The world is warming—not merely passing through one hot season
WMO recorded 2024 as the warmest year, with global mean temperature about 1.55°C above the pre-industrial level. The year 2025 remained the second or third warmest at about 1.43°C above the pre-industrial level, while 2015–2025 were the eleven warmest years on record. One year above 1.5°C is not the same as a permanent breach of the Paris Agreement goal, but it shows how close the world has come to that threshold.
The long-term driver is the accumulation of greenhouse gases from fossil energy, land-use change, industry, agriculture, and waste. El Niño and other natural variations can intensify or moderate a particular year, but they do not explain the multi-decade warming trend.
Indonesia is warming too, with seasonal and local amplifiers
BMKG analysis shows Indonesia's mean temperature increased by about 1.02°C over 1981–2024. In July 2026, the national mean was 27.0°C—about 0.8°C above the 1991–2020 July normal. Heat felt by communities is also shaped by El Niño, the dry season, reduced cloud cover, humidity, and the urban heat-island effect where concrete dominates and green space is limited.
Conditions are not uniform across Indonesia. Java, Bali, Nusa Tenggara, dense cities, small islands, and coastal zones face different risks. Climate change therefore needs to be translated into a source-water and system-readiness assessment for each location.
Quantity: water does not simply disappear—it arrives at different times and places
Higher temperatures increase evaporation from soil, vegetation, rivers, and reservoirs while also increasing water demand. Longer dry periods can reduce river, spring, reservoir, and groundwater recharge. As sources decline, groundwater abstraction often rises, increasing the risk of land subsidence and seawater intrusion in coastal areas.
Extreme rainfall does not automatically improve supply. Water falling too quickly is more likely to become runoff and flooding than to infiltrate or be stored—especially where buildings and roads cover the ground. A place can therefore flood during the wet season and still face clean-water shortages several months later.
Quality: heat, drought, and flooding create different risks
During hot, low-flow conditions, salts, nutrients, organic matter, and pollutants can become more concentrated. Warmer water can reduce dissolved oxygen and support algal growth in nutrient-rich waters. In coastal areas, seawater intrusion can increase salinity, TDS, chloride, and corrosion risk.
During heavy rain and flooding, raw water may experience sharp turbidity increases and receive sediment, waste, sewage, microorganisms, fertilisers, pesticides, or surface chemicals. Rapid change can overwhelm treatment systems. Water quality must therefore be assessed across seasons and managed through the source, treatment, storage, distribution, and point of consumption.
Contributions to begin at home and at work
- ✓Reduce emissions by using energy efficiently, setting air conditioning sensibly, and choosing lower-emission travel where practical.
- ✓Monitor the water meter and promptly repair leaks in taps, pipes, toilets, or tanks.
- ✓Match water quality to the need; use rainwater for suitable non-drinking purposes when safely designed and separated.
- ✓Keep oil, medicines, paint, chemicals, and waste out of drains and water bodies.
- ✓Protect trees, open soil, recharge areas, wetlands, and mangroves so the environment can retain water more effectively.
- ✓For facilities and businesses, prepare a water balance, test water in wet and dry seasons, and plan for drought, flooding, and source changes.
The ARS perspective
Climate change reinforces the principle Source Water × Use × Risk × Lifecycle. Future water systems cannot be designed from a single test result or only for average conditions. ARS considers source variation, real demand, seasonal risk, process control, maintenance, and verification so a solution remains reliable as conditions change. The goal is to move from treating water after a problem appears to managing risk before supply is disrupted.
Official references
This material provides general education. It does not replace laboratory testing, applicable local requirements, or a professional assessment of a specific water system.