The water cycle is disrupted, because rising temperatures push much more freshwater toward the poles than previously estimated by climate models.
Rising global temperatures have shifted at least twice the amount of freshwater from warm regions to Earth’s poles than previously thought, as the water cycle intensifies, according to a new analysis.
Climate change has intensified the global water cycle by as much as 7.4%, compared with previous model estimates of 2% to 4%, suggests research published in the journal Nature.
The water cycle describes the movement of water on Earth: it evaporates, rises into the atmosphere, cools and condenses into rain or snow and returns to the surface.
“When we learn about the water cycle, we traditionally think of it as an unchanging process that constantly fills and replenishes our dams, our lakes and our water sources,” said the study’s lead author, Dr. Taimoor Sohail, from the University of the New South. Wales, he said.
But scientists have long known that rising global temperatures are intensifying the global water cycle, with dry subtropics likely getting drier as fresh water moves into humid regions.
The water cycle is changing
Last August, the Intergovernmental Panel on Climate Change’s sixth assessment report concluded that climate change will cause long-term changes in the water cycle, resulting in stronger and more frequent droughts and extreme rainfall events.
Sohail said the volume of additional freshwater that had already been pushed toward the poles as a result of an intensified hydrological cycle was much greater than the data suggests. climate models previous.
“These dire predictions that were laid out in the IPCC are potentially going to be even more intense,” he said.
Scientists estimate that the volume of additional freshwater that moved from warmer regions between 1970 and 2014 is between 46,000 and 77,000 cubic km.
“We are seeing more water cycle intensification than we expected, and that means we need to move even faster towards a net-zero emissions path.”
The team used ocean salinity as a proxy for precipitation in their research.
“The ocean is actually saltier in some places and less salty in others,” Sohail said. “Where rain falls into the ocean, it tends to dilute the water, making it less saline… Where there is liquid evaporation, you end up with salt.”
More accurate measurement methods
The researchers had to account for the mixing of water due to ocean currents.
“We’ve developed a new method that basically tracks … how the ocean moves with reference to this cooling or salinization,” Sohail said. “It’s like a rain gauge that’s constantly moving.”
Richard Matear, a senior fellow at the CSIRO Center for Climate Science, who was not involved in the research, said the study suggests that existing climate models have underestimated the potential impacts of climate change on the water cycle.
“There has been a dramatic increase in our ability to monitor the ocean,” he said.
“Observation datasets [como los utilizados en el estudio] they are really ripe to see how global warming is changing the climate system and the implications it could have on important things like the hydrological cycle.”
By Donna Lu. Article in English