Climate change is impacting mountain regions, which cover about a quarter of the Earth’s land surface and are home to around 1.1 billion people. They are known as the “water towers of the world” because river basins with headwaters in the mountains supply freshwater to over half of humanity, including in the Himalaya-Hindu Kush and Tibetan Plateau region, known as the Third Pole.
The cryosphere – or frozen water – is hit hard by climate change. Glaciers are retreating, snow and ice are melting and permafrost is thawing. This translates into a short-term increase in landslides, avalanches and floods and a long-term threat to the security of water supplies for billions of people.
The Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and the Cryosphere in a Changing Climate said that smaller glaciers found for example in Europe, eastern Africa, the tropical Andes and Indonesia are projected to lose more than 80% of their current ice mass by 2100 under high emission scenarios. The retreat of the high mountain cryosphere will continue to adversely affect recreational activities, tourism, and cultural assets.
As mountain glaciers retreat, they are also altering water availability and quality downstream, with implications for many sectors such as agriculture and hydropower.
Limiting warming would help people adapt to changes in water supplies in mountain regions and beyond, and limit risks related to mountain hazards.
Glaciers and ice sheets in polar and mountain regions are losing mass, contributing to an increasing rate of sea level rise, together with expansion of the warmer ocean.
While sea level has risen globally by around 15 cm during the 20th century, it is currently rising more than twice as fast – 3.6 mm per year – and accelerating, according to the IPCC report.
WMO’s Global Crysophere Watch is an international mechanism for supporting all key cryospheric in-situ and remote sensing observations. It provides authoritative, clear, and useable data, information, and analyses on the past, current and future state of the cryosphere.
WMO convened a High Mountain Summit in October 2019 to identify priorities to protect high mountains and the cryosphere. It commits itself to a new Integrated High Mountain Observation and Prediction Initiative as one of the tools to address the challenges of climate change, melting snow and ice and water-related hazards and stress.
It agreed a goal that people who live in mountains and downstream should have open access to hydrological, cryospheric, meteorological, and climate information services to help them adapt to and manage the threats imposed by escalating climate change.
The current rate of global mean sea-level rise of 5mm/year corresponds to a volume of water discharged by the Amazon river in about 3 months.