12/8/14, "Study: Causes of Calif. drought are natural, not man-made," USA Today, Doyle Rice
"Natural weather patterns and climate variability, not man-made global warming, are causing the historic drought that's parching California, says a study out today from federal scientists.
"It's important to note that California's drought, while extreme, is not an uncommon occurrence for the state," said Richard Seager, report lead author and professor with Columbia University's Lamont Doherty Earth Observatory. The report, "Causes and Predictability of the 2011-14 California Drought," was sponsored by the National Oceanic and Atmospheric Administration (NOAA).
The report did not appear in a peer-reviewed journal, but was reviewed by other NOAA scientists.
"In fact, multi-year droughts appear regularly in the state's climate record, and it's a safe bet that a similar event will happen again," he said.
The persistent weather pattern over the past several years has featured a warm, dry ridge of high pressure over the eastern North Pacific Ocean and western North America. Such high-pressure ridges prevent clouds from forming and precipitation from falling.
The current study notes that this ridge — which has resulted in decreased rain and snowfall since 2011 — is almost opposite to what computer models predict will result from human-induced climate change.
The NOAA report shows that mid-winter precipitation is actually projected to increase due to human-induced climate change over most of the state. Seager said that a low-pressure system, not a high-pressure system, would likely form off the California coast because of climate change. Low pressure creates clouds and precipitation.
Some outside climate scientists criticized the report, saying it didn't take into effect how record warmth worsened the drought.*
"The authors of the new report would really have us believe that is merely a coincidence and has nothing to do with the impact of human-caused climate change?," Penn State meteorologist Michael Mann wrote in the Huffington Post Monday."Frankly, I don't find that even remotely plausible."
Mann cites the fact that the NOAA report focuses primarily on the lack of precipitation, not the unusually high temperatures that have been measured in the oceans as well as across the state of California.*
So far this year, California is having its warmest year in 120 years of weather records, the National Climatic Data Center reported Monday."...
[Ed. note: No link is provided for the above statistic.]
(continuing): Peer-reviewed studies are divided on whether the drought can be blamed on climate change." via Drudge
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* 9/16/14 peer reviewed PNAS study on US west coast land and ocean temperatures 1900-2012 finds humans didn't "worsen" temperatures there, that winds were the major factor:
9/16/14, "Atmospheric controls on northeast Pacific temperature variability and change, 1900–2012," PNAS.org, James A. Johnstone and Nathan J. Mantua
9/16/14, "Supplemental Information," PNAS.org, Johnstone and Mantua
"Climate Dataset Comparison for the NE Pacific, 1900-2012, Sea Surface Temperature."...p. 4
Significance: "It presents a significant reinterpretation of the region’s recent climate change origins, showing that atmospheric conditions have changed substantially over the last century, that these changes are not likely related to historical anthropogenic and natural radiative forcing, and that dynamical mechanisms of interannual and multidecadal temperature variability can also apply to observed century-long trends."
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Press accounts of above PNAS study from Seattle Times and LA Times:
"We do not see a human hand in the warming of the West Coast,” said co-author Nate Mantua, now with NOAA Fisheries’ Southwest Fisheries Science Center. “That is taking people by surprise, and may generate some blowback.”"..."Century-long warming around the NE Pacific margins, with the strongest trends observed from 1910–1920 to 1940."...
9/22/14, "Study says natural factors, not humans, behind West Coast warming," Seattle Times, Craig Welch
"The rise in temperatures along the West Coast over the past century [of between .5 to 1C] is almost entirely due to natural forces — not human emissions of greenhouse gases, according to a major new study...."
"It has been a subject of debate for years: How much has global warming contributed to a documented rise in temperatures along the West Coast?
A new study published Monday in a major research journal suggests the answer thus far, particularly in the Northwest, is: hardly any.
An average coastal temperature increase of 1 degree Celsius since 1900 along the West Coast appears more likely to be the result of changes in winds and air circulation over the eastern Pacific Ocean, two former University of Washington scientists found. And the researchers said they could find no evidence that those weather patterns were being influenced by human greenhouse-gas emissions.
“It’s a simple story, but the results are very surprising: We do not see a human hand in the warming of the West Coast,” said co-author Nate Mantua, now with NOAA Fisheries’ Southwest Fisheries Science Center. “That is taking people by surprise, and may generate some blowback.”
Climate scientists for years have acknowledged that Pacific Northwest weather can vary naturally year to year — or even decade to decade. But many have argued that human burning of fossil fuels is already a huge factor driving up regional temperatures.
But the new research by Mantua and lead author Jim Johnstone, formerly with the UW’s Joint Institute for the Study of the Atmosphere and Oceans, suggests that natural variation in weather accounts for the vast majority of regional temperature increases for the last 113 years.
The study found wind responsible for more than 80 percent of the warming from Northern California to the Northwest.
In Southern California, winds accounted for about 60 percent.
“It was a big eye-opener,” Johnstone said. “The winds have changed in a manner that explains virtually all of the coastal ocean warming. The winds appear to decide it all.”
Both authors were quick to point out that their study does not in any way refute that temperatures globally are on the rise or that humans are responsible for that trend. The Northwest just happens to be a region where wind and weather swing far more wildly than, say, the tropics, drowning out any climate signal.
“This doesn’t say that global warming is not happening,” Mantua said. “It doesn’t say human-caused climate change isn’t happening globally. It’s a regional story.”
Nor does it suggest that greenhouse gases won’t be a significant regional factor in the future.
But it does raise questions about how well global climate models can be used to predict the near-term for specific regions.
“There’s been so much pressure to get local and regional climate information, because that’s where people live and plan and experience the climate,” Mantua said. “But this raises some questions about whether the models are capturing the connection between human-caused changes and natural variability well enough to interpret these local and regional records.”
Said Johnstone: “There are projections, based on carbon-dioxide emissions, that predict substantial warming here for the next few decades. Having looked at the way the temperatures actually behave, I’d be hesitant to say if that’s the case. I don’t know whether it will warm or cool or stay flat.”
The study, published in the Proceedings of the National Academy of Sciences, raised eyebrows among several scientists.
“That sort of flies in the face of many, many years of research and modeling,” said John Abatzoglou, a climatologist at the University of Idaho, who co-authored a study earlier this year that deemed human issues a leading cause of temperature rise in the Northwest. “That leads me to question whether or not the results are robust.”
Others called the paper “significant” and said Johnstone and Mantua highlighted the thorny work of trying to tease apart the details that are driving global change.
“We can’t just assume that if it’s warming it must be climate change,” said UW atmospheric scientist John M. Wallace.
Mantua agreed: “The climate system isn’t that simple. History has been playing tricks on us.” In fact, the road to their conclusions started in the fog.
A few years ago, Johnstone was trying to understand why fog in Northern California had declined so precipitously. He determined it was linked closely to sea and air temperatures and regional air-circulation patterns, which he tracked back to the early 1900s.
But then he had another question: How closely tied were temperatures with these regional winds?
”I didn’t have to dig hard for the answer at all,” Johnstone said. “It just seemed to present itself.”
He found that temperature dating back to 1900 was very consistently linked to coastal winds. But Johnstone and Mantua could find no link suggesting that climate change had altered those winds.
Guillaume Mauger, a UW climate scientist, said he had a few questions about the details of the study but didn’t dispute the findings.
“As these things go, it’s likely to get watered down the more people look into it, but it looks like they’ve done their homework well,” he said.
Abatzoglou, however, was skeptical about the quality of the early 20th-century data the study’s authors relied upon to reach their conclusions.
“The principles they are putting forth in the paper I agree with, but as you go back further and further in time you start to increase the amount of error inherent in the data,” he said.
But he and Amy Snover, head of UW’s Climate Impacts Group, said the larger point is that the study doesn’t change the long-term trend.
“I think what it does show is that there are aspects of regional climate that these models could do better at,” Snover said. “But we know we’re in for a bumpy ride. We know that the influence of humans on climate is only growing over time. We expect over coming decades for that influence to get bigger and bigger.”
On that, the study’s authors agreed.
“Global warming is still proceeding,” Mantua said. “And it’s still a really huge deal that’s going to shape the future and be a bigger and bigger part of our story.”"
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LA Times: "Most of the warming in the region occurred before 1940, when greenhouse gas concentrations were lower and winds were weaker, the study found."...
9/22/14, "West Coast warming linked to naturally occurring changes," LA Times, Tony Barboza
"Naturally occurring changes in winds, not human-caused climate change, are responsible for most of the warming on land and in the sea along the West Coast of North America over the last century, a study has found.
The analysis challenges assumptions that the buildup of greenhouse gases in the atmosphere has been a significant driver of the increase in temperatures observed over many decades in the ocean and along the coastline from Alaska to California.
Changes in ocean circulation as a result of weaker winds were the main cause of about 1 degree Fahrenheit (about .55C) of warming in the northeast Pacific Ocean and nearby coastal land between 1900 and 2012, according to the analysis of ocean and air temperatures over that time. The study, conducted by researchers from the National Oceanic and Atmospheric Administration and the University of Washington, was published Monday by the Proceedings of the National Academy of Sciences.
Natural, wind-driven climate patterns in the Pacific Ocean, such as El Niño and the Pacific Decadal Oscillation, are already known to exert a powerful influence on sea and land temperatures over years and even decades.
This latest research shows that similar changes in atmospheric and ocean circulation
can drive trends that last a century or longer, overshadowing the effects of human-generated increase in greenhouse gases, the
study's authors said....
If global warming had been the most powerful influence on land and sea temperatures, those temperatures would have been different, the study's authors said. Most of the warming in the region occurred before 1940, when greenhouse gas concentrations were lower and winds were weaker, the study found. In contrast, winds have strengthened since 1980 and coastal ocean cooled, even as the rise in greenhouse gases has accelerated."...
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"A 1 Celsius change is a change of 1.8 Fahrenheit while a 1 Fahrenheit change translates to a change of 0.55 Celsius."
http://fahrenheittocelsius.com/
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Dr. Mann's own work for PNAS includes:
7/5/11, "Reconciling anthropogenic climate change with observed temperature 1998–2008," PNAS.org
"Abstract
.
Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008."
"Robert K. Kaufmanna,1 ,Heikki Kauppib, Michael L. Manna, and James H. Stockc"...
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1994 NY Times article on history of California droughts:
7/19/1994, "Severe Ancient Droughts: A Warning to California," NY Times, by William K. Stevens
"Beginning about 1,100 years ago, what is now
California baked in two droughts, the first lasting 220 years and the
second 140 years. Each was much more intense than the mere six-year dry
spells that afflict modern California from time to time, new studies of
past climates show. The findings suggest, in fact, that relatively wet
periods like the 20th century have been the exception rather than the
rule in California for at least the last 3,500 years, and that
mega-droughts are likely to recur."...
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