which human activities make the urban environment significantly warmer than rural areas, said Erandathie Lokupitiya, a professor of environmental science at the University of Colombo. “In an urban setting, there are buildings, tarred roads and cemented pavements which can absorb heat and then release them,” she said.

Studies also show how the heat in Colombo, Sri Lanka’s commercial capital, has risen over time.

In this era of climate change, cities should be designed strategically to mitigate increasing threats emanating from heat stresses, said Jagath Munasinghe, an urban planner at the University of Moratuwa. “There are wind corridors that can help to naturally cool the urban environment, reducing the heat through a natural windfall. Colombo is a coastal town, so there is sea breeze that can help build strong wind tunnels if planned carefully,” Munasinghe said. Air flows to , wetlands and open spaces father inland that could receive continuous airflow. It could provide an effective method to reduce the city’s heat, Munasinghe told Mongabay.

The plants are nature’s air purifiers, as their evaporation adds water vapor to the atmosphere. But urban areas are rapidly losing greenery, making them unhealthy and uncomfortable to live in, so regreening cities should become a priority, Munasinghe said.

“Trees can be planted along the wind corridors, so the air will get naturally cool,” Munasinghe said. Greening cities has multiple advantages, but vegetation should be planted well based on a feasibility study to make it sustainable, he added.

Heat impact on biodiversity

Not only humans but animals, plants and ecosystems should brace for the inevitable impacts from increased heat stress. “The impact would be more for smaller animals; for example, it is estimated that a small increase in temperature could wipe out some insects and sensitive animals,” Lokupitiya said.

However, corals may be the most impacted by such heat stress, as higher ocean temperatures can make corals bleach and die. “May and June are the months when corals get bleached due to increased temperature resulting from extreme heat. These delicate organisms get severely impacted by heat stress,” said Arjan Rajasuriya, a coral scientist and a former researcher at the National Aquatic Resources Research and Development Agency.

Some corals revive and are resilient to heat stress, but in a prolonged event, more corals bleach. The impact could be worse for corals in shallower seas and those in areas where water is stagnated, Rajasuriya added.

Sri Lanka needs more research to analyze the possible impacts of such heat stress and overall impacts of climate change, said Devaka Weerakoon, fauna coordinator for the IUCN Red List. The impacts of the changing climate could be greater along the borders of the country’s climatic zones, so more studies are required to project the possible impacts of climate change on living organisms, Weerakoon told Mongabay.