- Climate change is causing the Muda River Basin in Malaysia to heat up, intensifying floods in the monsoon season and droughts in the dry season.
- A modelling study shows that solar radiation modification (SRM) could reduce these impacts in the future.
- However, one type of SRM could worsen dry season impacts in the medium and long term (2045-2084).
- The results differ from a similar study on another region in Malaysia, showing the importance of local studies.
A Degrees-funded team, led by Prof. Mou Leong Tan from Universiti Sains Malaysia, has investigated how SRM could affect temperature and precipitation extremes in northern Peninsular Malaysia. In Malaysia, climate-change-induced extreme precipitation in wet seasons is causing severe floods, while extreme dryness in between is causing worse droughts. For example, extreme precipitation from mid-December 2021 to early 2022 led to devastating flooding, killing more than 50 people, affecting more than 125,000 people, and resulting in financial losses of nearly US$1.5 billion. To find out whether SRM could help moderate some of these changes, the team compared the potential impacts of its use with the impacts of climate change. They found that while SRM methods would be effective at reducing temperature and rainfall extremes, their impact on dry-season rainfall was more complex, and varied with SRM type and time scale.
Future projections
A previous study by the team on a different river basin in eastern Peninsular Malaysia found that SRM would lower rainfall in both wet and dry seasons. The Muda River Basin represents a new case study of a tropical region with a different rainfall regime, which plays a crucial role as a freshwater source for agricultural, industrial and domestic use in northern Peninsular Malaysia. They used the latest climate models to compare four scenarios for the region: unabated climate change (‘worst-case’, leading to up to 5°C warming by 2100), some mitigation of climate change (‘middle-of-the-road’, leading to around 3°C warming), and two scenarios that use SRM to reduce unabated warming to the level of the middle-of-the-road scenario. The two SRM scenarios modelled were global solar dimming, where less of the Sun’s energy reaches the atmosphere (for example using hypothetical structures in space to reflect sunlight), and stratospheric aerosol injection, where reflective particles are introduced into the upper atmosphere to similar effect. Under each scenario, the team modelled the projected temperature and rainfall patterns, including how Malaysia’s wet and dry seasons would be affected over the short term (out to 2044), mid-term (2045-2064) and long term (2065-2084).
Rainfall results
Under both climate change scenarios in the model, temperatures and wet-season rainfall over the basin dramatically increased, with the worst-case scenario causing the most extreme changes. Both SRM scenarios reduced the temperature rises compared to the worst-case scenario, but the impact on rainfall was much more variable. While both SRM methods showed promise in reducing extreme wet-season rainfall, likely preventing more serious flooding in the monsoon seasons, the effect on the dry seasons could make some droughts worse. The modelling showed that using stratospheric aerosol injection as the SRM method decreased rainfall in the dry season in the medium and long term. The increased dryness represents both less monthly rainfall and more consecutive days without rainfall. Mou Leong said: “The potential increases in dry spells for the Muda River Basin could indirectly affect agricultural and freshwater supplies, posing considerable challenges to farmers. This result, together with our previous research on another river basin in Malaysia, shows how important it is to conduct local studies. “As well as more local studies, further investigation using additional climate, crop and hydrological models, as well as different solar geoengineering experiments, are sorely needed. Such research could provide as crucial guidance to policymakers and local stakeholders.”
‘Assessment of solar geoengineering impact on precipitation and temperature extremes in the Muda River Basin, Malaysia using CMIP6 SSP and GeoMIP6 G6 simulations’ by Mou Leong Tan, Yi Lin Tew, Juneng Liew, Govindasamy Bala, Mari R. Tye, Chun Kiat Chang, and Nurfashareena Muhamad is published in Science of The Total Environment.
