Rising temperatures pushing much more freshwater towards poles than climate models previously estimated
|
|
Fog on the western slope of the Andes mountains in Ecuador.
Climate change has intensified the water cycle – the movement of
water on Earth – by about twice as much as models had predicted,
research shows. Photograph: Rosanne Tackaberry/Alamy
|
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 published in the
journal
Nature
suggests.
The water cycle describes the movement of water on Earth – it evaporates,
rises into the atmosphere, cools and condenses into rain or snow and falls
again to the surface.
“When we learn about the water cycle, traditionally we think of it as some
unchanging process which is constantly filling and refilling our dams, our
lakes, and our water sources,” the study’s lead author, Dr Taimoor Sohail of
the University of New South Wales, said.
But scientists have long known that rising global temperatures are
intensifying the global water cycle, with dry subtropical regions
likely to get drier
as freshwater moves towards wet regions.
|
Sohail said the volume of extra freshwater that had already been pushed to the poles as a result of an intensifying water cycle was far greater than previous climate models suggest.
“Those dire predictions that were laid out in the IPCC will potentially be even more intense,” he said.
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.
“We’re seeing higher water cycle intensification than we were expecting, and that means we need to move even more quickly towards a path of net zero emissions.”
The team used ocean salinity as a proxy for rainfall in their research.
|
“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.
“We developed a new method that basically tracks … how the ocean is moving around with reference to this freshening or salinification,” Sohail said. “It’s kind of like a rain gauge that’s in constant motion.”
Dr Richard Matear, a chief research scientist in the CSIRO Climate Science Centre, who was not involved in the research, said the study suggested existing climate modelling has underestimated the potential impacts of climate change on the water cycle.
“There’s been a dramatic uplift in our ability to monitor the ocean,” he said.
“Observational datasets [like those used in the study] are really ripe for revisiting how global warming is changing the climate system, and the implications it might have on important things like the hydrological cycle.”
Links
- Observed poleward freshwater transport since 1970 (pdf)
- How will climate change affect rainfall?
- Global water crisis will intensify with climate breakdown, says report
- Productivity Commission says new Australian water deal must recognise climate change
- CSIRO Climate Science Centre
- A climate emergency: what happens when the taps run dry?
- Climate change has cut Australian farm profits by 22% a year over past 20 years, report says
- Water resources minister 'totally' accepts drought linked to climate change
No comments :
Post a Comment