Environmental news from California and beyond

Category: Climate: global warming

Advocacy group's extreme weather map brings climate change home

Climate change much? A new map published today by the Natural Resources Defense Council makes it plain that extreme weather attributable to climate change isn’t something that only happens in other parts of the world. Chances are you’ve had your own Hurricane Irene, or drought, or something like it in your own backyard.

The interactive map lays out 2,941 monthly weather records broken in communities throughout the U.S. from January thru October of this year, and traces an onslaught of severe storms, drought, flooding and calamity. The point is to show how climate change is affecting your community every day.

“We did this analysis because we wanted to aggregate state-by-state what had happened for people, so they could see it on the map,” said Kim Knowlton, senior scientist in the Health and Environment program at the NRDC. “I think it’s pretty stunning: One can see in the Northeast how much record-breaking rainfall; in the South, in particular, how much record-breaking heat. We have icons, too, for drought and wildfire. For snowfall, all over the Midwest and the Northeast.”

An interesting interactive element plays the entire year like a video, showing rain, flood and storms surging across the country.

So what? A weather map of any year might look like this, right?

Not necessarily. These are all record events, so they didn’t happen quite this way before. One of the criteria for the data was that it had to break records at a weather stations with a data record of 30 years or more.

The map, Knowlton said, shows “how climate change could increase either the frequency or the intensity or the extent of some of these unfortunately rather damaging extreme events, and the kind of preparedness steps we need to be taking. Because there is a heck of a lot we can be doing to prepare ourselves to better meet these challenges.”

Like, for instance, pass meaningful climate change legislation. Or, at least, prepare for the consequences of these big events on the health of the populace. Knowlton points out that illness and injury to humans, which can add billions of dollars to the cost of a major weather event, are often not included in damage reports. The NRDC just published a report about this in collaboration with the University of California.

“In concert, the extreme weather map from 2011, plus the climate-health vulnerability map, together give a very rich picture of what we need to think about in the future,” Knowlton said.


New Cook Island shark sanctuary proposed

Barbara Boxer seeks climate-change action from summit

Inupiat whaling, drilling at stake in recent Alaska mayor's race

-- Dean Kuipers

Graphic: An interactive map produced by the Natural Resources Defense Council shows 2,941 record-breaking weather events recorded across the U.S. from January through October. Credit: Natural Resources Defense Council

Sen. Barbara Boxer seeks climate-change action from summit

Sen. Barbara Boxer at climate change summit

U.S. Sen. Barbara Boxer (D-Calif.) stepped up Wednesday to deliver an appeal from Capitol Hill for action at the mostly lackluster U.N. Framework Convention on Climate Change, which wraps up this week in Durban, South Africa. Her speech was delivered to an almost-empty Senate TV/radio gallery, which is indicative of the low priority given ongoing greenhouse gas treaty negotiations by the federal government and the media.

Audience shortfall be damned, Boxer soldiered on, registering her support for urgent action in Durban and beyond, and attacking climate deniers who have slowed progress toward reform. She and 15 other senators sent a letter to Secretary of State Hillary Rodham Clinton looking for a “strong and ambitious outcome” in Durban.

“Although I am not there with you in person, it in no way lessens my commitment to the work that you are doing in Durban and the importance of your mission to address climate change,” Boxer said. A text of the speech was also provided to the media.

“This massive threat to the environment and human health that is posed by climate change requires us to put aside partisan differences, to find common ground and to demand immediate international action.”

The speech was delivered against a backdrop of years of failed attempts by Congress to pass meaningful legislation that would curb greenhouse gas emissions, or to even set targets for those reductions. The comments addressed directly the United States’ refusal to ratify the 1997 Kyoto Protocol, which did set reduction targets and which is regarded as a failure of leadership on the part of the U.S., especially in Europe. Key provisions of the Kyoto treaty will expire in 2012 without further action.

Boxer had two main points in her presentation: one, that climate change is already costing us huge money, and two, that global-warming deniers are endangering lives.

On the first point, she cited National Oceanic and Atmospheric Administration studies that have tracked the cost of large storms and found that from January to August 2011, 10 or more weather disasters caused over $1 billion in damages — a record — and that the country is plagued by widespread drought and wildfires.

She also cited a recent report by the Union of Concerned Scientists tagging the public health consequences of increased ozone pollution caused by higher temperatures by the year 2020, including: $5.4 billion in increased health costs, 2.8 million more acute respiratory symptoms, and several other startling figures.

Boxer seemed to save particular ire for global-warming deniers, however, saying, “The message I have for climate deniers is this: You are endangering humankind.”

To punch this home, she quoted a Pentagon study saying climate change was real and would have serious impacts on defense, diplomacy and economics.

“It is time for climate deniers to face reality, because the body of evidence is overwhelming and the world’s leading scientists agree,” Boxer said.

The Durban conference ends Friday.


Illinois sequestration project is first in the U.S. for man-made CO2

NPR reports Kyoto Protocol in trouble in Durban

Brown cloud might be intensifying storms over Indian Ocean

— Dean Kuipers

Photo: U.S. Sen. Barbara Boxer in the Senate TV/radio room calling for ambitious and credible action at the U.N. climate change conference that ends this week in Durban, South Africa. Credit: U.S. Senate Photo Studio.

Illinois sequestration project is first in U.S. for man-made CO2

A demonstration project in Illinois is the first in the U.S. to begin pumping over a million metric tons of man-made liquid CO2 into permanent underground storage. The Midwest Geological Sequestration Consortium announced this week that its project in Decatur, Ill., had begun injecting carbon dioxide into sandstone formations 7,000 feet below ground.

Carbon dioxide capture and sequestration is a key strategy for combating the industrial emissions that contribute to global warming. In this case, the carbon dioxide is a byproduct of ethanol production in a nearby plant run by Archer Daniels Midland. The project is a joint project by the Illinois State Geological Survey (ISGS) of the Prairie Research Institute, ADM and the U.S. Department of Energy Office of Fossil Energy.

Robert J. Finley, leader of the project and director of the Advanced Energy Technology Initiative at the ISGS at the University of Illinois, was excited to talk about it, saying: “In the Midwest, and specifically here in Illinois, we’re beginning to document that the geology is very suitable for the storage of carbon. The production of biofuels from crop products can be a very effective way to reduce the carbon footprint of our liquid fuels because you’re taking that liquid CO2 and putting it in the ground.”

Making ethanol, then, becomes a carbon pump. Plants such as corn fix CO2 that is taken from the air. Then, during the production of ethanol for fuel, the CO2 is released and captured, dehydrated and compressed into a liquid, then run through a short pipeline and directly into the ground.

Finley points out that, as a demonstration project, working with an ethanol plant has distinct advantages. With a coal-fired power plant, for example, much of the expense of a sequestration project involves separating the CO2 from the other gases in the smokestack emissions, which are about 12% to 14% carbon dioxide. The fermentation tanks in ethanol production, however, produce about 99.9% carbon dioxide, which is then easily gathered at low cost at the rate of about 1,000 metric tons per day.

“The research that we’re doing is very much on the subsurface geologic environment, to make sure that we can do this safely and effectively, and that we can monitor the CO2,” says Finley. “So we’re using our research dollars to answer these important questions about safety and effectiveness, and we don’t have to use our Department of Energy-funded dollars to just try to get our flow of CO2.”

The Illinois project is one of seven regional partnerships studying sequestration around the country, and the first to use a man-made CO2 source. The project takes advantage of the massive Mt. Simon Sandstone, which is below several layers of shale that serve as a cap to keep the liquid in place. The storage capacity of Mt. Simon is estimated at 11 to 151 billion metric tons.

Establishing that million-metric ton projects are feasible is important because a medium-sized 500 MW coal-fired power plant produces about 3 million metric tons of CO2 per year, and are a key target for sequestration projects.

Finley points out that the Decatur project is not related to the troubled FutureGen project, which sought to build an advanced coal-to-gas power plant in Illinois and sequester its emissions, then was revised to refit a Meredosia plant after Obama took office. That project has been plagued by cost overruns, and major partners have pulled out at various points of the project. He does say, however, that some of the technology that would be used to do that sequestration, and the actual sandstone formation used, would be the same.

The Decatur experiment is expected to continue injecting CO2 for the next three years, and has drawn significant interest from other scientists and industrial concerns around the world.

[For the record, Dec 2, 2011, 11:45 AM: This post has been corrected. The photograph and photographer were miscredited, and the original text failed to identify the Illinois State Geological Survey of the Prairie Research Institute as a partner in the consortium.]


UN Durban climate conference wrangles funds for poor countries

Brown cloud might be intensifying storms over the Indian Ocean

Obama proposes CO2 regulations

-- Dean Kuipers

Photo: The Midwest Geological Sequestration Consortium verification well in Decatur, Ill. The project is the first to sequester 1 million metric tons of man-made CO2 in limestone formations below ground. Credit: Daniel Byers for the Midwest Geological Sequestration Consortium

NPR reports Kyoto Protocol in trouble in Durban

UN climate talks in Durban
You may have noticed that news coverage of the U.N. climate talks in Durban, South Africa, has been minimal, at best, and that’s clearly because -– just like in Copenhagen last year -– there has been almost no mention of the 1997 Kyoto Protocol, which was put in place to set reduction targets for important greenhouse gases. Without a big, juicy target, the conference lacks the drama to merit mention on even the eco-blogs.

Key aspects of the Kyoto treaty expire in 2012, and NPR boldly goes where no one else seems to want to tread, addressing the more-than-hypothetical: What if Kyoto elapses and nothing happens?

Answer? We’re in trouble. As noted in previous posts on this blog, international treaties have been effective in dealing with global issues like the hole in the ozone layer (Montreal Protocol). More important, without the Kyoto treaty, or something like it, the 192 nations attending the conference don’t really have a framework for setting emission-reduction targets or tackling this in any global way.

The U.S. is still not a signatory to the Kyoto treaty, and China, now the world’s biggest CO2 emitter, wasn’t even covered by it, since it was treated as a “developing” nation.


UN Durban climate conference wrangles over funds for poor countries

NOAA greenhouse gas index climbs

Brown cloud might be intensifying storms over Indian Ocean

-- Dean Kuipers

Photo: Head of the Polish delegation Tomasz Chruszczow, left, and European Union Climate negotiator Artur Runge-Metzenger speaks during a news conference at the United Nations Climate Change Conference in Durban, South Africa. Almost 200 nations began global climate talks on Monday with time running out to save the Kyoto Protocol. Credit: Rogan Ward/Reuters.

U.N. Durban climate conference wrangles over funds for poor nations

DURBAN, South Africa — International climate negotiators were at odds Tuesday on how to raise billions of dollars to help poor countries cope with global warming. A major shipping group is willing to help, endorsing a proposal for a carbon tax on vessels carrying the world's trade.

Details of the tussle over the funding emerged as the U.N.’s weather agency reported that 2011 was tied as the 10th-hottest year since record-keeping began in 1850. Arctic sea ice, a barometer for the entire planet, had shrunk to a record-low volume, said the World Meteorological Organization.

Putting the final touches on what's known as the Green Climate Fund is a top issue at the 192-party U.N. climate conference that was in its second day Tuesday in the South African coastal city of Durban, and one of the keys to a strategy to contain greenhouse gas emissions and keep global warming within manageable limits.

The two-week conference is to finalize a plan on managing climate finances, due to scale up to $100 billion annually by 2020.

The International Chamber of Shipping, representing about 80% of the world's merchant marine, joined forces with aid groups Oxfam and WWF International on Tuesday to urge the conference to adopt guidelines for a levy on carbon emissions by ships.

Details of any levy would be worked out by the International Maritime Organization, the U.N. agency regulating international shipping, the aid groups and the chamber said in a joint statement.

“Shipping has to take responsibility for the emissions and get to grips and drive them down, and they see that the best way to do that is to have a universal charge applied to all ships that is going to generate billions of dollars” to fight climate change, Tim Gore of Oxfam said on the sidelines of the conference.

About 50,000 cargo ships carry 90% of world trade, and most ships are powered by heavily polluting oil known as bunker fuels. Last July the U.N. maritime organization decided that new cargo vessels must meet energy-efficiency standards and cut pollution.

It was the first climate change measure to apply equally to countries regardless of whether they are from the industrialized or developing world.

At the conference, differences came into focus over the Green Climate Fund.

Delegations disagreed about how independent the fund will be, by whom it will be guided and whether the bulk of the money will come from public funds and government aid or from private sources and investments.

A 40-nation committee worked on a draft agreement in several lengthy meetings over the last year, but a consensus at the final meeting last month was blocked by objections from the United States and Saudi Arabia. Now negotiators in Durban must settle the final disputes.

“We are going to have a very thorough and open discussion on that very contentious paper,” said Pedro Pedroso, the delegate from Cuba.

U.S. delegate Jonathan Pershing said Monday that the U.S. has “substantive concerns” about the committee's plan, but “we believe these issues can be fixed.”

Washington wants to ensure that private investments are not hamstrung by bureaucracy and that they can bypass any approval process by governments.

The world temperatures report released Tuesday provided a bleak backdrop to negotiators seeking ways to limit pollution blamed for global warming.

2011 has been a year of extreme weather, the WMO reported. Drought in East Africa has left tens of thousands dead; lethal floods submerged large areas of Asia; the United States suffered 14 separate weather catastrophes with damage topping $1 billion each, including severe drought in Texas and the Southwest, heavy floods in the Northeast and the Mississippi Valley, and the most active tornado season ever known.

“The science is solid and proves unequivocally that the world is warming,” said R.D.J. Lengoasa, the WMO's deputy director, and human activity is a significant contributor.

“Climate change is real, and we are already observing its manifestations in weather and climate patterns around the world,” he said.


Brown cloud might be intensifying cyclones over Indian Ocean

'Snowtober' fits U.N. climate change predictions

NOAA greenhouse gas index climbs

-- Associated Press

Photo: Cyclists power lights on an installation depicting a Baobab tree, part of a renewable-energies display during the United Nations Climate Change Conference 2011 in Durban, South Africa. Credit: Nic Bothma/EPA

CO2 sensitivity possibly less than most extreme projections

A new study in the journal Science suggests that the global climate may be less sensitive to carbon dioxide fluctuations than predicted by the most extreme projections, and maybe slightly less than the best estimates of the Intergovernmental Panel on Climate Change.

Andreas Schmittner, a climate scientist at Oregon State University in Corvallis, Ore., and lead author on the new study, notes that, while man-made global warming is happening and tiny changes in global average temperatures can have huge and deleterious effects, the atmosphere may not be as sensitive to carbon dioxide change as has been reported.

“We used paleoclimate data to look at climate sensitivity to CO2 doubling in the atmosphere, and we are coming up with a somewhat lower value,” says Schmittner.

A 2007 IPCC report addressed the climate sensitivity to carbon dioxide, estimating that air near the surface of the earth would warm 2 to 4.5 degrees Celsius with a doubling of atmospheric carbon dioxide from pre-Industrial (pre-1850) standards. The mean value of that estimate was 3.0 degrees. Thus, if the amount of carbon dioxide in the atmosphere doubled from the amount in 1850, we’d expect a 3 degree C rise in temperature.

Schmittner’s study, however, took a longer view.

“We looked at the paleoclimatic record from the Last Glacial Maximum, which was 19,000-23,000 years before the present. At that time, the planet was much colder than today: There were huge ice sheets over Canada and Northern Europe; the sea levels were much lower, 120 meters lower than today; and C02 levels were also lower, were at 185 ppm. Other greenhouse gas concentrations in the atmosphere were also lower, and there was more dust in the atmosphere,” he said.

Researchers involved with this study compiled large data sets of land and ocean surface temperature reconstructions from that Last Glacial Maximum, when the last ice age was at its peak, and then ran them through the climate models they’ve been using for years, inserting a range of sensitivity numbers from near zero degrees to as high as 8 degrees. Their results showed that temperatures didn’t change as much as would be predicted using the most dire sensitivity numbers. Some independent studies have suggested that carbon dioxide sensitivity might be 10 degrees or higher.

“In fact, a climate sensitivity of more than 6 [degrees] would completely freeze over the planet,” Schmittner pointed out, referring to the ice age. Which, of course, didn’t happen. The ice sheets and glaciation only reached so far toward the equator and then stopped. “So, from that observation alone that it was pretty clear to me that those high climate sensitivities are out of the question, as they are virtually impossible.”

“The best-fitting models had a climate sensitivity of about 2.3-2.4. So that is slightly less than the IPCC best estimate of 3.”

Applying those findings to the future atmosphere, a doubling of carbon dioxide from 1850 levels might mean a rise of 2.4 degrees, rather than 10 or more.

Schmittner points out, however, that there are uncertainties associated with the climate modeling he was using. For instance, the study was unable to take into account changes in clouds on the absorption on sunlight. He expects that the range of climate sensitivities found by the study would expand if cloud changes could be figured in.

Still, Schmittner notes, tiny numbers mean enormous changes. “The temperature reconstructions, they hold a cautionary tale for us,” he says, commenting that even with glaciers covering much of the earth, the ocean temp only went up 2 degrees C.

“If we look at model projections for the future, that suggests temperature changes on the global average of 2-4 degrees are possible. Now, that’s in the similar range to what we had between the Last Glacial Maximum and today. These numbers sound small, but some regions change very dramatically.”


NOAA greenhouse gas index climbs

Greenhouse gases, water vapor and you

Doug Brinkley, Rep. Don Young squabble over Arctic refuge

-- Dean Kuipers

Photo: A coal-burning power station located next to a lake on the outskirts of Beijing. A new study suggests that the global climate may be slightly less sensitive to carbon dioxide in the atmosphere than previously believed, and much less sensitive than the most extreme projections. Credit: David Gray / Reuters

Court ruling keeps Yellowstone grizzlies on 'threatened' list

A ruling by the U.S. 9th Circuit Court of Appeals struck down the U.S. Fish and Wildlife Service's 2007 decision to remove the "threatened" designation for Yellowstone grizzly bears under the Endangered Species Act
Conservationists won a major battle Tuesday in their campaign to protect Yellowstone grizzly bears when a federal appeals court ruled that the U.S. Fish and Wildlife Service erred in removing Endangered Species Act protections for "one of the American West's most iconic wild animals."

The ruling by the U.S. 9th Circuit Court of Appeals struck down the wildlife agency's 2007 decision to remove the "threatened" designation for the bears under the Endangered Species Act.

Tuesday's ruling cited climate change as having accelerated a beetle infestation destroying the bears' vital white-bark pine food source. The grizzly is only the second wildlife species, after the polar bear, to earn protection in recognition of harm caused by global warming. Both are considered "threatened."

The three-judge panel embraced conservationists' warnings that the decline in the grizzlies' fodder would likely drive them to forage in more populous areas around the park, increasing incidents of confrontation between humans and the omnivorous bears.


Christo river wrap gets BLM approval

Karen Dawn's Thanksgiving turkey rescue

Peter Brown back onboard with Sea Shepherd

-- Carol Williams and Julie Cart

Photo: A grizzly wanders through open brush inside Yellowstone National Park. Credit: James Peaco / Associated Press

The Sierra Club 's Carl Pope to step down as chairman

Carl Pope It's official: Carl Pope announced Friday that he is stepping down from his position as chairman of the Sierra Club to devote most of his time to working with environmental organizations, corporations and organized labor in the "green economy."

Pope, 66, who served the club for 17 years as executive director, announced his career change in an email to club members on Friday:

"Dear Sierra Club Colleagues,
After 38 years with the Sierra Club, I am opening my dance card to new partners. In December, I shall stand down as Chairman to undertake a new initiative. My hope is to pull together a broad front of environmental groups, labor unions, clean-economy innovators, mainline manufacturers, civil rights organizations, and state and local officials to insist that candidates for public office in 2012 address the role of innovation, clean technology, and manufacturing in rebuilding the American economy and restoring the American middle class. 
I will continue to serve as a consultant to the Sierra Club and to fund-raise on the Club's behalf through 2012, but this shift in my professional focus marks the close of my career as a full-time Club employee with broad-spectrum responsibility. Each of my previous Club roles, including my tenure as Chairman, has been a privilege and an opportunity, largely because of the incredible staff and volunteer colleagues with whom I have had the good fortune to work. I look forward to continuing many of those relationships -- and to building new ones as my role outside the Club develops.
There are simply too many of you to thank and too much to be grateful for. So, for now, let's just keep fighting the good fight.

 Christo river wrap gets BLM approval

Grand Canyon mining ban moves forward

Super committee could gut national parks budget

-- Louis Sahagun

 Photo: Sierra Club Chairman Carl Pope, who has announced he is stepping down. Credit: David Butow/For The Times

Greenhouse gases, water vapor and you

Several readers pointed out an omission in last week’s post about the National Oceanic and Atmospheric Administration’s release of its Annual Greenhouse Gas Index, which showed that man-made gases that contribute to global warming continued a steady rise. The post -– and the AGGI –- mentioned carbon dioxide, methane, nitrous oxide and other gases, but failed to mention the biggest contributor to global warming: plain old water vapor.

“I want to comment that the way-dominant greenhouse gas in the atmosphere is not mentioned, namely water vapor,” writes Ken Saunders of Pacific Palisades. “Water vapor accounts for about 97 percent of the total (natural plus man-emitted) greenhouse warming of the planet. See, e.g., John Houghton's ‘The Physics of Atmospheres, 3rd edition,’ Cambridge University Press, 2002.”

This is true, water vapor is the major player in the greenhouse effect and is often omitted from reports and reporting about global warming -– mostly because it is more of a symptom than a cause in global climate change, and cannot be easily mitigated.

Tom Boden, director of the U.S. Energy Department’s Carbon Dioxide Information Analysis Center at Oak Ridge National Laboratory, acknowledges in an email: “Folks are right when they state water vapor is a powerful greenhouse gas and not routinely measured directly in the atmosphere. Atmospheric water vapor is difficult to measure, highly reactive, and variable in amount due to meteorological conditions (i.e., atmospheric water vapor is continuously being generated from evaporation and continuously removed by condensation).”

“Water vapor is the most important greenhouse gas and natural levels of [carbon dioxide, methane and nitrous oxide] are also crucial to creating a habitable planet,” writes John Reilly, professor at MIT and co-director of the Joint Program on the Science and Policy of Global Change, Center for Environmental Policy Research, in an email.

That idea leads many to believe that global warming is natural and cannot be affected much by human activity. Reader Roy W. Rising of Valley Village writes: “Today's report focuses on a bundle of gases that comprise a very small part of total of ‘greenhouse’ gases. It totally disregards the long-known fact that about 95% of all ‘greenhouse’ gases is WATER VAPOR! Spending billions of dollars to alter a few components of the 5% won't affect the natural course of climate change.” 

Reilly warns, however, that scientists don’t blame water vapor or clouds for global warming.

“Concerns about global warming are about how human beings are altering the radiative balance,” says Reilly. “While some of the things we do change water vapor directly, they are insignificant. Increasing ghg's [greenhouse gases] through warming will increase water vapor and that is a big positive feedback [meaning: the more greenhouse gases, the more water vapor, the higher the temperature]. But the root cause are ghg's. So in talking about what is changing the climate, changes in water vapor are not a root cause.”

Water vapor is, however, included in modeling used to study global warming. Boden adds: “We do measure water vapor fluxes routinely at the Earth's surface in terrestrial systems. All climate models account for water vapor in the processes of evaporation, condensation and transpiration. Since water vapor is naturally occurring and mostly driven by natural processes it would be difficult to mitigate (e.g., cap on a lake) and thus does not enter into reduction discussions.”

So, when NOAA’s Jim Butler confirmed in our previous post that carbon dioxide, nitrous oxide, methane, and two CFCs cause 95% of global warming, he meant that these five gases are at the root of a complex reaction that also involves water vapor and any number of other factors. The fact that you and I are responsible for generating a bunch of those man-made gases makes them the five to watch.

Thanks for placing your comments on the blog.


NOAA greenhouse gas index climbs

Hewlett-Packard tops Greenpeace guide to greener electronics

Obama proposal would open Arctic and Gulf of Mexico to oil drilling

-- Dean Kuipers

Photo: Britney Waugh stands in Fogscreen, an exhibit at WIRED NextFest 2007 in which pictures are projected onto a vapor "screen" that is dry to the touch. Credit: Al Seib/Los Angeles Times.

Tree rings document ancient Western megadrought

PineResearchers say they have found new evidence of prolonged drought in parts of the West, suggesting megadroughts are not the rarity Westerners would like them to be.

Analyzing corings taken from ancient living and dead bristlecone pines in the San Juan Mountains of Colorado, University of Arizona scientists found signs of extreme drought in the 2nd century that matches or exceeds the better-known droughts of the medieval period.

The composite tree-ring chronology, extending from 268 BC to AD 2009, shows that the longest dry periods in the entire record occurred during the first four centuries AD. The most pronounced drought lasted for about five decades in the second century.

Comparing their findings with two other tree-ring studies, the researchers concluded that the 2nd century drought was regional, extending from southern New Mexico north and west into Idaho.

Paleoclimatologist Connie Woodhouse, a co-author of the study that will be published in the journal Geophysical Research Letters, said scientists have wondered if the severe Western droughts that occurred between 900 and 1400 were unique.

The new tree ring record indicates they weren't -- and could occur again. “There is no good reason that we shouldn’t expect to have those,” Woodhouse said.

She added that researchers are not sure of the causes of the megadroughts but speculate that above-average temperatures and persistent La Nina ocean conditions may have contributed to them.


The energy, and expense, of bringing water to the Southland

Bounty at Lake Powell follows record dry stretch

For water researchers, an atmosphere full of questions

--Bettina Boxall

Photo: University of Arizona geoscientist Cody Routson takes a tree ring sample from a bristlecone pine. Credit: Mark Losleben / University of Arizona Laboratory of Tree-Ring Research


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