Climate Change Has Intensified The Global Water Cycle

Climate Change Has Intensified The Global Water Cycle

Climate scientists have been saying for years that one of the many downsides of a warming planet is that both droughts and torrential rains are both likely to get worse. That’s what climate models predict, and that’s what observers have noted, most recently in the IPCC’s report on extreme weather, released last month. It makes physical sense, too. A warmer atmosphere can absorb more water vapor, and what goes up must come down — and thanks to prevailing winds, it won’t come down in the same place.

The idea of changes to the so-called hydrologic cycle, in short, hangs together pretty well. According to a new paper just published in Science, however, the picture is flawed in one important and disturbing way. Based on measurements gathered around the world from 1950-2000, a team of researchers from Australia and the U.S. has concluded that the hydrologic cycle is indeed changing. Wet areas are getting wetter and dry areas are getting drier. But it’s happening about twice as fast as anyone thought, and that could mean big trouble for places like Australia, which has already been experiencing crushing drought in recent years.

More than 3,000 robotic profiling floats provide crucial information on upper layers of the world's ocean currents. Credit: Alicia Navidad/CSIRO.

The reason for this disconnect between expectation and reality is that the easiest place to collect rainfall data is on land, where scientists and rain gauges are located. About 71 percent of the world is covered in ocean, however. “Most of the action, however, takes place over the sea,” lead author Paul Durack, a postdoctoral fellow at Lawrence Livermore National Laboratory, said in a telephone interview. In order to get a more comprehensive look at how water is exchanged between the surface and the atmosphere, that’s where Durack and his colleagues went to look.

Nobody has rainfall data from the ocean, so Durack and his collaborators looked instead at salinity — that is, saltiness — in ocean waters. The reasoning is straightforward enough. When water evaporates from the surface of the ocean, it leaves the salt behind. That makes increased saltiness a good proxy for drought. When fresh water rains back down on the ocean, it dilutes the seawater, so decreased saltiness is the equivalent of a land-based flood.

Fortunately, as the scientists make clear, research ships have been taking salinity measurements for decades in most of the planet’s ocean basins, so it’s possible to see where and how fast salinity has been changing. And it turns out that the saltiness has been increasing, especially in the waters surrounding Australia, southern Africa and western South America — all places where drought has increased as well.

The climate models weren’t really wrong, Durack hastened to add. “They’re accurately capturing the spatial patterns in hydrologic changes, and they’ve got the basic physics right. They’re just providing very conservative estimates of how big the changes are, and now we’re starting to understand that.”

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Scientists have also stated that the melting ice in the Arctic which is now melting at an accelerated pace has indeed played a part in the bitter winter seen in Europe in league with the lack of winter we saw here. Jet stream and wind patterns change as the ice melts and that melting also warms the ocean water causing a positive feedback loop due to the sun being absorbed into the open water. This in turn is melting the perennial ice even below the surface and causing refreezes to be thinner and less resilient to the warming temperatures and changing wind patterns. This warming air brings with it more moisture ( 7% more as was stated by climate scientists last year with a 1 degree rise in sea surface temperatures that is significant) and that has souped up the hydrological cycle wherein we are seeing more severe rain events, storms and also more evaporation of ocean water that is then dumped elsewhere.

This is a global cycle not just about one place and it is affecting agriculture in places where this rain is either not falling or falling too intense thus either drowning crops in floods, or drying them in drought. The Amazon and East Africa are two good examples. And it is a combination of factors that need to be put in play to work to slow down these effects. Corporations getting off the hook by oil minions just talking about population being the only culprit is a red herring. A revenue neutral carbon tax that seeks to hold polluters accountable and give back money to consumers to spur renewable investment would go a long way in jumpstarting the economy and cleaning our atmosphere. Sustainable agriculture/CO2 soil sequestration on a global scale could also decrease emissions by 40% and that would make a difference. And of course, conservation should always be the priority.

A growing population is certainly a challenge to our future, but if we institute measures that will ensure access to family planning besides giving people an option that is affordable and clean regarding energy choices and how they grow food that will help bring them out of poverty (which does have an affect on global birth rates) that will be key in working to stave off the worst effects while also planning for what we have already brought on ourselves. You can't institute change like this with only one answer, but none of those answers that are status quo will work either.

It is going to take a concerted effort by all of us beyond politics to solve this. Will, moral will is a resource we cannot afford to run out of. The climate crisis is the true test of our humanity. If we fail this test, there will be no other.