Lab researchers find tie in rain, global warming

Higher temperatures could make wet regions wetter

A new study by Lawrence Livermore National Laboratory scientists shows that observed changes in global (ocean and land) precipitation are directly affected by human activities and cannot be explained by natural variability alone.

The research appeared in the Nov. 11 online edition of the Proceedings of the National Academy of Sciences.

Emissions of heat-trapping and ozone-depleting gases affect the distribution of precipitation through two mechanisms. Increasing temperatures are expected to make wet regions wetter and dry regions drier (thermodynamic changes); and changes in atmospheric circulation patterns will push storm tracks and subtropical dry zones toward the poles.

"Both these changes are occurring simultaneously in global precipitation and this behavior cannot be explained by natural variability alone," said the Livermore Lab's lead author Kate Marvel. "External influences such as the increase in greenhouse gases are responsible for the changes."

The team compared climate model predications with the Global Precipitation Climatology Project's global observations, which span from 1979-2012, and found that natural variability (such as El Niños and La Niñas) does not account for the changes in global precipitation patterns.

While natural fluctuations in climate can lead to either intensification or poleward shifts in precipitation, it is very rare for the two effects to occur together naturally.

"In combination, man-made increases in greenhouse gases and stratospheric ozone depletion are expected to lead to both an intensification and redistribution of global precipitation," said Céline Bonfils, the other Livermore Lab author.

"The fact that we see both of these effects simultaneously in the observations is strong evidence that humans are affecting global precipitation," she added.

Marvel and Bonfils identified a fingerprint pattern that characterizes the simultaneous response of precipitation location and intensity to external forcing.

"Most previous work has focused on either thermodynamic or dynamic changes in isolation," Marvel said. "By looking at both, we were able to identify a pattern of precipitation change that fits with what is expected from human-caused climate change."

By focusing on the underlying mechanisms that drive changes in global precipitation and by restricting the analysis to the large scales where there is confidence in the models' ability to reproduce the current climate, "we have shown that the changes observed in the satellite era are externally forced and likely to be from man," Bonfils added.


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Posted by Johannsf
a resident of Another Pleasanton neighborhood
on Nov 12, 2013 at 9:28 am


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Posted by Harry
a resident of Valencia
on Nov 12, 2013 at 9:43 am

Aren't these guys supposed to be figuring out how to make my companies more profitable? Who cares about this global warming nonsense? If it gets cold, I turn my thermostat up. If it gets warm, I turn to my air conditioning. What's the problem? I want more profits!!!

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Posted by Brian
a resident of Kottinger Ranch
on Nov 12, 2013 at 5:08 pm

I've lived in the bay area all my life, and I sure remember it raining more when I was a kid back in the 60s. I'm no liberal, and I think a lot of people push the notion of global warming to further their own agenda, but it sure seems like the weather has changed significantly over the past 40 years.

I can't believe the dolts who say changes in climate don't matter. When's the last time it rained significantly in the bay area? It's the middle of November and it's still in the upper 70s! Where do these fools think their water comes from? Have you been by Lake Shasta lately? I've *never* seen it so low.

Yeah, it could just be natural variation, but to suggest that it doesn't matter - no matter what the cause - is to just bury your head in the (very dry) ground.

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Posted by believer
a resident of Another Pleasanton neighborhood
on Nov 12, 2013 at 5:48 pm

When the ocean covers SF ,then the Rights will believe. So much for the deniers of the world. Keep up the good work Lab. Of course the rights will want you to work on the nukes!

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Posted by The Lone Stranger
a resident of Ruby Hill
on Nov 12, 2013 at 9:22 pm

Mother Earth will survive anthropogenically-triggered global climate change. The Earth has survived bombardment by asteroids, a shift in the magnetic poles, etc...and She will survive us.

I've given up trying to educate people about global climate change, for two reasons: 1. It's too late to reverse the changes already underway and 2. I might be wrong about #1 and then the human race might survive, and we really don't deserve to.

Raccoons are pretty smart. I guess they'll inherit the Earth.

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Posted by Arrogant
a resident of Another Pleasanton neighborhood
on Nov 13, 2013 at 12:36 am

It is hard to even read the Arrogance of those who actually believe they have power over Mother Earth, who has been doing her own thing for billions of years. She freezes during ice ages, then warms gradually over centuries and millennia. She's done this several times. The only difference is in the previous 'warming' periods we didn't have social media sending pictures and information around the world in a matter of hours. Severe storms happened in early Roman times but there were no photos to share with the world. It's all like ..If nobody's around,does the tree make a sound when it falls? Same is true of 'warming', severe storms', etc. They have happened many times before, there was just no way of communicating the events. I simply cannot believe the gullible idiots and political whores who are causing billions and billions of our dollars spent in America and elsewhere. Our country could so help our future with a long list of jobs, structure replacements, discoveries, etc rather than this money grubbing folly of the Al Gores.
A good place to start reality thinking is to STOP the insanity of putting corn in cars!!. As a society we will pay for such behavior. Corn is used in every product in our pantries, and prices that are now out of reach of many hungry people because we are allowing cars are hogging our food. Demand the insanity stop. Politicians and Iowa corn. Do you think there might be some graft and lobby bribes??? That should be the number one budget saving cut !!! It's not just politicians who have lost common sense and the ability to reason, it's the stupid public who are willing partners in the absurd. Other countries are ahead of us in many ways. All of South America has been using easier, cheaper, more abundant switch grass for gas. But there's little money sharing in that. We chose the more complicated, dirtier, and much more expensive route of corn substitute. Stupid, expensive, corruption, and shortages.

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Posted by Al
a resident of Another Pleasanton neighborhood
on Nov 13, 2013 at 5:40 am

The key words are "intensification" and "redistribution." The droughts get drier; the rain becomes deluges; wind is greater. And the pattern in your local area is likely to be different. Isn't that what we are already seeing in recent big storms? My impression (from reading) is that the SF Bay Area is in a middle, not-sure area: the violence of the weather both north and south of us (Pacific NW and LA area) is expected to become more extreme, but we are in the middle where some of the factors peter out some. There is so much we do not know (but intensification and redistribution sure seem likely or even certain, based on this study and many others that say it less clearly), and even if what I say proves roughly correct (that the worst effects are less likely here), all we need is the one big bad storm to wreak havoc that will affect the darn liberals and adamant T-party know-nothings alike.. Like in the Phillippines.

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Posted by To Arrogant
a resident of another community
on Nov 13, 2013 at 9:24 am

Dear Arrogant,
Thank you for your fact-filled, data driven analysis of Mother Earth and climate. I always appreciate reading blogs from knowledgeable research scientists. Can you please provide the literature references for "Roman times" and "falling trees"? I also enjoy how you carefully craft your arguments with debate terms such as "idiot" and "stupid" and "whores".

Best Regards, your fond reader

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Posted by Sam
a resident of Oak Hill
on Nov 13, 2013 at 10:00 am

"Arrogant" wrote: "It is hard to even read the Arrogance of those who actually believe they have power over Mother Earth, who has been doing her own thing for billions of years. She freezes during ice ages, then warms gradually over centuries and millennia. She's done this several times. The only difference is in the previous 'warming' periods we didn't have social media sending pictures and information around the world in a matter of hours."

It's true that there have been many ice ages followed by warming trends, but I don't think that you understand the difference between the ice age cycles and what we are apparently observing here with "global warming". The ice ages involved significant global temperature changes over 10's of thousands of years. What we are seeing now is a change of about 1 C in the average global surface temperature over just 50 years, which is a blink of an eye compared to the time scales over which the ice ages occurred.

This reminds me of arguments concerning the extinction of species here on Earth. Some people have pointed out that extinction is a natural process and that all throughout the planet's history species have been going extinct while other new species have been evolving. That's true, but what that argument fails to note is that the rate of species extinctions is now much, much higher (around 10x or so higher, I seem to recall) than it was before man started having a profound influence on the environment.

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