Understanding spatiotemporal variability in precipitation and temperature and their future projections is critical for assessing environmental hazards and planning long-term mitigation and adaptation. In this study, 18 Global Climate Models (GCMs) from the most recent Coupled Model Intercomparison Project phase 6 (CMIP6) were employed to project the mean annual, seasonal, and monthly precipitation, maximum air temperature (Tmax), and minimum air temperature (Tmin) in Bangladesh. The GCM projections were bias-corrected using the Simple Quantile Mapping (SQM) technique. Using the Multi-Model Ensemble (MME) mean of the bias-corrected dataset, the expected changes for the four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) were evaluated for the near (2015–2044), mid (2045–2074), and far (2075–2100) futures in comparison to the historical period (1985–2014). In the far future, the anticipated average annual precipitation increased by 9.48%, 13.63%, 21.07%, and 30.90%, while the average Tmax (Tmin) rose by 1.09 (1.17), 1.60 (1.91), 2.12 (2.80), and 2.99 (3.69) °C for SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5, respectively. According to predictions for the SSP5-8.5 scenario in the distant future, there is expected to be a substantial rise in precipitation (41.98%) during the post-monsoon season. In contrast, winter precipitation was predicted to decrease most (11.12%) in the mid-future for SSP3-7.0, while to increase most (15.62%) in the far-future for SSP1-2.6. Tmax (Tmin) was predicted to rise most in the winter and least in the monsoon for all periods and scenarios. Tmin increased more rapidly than Tmax in all seasons for all SSPs. The projected changes could lead to more frequent and severe flooding, landslides, and negative impacts on human health, agriculture, and ecosystems. The study highlights the need for localized and context-specific adaptation strategies as different regions of Bangladesh will be affected differently by these changes.

Climate change (CC) is impacting the hydrology in the basins of the Himalayan region. Thus, this could have significant implications for people who rely on basin water for their lives and livelihoods. However, there are very few studies on the Himalayan river basins. This study aims to fill this gap by presenting a water balance for the Brahmaputra River Basin using the Soil and Water Assessment Tool (SWAT). Results show that snowmelt contributed about 6% of the total annual flow of the whole Brahmaputra, 21% of the upper Brahmaputra, and 5% of the middle Brahmaputra. The basin-wide average annual water yield (AWY) is projected to increase by 8%, with the maximum percentage increase in the pre-monsoon season. The annual snowmelt is projected to decrease by 17%, with a marked decrease during the monsoon but an increase in other seasons and the greatest percentage reduction in the upper Brahmaputra (22%). The contribution of snowmelt to AWY is projected to decrease while rain runoff will increase across the entire Brahmaputra and also in the upper and middle Brahmaputra. The impact assessment suggests that the upper Brahmaputra will be most affected by CC, followed by the middle Brahmaputra. The results can be used to support future water management planning in the basin taking into account the potential impact of CC.

Mangrove forests protect coastlines from erosion, enhance biodiversity, store carbon, and support coastal communities. These ecosystems rely on hydrological conditions. This paper reviews past, present, and future hydrological characteristics of Bangladesh’s Sundarbans to guide restoration and sustainable development. It examines historical and projected hydrological indicators, addressing knowledge gaps and suggesting strategies. Renowned for productivity, biodiversity, and socio-economic benefits, the Sundarbans depend on seasonal freshwater from the Ganges River. However, threats from climate change and human activities, including reduced freshwater flow due to India’s Farakka Barrage on the Ganges, rising salinity, cyclones, and pollution, endanger these ecosystems. The primary threat is mangrove destruction for alternate land use and reduced sediment supply due to upstream dam construction. Sea-level rise is a secondary concern, as a healthy Sundarbans delta could naturally accrete with adequate sediment input and mangrove growth. Sustainable management practices are critical, including maintaining upstream water flow, minimizing deforestation, and rehabilitating degraded areas. Alternative livelihoods and strategies addressing salinity rise are essential. Long-term approaches should adopt adaptive management and ensure sustainable resource use. Policy actions must regulate human activities, mitigate cyclone impacts, ensure freshwater availability, halt harmful industries, and promote awareness and surveillance. Protecting mangroves to reduce CO₂ emissions and advancing research are vital.

The Sundarbans mangrove ecosystem, the world’s largest contiguous mangrove forest, is under pressure from changing salinity due to climate change, reduced freshwater input from upstream rivers, and tidal dynamics in the Bay of Bengal. Despite its ecological and socio-economic significance, previous studies have not provided a comprehensive, location-specific assessment of salinity that explicitly links spatial heterogeneity with hydroclimatic drivers. This study synthesised and analysed the best available data in the Bangladesh Sundarbans over the 26 years to quantify the characteristics, trends, and interrelationships of these variables spatially and temporally. The results reveal that salinity has been consistently higher in the western part of the Sundarbans, and extreme salinity levels have increased since 2010. There has been a statistically significant decrease in the freshwater inflow from the Ganges through the Gorai River (at the Gorai railway bridge location) since the early 1980s, which has led to increased downstream salinity. Strong statistical correlations enabled robust predictions of salinity as a function of rainfall and temperature. A rising water level trend at Hiron Point is attributed to the rise in sea levels. The absence of long-term measurement data prevents the exploration of salinity dynamics in the numerous creeks that crisscross the mangrove ecosystem. It is crucial to establish continuous monitoring and assessment to better understand and manage the impacts of climate change and development on the Bangladesh Sundarbans and similar coastal ecosystems worldwide. Graphical abstract

Droughts have severely affected Afghanistan over the last four decades, leading to critical food shortages where two-thirds of the country’s population are in a food crisis. Long years of conflict have lowered the country’s ability to deal with hazards such as drought which can rapidly escalate into disasters. Understanding the spatial and temporal distribution of droughts is needed to be able to respond effectively to disasters and plan for future occurrences. This study used Standardized Precipitation Evapotranspiration Index (SPEI) at monthly, seasonal and annual temporal scales to map the spatiotemporal change dynamics of drought characteristics (distribution, frequency, duration and severity) in Afghanistan. SPEI indices were mapped for river basins, disaggregated into 189 sub-catchments, using monthly precipitation and potential evapotranspiration derived from temperature station observations from 1980 to 2017. The results show these multi-dimensional drought characteristics vary along different years, change among sub-catchments, and differ across temporal scales. During the 38 years, the driest decade and period are 2000s and 1999–2022, respectively. The 2000–01 water year is the driest with the whole country experiencing ‘severe’ to ‘extreme’ drought, more than 53% (87 sub-catchments) suffering the worst drought in history, and about 58% (94 sub-catchments) having ‘very frequent’ drought (7 to 8 months) or ‘extremely frequent’ drought (9 to 10 months). The estimated seasonal duration and severity present significant variations across the study area and among the study period. The nation also suffers from recurring droughts with varying length and intensity in 2004, 2006, 2008 and most recently 2011. There is a trend towards increasing drought with longer duration and higher severity extending all over sub-catchments from southeast to north and central regions. These datasets and maps help to fill the knowledge gap on detailed sub-catchment scale meteorological drought characteristics in Afghanistan. The study findings improve our understanding of the influences of climate change on the drought dynamics and can guide catchment planning for reliable adaptation to and mitigation against future droughts.