Rainfall

Australia

While there has been little change to total Australian rainfall since 1900, rainfall patterns have changed significantly.

Figure 3: Trend in Annual Total Rainfall 1900-2008 (mm/10yrs)
Source: Bureau of Meteorology, Trend maps - Australian Climate Variability and Change

 Rainfall 2008

Changes to rainfall patterns are even more apparent when examined over the last 58 years. Eastern Australia has become signficantly drier with some areas receiving a reduction of 50mm/10 years while areas in north western Australia are receiving 50mm/10 years more rainfall.

 rainfall trends

 

Trend in Annual Total Rainfall 1950-2008 (mm/10yrs)
Source: Bureau of Meteorology, Trend maps - Australian Climate Variability and Change

Rainfall declines have significant implications for water availability. For example, inflows into Perth’s dams averaged 338 Gigalitres per year between 1911-1974 and only 81.8 GL between 2001-2006.

 reduced inflows to dams

Reduced Inflow into Perth Dams
Source: Water Corporation, Yearly Stream Flow for Major Surface Water Sources
 

Globally

It is difficult to determine a global trend in rainfall as changes have been spatially variable over the last century.

On a regional basis increases in annual precipitation have occurred in the higher latitudes of the Northern Hemisphere and southern South America. Decreases have occurred in the tropical region of Africa and southern Asia.

There are difficulties in measuring precipitation so results are checked against other variables including observed changes in stream flow, lake levels, and soil moisture.