The deadly landslides that struck Kerala’s Wayanad district earlier this month, claiming the lives of over 350 people, were significantly amplified by climate change, according to a new study by World Weather Attribution (WWA). This international team of leading scientists found that human-caused climate change made the heavy rainfall that triggered the landslides about 10% heavier.
The study, published on the WWA website on August 14, highlights the urgent need for more robust assessments of landslide risk and improved early warning systems in hillside regions of northern Kerala to prevent similar disasters in the future.
The WWA scientists analyzed climate models with high enough resolution to accurately reflect rainfall in the small study area. Their analysis revealed that the intensity of rainfall during the crucial period was increased by 10% due to climate change. They concluded that climate change has made single-day monsoon downpours in Wayanad about 10% heavier.
The study emphasizes that such intense bursts of monsoon rainfall are expected to become even heavier in the future, further increasing the risk of deadly landslides. This alarming trend is projected to continue until the world shifts away from fossil fuels and embraces renewable energy sources.
The analysis also underscores the importance of taking proactive measures to mitigate the risk of landslides. It recommends minimizing deforestation and quarrying activities, which can exacerbate slope instability. Furthermore, it stresses the critical need for improved early warning and evacuation systems to protect communities in northern Kerala from future landslides and floods.
The Wayanad landslides occurred after an exceptional spell of monsoon rain on July 30, when over 140 mm of rain fell in a single day – nearly a quarter of London’s annual rainfall. This intense rainfall fell on already saturated soils, which had been drenched by two months of seasonal monsoon rains, triggering catastrophic landslides and floods in the Wayanad district. The 150 mm of rainfall that fell over 24 hours in Wayanad is the third heaviest on record in Kerala.
The study was conducted by a team of 24 researchers from universities and meteorological agencies across India, Malaysia, the United States, Sweden, the Netherlands, and the United Kingdom. The research team emphasizes that the Wayanad landslides are a stark reminder of climate change’s real-time impact. Mariam Zachariah, a researcher at the Grantham Institute – Climate Change and the Environment, Imperial College London, stated, “The extreme burst of rain that dislodged an entire hillside and buried hundreds of people was intensified by human-caused warming.”
The study’s key findings highlight the gravity of the situation:
* The Wayanad landslides resulted in devastating loss of life and occurred in a mountainous region with loose, erodible soils after 140mm of precipitation fell on saturated soils.
* In today’s climate, which is 1.3°C warmer than it would have been at the beginning of the industrial period, an event of this magnitude is expected to occur about once every 50 years.
* The event is the third heaviest one-day rainfall event on record, with heavier spells in 2019 and in 1924, and surpasses the very heavy rainfall in 2018 that affected large regions of Kerala.
* Overall, the available climate models indicate a 10% increase in intensity. Under a future warming scenario where the global temperature is 2°C higher than pre-industrial levels, climate models predict even heavier 1-day rainfall events, with a further expected increase of about 4 per cent in rainfall intensity.
* Given the small mountainous region with complex rainfall-climate dynamics, there is a high level of uncertainty in the model results. However, the increase in heavy one-day rainfall events is in line with a large and growing body of scientific evidence on extreme rainfall in a warming world, including in India, and the physical understanding that a warmer atmosphere can hold more moisture, leading to heavier downpours.
* While the linkage between land cover and land use changes and landslide risk in Wayanad is mixed in the limited existing studies, factors such as quarrying for building materials, and a 62 per cent reduction in forest cover, may have contributed to the increased susceptibility of the slopes to landslides when the heavy rain fell.
* 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, raising the need for adaptation actions that may include reinforcing susceptible slopes, landslide early warning systems, and construction of retaining structures to protect vulnerable localities.
