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Changes in Sea Saltiness Show We’re Affecting the Climate

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The question of how human activity affects hurricanes has been much on peoples’ minds lately, for obvious reasons. But the influence of heat-trapping greenhouse gases are far broader than that, and scientists are wrestling on many different fronts with exactly the same issue: can we detect the fingerprint of human activity on any number of climate indicators?

Increasingly, the answer is yes. The latest example, published in Geophysical Research Letters, looks at the planet’s hydrological cycle, the evaporation, precipitation and river flow that constantly redistribute water from ocean to sky to ocean. Theory says that global warming should pull more water from the oceans, that rainstorms should become intense in some areas as a result, and that these local deluges should leave other areas drier than they were before. Observations show that this is indeed happening.

Average salinity near ocean surface, May 27 to June 2, 2012 as measured by satellite.
Credit: NASA

But that alone doesn’t prove that humans are the cause; these changes could also, in theory, be natural, caused by changes in the Sun’s brightness, or volcanoes, or other factors. “You always have to make sure natural variability isn’t causing the changes,” said lead author David Pierce, of the Scripps Institution of Oceanography in La Jolla, Calif. “That’s important.”

The new study does just that. By looking at rainfall patterns at sea rather than on land, the authors have been able to show that changes in the hydrological cycle are happening across broad areas of the planet in ways that can’t be explained without invoking human activity.

“We ran 20 different climate models, and with most of them we did runs that included human effects and runs that didn’t,” Pierce said. The runs including human effects — greenhouse gases from fossil-fuel burning, mostly — matched the real-world observations better than the runs without them. 

That’s especially significant, Pierce said, because he and his colleagues relied a new generation of climate models developed for the Intergovernmental Panel on Climate Change (IPCC). The U.N.-sponsored body, which distills a vast amount of climate research into major reports issued every five years or so, will be issuing its fifth such assessment starting in 2013.

On land, you measure changes in rainfall patterns with rain gauges; at sea, where evaporating water leaves salt behind and fresh rainwater dilutes the ocean’s saltiness, you do it by measuring salinity

“We have observations of salinity going back 50 years all over the ocean,” Pierce said. “Huge numbers of scientists would agree that it’s been changing” and earlier studies, including one by co-author Paul Durack, of Lawrence Livermore National Laboratory, had shown similar patterns. But many of those studies had looked at ocean saltiness only at the surface; this new one was based on measurements going down to 2000 feet.

The new study confirms that salinity is rising in some parts of the ocean and falling in others. In the North Atlantic, for example, there has been more evaporation and less rainfall, Pierce said, so that ocean basin is getting saltier.

In the Pacific, the opposite has been happening — in general, anyway. “The North Atlantic has a fairly constant profile, but if you look at the part of the Pacific between Japan and Australia, you see real differences in salinity as you go,” Pierce said.

The advantage of looking in the seas rather than on land is that more than 70 percent of the planet’s surface is covered with ocean. “People have looked at rain gauge measurements, but salinity captures the hydrological cycle at a global scale,” Pierce said.  “It’s measured with a completely independent set of instruments, and it’s done by different researchers.” 

In other words, if you get the same answer with two entirely different methods it’s more likely to be the right answer.

“For me, the salinity itself isn’t a big deal; it’s the changes in the hydrological cycle, which bring more rains, drought and floods on land,” Pierce said.

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Climate Change Has Intensified the Global Water Cycle
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New Study Ties Hurricane Strength To Global Warming 
Global Warming May Be Shifting Summer Weather Patterns 
September Bookends the Warmest 12 Months on Record 
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CO2 May Fragment Glaciers, Driving Ice Into the Sea Faster 
Pacific Ocean Patterns Tied to Violent Tornado Outbreaks 
Rising Ocean Temps Threaten Ocean Food Chain

Comments

By mememine (54434)
on November 6th, 2012

Since lazy copy and paste news editors have the same access to the facts as the reader do, let’s have a look at reality:
Climate Change Science was a War Crime:
The big green fear machine’s “pessimism and panic” approach to planetary stewardship had condemned billions to the greenhouse gas ovens for 26 years of needless CO2 death threats to our children. And not once had the IPCC ever said it “will” happen despite their claims of being at the brink….maybe. Not one IPCC warning isn’t peppered with maybe and could be and might be….... Science needs to be clear in it being a crisis or not. You can’t have a little climate crisis and real planet lovers welcome the good news of scientific exaggeration. Get up to date because this is costing Dems the White House now. Threatening the voter’s kids isn’t working anymore.
Help my house could be on fire maybe for sure? Meanwhile, the entire world of SCIENCE, lazy copy and paste news editors and obedient journalists, had condemned our kids to the greenhouse gas ovens of an exaggerated “crisis” and had allowed bank-funded and corporate-run “CARBON TRADING STOCK MARKETS” to trump 3rd world fresh water relief, starvation rescue and 3rd world education for just over 26 years of insane attempts at climate CONTROL.
*In all of the debates Obama hadn’t planned to mention climate change once.
*Obama has not mentioned the crisis in the last two State of the Unions addresses.
*Occupywallstreet does not even mention CO2 in its list of demands because of the bank-funded carbon trading stock markets run by corporations.
*Julian Assange is of course a climate change denier.
*Canada killed Y2Kyoto with a freely elected climate change denying prime minister and nobody cared, especially the millions of scientists warning us of unstoppable warming (a comet hit).
So how does melting prove that after millions of years my SUV’s life giving CO2 is now causing it instead of the mighty powers of the cosmos?

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By catman306 (30622)
on November 6th, 2012

Is anyone keeping track of global oxygen levels, in the same sort of way as is kept on carbon dioxide in Hawaii?  It seems that O2 was nearly 20% of the atmosphere 50 years ago.  But it may be falling.  Is there a link to such a month by month study?

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By Milt Burgess (San Diego, CA 92108)
on November 8th, 2012

Fifty years is a nanosecond in the billions of years-old earth.  That’s the problem. There is no question whether the climate is changing or not. It is, and has been since the earth was formed eons ago.. Whether human activity has anything to do with it is nothing but an unproven theory at this point. Check back in say a million years and possibly conclusions can be drawn. Over the past 50 years the same scientists who are working up proposals to obtain grant money for studying the climate have gone from global cooling to global warming to just climate change. If there is someone out there who thinks they can build a model that predicts world-wide hydrologic cycles for the entire blue planet, there are tulips for sale in Holland they may be interested in.

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