New research confirms the influence of global warming on global precipitation. As temperatures rise, wet regions get wetter and dry regions get drier.

To measure the amplification of the water cycle, researchers from the University of Southampton collected and analyzed ocean water samples from around the globe. Salinity is affected by the outflow of freshwater. In wet regions, freshwater is spilled into the ocean in abundance, diluting ocean water and suppressing salinity levels. The opposite is true of dry regions, where water resources are likely to become increasingly scarce.

The real-world findings suggest the rate of water cycle amplification has been overestimated by models. Wet regions are getting wetter and dry regions are getting drier, just not quite as quickly as simulations suggest. But the discrepancy is minor, researchers say.

The researchers used measurements of salinity throughout the global and deep oceans over the last 60 years to estimate how much global rainfall is changing.

The researchers found that the regions, which are relatively wet, like Northern Europe are getting wetter and dry regions are getting drier both by about 2 per cent over the last 60 years. This process is called amplification of the water cycle.

Previous research indicates that amplification of the water cycle, is happening at 7 per cent per 1°C of global warming. The new study estimates that amplification happens at about three to four per cent per 1°C. The research team believe this is probably due to a weakening of the atmospheric circulation which transports freshwater from the dry to wet regions of the globe. 

Nikolaos Skliris, a research fellow at Southampton, said in a news release that their findings match  what has been predicted by models of a warming climate.

Skliris also added that the agreement between climate models and observations over the recent past is another important finding of this study because it adds confidence to climate model projections of water cycle amplification under greenhouse gas emission scenarios.