UN-Water Publishes Analytical Brief on Water for Climate Mitigation

In November, the UN-Water Expert Group on Water and Climate Change published the UN-Water Analytical Brief on Water for Climate Mitigation. The UN-Water Expert Group supports cooperation and coordination of UN-Water Members and Partners on water and climate change-related issues. 

The analytical brief discusses the dependency of climate mitigation on the use of water and the effective management of water resources and of water and sanitation services. ‘Water’ in this report refers to terrestrial inland water (which may be surface water or groundwater), and for some uses could be desalinated seawater. 

The report refers in its structure to the listed measures of The Intergovernmental Panel on Climate Change (IPCC)  that has assessed that limiting global warming to 1.5 or 2°C requires limiting the concentration of greenhouse gases in the atmosphere. This can be done by reducing the emissions of carbon dioxide and other greenhouse gases such as methane and nitrous oxide and/or by increasing the ‘sinks’ – anything that removes carbon from the atmosphere faster than it is released – such as through replanting of degraded areas. Actions to achieve this reduction are grouped by IPCC into ‘climate mitigation measures’, taken up in the report in Annex 1. The measures are based on findings of the The International Universities Climate Alliance (IUCA) 2024, which has estimated the water requirements of a number of the climate mitigation measures assessed by the IPCC, tabulated in Annex 2 in the IPCC report. 

The Role of Water in Mitigation
Water is a necessary input to many of the clean energy measures (such as hydropower or geothermal energy) that are needed for the energy transition away from fossil fuel-based energy, as well as for measures to ensure carbon dioxide removal from the atmosphere. These measures need sufficient water supply to achieve climate mitigation and other benefits required from them. Effective water and wastewater management can also contribute directly towards emission reduction targets as poorly managed wastewater and sanitation systems, and some wetlands, reservoirs, and irrigation systems, are sources of emissions of greenhouse gases, especially methane and nitrous oxide. Their emissions can be reduced through improved management of water and sanitation services, providing multiple social, economic, and environmental benefits which can add value to any climate finance contribution.

The implementation of many mitigation measures required to limit global warming to 1.5 or 2 degrees Celsius will affect demand for water and its availability for other purposes and in different places. For example, the phasing out of fossil fuels will reduce water demand by thermal coal power plants, enabling water in their locations to be redeployed to support other objectives. However, many alternative low emission energy sources will increase water demand and will need assured water supply in their locations for their successful implementation.

Water availability may influence which climate mitigation measures to implement, how and where, and inform decisions on how to secure and sustain the necessary water supply. Identifying and reducing water-related risks by applying integrated water resources management (IWRM) and sustainable wastewater management approaches should facilitate financing while contributing to successful climate mitigation and limiting further global warming.

The IPCC has advised  that the sustainable development framework can be used to evaluate the long-term implications of climate mitigation actions on sustainable development and vice versa, and that the feasibility of implementing different sectoral mitigation options depends on how societies prioritise mitigation actions relative to other products and services. While progress in achieving the SDGs differs greatly between regions and countries, and within countries, current global data show that none of the SDG 6 targets are currently within reach globally: 2.2 billion people lack safely managed drinking water; roughly half of the world’s population experiences severe water scarcity for at least part of the year; and 3.5 billion people lack safely managed sanitation. The report states that indeed, less progress is being made on SDG 6 than on any of the other SDGs. Ideally, the report states, planning and implementation of nationally determined contributions  (NDCs) will be closely aligned with planning and implementation of Sustainable Development Goal (SDG) 6 with its water and sanitation targets.

Climate mitigation actions involving trade-offs with other water uses will require substantial consultation and engagement, particularly in cross-border systems. Regional and transboundary cooperation can help with optimizing the use of water resources for many kinds of climate action. Aligning climate mitigation and water objectives requires that water availability and usage is considered in all climate related planning, particularly in the preparation of NDCs, and that climate change is considered in all water, sanitation and hygiene strategic planning, including for shared transboundary water resources. 

Many global and regional organisations can support country-wide planning for the climate mitigation options and IWRM and sustainable wastewater management, necessary for securing the water requirements of mitigation actions. This includes UN system-wide support to developing countries for the preparation of their next NDCs.
According to the authors, the way forward entails that as countries review and update their NDCs, now is the time to understand how action on water and sanitation can contribute to climate solutions.