‘Urban heat is a huge challenge — India has a history of mitigations like city trees’

Vivek Shandas teaches climate adaptation at

Portland

State University. Speaking to Times Evoke, he discusses why the world’s cities are heating up:
My area of research is the intersection of climate change, cities and adaptation to climate stressors. I use spatial analyses techniques, systematic scientific approaches and community engagement to understand climate stressors and adaptations in cities. One of the phenomenal research is the ‘

urban

heat island’ effect, first documented in the 1850s. This measures the differentiation between a city in temperature and humidity compared to adjacent areas which don’t have built environments or roads, buildings, etc. That difference is the ‘urban

heat

island’ effect. We’ve learnt of factors since that contribute to this phenomenon — these include materials used to build cities like asphalt, concrete, bricks and other supplies which are very dense in their composition. Often, the darker colours we paint these in also absorb and retain short-wave radiation from the sun.



This contrasts with green spaces that absorb such radiation but dissipate it relatively quickly. Trees and plants also transpire water which cools the environment further. Hard materials hold onto heat and amplify temperatures — this is a primary contributor to urban heat. Other factors include the configuration of buildings — with big buildings amassed along a waterway, like in Mumbai and other coastal cities, the wind coming off the waterway can get blocked. When buildings are placed close together as well, they reduce the convective movement of air which makes it stagnate and heat.

Picture source: iStock



We’ve also found temperature anomalies within a city — these are termed ‘hot spots’ where the relative difference between neighbourhoods or streets can vary upwards of twelve degrees Celsius. That suggests physical factors amplify heat even between streets. As it gets hotter — last year, India saw more days above 40 degrees than any prior year — that difference also increases. On a 40-degree Celsius day, a ten-degree difference between two neighbourhoods can become 20 degrees.

This is hugely concerning. Our studies show hotter areas tend to have more built-up infrastructure. This doesn’t mean only tall buildings — relatively lower but large, low-slung buildings, one to two stories tall, made of bricks or cinder blocks, surrounded by concrete or built-up parking lots, let the sun’s radiation hit surfaces, holding that heat for a long time. Planners should ensure such areas have place to plant trees which significantly reduce the temperature. As physical scientists, we’ve measured city temperatures across North America, the Middle East, Latin America and Asia — we found the hottest locations tend to coincide with lower-income areas.



Some term this ‘the luxury effect’ or the fact that wealthier people have space for greenery. However, this only points a finger of blame at the individual. I felt this was more of a systemic issue, driven by a larger set of policies. In 2020, we published a landmark study, showing how, in the US, the 1930s’ policies of segregation and exclusionary red-lining, where certain areas were marked out with red lines for immigrants, the poor and non-white populations, had a consistent correlation with the hottest city spaces. This showed the effects of a systemic policy and planning protocol in who experiences the hottest temperatures now.

These findings have resonances for India where over 7,40,000 people perish annually due to heat, most from lower-income groups. With 481 million urban residents and cities growing fast with in-migration, we are confronting severe impacts on those with the least capacity to cope. We need to examine whether we are building cities in ways that amplify temperatures. From a planning approach, we must increase green spaces. India has a rich history of cooling trees in cities. I grew up in Bengaluru amidst sprawling banyans and lush mango groves — this has changed over the last two decades with vast urban deforestation. We need to reverse this trend, creating city afforestation. If we start planting today, by the time the even hotter 2030s arrive, those trees will provide life-saving shade.

Globally, temperatures are breaching 50 degrees Celsius regularly now — but our built environment is not ready for this. I live in the Pacific northwest of the US. When the heat dome phenomenon descends on us, railway tracks buckle, electricity lines melt and roadways crack. The scale at which these high temperatures are impacting urban environments is unprecedented. It makes planning for adaptations and mitigations urgent.

Stay updated with the latest news on Times of India. Don't miss daily games like Crossword, Sudoku, Location Guesser and Mini Crossword. Spread love this holiday season with these Christmas wishes, messages, and quotes.