Facts and Figures

Climate change is intensifying the global hydrological cycle

  •  A review of recent changes in the global water cycle that analysed more than 100 studies (based on observations) found rising global and regional trends in runoff, floods and droughts, and other climate related events and variables in the second half of the 20th century that together support the perception of an intensification of the hydrologic cycle.
  • Tundra and Arctic regions face the loss of permafrost and the potential for methane release with greater warming at the poles.
  • Mountains are seeing shortened and earlier snow and ice melt and related changes in flooding. At higher altitudes increased winter snow can lead to delayed snow melt. 
  • Wetlands will be negatively affected where there is decreasing water volume, higher temperatures and higher intensity rainfall.
  • The IPCC report suggests that by 2050 annual average runoff will have increased by 10%-40% at high latitudes and decreased by 10%-30% over some dry regions at mid-latitudes and semi-arid low latitudes.
  • Documented trends in floods show no evidence for a globally widespread change. 
  • More intense droughts, affecting more people and linked to higher temperatures and decreased precipitation, have been observed in the 21st century. 
  • A study of spatial and temporal changes in streamflow droughts using a dataset of more than 600 daily European streamflow records from the European Water Archive of the UNESCO Flow Regime from International Experimental Data (FRIEND) detected no significant changes for most stations. However, distinct regional differences were found. 
  • Mediterranean ecosystems are diverse and vulnerable, susceptible to changes in water conditions. Even with a temperature rise of 2ºC, the Southern Mediterranean may lose 60%-80% of species.

Related themes: Climate Change and Adaptation; Uncertainty and Risk; Ecosystems

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