Not only does the wet get wetter over land, but the driest areas get wetter too
From the UNIVERSITY OF NEW SOUTH WALES and the “Flannery says permanent drought over Australia” department
Global warming will increase rainfall in some of the world’s driest areas over land, with not only the wet getting wetter but the dry getting wetter as well.
New research published today in Nature Climate Change has revealed that in the Earth’s dry regions, global warming will bring an overall increase in rainfall and in extreme precipitation events that could lead to flash flooding becoming a more regular event.
“We found a strong relationship between global warming and an increase in rainfall, particularly in areas outside of the tropics,” said lead author Dr Markus Donat from the ARC Centre of Excellence for Climate System Science.
“Within the tropics we saw an increase in rainfall responding to global warming but the actual rate of this increase was less clear.”
Unfortunately for societies, businesses and agricultural activities that exist in arid regions, the expected increase in rainfall over dry areas does not necessarily mean that more water will become available according to the researchers. The additional heat caused by global warming will likely lead to increased evaporation. This means that while there may be more extreme flooding events it may have little impact on overall water storage rates.
“The concern with an increased frequency and in particular intensity of extreme precipitation events in areas that are normally dry is that there may not be infrastructure in place to cope with extreme flooding events,” said Dr Donat.
“Importantly, this research suggests we will see these extreme rainfall events increase at regional levels in dry areas, not just as an average across the globe.”
The researchers were able to reach this conclusion because they looked at regions with similar characteristics rather than trying to compare complex climate variations found when comparing one country or continent with another.
This meant that dry regions in Australia were compared with similarly dry regions in Asia, Africa and many other countries. At the same time, wetter regions across different countries were also compared. This allowed the researchers to directly compare like with like.
Importantly, the findings remained consistent across observations and models.
“With precipitation climate models and observations don’t always tell the same story regarding regional changes, but we were very surprised to find that our results turned out to be highly robust across both,” said Dr Donat.
“It appears the uncertainties in climate models were greatest where the observational uncertainties were greatest. This suggests that improved observations will be vital for those planning for climate change if they are to reasonably determine how future precipitation will change in every corner of the world with global warming.”
More extreme precipitation in the world’s dry and wet regions
Markus G. Donat, Andrew L. Lowry, Lisa V. Alexander, Paul A. O’Gorman & Nicola Maher
Nature Climate Change (2016) doi:10.1038/nclimate2941
Received 23 July 2015 Accepted 20 January 2016 Published online 07 March 2016
Intensification of the hydrological cycle is expected to accompany a warming climate1, 2. It has been suggested that changes in the spatial distribution of precipitation will amplify differences between dry and wet regions3, 4, but this has been disputed for changes over land5, 6, 7, 8. Furthermore, precipitation changes may differ not only between regions but also between different aspects of precipitation, such as totals and extremes. Here we investigate changes in these two aspects in the world’s dry and wet regions using observations and global climate models. Despite uncertainties in total precipitation changes, extreme daily precipitation averaged over both dry and wet regimes shows robust increases in both observations and climate models over the past six decades. Climate projections for the rest of the century show continued intensification of daily precipitation extremes. Increases in total and extreme precipitation in dry regions are linearly related to the model-specific global temperature change, so that the spread in projected global warming partly explains the spread in precipitation intensification in these regions by the late twenty-first century. This intensification has implications for the risk of flooding as the climate warms, particularly for the world’s dry regions.