In January this year, data from two leading global organisations told us what we already sort of knew — that 2023 was the hottest year on record, and 2024 could potentially be worse. America’s National Aeronautics and Space Administration (NASA) and Europe’s Copernicus Climate Service simultaneously published data that should alarm the most hardline of global warming sceptics. Two months later, the World Meteorological Organization (WMO) published its independent study that confirmed the NASA and Copernicus conclusions.
NASA said global temperatures last year were around 1.2 degrees Celsius above the average for its baseline period (1951-1980). Copernicus told us that 2023 marks the first time on record that every day within a year has exceeded 1°C above the 1850-1900 pre-industrial level. Close to 50% of days were more than 1.5°C warmer than the 1850-1900 level, and two days in November were, for the first time, more than 2°C warmer. Meanwhile, the WMO report confirmed that 2023 saw the global average near-surface temperature at 1.45 °Celsius above the pre-industrial baseline. It was the warmest ten-year period on record.
The Centre for Science and Environment, which has been publishing the ‘State of India’s Environment’ report annually since 2014, said in its 2024 report that India witnessed its warmest ever August and September in 122 years, as per the Indian Meteorological Department (IMD). February 2023 was also the warmest ever February on record since 1901. On September 12 last year, Srinagar recorded its second hottest day in September in 132 years. More than 3200 people died directly as a result of heat waves, and around two million hectares of cropland were damaged.
This year so far has not been any different.
Urban agglomerations are grappling with extreme heat, raising questions about whether these temperature increases are due to local influences and global climate change. It is not a simple answer, but if we have to understand urban heat and mitigate its effects to a certain degree, then we ought to understand what really contributes to you and me sweating more. Our grandparents were essentially right in cribbing about every year being hotter than the previous one.
While the worldwide impact brings warm spells of air from the ocean currents, the intensity of heat depends on microclimatic conditions within the city. What drives these changes, then? Is it global factors, or local anthropogenic activities such as emissions?
Policymakers need to understand underlying causes behind increasing urban temperatures, only then will they be able to formulate effective mitigation measures.
This knowledge also empowers us, the citizens, as our actions can significantly influence local anthropogenic activities.
What makes our cities hot?
Simply put, the sun and the earth have a heat exchange programme. We can’t see it, but it’s there. In theory, this means that the earth should return to space an amount of heat equivalent to what it receives from the sun. But that is not the case. Human activity such as burning fossil fuels and rampant construction of concrete structures add heat to our atmosphere, delaying emissions and creating an imbalance.
In technical terms, this is called the Urban Heat Island (UHI) effect, where cities become warmer than their rural surroundings by approximately 2-5 degrees Celsius. While this phenomenon can benefit cities in colder climates by reducing the need for heating, it poses severe challenges in warmer areas.
In Indian cities, the UHI effect has several — and severe — negative consequences. It alters the urban microclimate, creating new zones of intense heat, increasing the demand for air conditioning and compromising thermal comfort. It heightens the risk of heat-related health issues, such as heat exhaustion and heatstroke, exacerbates chronic health conditions, encourages the spread of infectious diseases and significantly affects the mental well-being of the most vulnerable groups, particularly children and the elderly.
At the regional level, climate change is increasingly recognized as a primary driver of escalating global heat waves. These extreme heat events are becoming more common worldwide, accompanied by delayed monsoons and atypical wind patterns.
The El Niño effect, characterized by unusually high ocean temperatures, significantly affects marine ecosystems and nearby terrestrial environments. India, bordered by the ocean on three sides, is particularly vulnerable. The country's coastal states face severe consequences, including drought, altered weather conditions and unpredictable rainfall that can be excessively heavy or scant.
These environmental changes lead to a rise in heat-related health issues within these regions.
Can we minimise the impact?
Let’s face the truth: The effects of global and local heat phenomena are relentless and far-reaching. Of course it’s daunting, but studies have suggested that this is not a lost cause. Citizens and policymakers alike can take practical steps to lessen the harsh effects of heat on our urban environments.
Citizens can adopt interim solutions, such as moving to a cool place under the shade or keeping hydrated, recommended by the National Disaster Management Authority, to combat the immediate threats posed by heatwaves. However, these are only a short-term fix. For enduring resilience, both individuals and policymakers must implement sustainable strategies that extend well beyond the fleeting duration of a heatwave.
As cities grapple with soaring temperatures, whether from UHI or broader climate change, the quest for cool has never been more critical. Strategies like planting trees, creating water bodies and improving ventilation can potentially mitigate urban swelter. There’s a catch — these one-size-fits-all solutions don't always align with each city’s unique challenges.
Therefore, it’s time to explore some fresh and even counter-intuitive strategies that cater specifically to the diverse needs of urban environments. How can cities innovate to keep the mercury at bay while considering their specific geographical and cultural contexts?
Think beyond UHI mapping
Cities should go beyond simply mapping areas of high heat and focus on identifying the root causes of rising temperature. With their complex morphologies, urban areas often intensify the heat impacts of global climate change, effectively turning cities into heat magnifiers. The confluence of dense structures and human activities in these areas exacerbates the heat, highlighting the urgent need to address and minimise the local contributions to global warming.
By pinpointing the specific sources of anthropogenic emissions within cities by precisely mapping and modelling using remote sensing, urban planners can effectively tailor their strategies to map and mitigate these critical ‘heat pockets’. This shift in focus could be a game-changing step toward making our cities cooler and more sustainable in the face of rising global temperatures. Government authorities need to appoint expert empowered committees to get this done.
Using satellite imagery and ground-based observations, countries like Singapore and Hong Kong are at the forefront of researching anthropogenic heat emissions (AHE). These areas, known for their intense summer heat, are developing sophisticated strategies to combat temperature increases directly attributable to human activity.
AHE is vital research not confined to regions traditionally affected by extreme heat. European cities also make significant strides under the famous Euroflux project, employing numerical models and remote sensing techniques to map anthropogenic emissions. This data is crucial for urban planners and policymakers striving to understand and adapt to micro-climatic variations, ensuring cities are better prepared to handle the challenges posed by urban heat.
In India, despite possessing a robust network of satellite assets, a crucial gap remains in our environmental monitoring capabilities—the absence of sensors capable of detecting land surface heat. This limitation hinders our ability to map temperature anomalies accurately.
Moreover, urban areas typically focus on monitoring basic weather parameters such as temperature, humidity, and wind speed, overlooking advanced metrics such as flux measurements that could offer deeper insights into environmental conditions. The time has come for a strategic shift. By embracing more sophisticated monitoring techniques, including flux measurements, India can enhance its approach to environmental management. This advancement is not merely about improving data quality; it's about ensuring a sustainable future and fostering a comprehensive strategy for life on Earth. This proactive step would pave the way for smarter, more resilient urban planning and a healthier living environment for all.
(Dr Y Nithiyanandam heads the geospatial programme at Takshashila Institution and is a globally recognised expert on urban heat phenomena.)