The scientists project that dry regions such as temperate Australia will become drier and wet regions such as the tropics will become wetter. Image: Schlling2SCIENTISTS in the USA and Australia have revealed in a new study that there is a clear link between rising global temperatures, changing rainfall patterns and oceanic salinity levels.
The study, ‘Ocean Salinities Reveal Strong Global Water Cycle Intensification during 1950–2000’, published in the journal Science reported that changing oceanic salinity levels are a ‘fingerprint’ of climate change.
Australian scientists from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Lawrence Livermore National Laboratory, USA, analysed data taken from the world’s oceans over the last 50 years.
By examining observed global surface salinity levels and the relationship between salinity, rainfall and evaporation in climate models, the study concluded the global water cycle has already intensified by 4 per cent since 1950.
This is twice the rate predicted by current models.
Lead author Dr Paul Durack says “salinity shifts in the ocean confirm climate and the global water cycle have changed.”
“These changes suggest that arid regions have become drier and high rainfall regions have become wetter in response to observed global warming,” he says.
The study predicts that with a predicted temperature rise of 3C by the end of the century, a 24 per cent intensification of the water cycle may occur.
According to co-author Dr Richard Matear, the “warming of the Earth’s surface and lower atmosphere is expected to strengthen the water cycle largely driven by the ability of warmer air to hold and redistribute more moisture.”
“The ocean matters to climate—it stores 97 per cent of the world’s water; receives 80 per cent of all surface rainfall and; it has absorbed 90 per cent of the Earth’s energy increase associated with past atmospheric warming.”
He says the intensification of the water cycle is an escalation in the patterns of exchange between evaporation and precipitation.
“Unlike measuring precipitation on land which is very variable, the ocean provides a more reliable rain gauge,” he says.
The scientists project that dry regions such as temperate Australia will become drier and wet regions such as the tropics will become wetter.
“We will have greater extremes at both ends of Australia, from the northern tropical climates to the central and southern temperate climates.
Changing rainfall patterns will have immense implications for agricultural and natural systems in Australia,” he says.
Durack says that the “redistribution of rainfall will affect food availability, stability, access and utilisation.”
