Climate Change intensify water cycle at twice predicted rate

Climate change numbered. Creatice Commons.

February 28, 2022SANDRP

This should be worrying all water managers, particularly in monsoon driven climate like India. New Research by New South Wales University Science and published in Nature in Feb 2022, based on changes in salinity of sea, a new method, says that the climate change is intensifying the water cycle at more than double the predicted rate. This is also likely to have huge impact on the rainfall pattern and possible increase in frequency of high intensity rainfall events and storms, besides other impacts. This will also have impact on the Probable Maximum Precipitation and Probable Maximum Floods in the dam catchments, and would mean the current spillway capacity of many of our dams wont be adequate. All this also means increased frequency high intensity floods and disasters. Unfortunately, CWC or state dam managers in India are not even looking at these figures. India also needs to urgently take up research into all these aspects for assessing India specific impacts.

Climate Change Intensifying Water Cycle Much Faster Than Predicted Rising global temperatures have shifted at least twice the amount of freshwater from warm regions towards the Earth’s poles than previously thought as the water cycle intensifies, according to new analysis. Climate change has intensified the global water cycle by up to 7.4% – compared with previous modelling estimates of 2% to 4%, research of University of New South Wales published in the journal Nature suggests.

– The scientists estimate the volume of extra freshwater that shifted from warmer regions between 1970 and 2014 is between 46,000 and 77,000 cubic kms.

– The team used ocean salinity as a proxy for rainfall in their research. “The ocean is actually more salty in some places and less salty in other places,” Sohail said. “Where rain falls on the ocean, it tends to dilute the water so it becomes less saline … Where there is net evaporation, you end up getting salt left behind.” The researchers had to account for the mixing of water due to ocean currents. https://www.theguardian.com/environment/2022/feb/24/climate-change-is-intensifying-earths-water-cycle-at-twice-the-predicted-rate-research-shows (23 Feb 2022)

Rising global temperatures have been making this system more extreme: water is moving away from dry regions towards wet regions, causing droughts to worsen in parts of the globe, while intensifying rainfall events and flooding in others. In other words, wet areas are getting wetter, and dry areas are getting drier. Lead author of the study is Dr Taimoor Sohail, a mathematician and postdoctoral research associate at UNSW Science. The movement of freshwater from warm to cold areas forms the lion’s share of water transport. The water cycle leaves a signature on the ocean salt pattern – and by measuring these patterns, researchers can trace how the cycle changes over time.

– When Dr Sohail and the team compared their findings to 20 different climate models, they found that all the models had underestimated the actual change in warm-cold freshwater transfer. (Reference: Sohail T, Zika JD, Irving DB, Church JA. Observed poleward freshwater transport since 1970. Nature. 2022;602(7898):617-622. https://www.nature.com/articles/s41586-021-04370-w) https://www.technologynetworks.com/applied-sciences/news/climate-change-is-intensifying-the-earths-water-cycle-much-faster-than-predicted-358918   (24 Feb. 2022)

- South Asia Network on Dams, Rivers and People