Drought and predictions of doom for the Southwest

Tony Davis has another climate scare story in the Arizona Daily Star: “Study: Worst SW drought in 1,000 years coming.” We should expect more stories like this because polling shows that “global warming” is not of great concern among the public, but many interests such as the money-grubbing IPCC, the EPA, and alternative energy companies depend on maintaining the myth of CO2-caused global warming. Tony writes: “Due to human-caused global warming, this region and the Great Plains are likely to experience droughts from 2050 to 2100 that are worse than the ‘megadroughts’ that lasted up to 60 years in the Southwest in pre-Medieval times, the study said.”

You can read the full study here. If you do, you will find that the study is based on failed computer models, statistical inference, and manipulation of data.

Bob Tisdale has some comments about this paper at the WattsUpWithThat blog. The thing about Bob is that he has this nasty habit of comparing computer model predictions against actual observational data.

Below, I show one of Bob’s graphs. This graph compares June-July-August precipitation data from 1979-2014 for both climate models (red) and observations (blue).

SW precipitation model data comparison

There are two things to notice about this graph. First, the models have always predicted that there would be twice as much precipitation than has actually occurred. Therefore a “modeled drought” might just be the model’s approach toward reality. Second, all the models show a slight decreasing trend in precipitation when in reality there has been a slight increasing trend in precipitation.

The drought scare seems to be a persistent theme. Back in August, Tony had another drought scare story featuring some of the same researchers (see: Megadrought and the Arizona Daily Star). In that previous story the researchers had this disclaimer:

“An obvious limitation of our work is that it is ‘blind’ to certain aspects of dynamically-driven changes in prolonged drought risk. For instance, changes in the magnitude, frequency, or teleconnection patterns of El Nino and La Nina (e.g., Coats et al. 2013) may alter the statistics of interannual variability in ways that are not captured by our simple models. Further, megadrought statistics over the last millennium may be forcing-dependent, as suggested by Cook et al. (2004), for instance, which shows that megadroughts were more common during the medieval climate era of 850-1200 CE. Another very serious limitation is imposed by the reliability of the models themselves to make realistic predictions of changes in climatological precipitation for the end of the 21st century.”

One other thing, both Tony Davis and the study authors claim “human-caused global warming.” Yet, to my knowledge, no one has presented any physical evidence to support the contention that our carbon dioxide emissions are a significant factor.

In a previous article, I show, with observational evidence, that the much touted enhanced greenhouse effect from our carbon dioxide emissions does not exist, see: Evidence that CO2 emissions do not intensify the greenhouse effect .

See also:

Carbon dioxide and the greenhouse effect

Climate change in perspective


Forest thinning may increase runoff and supplement our water supply

Thinning of southwestern forests, partly to curb devastating forest fires, has long been a controversial subject. In general, forest thinning has been opposed by environmental groups.

Now, however, a new study (“Effects of Climate Variability and Accelerated Forest Thinning on Watershed-Scale Runoff in Southwestern USA Ponderosa Pine Forests” published October 22, 2014) conducted by The Nature Conservancy and Northern Arizona University recommends accelerated forest thinning by mechanical means and controlled burns in central and northern Arizona forests. The study estimates that such thinning will increase runoff by about 20 percent, add to our water supply, and make forests more resilient. You can read the entire study here.

Forest thinning study area

The study abstract reads:

The recent mortality of up to 20% of forests and woodlands in the southwestern United States, along with declining stream flows and projected future water shortages, heightens the need to understand how management practices can enhance forest resilience and functioning under unprecedented scales of drought and wildfire. To address this challenge, a combination of mechanical thinning and fire treatments are planned for 238,000 hectares (588,000 acres) of ponderosa pine (Pinus ponderosa) forests across central Arizona, USA. Mechanical thinning can increase runoff at fine scales, as well as reduce fire risk and tree water stress during drought, but the effects of this practice have not been studied at scales commensurate with recent forest disturbances or under a highly variable climate. Modifying a historical runoff model, we constructed scenarios to estimate increases in runoff from thinning ponderosa pine at the landscape and watershed scales based on driving variables: pace, extent and intensity of forest treatments and variability in winter precipitation. We found that runoff on thinned forests was about 20% greater than unthinned forests, regardless of whether treatments occurred in a drought or pluvial period. The magnitude of this increase is similar to observed declines in snowpack for the region, suggesting that accelerated thinning may lessen runoff losses due to warming effects. Gains in runoff were temporary (six years after treatment) and modest when compared to mean annual runoff from the study watersheds (0–3%). Nonetheless gains observed during drought periods could play a role in augmenting river flows on a seasonal basis, improving conditions for water-dependent natural resources, as well as benefit water supplies for downstream communities. Results of this study and others suggest that accelerated forest thinning at large scales could improve the water balance and resilience of forests and sustain the ecosystem services they provide.

The study also notes that in “ponderosa pine forests of central Arizona, stand densities range from 2 to 44 times greater than during pre-settlement conditions” and all that extra foliage sucks up water and loses it through evapotranspiration, thereby decreasing the availability of water for downstream users and wildlife.

Congress has authorized a program called the Four Forest Restoration Initiative (4FRI) that will accelerate the use of mechanical thinning and prescribed burns across four national forests, treating 238,000 ha (588,000 acres) in the first analysis area over the next 10 years. That program should be expanded.

Curve-billed Thrasher – a bold and inquisitive bird

The curve-billed thrasher is a common bird in the southwest. You may recognize it from its distinctive call, a sharp and loud “whit-wheat.” It also has various non-repeating songs. Listen to recordings from the Cornell Lab of Ornithology here. (The beginning of the third recording has the distinctive call.)

Curve-billed thrasher

The curve-billed thrasher has a body length of just over 10 inches and a wingspan of 13 inches. It lives southern Arizona, southern New Mexico, south Texas, and Mexico. According to Cornell, “The Curve-billed Thrasher that lives in the Sonoran Desert of Arizona and northwestern Mexico looks different than [sic] the form that lives in the Chihuahuan Desert of Texas and central Mexico, and they may be separate species. The Texas and eastern bird has a lighter breast, more contrasting spots, pale wingbars, and white tail corners. The more western form has a grayer breast with less obvious spots, inconspicuous wingbars, and smaller, more grayish tail corners.”

These birds eat mainly insects, fruit, berries, and seeds. They forage on the ground using their bills to flick aside debris and dig in the soil, hence the name “thrasher.”

According to the Arizona-Sonora Desert Museum, “Curve-billed Thrasher nesting begins in mid-March to early April. The nest, a loose cup of thorny twigs, is built 3 to 5 feet above the ground in cholla, yucca, or mesquite. It lays two to four turquoise-colored eggs that are incubated for twelve to fifteen days. The altricial young leave the nest at fourteen to eighteen days. Curve-billed Thrashers may tear apart Cactus Wren nests when good nesting sites are at a premium.”

Curve-billed thrashers have adapted well to growing human population and even thrive in cities.

There are three other thrashers in the southwest, but the curve-billed thrasher has the largest range. Cornell notes the other three thrashers:

Bendire’s Thrasher has shorter, straighter bill with a pale area at the base, finer, more triangular spots on breast, and yellower eyes. Juvenile Curved-bill Thrasher may have yellow eyes and straighter bill.
Crissal Thrasher has plain breast and dark rusty under the tail.
California Thrasher has a plain reddish brown underside and dark eyes, and there is very little range overlap with the Curve-billed Thrasher.

Thrasher range map

Other birds of the Sonoran Desert:

American Kestrel

Barn Owls

Cactus Wren

Cardinals, Pyrrhuloxias and Phainopeplas

Cooper’s Hawks – swift predators

Creatures of the night – Nighthawks and Poorwills

Gambels Quail

Great Blue Heron

Harris’ Hawks, Wolves of the Air

Observations on Mourning Doves

Parrots in the desert?

Peregrine Falcons

Ravens and Crows

The greater roadrunner, a wily predator

The Great Horned Owl

Vultures, the clean-up crew

Way of the Hummingbird

Western Screech Owl

University of Arizona Scientists Find Evidence of Roman Period Megadrought

Work at UA’s Tree Ring Lab, studying old trees from the San Juan Mountains in Colorado indicates a megadrought about 1,800 years ago.

From the press release:

A new study at the UA’s Laboratory of Tree-Ring Research has revealed a previously unknown multi-decade drought period in the second century A.D. The findings give evidence that extended periods of aridity have occurred at intervals throughout our past.

Almost nine hundred years ago, in the mid-12th century, the southwestern U.S. was in the middle of a multi-decade megadrought. It was the most recent extended period of severe drought known for this region. But it was not the first.

 The second century A.D. saw an extended dry period of more than 100 years characterized by a multi-decade drought lasting nearly 50 years, says a new study from scientists at the University of Arizona.

 UA geoscientists Cody Routson, Connie Woodhouse and Jonathan Overpeck conducted a study of the southern San Juan Mountains in south-central Colorado. The region serves as a primary drainage site for the Rio Grande and San Juan rivers.

 “These mountains are very important for both the San Juan River and the Rio Grande River,” said Routson, a doctoral candidate in the environmental studies laboratory of the UA’s department of geosciences  and the primary author of the study, which is upcoming in Geophysical Research Letters.

 The San Juan River is a tributary for the Colorado River, meaning any climate changes that affect the San Juan drainage also likely would affect the Colorado River and its watershed. Said Routson: “We wanted to develop as long a record as possible for that region.”

 Dendrochronology is a precise science of using annual growth rings of trees to understand climate in the past. Because trees add a normally clearly defined growth ring around their trunk each year, counting the rings backwards from a tree’s bark allows scientists to determine not only the age of the tree, but which years were good for growth and which years were more difficult.

 “If it’s a wet year, they grow a wide ring, and if it’s a dry year, they grow a narrow ring,” said Routson. “If you average that pattern across trees in a region you can develop a chronology that shows what years were drier or wetter for that particular region.”

 Darker wood, referred to as latewood because it develops in the latter part of the year at the end of the growing season, forms a usually distinct boundary between one ring and the next. The latewood is darker because growth at the end of the growing season has slowed and the cells are more compact.

 To develop their chronology, the researchers looked for indications of climate in the past in the growth rings of the oldest trees in the southern San Juan region. “We drove around and looked for old trees,” said Routson.

 Literally nothing is older than a bristlecone pine tree: The oldest and longest-living species on the planet, these pine trees normally are found clinging to bare rocky landscapes of alpine or near-alpine mountain slopes. The trees, the oldest of which are more than 4,000 years old, are capable of withstanding extreme drought conditions.

 “We did a lot of hiking and found a couple of sites of bristlecone pines, and one in particular that we honed in on,” said Routson.

 To sample the trees without damaging them, the dendrochronologists used a tool like a metal screw that bores a tiny hole in the trunk of the tree and allows them to extract a sample, called a core. “We take a piece of wood about the size and shape of a pencil from the tree,” explained Routson.

 “We also sampled dead wood that was lying about the land. We took our samples back to the lab where we used a visual, graphic technique to match where the annual growth patterns of the living trees overlap with the patterns in the dead wood. Once we have the pattern matched we measure the rings and average these values to generate a site chronology.”

 “In our chronology for the south San Juan mountains we created a record that extends back 2,200 years,” said Routson. “It was pretty profound that we were able to get back that far.”

 The chronology extends many years earlier than the medieval period, during which two major drought events in that region already were known from previous chronologies.

 “The medieval period extends roughly from 800 to 1300 A.D.,” said Routson. “During that period there was a lot of evidence from previous studies for increased aridity, in particular two major droughts: one in the middle of the 12th century, and one at the end of the 13th century.”

“Very few records are long enough to assess the global conditions associated with these two periods of Southwestern aridity,” said Routson. “And the available records have uncertainties.”

 But the chronology from the San Juan bristlecone pines showed something completely new:

 “There was another period of increased aridity even earlier,” said Routson. “This new record shows that in addition to known droughts from the medieval period, there is also evidence for an earlier megadrought during the second century A.D.”

 “What we can see from our record is that it was a period of basically 50 consecutive years of below-average growth,” said Routson. “And that’s within a much broader period that extends from around 124 A.D. to 210 A.D. – about a 100-year-long period of dry conditions.”

 “We’re showing that there are multiple extreme drought events that happened during our past in this region,” said Routson. “These megadroughts lasted for decades, which is much longer than our current drought. And the climatic events behind these previous dry periods are really similar to what we’re experiencing today.”

 The prolonged drought in the 12th century and the newly discovered event in the second century A.D. may both have been influenced by warmer-than-average Northern Hemisphere temperatures, Routson said: “The limited records indicate there may have been similar La Nina-like background conditions in the tropical Pacific Ocean, which are known to influence modern drought, during the two periods.”

 Although natural climate variation has led to extended dry periods in the southwestern U.S. in the past, there is reason to believe that human-driven climate change will increase the frequency of extreme droughts in the future, said Routson. In other words, we should expect similar multi-decade droughts in a future predicted to be even warmer than the past.


This is interesting research that shows extreme weather is part of the natural cycle.  Drought cycles are most closely correlated with various solar cycles of 1,533 years (the Bond cycle), 444 years, 170 years, 146 years, and 88 years (the Gleissberg cycles).  Asmerom,et al. report that periods of increased solar radiation correlate with periods of decreased rainfall in the southwestern United States (via changes in the North American monsoon).   These solar cycles control the Pacific Decadal Oscillation and the El Nino system which control weather and climate in the southwest.

I was amused by some of the terminology.  The authors refer to the “medieval period” and “Roman period” rather than the more commonly used terms “Medieval Warm Period” and “Roman Warm Period.”  This may reflect a concession to one of the co-authors, Overpeck, who is reputed to have told another scientist that we had to get rid of the Medieval Warm Period because it gave the lie to Michael Mann’s infamous hockey stick graph.  The last paragraph if the press release may also reflect a reluctance to admit that natural variation is dominant.

This graphic below shows where the Roman Period fits in with the other warm/cold cycles since the end of the last glacial epoch:


Reference cited:

Asmerom, Y., Polyak, V., Burns, S. and Rassmussen, J. 2007. Solar forcing of Holocene climate: New insights from a speleothem record, southwestern United States. Geology 35: 1-4.

See also:

Drought in the West

Droughts in the Southwest put in perspective

El Niño, bristlecone pines, and drought in the Southwest

Droughts in the Southwest put in perspective

The severe drought in Texas this year has fueled speculation that alleged human-caused global warming has somehow caused “unprecedented” conditions. But real research data show that the current drought is not unprecedented and is part of a natural cycle. There have been much more severe and persistent droughts in the past before humans began emitting signification amounts of carbon dioxide into the atmosphere. This post focuses on research from the University of Arizona and the Lamont-Doherty Earth Observatory of Columbia University.

From the University of Arizona and Arizona State University we have “A 1,200-year perspective of 21st century drought in southwestern North America.”

The Abstract reads in part:

A key feature of anticipated 21st century droughts in Southwest North America is the concurrence of elevated temperatures and increased aridity. Instrumental records and paleoclimatic evidence for past prolonged drought in the Southwest that coincide with elevated temperatures can be assessed to provide insights on temperature-drought relations and to develop worst-case scenarios for the future. In particular, during the medieval period, AD 900–1300, the Northern Hemisphere experienced temperatures warmer than all but the most recent decades. Paleoclimatic and model data indicate increased temperatures in western North America of approximately 1 °C over the long-term mean. This was a period of extensive and persistent aridity over western North America. Paleoclimatic evidence suggests drought in the mid-12th century far exceeded the severity, duration, and extent of subsequent droughts. The driest decade of this drought was anomalously warm, though not as warm as the late 20th and early 21st centuries. The convergence of prolonged warming and arid conditions suggests the mid-12th century may serve as a conservative analogue for severe droughts that might occur in the future. The severity, extent, and persistence of the 12th century drought that occurred under natural climate variability, have important implications for water resource management. The causes of past and future drought will not be identical but warm droughts, inferred from paleoclimatic records, demonstrate the plausibility of extensive, severe droughts, provide a long-term perspective on the ongoing drought conditions in the Southwest, and suggest the need for regional sustainability planning for the future.

This paper goes on to discuss the role of El Niño-La Niña cycles and sea-surface temperature, but the paper does not really address cause of the droughts. The theme of this paper is that past droughts are associated with warm periods and that continued warming may portend more severe droughts in our future. However, the authors partly contradict themselves by saying that the more severe droughts of the Medieval period occurred when the temperatures were cooler than the current warm period.

It seems we have a complex interplay of natural cycles which are not completely understood.

From Cornell, we have “The characteristics and likely causes of the Medieval megadroughts in North America.” and a very interesting graph:

Droughts in the west

  This graph shows that while the current drought is severe, it is much less severe than droughts during the Medieval Warm Period, a time before humans were emitting much carbon dioxide into the atmosphere.

The paper presents three conclusions:

1) The similarity of the spatial patterns suggests that the physical processes that caused the modern droughts also caused the medieval megadroughts.

2) The global atmosphere ocean conditions that currently cause modern droughts for a few years at a time were the prevailing ocean climate during the medieval period.

2) Despite the shift in the mean tropical ocean climate ENSO variability continued as now but oscillating about a colder mean state.

The authors also present an archaeological speculation:

The medieval megadroughts may also have left their signature on the human environment of the West. The great cliff cities in the four corners region of the West such as at Chaco Canyon and Mesa Verde were all abandoned towards the end of the drought. These societies were based on irrigated agriculture. Although there remains much debate about why these highly organized Indian societies collapsed, archaeologists are revisiting the idea that decades of dry conditions were part of the reason.

With both papers we see that data collection is one thing, interpretations are another.

See also:

Drought in the West

El Niño, bristlecone pines, and drought in the Southwest

EL NINO behavior, climate models predict opposite of what really happens