Bhutan is highly vulnerable to the impacts of climate change and is already facing the impacts of climate change such as extreme weather and changing rainfall patterns.
The most significant impact of climate change in Bhutan is the formation of supra glacial lakes due to the accelerated retreat of glaciers with increasing temperatures, according to the report on the Analysis of Historical Climate and Climate Change Projection by National Center for Hydrology and Meteorology (NCHM).
The study on Historical Climate Data Analysis and Climate Change Projection for Bhutan discusses data and methods used to study the past and future climate change projections for Bhutan.
The findings of the study indicate future increases in temperature and rainfall for Bhutan under future climate scenarios based on two scenarios called Representative Concentration Pathways 4.5 and 8.5.
The climate projections for Bhutan have been assessed over the two future climate periods of 2021 to 2050 and 2070 to 2100.
Under the RCP 4.5 scenario, the climate projection for surface temperature indicates an increase of about of 0.8 degree celsius to 1.6 degree celsius during 2021-2050 and about 1.6 degree celsius – 2.8 degree celsius towards the end of the century 2070-2099.
Overall the climate projection of surface temperature under the RCP 4.5 scenario indicated an increase in about of 0.8 degree celsius to 2.8 degree celsius from 2021-2100.
Higher numbers are projected under the RCP 8.5 scenario with climate projection for surface temperature indicated increase of about 0.8 degree celsius to more than 3.2 degree celsius towards the end of the century.
The mean annual rainfall over Bhutan is likely to increase in the future. Under the RCP 4.5 scenario, the mean annual rainfall over Bhutan indicates an increase of about 10 per cent to 30 per cent on the mean annual scale, with summer rainfalls between 5 per cent to 15 per cent.
Under the RCP 8.5 scenario, the mean annual rainfall indicates an increase of about 10 per cent to 20 per cent during 2021-2050 and with more than 30 per cent increase all over Bhutan towards the end of the century 2070-2100. Under both scenarios, there is an indication of an increase in the rainfall trend.
The report says, “Even though Bhutan is a net sequester of greenhouse gases (GHG), the effects of climate change and variability are becoming increasingly visible. Precarious geographical location and effects of climate variability and change have highly exposed Bhutan to a diversity of hazards, including cyclone induced storms, flash floods, landslides, earthquakes, glacial lake outburst floods (GLOF) and droughts”.
The report also says, “GLOF events were experienced in the country in 1957, 1960, 1968 and 1994. The 1994 GLOF event from Luggye Tsho killed 21 people, damaged 91 houses and 1,781 acres of land. The heavy rainfall brought about by Cyclone Aila in 2009 caused Bhutan to incur an estimated loss of US$ 17 million”.
The report further states, “The country is also increasingly experiencing prolonged and extreme droughts in some parts of the country, which in turn increases the risk of loss of biodiversity, forest fires, reduction of crop yield and agricultural productivity. Unseasonal and intense rainfall and hailstorms can destroy crops thereby affecting farmers who are caught unprepared”.
“Heavy rainfall triggering floods and flash floods are a recurring phenomenon in Bhutan, especially during the summer monsoon. In July 2016, the southern part of the country experienced a flash flood triggered by intense monsoon rainfall displacing more than 100 families and damaging infrastructures”, report states.
“Landslides are a major problem for the roads sector, the only transport during the summer monsoon. With most of the rivers confined in narrow gorges, blockage of rivers by landslides risks the formation of artificial dams that pose a great danger to downstream settlements and assets such as hydropower due to landslide dam outburst flood (LDOF). Extreme weather events have significant socio-economic consequences and adversely affect people’s livelihoods and well-being”, report claims.
The report says erratic rainfall patterns are already impacting agricultural productivity. Farmers increasingly report instability in crop yields, loss in production, declining crop quality, and decreased water availability for farming and irrigation.
Changes in precipitation pattern are impacting the availability of water for drinking and energy production in the short, medium and long-term, with cycles of flooding during monsoons and very low flows and drying streams during other seasons. Extreme weather events expose infrastructure assets (such as hydropower and road network) to increased risk of floods and landslides”.
This report was submitted by NCHM to GNHC and to the World Bank under the Strategic Program for Climate Resilience (SPCR) Project. The findings from this study provide initial assessments of possible future changes of climate over Bhutan.