At a recent climate change conference in India, scientists presented a striking visual. A global map displayed how 2024 temperatures diverged from historical norms, with deep red hues indicating temperature increases of 1°C to 2°C across many regions. Yet, amid this sea of red, India appeared as a conspicuous pale spot—suggesting significantly less warming.
Despite enduring back-to-back years of blistering heat and record-breaking temperatures, India has experienced a smaller increase in average annual temperatures than much of the world. Since 1901, the country’s mean temperature has risen by less than 0.7°C, which is about half of the global average. This finding may come as a surprise to many Indians bracing for another scorching summer.
The reasons behind this slower rate of warming remain unclear. The climate change conference, jointly hosted by the Indian Ministry of Environment and Harvard University, showcased various hypotheses but underscored that the phenomenon is still not fully understood. Although it’s known that tropical regions generally warm at a slower pace than the poles, other India-specific factors may be at play, such as air pollution and extensive irrigation. “I don’t think this is yet sufficiently settled,” said Peter Huybers, a climate scientist at Harvard. He emphasized that gaining clarity on this issue could greatly benefit India’s future climate planning.
One leading theory centers on air pollution. The Indo-Gangetic Plain, stretching from Pakistan through northern India to Bangladesh, is one of the most densely populated regions in the world. It suffers from severe air pollution due to a combination of industrial activities, traffic emissions, dust, cooking methods, and agricultural fires. This pollution includes aerosols that reflect sunlight, which could be contributing to regional cooling. Worldwide, similar pollution has been credited with partially offsetting the warming effects of greenhouse gases throughout the 20th century.
Recent studies suggest that as pollution levels decline, warming may accelerate. A 2024 study supported this idea, and another found that pollution reduction efforts in China raised average temperatures by 0.1°C between 2013 and 2019. These findings highlight a paradox: while India desperately needs to improve its air quality to prevent the over 1 million pollution-linked deaths annually, such cleanup efforts might inadvertently speed up the pace of warming.
During the conference, American climate experts drew attention when they predicted that India could warm twice as quickly in the coming decades. However, not all scientists are convinced that pollution is the primary factor behind India’s slower warming. Aerosol pollution in India includes high levels of soot, which, unlike other particles that reflect sunlight, actually absorb it and contribute to warming. Raghu Murtugudde, a professor emeritus at the University of Maryland now based in Mumbai, explained that the overall effect of aerosols remains ambiguous. “It’s not yet clear whether the net impact of aerosols is cooling or warming,” he noted. While satellite data point to a net cooling effect, ground-level observations haven’t confirmed this trend.
Moreover, Murtugudde pointed out a seasonal discrepancy that complicates the pollution theory. The winter months in India—when aerosol levels peak—have also witnessed the most significant warming. “Aerosols don’t seem to explain the seasonal pattern,” he said.
Murtugudde suggests that changes in wind patterns may offer another explanation. In a 2023 study, he and colleagues observed that accelerated warming over the Middle East has pulled monsoon winds northward over the Arabian Sea. This shift has been linked to increased rainfall and flooding in regions like Pakistan and northwestern India, which are traditionally dry. He is now exploring whether similar wind changes during other seasons might contribute to India’s relatively muted warming trend.
Another factor that may be influencing India’s climate is the large-scale expansion of irrigation in the northern part of the country. Irrigation increases evapotranspiration—the combined process of water evaporating from soil and transpiring from plants—which absorbs heat and cools the air. A 2016 study co-authored by Huybers found that this mechanism had cooled peak summer temperatures in the U.S. Midwest. A 2020 study reached a similar conclusion globally, emphasizing that irrigation particularly dampened warming over South Asia.
Still, the irrigation hypothesis is not universally accepted. Some Indian scientists argue that estimates based on satellite imagery and global datasets may be exaggerating the amount of water used for irrigation in northern India, particularly during summer when ground-based measurements show lower irrigation levels. This discrepancy raises doubts about whether irrigation can fully explain the observed temperature trends.
Govindasamy Bala, a professor at the Centre for Atmospheric and Oceanic Sciences at the Indian Institute of Science, remains skeptical of all these theories. According to Bala, there is no mystery. He believes India’s slower warming is simply a function of its geographic location in the humid tropics and natural variability within the climate system. While pollution and irrigation might have local effects, he argues, they are not significant at the national scale. “They could also be just noise,” Bala said.
To unravel the underlying causes, more targeted research is needed. “Untangling these factors will require a focused study to understand how they interact and evolve over time,” said Huybers. Murtugudde added that the reason the slower warming seems puzzling is “only because we haven’t paid attention.”
Indeed, scientific efforts have largely concentrated on the extremes of India’s climate—such as the increasingly deadly summer heat waves. Last summer alone, heat waves claimed more than 700 lives, according to one estimate. There is no doubt among experts that future summers will be even more dangerous.
However, better understanding of the historical climate trend in India could lead to more accurate projections and improved preparation. Even if India has warmed less than other nations so far, the trajectory may shift rapidly as environmental policies evolve and natural systems adjust.
In a world grappling with rising temperatures, India’s anomalously slow warming pattern offers both a mystery and a potential guide. By deciphering this phenomenon, scientists hope to equip the country—and perhaps others in similar climatic zones—with the tools to navigate an uncertain future.