Explaining Extreme Events of 2013 from a Climate Perspective — American Meteorological Society

Click here to download the report (Herring, S. C., M. P. Hoerling, T. C. Peterson, and P. A. Stott, Eds., 2014: Explaining Extreme Events of 2013 from a Climate Perspective. Bull. Amer. Meteor. Soc., 95 (9), S1–S96.) Here’s the abstract:

Attribution of extreme events is a challenging science and one that is currently undergoing considerable evolu- tion. In this paper, 20 different research groups explored the causes of 16 different events that occurred in 2013. The findings indicate that human-caused climate change greatly increased the risk for the extreme heat waves assessed in this report. How human influence affected other types of events such as droughts, heavy rain events, and storms was less clear, indicating that natural variability likely played a much larger role in these extremes. Multiple groups chose to look at both the Australian heat waves and the California drought, providing an opportunity to compare and contrast the strengths and weak- nesses of various methodologies. There was considerable agreement about the role anthropogenic climate change played in the events between the different assessments. This year three analyses were of severe storms and none found an anthropogenic signal. However, attribution assessments of these types of events pose unique challenges due to the often limited observational record. When human-influence for an event is not identified with the scientific tools available to us today, this means that if there is a human contribution, it cannot be distinguished from natural climate variability…


Introduction. Welcome rains over northeast Colo- rado starting on 9 September 2013 turned into a deluge during 11 September and continued through 15 September. Boulder, an epicenter of this regional event (http://www.crh.noaa.gov /bou/?n=stormtotals_092013), almost doubled its daily rainfall record (from 12.2 cm in July 1919 to 23.1 cm on 12 September 2013), with 43.6 cm for the week. Widespread flooding took 10 lives and caused at least $2 billion in property damage, second only to the June 1965 floods of eastern Colorado (http://www.reuters.com/article/2013/09/19/us-usa-colorado-flooding-idUSBRE98H1BA20130919).

Events of similar magnitude are not unprecedented during summer in the Colorado Front Range (Hansen et al. 1978; McKee and Doesken 1997). Some reach that size in a few hours and are more localized (e.g., Big Thompson in late July 1976), while others take longer and have larger footprints as in June 1965 and September 1938. Interestingly, attributes of the 2013 event, including its late-summer occurrence, regional scale, long duration, and slowly changing atmospheric circulation (see Gochis et al. 2014, manuscript submitted to Bull. Amer. Meteor. Soc.) that transported extreme moisture into the Front Range, also characterized the 1938 event.

Does the recent occurrence of this extreme event indicate that its likelihood has increased due to global warming? Globally, the atmosphere has become warmer and moister, with the observed rate of increase since the 1970s broadly consistent with that expected from the Clausius–Clapeyron relation (~7% per °C; Hartmann et al. 2014). Heavy precipitation events have increased over much of the United States since 1901, however, with no sig- nificant long-term trends over the northern Great Plains or Southwest (Kunkel et al. 2013). Further, the relationship between heavy precipitation and atmospheric water vapor varies seasonally, with moisture availability rather than moisture-holding capacity being a more dominant factor in summer than winter (Berg et al. 2009). Thus, the answer to our question cannot be readily gleaned from globally and annually averaged statistics but requires careful consideration of place and time…

Conclusion. Our analysis of the GEOS-5 simulations leads to a diagnosis that the occurrence of extreme five-day rainfall over northeast Colorado during September 2013 was not made more likely, or more intense, by the effects of climate change. From an observational perspective, analogous events have occurred before in the Front Range, perhaps most strikingly similar in September 1938, long before appreciable climate change.

Although our model results suggest that the occurrence of this recent extreme has become less probable over northeast Colorado due to climate change, model projections do show an increase in the intensity of maximum five-day precipitation over the globe and for annual averages as a whole by the end of the 21st century (Sillman et al. 2013). Yet, a slight decline in intensity of the maximum five-day precipitation over the central Great Plains during summer is also projected (Sillman et al. 2013), emphasizing that global and annual perspectives of climate change may not always pertain to events at a specific place and time.

A strength of our study is the availability of an ensemble of long-term climate simulations spanning 1871–2013, conducted at 1° spatial resolution, that permits an analysis of statistical properties of the change in extreme events. For the purpose of study- ing regional five-day rainfall events over northeast Colorado, the GEOS-5 model has the attribute of re- alistically characterizing the tails of the distribution. A weakness of our study is that results are based on a single model and thus require confirmation using additional models. Also, the physical reasons for the decline in simulated frequency of extreme five-day rainfall over northeast Colorado during September are not addressed. Better understanding of the deliv- ery mechanisms for atmospheric moisture that pro- duce heavy rain events and how those mechanisms respond to global warming will be critical.

From Climate Central (Bobby Magill):

…climate change may have had little to do with those extreme rains, and global warming could reduce the likelihood that they’ll happen again, according to a new study, which is disputed by one of the nation’s most prominent climatologists.

The new study, published Monday in a supplement to the Bulletin of the American Meteorological Society (BAMS) analyzing climate change’s role in extreme weather events across the globe in 2013, uses a single computer model to reach its conclusion and says the results have yet to be confirmed by other models.

Using a computer model called GEOS-5, the study concludes climate change made last September’s rains neither more likely nor more intense. Similar events have occurred in the past before human-caused climate change was a factor in any region’s weather, the study says…

He said the local geography, where the Great Plains end abruptly at the point where the Rocky Mountains rear skyward out of the prairie near Boulder, lends itself to greater precipitation due to the orographic effect. The orographic effect is the way landscape topography, mountains in Colorado’s case, affects local weather.

Hoerling cautioned that more research needs to be done to confirm his team’s findings, and the study should not be viewed as the final word on climate change’s role in the Colorado floods.

“We don’t have a lot of answers,” he said. “It raises more questions.”

One critic of the study, which was announced with a news release under the headline, “Climate Change Not to Blame for 2013 Colorado Floods,” didn’t mince words after it was published.

“There is no justification for the headline of the news release at all, and the study has little relevance to the flood in Colorado in September 2013,” said National Center for Atmospheric Research senior scientist Kevin Trenberth, who is also based in Boulder. “They ask the wrong questions, do the wrong analysis with inadequate tools and come up with the wrong answer.”

In any extreme rainfall event, the weather situation is always the main player in how such a storm develops, but says nothing about the role of climate change, Trenberth said in a written statement.

“They do note the importance of having abundant moisture in the region in order to produce high enough rainfall amounts,” he said. “But they fail to analyze where the moisture comes from.”

Water vapor above Denver hit a record during the rains at the same time as sea surface temperatures south of Baja California, Mexico, were briefly 30°C, about 1°C warmer than normal, making it the hottest spot for the ocean in the Western hemisphere, Trenberth said.

“An incredible 75 mm of moisture was recorded in the atmosphere in that region by NASA satellites,” Trenberth said in his statement.

High sea surface temperatures (SSTs) led to the large-scale convergence of moisture into the region, and it was siphoned north by a very unusual pattern in the atmosphere creating a large river of moisture flowing straight toward Colorado, he said.

“I think there is no doubt that those extremely high SSTs and record water vapor amounts likely would not have occurred without climate change,” Trenberth said. “This study is largely irrelevant; it misses the big picture and gets the wrong answer.”

Hoerling said the study’s model accounted for high sea surface tempertures in the Pacific, the river of moisture flowing toward the state and other factors. He said he is perplexed as to why Trenberth was unaware of that.

“I’m confident that other experiments will repeat the experiments we published in this BAMS report, and those will help reveal if the indications from the first such effort are robust or not,” Hoerling said.

Colorado State Climatologist Nolan Doesken told Climate Central that the study’s conclusions do not surprise him.

“Maybe it will be more obvious in 35 years, but from a 2014 vantage point here in our part of the country, changes in temperatures on a seasonally and annually averaged time frame do show a trend; precipitation probably does not, and the extreme tail of the precipitation distribution — the really big ones — are just too few and far between here to yet get much of a handle on,” Doesken said.

Giant floods and extreme rain happened in the same region at least twice in the 20th century, so it’s hard to peg climate change on something that has ample precedent in the area, and even harder to associate local extreme events to an increase in global greenhouse gas emissions, he said.

Figuring out what can and should be saved in the face of a mass extinction we helped author — @RefriedBrean

Student water field conference visits Orchard Mesa Irrig Dist, learns about BOR, Grand Valley water #ColoradoWater

The Fountain Creek District launches series of meetings to iron out rights protection with flood mitigation

Fountain Creek Watershed
Fountain Creek Watershed

From The Pueblo Chieftain (Chris Woodka):

The question of how flood control projects on Fountain Creek can be built without harming water rights will be taken up next month in the heart of farm country.

The Fountain Creek Watershed Flood Control and Greenway District will host the first of a series of meetings to discuss the issue during the winter water meeting set for Oct. 17 at Otero Junior College in La Junta.

The winter water meeting will be hosted by the Southeastern Colorado Water Conservancy District and will bring together some of the largest ditch companies east of Pueblo.

The group determines how a court-decreed program that allows farmers to store water in Lake Pueblo or ditch company reservoirs outside the growing season will operate.

That’s similar to the issue at hand on Fountain Creek, where flood control dams have been proposed, primarily to protect property in Pueblo.

At the July meeting of the Arkansas Basin Roundtable, a grant that proposed to look at the feasibility of Fountain Creek dams was rejected out of hand because several farmers objected to altering water rights to accommodate the dams.

They argued that junior water rights would be injured by such storage.

The timed release of water at more useful times in programs such as the winter water program could actually enhance water rights, however. Some have said this is possible with flood control dams.

In fact, the Denver Urban Drainage District is attempting to work through the same issue, Executive Director Larry Small told the board.

“We need to make it clear we have no intention of harming anyone’s water rights,” Pueblo County Commissioner Terry Hart said.

Several other meetings are planned by the Fountain Creek district to determine if flood control can be done in a way that keeps junior rights whole.

Meanwhile, the district is starting to prioritize spending prior to Colorado Springs’ $50 million payment as part of the Southern Delivery System. Here’s a report from Chris Woodka writing for The Pueblo Chieftain:

A district formed to improve Fountain Creek wants to start planning how it will use $50 million in funding that will begin arriving when the Southern Delivery System pipeline comes on line.

“We have to get an idea of what our priorities are before a dime arrives,” said Pueblo County Commissioner Terry Hart, a member of the Fountain Creek Watershed Flood Control and Greenway District board.

The $50 million will be paid to the district over five years by Colorado Springs Utilities as part of its 1041 agreement with Pueblo County. The money is for building flood control projects that primarily benefit Pueblo, such as a dam or series of dams.

SDS is projected to be fully permitted and online as soon as 2016, so the checks could begin coming in early 2017.

The district does not want to be put in a position of having to directly spend the money, but wants to use it to leverage funding from other sources.

“The projects identified so far exceed $100 million,” Hart said. “There could be even more as we branch out of the core area. We need to find the best ways to leverage other grants.”

Hart asked the board to form a committee specifically to look at how the money would be spent. It would include representatives from Pueblo County, the district and Utilities.

That conversation comes even as the district watches the progress of a stormwater vote in El Paso County this November and sets its budget for next year.

The vote will determine whether Colorado Springs and its neighbors will agree to fund stormwater improvements to the tune of $39 million annually beginning in 2016. That would satisfy other requirements of the 1041 agreement.

The district also is looking at whether its own budget could be paid with advance interest payments from Colorado Springs Utilities or if it’s time to pass the hat again among member governments.

At the meeting, Hart noted that the district is relying heavily on voluntary contributions and must start looking at its real operating costs if it is to become sustainable.

Finally, water quality is a concern and responsibility on Fountain Creek as well. Here’s a report from Chris Woodka writing for The Pueblo Chieftain:

While the focus lately has been on reining in water on Fountain Creek, the quality of that water is important too.

“We have a statutory duty to clean up the Fountain Creek watershed,” said Pueblo County Commissioner Terry Hart Friday at the meeting of the Fountain Creek Watershed Flood Control and Greenway District. “There are significant problems that we still don’t know enough about.”

So the board caught up on the science of water quality from Del Nimmo and Scott Herrmann, who have spent years studying water quality on Fountain Creek, the Arkansas River and Lake Pueblo.

The three are interconnected, Nimmo explained.

“We have tremendous resources and they are all connected,” Nimmo said. “They are tied to the reservoir.”

Lesson 1: Invasive species in Lake Pueblo will have more opportunity to spread to Fountain Creek and reservoirs in Pueblo County when the Southern Delivery System pipeline is completed, Herrmann explained.

Lesson 2: Mercury has accumulated in the water and fish in the headwater areas of Fountain Creek and Monument Creek, where the scientists did not expect to find it. Nimmo’s theory is that emissions from power plants or from former smelters in both Pueblo and El Paso counties contributed to this, but that’s not been proved. He suggested the district think in terms of an “airshed” as well as a watershed.

Lesson 3: The researchers have baseline data about water quality prior to the large, destructive Waldo Canyon and Black Forest fires. They also collected samples of the charcoal-laden water after the first big rainfall following the Waldo Canyon Fire in 2012.

“This study needs to be repeated about now, in the next year, to see what effect the fire had,” Herrmann said.

Nimmo and Herrmann have headed up numerous Fountain Creek studies at Colorado State University-Pueblo over the past decade. Herrmann has studied aquatic life in Lake Pueblo since its construction in the early 1970s. Nimmo was involved in other studies on the Upper Arkansas River near Leadville as well.

“We need to continue this type of study,” Hart said. “It should be a district project.”

More Fountain Creek coverage here.

Pueblo water use down 3% for 2014

Pueblo photo via Sangres.com
Pueblo photo via Sangres.com

From The Pueblo Chieftain (Chris Woodka):

Puebloans have been stingy with water this year, and it’s likely going to cost the Board of Water Works.

“We’re going to be 3 percent short in water use,” said Seth Clayton, director of administrative services for the water board.

Pueblo is on pace to use less than 8 billion gallons, down about 250 million gallons from projections.

The reason was a cool, wet, early summer that reduced the need for outdoor watering. On the hottest summer days, it’s not unusual for the peak pumping in Pueblo to hit 50 million gallons per day.

This year, the peak came on June 30, when 46.5 million gallons were pumped. Part of the reason for lower pumping totals has been reduced use in city parks, which receive water at no cost.

“September has been better with the warm weather,” Clayton said.

The average household will use about 113,000 gallons this year, which is down from 117,000 gallons last year and the average of 127,000 gallons from 2004-14.

Treated water sales are expected to fall $1.68 million below projections, but will be offset by $1 million in raw water leases, Clayton added.

“Overall, we will be about $800,000 short on revenue, but we’ll make up most of that on reduced expenditures,” Clayton said.

Total revenues for the water board were projected to be $34.48 million at the beginning of this year.

More Pueblo Board of Water Works coverage here.

Fifty years of hydroelectric generation at Glen Canyon Dam #ColoradoRiver

A high desert thunderstorm lights up the sky behind Glen Canyon Dam -- Photo USBR
A high desert thunderstorm lights up the sky behind Glen Canyon Dam — Photo USBR

From the Associated Press (Terry Tang) via The Denver Post:

U.S. Interior Secretary Sally Jewell and other officials marked the 50th anniversary of power generation by Glen Canyon Dam, a structure that helped usher in a new era in the Southwest.

Glen Canyon Dam, situated near the Arizona-Utah border, is a source of water and power for seven states in a region prone to drought.

Jewell told the crowd that the dam is not without its controversy but was an engineering feat that was economically valuable to the future of the country. It’s a key part of the Colorado River Storage Project.

Since the 1960s, the structure in Page, Arizona, has blocked 90 percent of the sediment from the river from flowing downstream, turning the once muddy and warm river into a cool, clear environment that helped speed the extinction of fish species and endangered others.

Here’s the release from the US Bureau of Reclamation (Matthew Allen):

Today [September 27], at a ceremony on the crest of Glen Canyon Dam, Secretary of the Interior Sally Jewell joined other officials and dignitaries to kick off a celebration marking the 50th anniversary of power generation at Glen Canyon Dam.

“At the 50th anniversary of Glen Canyon Dam, we are not just standing at crest of this dam – we are standing at a crest of history in the West,” Secretary Jewell said. “Glen Canyon Dam harnessed the power of the Colorado River to open the West to millions of people by providing for their water and power needs. Today we celebrate the triumphs and sacrifices of the people and communities that made this immense undertaking possible.”

Secretary Jewell thanked the people and the community who have supported Glen Canyon from the early days of construction and the continuation of operations today including Facility Manager Jason Tucker, who oversees the operation of the dam for the Bureau of Reclamation and Todd Brindle, Superintendent of Glen Canyon National Recreation Area. She also praised Assistant Secretary of Water and Science Anne Castle, who is leaving Interior at the end of the month for new ventures, for her outstanding work with Reclamation, National Park Service and other Interior agencies on adaptive management of the Colorado River Basin.

In addition to Secretary Jewell, other guest speakers included, Assistant Secretary Anne Castle, Mayor of Page Bill Diak, Colorado Energy Distribution Association Executive Director Leslie James, as well as Former President of the Colorado Water Users Association Ron Thompson.

“The Colorado River has always been known for its superlatives – the most volatile supplies, the most iconic landscapes, the most dammed, the most litigated, and recently, the most threatened,” remarked Assistant Secretary Castle. “Collectively, we need to make this river, this basin, this economy, one that will endure into the future and ensure that our children and grandchildren will be able to enjoy the same benefits and gifts that this river has provided to all of us. Operation of Glen Canyon Dam that is based on sound science and that balances a complex set of interests has been and will continue to be key to that sustainable future.”

Glen Canyon Dam is a key unit of one of the most extensive and complex river resource developments in the world, providing vital water storage and power generation for the west. It allows the Upper Colorado River Basin States of Colorado, New Mexico, Utah and Wyoming to utilize their share of the Colorado River while providing the required delivery of water to the lower basin states of Arizona, California and Nevada.

Situated on the Colorado River in northern Arizona, near Page, Glen Canyon Dam is the second highest concrete-arch dam in the United States—710 feet above bedrock, second only to Hoover Dam, which stands at 726 feet. The structure impounds Lake Powell, the second largest man-made reservoir in the United States. The powerplant began generating clean, renewable hydropower on September 4, 1964. The inexpensive electricity generated by this facility contributes to the renewable energy footprint in the western United States and has contributed to the modernization of hydroelectric power that exists today and will continue into tomorrow.

Today Lake Powell can store nearly two years of the Colorado River’s average annual flow, helping mitigate the current drought; moreover, the powerplant produces 5 billion kilowatt hours of hydroelectric power each year – enough electricity to help supply the power needs for 5.8 million customers. It would take 2.5 million tons of coal or 11 million barrels of oil to generate the same amount of hydropower that Glen Canyon provides every year using clean, renewable hydropower. The many hundreds of miles of shoreline at Lake Powell provide opportunities for hiking, camping, swimming, boating and fishing. Glen Canyon Dam and the adjacent Carl B. Hayden Visitor Center annually host nearly one million people on guided tours.

“Glen Canyon Dam, its Powerplant and Lake Powell are critical components of Reclamation’s Colorado River Storage Project,” said Lowell Pimley, Acting Commissioner for the Bureau of Reclamation. “We are proud that this facility has and will continue to generate clean renewable hydropower, regulate the flow of the Colorado River, store water for multiple beneficial uses, help reclaim arid and semi-arid lands, provide flood protection and offer prime recreation opportunities to millions of Americans.”

The celebration continued after the ceremony with tours of the dam and powerplant, an antique car show, several displays related to power generation and water use from federal, state, and local partners. A special presentation by the Navajo tribe allowed visitors to see traditional Navajo dance. Additionally, at the event a video was premiered that was created by local Page High School students in collaboration with Reclamation titled, “I am Glen Canyon.”

For more information on the event or on Glen Canyon Dam and Powerplant, please contact Reclamations Upper Colorado Regional Public Affairs Officer Matthew Allen at 801-524-3774 or mrallen at usbr.gov.

More Colorado River Basin coverage here.

#ColoradoRiver supply concerns mounting — The Durango Herald #drought

Colorado River Basin including out of basin demands -- Graphic/USBR
Colorado River Basin including out of basin demands — Graphic/USBR

From The Durango Herald (Dale Rodebaugh):

The water in Navajo Reservoir could play a role in meeting Colorado River Compact obligations in the event of continued drought, said Bruce Whitehead, director of the Southwestern Water Conservation District.

Release of water to Lake Powell from Navajo Reservoir, Flaming Gorge Reservoir on the Green River in Utah and Blue Mesa Reservoir on the Gunnison River is one of three measures his district and the Colorado River District want implemented if water storage in the network that supplies seven Western states approaches crisis level, Whitehead said.

The other measures call for increasing the amount of water available and, lastly, reducing use.

“We’re not in crisis now,” Whitehead said. “The 2013-2014 water year has been almost normal as far as the amount of water in Lake Powell.

“But the reality is that in spite of some good water years, we’re in a 15-year drought,” Whitehead said. “We need a plan to meet a crisis if the same conditions continue.”

The three measures to meet a critical water shortage came out of a recent meeting of Southwestern and the Colorado River District, which between them cover the Western Slope.

The recommendations went to the Upper Colorado River Commission, which regulates water matters in Colorado, Wyoming, Utah and New Mexico, the Upper Basin states that supply Arizona, Nevada and California, the Lower Basin states…

The concern about Lake Powell is that if water drops below the level needed to generate electricity, federal agencies would lose $120 million a year in power sales.

The revenue from power sales funds among other things environmental programs such as protecting fish species in the San Juan River, Whitehead said.

If the water level in Lake Powell allows generation of power, there should be enough water to satisfy the 1922 Colorado River Compact, Whitehead said.

Again, Whitehead said, Lake Powell and Lake Mead aren’t at critical levels. But the Upper Colorado River Commission and counterparts in Lower Basin states are looking at what-if situations.

Thus, the recommendations from his district and the Colorado River District, Whitehead said…

Measures to increase the amount of water available through cloud seeding, removal of water-hungry nonnative vegetation such tamarisk and Russian olive and evaporation-containment methods are a first step, Whitehead said.

A second early step, Whitehead said, would be the release to Lake Powell of water from Navajo, Blue Mesa and Flaming Gorge reservoirs which, respectively, have acre-feet capacities of 1.7 million, 829,500 and 3.79 million.

The contributions of Navajo and Blue Mesa could be less than optimal because of contractual obligations, Whitehead said. Blue Mesa also generates electricity.

If the first two steps aren’t enough, water users would be affected directly, Whitehead said. The consumption of cities and agricultural users would be reduced. Fallowing of fields also could be required.

The two commissions said if water for agriculture is reduced, the loss must be shared by Colorado River water users on the Front Range.

Front Range users receive 500,000 to 600,000 acre-feet of water a year from Colorado River transmountain diversions, Whitehead said.

Another transmountain diversion sends 90,000 to 100,000 acre-feet a year to the San Juan/Chama Project from the Blanco and Navajo rivers, Whitehead said. Users in Santa Fe and Albuquerque benefit.

More Colorado River Basin coverage here.