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The question of whether climate change has fundamentally altered Sri Lanka’s monsoons is urgent and critical, given that the country’s very economy and livelihoods hinge on its rainfall patterns. Sri Lanka’s climate revolves around two dominant monsoon seasons: the southwest monsoon (Yala), from May to September, and the northeast monsoon (Maha), from December to February. Yet, recent disruptions in rainfall intensity and distribution have sparked alarm, forcing a deeper examination into the undeniable role climate change is playing in destabilizing these life-sustaining weather systems.
Historical Rainfall Patterns and Recent Shifts
Sri Lanka’s Department of Meteorology has revealed alarming data on the island’s rainfall patterns, showing a clear shift in both the timing and volume of precipitation. Seasonal forecasts for 2023 predict a drastic drop in rainfall across multiple regions, with key months seeing normal to below-normal levels. This disturbing trend aligns with the disruptive effects of global climate forces like the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), which are increasingly driving unpredictable weather patterns across the region. The evidence underscores the escalating threat of climate-induced volatility in Sri Lanka’s weather systems. Read here
Global Climate Trends
On a broader scale, data from NASA’s Earth Science Division reveal significant atmospheric changes globally, including a rise in sea surface temperatures and altered wind patterns, both of which directly impact monsoon behaviors. The IPCC’s Sixth Assessment Report highlights that, while global warming contributes to more erratic rainfall events in South Asia, the intensity of monsoons may not uniformly increase. Instead, the data suggest that monsoon rainfalls may become more unpredictable—with some regions experiencing droughts and others floods—due to changes in moisture flow and the overall weakening of monsoon winds. Read here
The trend-per-decade maps display the annual and seasonal linear trends in precipitation and average mean air temperature across the period, 1971-2020. These maps reveal significant spatial variability, with more pronounced changes in higher latitudes. Using individual climate models to investigate these trends provides a deeper understanding of the variability within the region, compared to multi-model ensemble perspectives. For Sri Lanka and surrounding areas, these trends highlight both historical shifts and future projections in rainfall patterns due to climate change. Via World Bank’s Climate Change Knowledge Portal
Coastal stations (Colombo, Katunayaka, and Ratmalana) experienced significant increases in SWM rainfall, whereas interior stations (Badulla, Bandarawela, and Ratnapura) saw similar trends during the Second Inter-Monsoon (SIM). The analysis, using the Generalized Extreme Value (GEV) distribution and Sen–Theil regression, reveals a recent island-wide shift towards increasing rainfall, despite historical fluctuations in trend slopes. Read here
Sri Lanka’s Vulnerability: Insights from CRIP and FAO
The Climate Resilience Improvement Project (CRIP) underscores Sri Lanka’s vulnerability to these shifts, particularly in its agricultural and water management sectors. The variability in rainfall is already impacting crop cycles, which rely heavily on predictable monsoon rains. Read here and here. Studies from the FAO’s AQUASTAT data confirm that the country’s water resources are under increasing stress due to erratic rainfall and extended dry periods, posing risks for food security and water availability. Read here
Climate Change Projections: The World Bank’s Perspective
The World Bank’s Climate Change Knowledge Portal offers projections for future rainfall patterns in Sri Lanka. According to their models, Sri Lanka can expect shorter, intense bursts of rain rather than the steady, prolonged monsoons that previously characterized the island’s seasons. These intense events could lead to more flash floods, particularly in urban areas, while rural regions might simultaneously face drought-like conditions during critical agricultural periods.
From 2020 to 2099, the precipitation distributions shift towards higher values implies an increased likelihood of extreme rainfall in the future. This could heighten the risks of flooding and other hydrological challenges, demanding more adaptive strategies for water resources and disaster management over the coming decades.
The graph shows historical precipitation trends (black) until the early 2000s, followed by future projections under multiple SSP (Shared Socioeconomic Pathway) scenarios. From around 2075, a significant departure from natural variability becomes evident, marked by a vertical dashed line. Under higher-emission scenarios like SSP5-8.5 (in red), the variability and intensity of precipitation show substantial increases. This suggests that extreme precipitation events may become more frequent and intense towards the end of the century, with higher uncertainties under different climate trajectories. Therefore, the ilustration indicates a strong shift towards higher variability and precipitation extremes in Sri Lanka’s future climate, especially under more severe emissions pathways. Policymakers and planners must consider these trends for disaster management and climate adaptation strategies to mitigate potential impacts.
The chart illustrates shifts in rainfall variability across months, with color-coded markers indicating the standard deviation (SD) of change. Green circles represent significant increases in rainfall (greater than 2.5 SD), while yellow circles indicate moderate increases (less than 2 SD). Brown circles show minimal variability (less than 1 SD). The projection highlights a marked increase in extreme precipitation events during the early months, with noticeable shifts occurring particularly in March and April.
Therefore, this projection suggests that under high-emission scenarios, Sri Lanka may experience more frequent and intense rainfall events, especially in the earlier part of the year, indicating potential changes to the traditional monsoon seasons. These shifts could lead to increased risks of flooding and other climate impacts, emphasizing the need for adaptive strategies to manage water resources and mitigate disaster risks.
Conclusion: The Future of Monsoons in a Warming World
Climate change is undoubtedly altering Sri Lanka’s rainfall patterns, but the full impact on its monsoons remains complex and multi-faceted. Factors such as rising global temperatures, shifting oceanic conditions, and changing atmospheric dynamics contribute to more erratic and unpredictable precipitation events. Sri Lanka may witness a future where monsoons deliver intense bursts of rain over shorter periods, increasing the risks of flash floods and water scarcity during critical agricultural seasons.
As the trends toward higher precipitation variability and extreme weather events become more evident, especially under high-emission scenarios, adaptation becomes crucial. Improved water resource management, disaster preparedness, and agricultural diversification will be essential to mitigate the negative consequences of these climatic shifts. Proactive policymaking that integrates climate projections will enable Sri Lanka to navigate the challenges of a rapidly changing monsoon system.
References:
https://climateknowledgeportal.worldbank.org/country/sri-lanka/trends-variability-projections
https://www.fao.org/aquastat/en
https://www.meteo.gov.lk/images/2023/Rainfall_Prob-FC-April-June-2023_w.pdf
https://www.meteo.gov.lk/index.php?lang=en
Advances in Meteorology, Volume: 2018, Issue: 1, First published: 27 December 2018, DOI: (10.1155/2018/4217917)
http://www.irrigationmin.gov.lk/climate-resilience-improvement-project-crip/
https://www.fao.org/aquastat/en/countries-and-basins/country-profiles/country/LKA
https://data.apps.fao.org/aquastat/?lang=en
Images/ Maps:
Banner Image: Photo by Bibhukalyan Acharya on Pexels
https://climateknowledgeportal.worldbank.org/country/sri-lanka/trends-variability-projections
