Climate change is not just about changes in temperature. The whole water cycle is also affected.
A warmer world means the atmosphere has the capacity to hold greater moisture.
So there are changes in the amount of water vapour, rainfall and the circulation of water in the atmosphere.
Rainfall has many characteristics, including amount, frequency, intensity and type.
- Rainfall diagram
- Surface runoff: movement of rain water over land surface into river channels
- Evaporation: liquid water held in the soil, lakes and rivers is heated by solar energy and becomes water vapour that rises into the atmosphere
- Precipitation: source of water onto the land surface
- Snow melt runoff: melting snow runs over land surface into channels
Long term changes in rainfall have been observed. The 20th Century has seen an increase in precipitation in Northern latitudes, but a downward trend in the tropics, particularly after the mid-1970s.
Areas that have seen an overall reduction in precipitation are also likely to have seen an increase in heavy rainfall events.
The maps and data shown here cover the period 1985 to 1999, represented as individual months and yearly average. There are global maps, maps for 18 of the world’s major river basins.
The maps make it possible to visualise the changes over a season as well as the year to year changes.
