A collaborative study conducted by researchers from India, Sweden, the United States, and the United Kingdom has revealed that human-induced climate change significantly contributed to the severity of the extreme rainfall event that triggered the landslides on July 30, killing more than 200 people in India’s southern state of Kerala.
The research by World Weather Attribution group, focused on assessing how climate change has altered the likelihood and intensity of such extreme weather events in the district of Wayanad, located in the mountainous Western Ghats, which was the hardest hit.
“The increase in climate change-driven rainfall found in this study is likely to increase the potential number of landslides that could be triggered in the future,” the study said.
The extreme rainfall not only triggered landslides but also caused widespread flooding, washing away bridges, inundating homes and roads, and leading to power outages across the region.
The soils in Wayanad were already highly saturated, a typical condition during the monsoon season. The heavy rainfall, which measured 140mm in a single day, exacerbated the situation, leading to catastrophic landslides. Wayanad has been identified as the most landslide-prone district in Kerala, a vulnerability highlighted in recent studies (Sharma, Saharia & Ramana, 2024).
Analysis and findings
The researchers analysed the one-day maximum rainfall (RX1day) during the monsoon season from June to September, focusing on northern Kerala. The findings indicate that the event in Wayanad was the third heaviest one-day rainfall event on record, surpassed only by similar events in 2019 and 1924.
In today’s climate, which is approximately 1.3°C warmer than pre-industrial levels, such an extreme rainfall event is expected to occur once every 50 years. The study also found that heavy one-day rainfall events have become about 17% more intense over the last 45 years, coinciding with a 0.85°C rise in global temperatures. Climate models predict a further increase in rainfall intensity under future warming scenarios, with a 4% rise expected if global temperatures reach 2°C above pre-industrial levels.
Despite some uncertainties in the models, the increase in extreme rainfall aligns with a growing body of scientific evidence linking climate change to more intense weather events, including in India. The study underscores the physical reality that a warmer atmosphere can hold more moisture, resulting in heavier downpours.
While the Indian Meteorological Department (IMD) accurately forecasted the extreme rainfall and issued state-level warnings, the broad scope of these warnings made it difficult to pinpoint which localities would be most affected by landslides. Effective early action was hindered by the lack of slope-specific landslide early warning systems, which are costly and challenging to implement.
The study suggests that reducing the exposure of people and assets to landslide-prone areas may be a more viable strategy. Additionally, changes in land use and cover, such as quarrying for building materials and a 62% reduction in forest cover, may have further increased the susceptibility of slopes in Wayanad to landslides.
