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Rising temperatures affect the entire climate system, leading to melting ice, warming oceans, and disruptions to the water cycle. These changes ultimately result in an intensification of certain extreme weather events.
Melting ice
Excess heat accumulating in the climate system speeds up the melting of glaciers and ice caps. The period from 2023 to 2025, therefore, recorded the greatest loss of glacial mass since records began in 1950 for the reference glaciers monitored globally.
Thermal expansion of the oceans
This melting of the ice is compounded by the thermal expansion of the oceans as they warm and increase in volume. The average total rate of sea-level rise (due to thermal expansion of the oceans and glacial melt) is accelerating. From 2.1 mm per year between 1993 and 2002, the rate of rise increased to 4.1 mm per year during the 2016–2025 period, nearly double the previous rate.
This acceleration has significant consequences on coastal areas, increasing their exposure to coastal flooding and storms.
Glacial mass loss and its effect on sea level
| Period / year | Glacial mass loss | Impact on sea level |
| 2000–2011 | ≈ 231 Gt/year | ≈ 0.64 mm/year |
| 2012–2023 | ≈ 314 Gt/year | ≈ 0.87 mm/year |
| 2023 | 548 Gt | ≈ 1.5 mm |
| 2024 | ≈ 450 Gt | ≈ 1.2 mm |
| 2025 | ≈ 410 Gt | ≈ 1.1 mm |
| 2000–2025 | ≈ 7 500 Gt since 2000 | - |
Gt = Gigatons / mm: millimeter
Sources: World Glacier Monitoring Service (WGMS), Copernicus Climate Change Service, GlaMBIE (Nature, 2025).
Disrupted water cycle
Warm air can hold more moisture, which exacerbates both droughts and heavy downpours. According to Global Water Monitor 2025 (1), extreme rainfall events have picked up globally: a 2.3% increase in maximum daily rainfall per decade has been observed, thereby contributing to an increased risk of flooding and landslides.
Indicators of global water cycle disruption
| Indicator | Value |
| Increase in extreme rainfall (maximum daily precipitation) | +2.3 % per decade |
| Increase in extreme heat days (>35°C) | +8.3 % per decade |
| Global river basins in “normal” conditions in 2025 | Only 1 in 3 (the 6th consecutive year of imbalance) |
| Increase in flooding since 2000 | 134% |
| Increase in the number and duration of droughts since 2000 | 29% |
Sources: Global Waters Storage (GWM), World Meteorological Organization (OMM), UN-Water
The water cycle is becoming more extreme, alternating more and more rapidly between excess and scarcity. Climate scientists refer to these rapid shifts as “climate whiplash,” which can occur in the same region just a few months apart.
Globally, water-related disasters in 2025 claimed the lives of nearly 5 000 people, displaced approximately 8 million people, resulting in economic losses exceeding 360 billion USD.
Global warming: the El Niño and La Niña phenomena
El Niño and La Niña are the two opposing phases of the ENSO (El Niño–Southern Oscillation) climate phenomenon, which correspond to variations in the surface temperature of the tropical Pacific Ocean, accompanied by changes in the atmosphere.
These two phenomena temporarily influence temperatures, precipitation, and the frequency of certain extreme weather events in different regions of the world.
- El Niño generally corresponds to an abnormal warming of the waters of the tropical Pacific. It tends to raise the global average temperature and can contribute to certain droughts, heat waves, or other extreme events, depending on the region.
- La Niña corresponds to an abnormal cooling of the waters. It can temporarily limit the rise in global temperatures, while contributing to other types of extreme events in certain regions.
It is noteworthy that El Niño and La Niña cycles may alter the frequency, intensity, and geographic distribution of extreme weather events from one year to the next.
Global warming therefore acts as an amplifier of their effects, exacerbating certain natural variations. A particularly strong El Niño episode can, for example, lead to exceptionally high temperatures in an already hot climate.
The impact of El Niño and La Niña phenomena: 2015-2025
| Year | Dominant ENSO phase* | Global insured losses (in billions USD) | Comments |
| 2015 | Strong El Niño | 40 | Relatively moderate level of insured losses. |
| 2016 | El Niño → La Niña | 58 | Increase in insured losses compared to 2015. |
| 2017 | La Niña | 151.4 | A sharp increase in claims experience, particularly as a result of Hurricanes Harvey, Irma, and Maria. |
| 2018 | La Niña → neutral → El Niño | 92 | Lower losses compared to 2017, but still at a high level |
| 2019 | Weak El Niño | 63 | A decrease in insured losses compared with the previous two years. |
| 2020 | La Niña | 99 | Significant impact of storms, fires, and other secondary hazards. |
| 2021 | La Niña | 118.8 | Insured losses exceed 100 billion USD for the first time since 2017. |
| 2022 | La Niña | 125 | Second consecutive year above 100 billion USD, driven in particular by Hurricane Ian. |
| 2023 | El Niño | 108 | Severe convective storms account for a significant portion of insured losses. |
| 2024 | El Niño → neutral → La Niña | ≈140.6 | Very high claims experience, driven in particular by hurricanes, floods, and convective storms. |
| 2025 | Weak La Niña → neutral | 107 | The figure remains above 100 billion USD, with the Los Angeles wildfires and storms accounting for a significant share. |
* The phases can change within the same year
