Record temperatures across most of the world in 2023 also affected water resources and water-related hazards. Heatwaves contributed to deepening and new droughts in South America and Canada. There were many extreme rainfall events, including several cyclones.
The global water cycle in 2023 was influenced by a change in circulation and ocean water temperatures in the Pacific Ocean from La Niña to El Niño conditions but against a backdrop of overall increasing sea surface temperatures due to global warming. The higher temperatures increase the strength and rainfall intensity associated with storm systems such as tropical cyclones. There were a relatively large number of such events in 2023, and the human and economic toll was large.
The year started with continuing heavy rain and flooding in the Philippines and the western USA. In February, cyclonic storm systems hit Madagascar, Malawi and Mozambique in southeast Africa, while heavy rain caused floods and landslides in southeastern Brazil. In April, southeast Asia was hit by a large-scale heatwave, followed by cyclone Mocha in Myanmar. The first half of the year also saw extremely dry conditions in northern Argentina and nearby regions and in southwestern Europe.
In May, record dry conditions in northern Italy were abruptly ended by heavy rainfall and flooding. An extremely wet season in South Korea, India and Pakistan brought landslides and flooding between June and August, while in Canada, very dry and hot conditions caused a record wildfire activity. From July onwards, very dry and recurrent hot conditions across South America led to a rapidly developing drought in the Amazon basin that intensified during the second half of the year.
In September, a Mediterranean cyclone or ‘medicane’ brought heavy rainfall to Greece and caused reservoir dams to fail in Libya, killing thousands. In November, several years of deepening drought in Somalia were interrupted by heavy rainfall and flooding, while nearby South Sudan largely remains in drought. The final weeks of 2023 brought severe storm systems with heavy rains and flooding to the northeast coast of Australia.
At the start of 2024, the greatest risk of developing or intensifying drought appears to be in Central and South America (except southern Brazil and Uruguay), southern Africa and western Australia. Regions unlikely to develop drought for at least several months include the Sahel region and the Horn of Africa, northern Europe, India, China and southeast Asia, and southern Brazil and Uruguay.
Key aspects of the water cycle in 2023 over the global land area were:
- Precipitation was close to average. There does not appear to be a clear trend towards more monthly high or low rainfall extremes.
- Average temperature was the highest recorded globally and in 77 countries. The frequency of record-warm months was also the highest observed.
- Relative air humidity was the second lowest on record, continuing a trend towards drier average and extreme conditions. Drier-than-normal conditions prevailed nearly everywhere.
- Despite warmer and drier conditions, high annual soil water conditions were observed in many regions.
- Vegetation vigour was the highest since 2001, continuing a steady increase over the last decades
- Surface water occurrence from water bodies and flood events was the second lowest in two decades, but months with record high water occurrence appear to be increasing globally.
- River flows were slightly lower than the previous year. Record high river flows appear to be getting more common, and record low flows less common.
- Lake volumes have been increasing over recent decades. High storage records are broken more often.
- Many dry and wet records in terrestrial water storage ‑ combining all parts of the terrestrial water cycle ‑ were broken in 2023, despite several missing months of missing data.
Find full details in the report ( PDF, 51p.).
