Human contribution to the current megadrought in the SW U.S. is 46%

The southwest U.S. is currently experiencing a once in a millennium megadrought,
comparable to the one in 1100 that lasted 40 years.

What tree rings reveal about America’s megadrought – a visual guide | US news | The Guardian

Bioclimatologist Park Williams and his team analyzed more than 1500 tree rings across the American southwest in order to determine soil moisture.The analysis goes back to 800 CE. Park Williams says that the current megadrought in the SW U.S. could exceed the severityof all megadroughts on his chart. His team claims that 46% of the severity is caused byhuman activities.

Scientists Said The West Was Entering A Megadrought. Now It’s Twice As Bad (forbes.com)

"In research published last year, scientists said the nearly two decades between 2000 and 2018 in the southwestern United States and northern Mexico was the driest such span since the late 1500s. It has become common to observe that the southwest is now increasingly in the grips of a so-called megadrought lasting for decades."

"And in the past half year drought in the west has reached new levels that make the trend described in that study from early 2020 seem quaint.""

"As of Tuesday, 26 percent of the western US is in exceptional drought status - the highest level of dryness - while 96 percent of the west is suffering from at least some level of drought."

"Prior to last November we have never seen more than 12 percent of the west in exceptional drought at any point in the past two decades of record-keeping."

 

Congress needs to pass a joint resolution condemning drought.

 

Maybe not so much.

". . . Just focusing on California and the Colorado basin, tree ring studies peg the present situation as only the fourth worst in the last millennium. Abandoned Chaco Canyon proves it was previously much worse. Chaco was abandoned about 1250 because of a worse western drought than at present. . . . "

Western US Drought Implications
2021 › 06 › 13 › western-us-drought-implications
2015 (peak previous drought year) that output was cut to 41% of 2012 pre-drought output, meaning that ... media (MSM) is abuzz about the present Western Drought allegedly caused by ‘anthropogenic climate change’

 

Graphing the data can shed light. Looks like the drought trend is down.
Roger Pielke Jr. Weighs in on This Week's Hysteria: Drought
2021 › 06 › 14 › pielke-jr-weighs-in-on-drought
curiousSo I graphed percent of CONUS in drought according to the US drought monitor, data is weekly from 1/2000 ... by drought category ... https://www.epa.gov/climate-indicators/climate-change-indicators-drought

 

It’s a blog - whatsupmybutt

 

Another link to a blog

 

So, I guess that settles it... or maybe it doesn't.

Warming Pushes Western U.S. Toward Driest Period in 1,000 Years - The Earth Institute - Columbia University



A representation of the summer moisture in the U.S. Central Plains and Southwest. The brown line represents the variation in dryness since the year 1000, based on data from the North American Drought Atlas; the lower the line on the graph, the drier the conditions. Colored lines to the right side of the graph represent what climate models see ahead: a trend toward dryness not seen in the previous millennium. Credit: Cook et al., Science Advances, 2005

During the second half of the 21st century, the U.S. Southwest and Great Plains will face persistent drought worse than anything seen in times ancient or modern, with the drying conditions “driven primarily” by human-induced global warming, a new study predicts.

The research says the drying would surpass in severity any of the decades-long “megadroughts” that occurred much earlier during the past 1,000 years—one of which has been tied by some researchers to the decline of the Anasazi or Ancient Pueblo Peoples in the Colorado Plateau in the late 13th century. Many studies have already predicted that the Southwest could dry due to global warming, but this is the first to say that such drying could exceed the worst conditions of the distant past. The impacts today would be devastating, given the region’s much larger population and use of resources.

“We are the first to do this kind of quantitative comparison between the projections and the distant past, and the story is a bit bleak,” said Jason E. Smerdon, a co-author and climate scientist at the Lamont-Doherty Earth Observatory, part of the Earth Institute at Columbia University. “Even when selecting for the worst megadrought-dominated period, the 21st century projections make the megadroughts seem like quaint walks through the Garden of Eden.”

“The surprising thing to us was really how consistent the response was over these regions, nearly regardless of what model we used or what soil moisture metric we looked at,” said lead author Benjamin I. Cook of the NASA Goddard Institute for Space Studies and the Lamont-Doherty Earth Observatory. “It all showed this really, really significant drying.”

The new study, “Unprecedented 21st-Century Drought Risk in the American Southwest and Central Plains,” will be featured in the inaugural edition of the new
online journal Science Advances, produced by the American Association for the Advancement of Science, which also publishes the leading journal Science.

 

You are just running from the data.

". . . We need to separate California from the Colorado Compact for purposes of analysis. The data sources for the facts below are primarily from the US government’s EIA at EIA.gov, from the California Energy Commission (CEC) at Energy/Ca.gov, and from an open access paper ERL 15 (2020) 094008. . . ."

 

You are still running from the data.

". . . So I graphed percent of CONUS in drought according to the US drought monitor, data is weekly from 1/2000

https://droughtmonitor.unl.edu/CurrentMap.aspx . . . "

 

Merely a model. Not data.

 

Now you are learning however it does not prove or disprove anything

 

That link you are so scared of is a Collaboration: "The U.S. Drought Monitor is produced through a partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration."

LINK

=====

Fact, Droughts are common in the Southwest.

 

Another evidence that you have nothing to offer for the rest of us here, you chose the easy way out because you are suffering from source prejudice and lack of knowledge.

 

This is what your prejudice causes you to miss, this is from a published science paper itself:

From AMS Journals

3. Results and discussion
3.1. Drought events

Using the drought definition described above, eight drought events in the CRB were identified for 1901–2014 (Figure 3). Three of these eight droughts correspond with some of the most well-known droughts in the United States: 1928–36 (the 1930s Dust Bowl), 1943–56 (the 1950s drought), and 2000–09 (the turn-of-the-century drought). The longest of the eight droughts was from 1943 through 1956 (14 years), and the shortest drought was from 1989 through 1991 (3 years) (Figure 3, Table 1). Although only 4 years in length, the coolest, driest, and most severe of the eight drought events (based on precipitation and runoff departures) spanned water years 1901–04 (Figure 3, Table 1). The warmest drought event, and one of the least severe in terms of mean precipitation and runoff departures, occurred from 2000 to 2009 (Figure 3, Table 1). Spearman’s rank correlation between the precipitation and runoff departures for the years covered by the eight droughts (Figure 3, Table 1) is 0.73 (p = 0.041), whereas the rank correlation between temperature and runoff departures for the eight droughts is only 0.02 (p = 0.955). These correlations indicate that precipitation deficits have been the principal climatic driver of the eight droughts (defined by mean percentiles of water-year runoff for the CRB) within the historic observational record.

Figure 3.


Drought are more common than you realize, it has happened 8 times since 1900 alone.

and this you missed as well:

Figure 5 illustrates the spatial patterns of mean percentiles of water-year runoff for each of the eight CRB drought events. The 1901–04 drought event (Figure 5a) was characterized by mean runoff percentiles below 30 for most of the CRB. For the other seven CRB drought events, the spatial patterns of drought conditions (i.e., low percentiles of mean CRB water-year runoff) are variable. For example, for the 1943–56 and 2000–09 drought events, the most widespread and driest conditions are primarily focused in the LCRB (Figures 5d,h), whereas for the 1959–64 and 1989–91 drought events, the driest conditions appear to have been largely focused in the UCRB (Figures 5e,g). For the 1928–36 drought, the lowest percentiles of runoff appear to have been on the west side of both the LCRB and UCRB (Figure 5c).

Figure 5.

 

Drought has been lessening since 2000.

 

Ha ha, you didn't address anything that Dr. Pielke wrote, you ran you ran to a paper built on modeling scenarios, that doesn't help you at all.

You ignored the posted links that Dr. Pielke provided in the article that led to many more links to published papers covering the subject he brought up.

It is OBVIOUS you didn't read any of it.

 

I have lived in the West since 1964, seen, felt droughts many times, it is a NORMAL phenomenon.

Since 1950, the rest of the country has been experiencing INCREASED Precipitation

POST 75 (LINK) you have already ignored:

Meanwhile other large areas of the country show INCREASE in Precipitation, 1970-2020:

Northern Rockies and Plains LINK +.20"/decade

South LINK +.20"/decade

Northeast LINK +.60"/decade

Ohio Valley LINK +.85"/decade

Upper Midwest LINK +.69"/decade

Southeast LINK +.17"/decade

That is ALL the rest of the country, all show INCREASE in Precipitation.

You are so gullible with the media and their one sided claims.

 

The topic is about the current drought in the southwestern U.S. and how it relates to previous droughts in this area over the past 1300 years. It is also about projections of future drought severity in the SW U.S. Projections are done with climate models and this is a way to determine how severe future drought
conditions will be under various carbon emission scenarios. Climate models also are used to determine how much humans have contributed to the severity of the current drought and how much humans will contribute to future projected droughts. It is not about drought in the continental U.S or the percent of the continental U.S. that was in drought from 2000 to 2021.

The the Colorado River Basin (CRB) was brought up and that covers the SW U.S. and it is worth discussing.
The water supply coming from the upper CRB is slowly declining and the demand for water has been steadily rising. Future declines of water flowing
into the upper CRB are expected in the future as a result of reduced snow melt.

Impacts in Colorado | Environmental Center | University of Colorado Boulder

Colorado relies heavily on the snowpack it receives during the winter months. When it comes to the economy skiing/riding is the second largest in the state, but when it comes to water we receive 70% from the snowpack. Unfortunately Colorado has seen a decrease in the average snowpack in the past couple of decades exacerbating existing problems of drought and water scarcity.


Dept. of Interior, 2016
OWDI Drought (doi.gov)

Since 2000, the Colorado River Basin (Basin) has been experiencing a historic, extended drought that has impacted regional water supply and other resources, such as hydropower, recreation, and ecologic services. During this time, the Basin has experienced its lowest 16-year period of inflow in over 100 years of record keeping, and reservoir storage in the Colorado River system has declined from nearly full to about half of capacity.
This period also ranks as the fifth driest 16-year period in the last 1,200 years (Meko et al., 2007a and 2007b).

While the current drought is severe and historic, the most extreme drought in the Colorado River Basin occurred in the mid-1100s (Meko et al. 2007a). The 1100s drought was characterized by a 25-year period of flows that were 15% lower than the long-term average of 14.8 maf and no higher-flow years (greater than 125% of average) for six decades. By comparison, the current drought is characterized by flows that are 16% lower than the long-term average with one year of higher flows (135% percent of average in 2011).

 

Large contribution from anthropogenic warming to an emerging North American megadrought | Science (sciencemag.org)

A trend of warming and drying
Global warming has pushed what would have been a moderate drought in southwestern North America into megadrought territory. Williams et al. used a combination of hydrological modeling and tree-ring reconstructions of summer soil moisture to show that the period from 2000 to 2018 was the driest 19-year span since the late 1500s and the second driest since 800 CE (see the Perspective by Stahle). This appears to be just the beginning of a more extreme trend toward megadrought as global warming continues.

Abstract
Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogenic climate change. We use hydrological modeling and new 1200-year tree-ring reconstructions of summer soil moisture to demonstrate that the 2000–2018 SWNA drought was the second driest 19-year period since 800 CE, exceeded only by a late-1500s megadrought. The megadrought-like trajectory of 2000–2018 soil moisture was driven by natural variability superimposed on drying due to anthropogenic warming. Anthropogenic trends in temperature, relative humidity, and precipitation estimated from 31 climate models account for 46% (model interquartiles of 34 to 103%) of the 2000–2018 drought severity, pushing an otherwise moderate drought onto a trajectory comparable to the worst SWNA megadroughts since 800 CE.

In Figure 3C we have the standard deviations from 19-year running mean values of soil moisture anomalies. One-quarter of 1 std. deviation more negative than any drought in the 20th century was defined as a megadrought. "The regionally averaged SWNA reconstruction (Fig. 1C) reveals four megadroughts that satisfy this criterion in the late 800s, mid-1100s, late 1200s, and late 1500s."

"The 21st-century prolonged drought event (still ongoing as of 2020 given our definition) registered its first negative SWNA 19-year anomaly in 1996–2014, and its most negative anomaly (2000–2018 was −0.76 σ; the late-1500s megadrought was the only reconstructed event with a more negative 19-year soil-moisture anomaly than that in 2000–2018 (Fig. 1C). "




Fig. 1 Summer soil-moisture reconstruction for SWNA.

(A) Cross-validated reconstruction skill (R2) using tree-ring records that extend to 800 and 1700 CE (green contour: R2 ≥ 0.5; gray: reconstruction does not extend to 800 CE; yellow box: SWNA). (B) Time-resolved cross-validated R2 of the SWNA regional reconstruction. The inset shows observations versus cross-validated reconstructions during the 1901–1983 calibration interval using tree-ring records extending back to 800 and 1700 CE. (C) Time series of reconstructed (red) and observed (blue) 19-year running-mean standardized SWNA soil moisture (gray: 95% reconstruction confidence interval; blue horizontal line: 2000–2018 mean; pink and green shading: the five drought and pluvial periods with the most-negative and most-positive 19-year soil-moisture anomalies, respectively). (D) Maps of the local rank of the most negative 19-year anomaly to occur during each of the five drought events highlighted in (C). In the maps, the aqua color indicates no negative 19-year anomaly, and numbers in the top left corners indicate the rank of the most negative regionally averaged 19-year anomaly during each drought event.

 

Really ? Then why do you not formally write that hypothesis up as a research paper and get it published ?

 

For good reason - it came from a blog ergo was opinion at best

 

This is also from the Science Magazine article described above. This article does mention that "the 2000–2018 drought was preceded by the wettest 19-year period (1980–1998 in at least 1200 years (Fig. 1C). Climate models project enhanced precipitation variability across much of the globe as a result of anthropogenic climate change, and this includes a slight 21st-century trend toward greater decadal precipitation swings in SWNA (37). This tendency is also apparent in model simulations of summer 0- to 200-cm soil moisture, but this simulated effect does not emerge until the second half of the 21st century (fig. S14). Regardless of the anthropogenic impact on multidecadal variability, the 1980–2018 wet-to-dry transition was hastened by the background drying forced from anthropogenic warming.


"The atmosphere and ocean anomalies that drove past megadroughts very likely dwarfed those that occurred during 2000–2018, but superposition of the 2000–2018 climate dynamics on background anthropogenic soil drying put an otherwise moderately severe soil-moisture drought onto a trajectory characteristic of the megadroughts of 800–1600 CE. Critical to the megadrought-like trajectory of the 21st-century event were enhanced evaporative demand, early snowpack loss, and a broad spatial extent, all promoted by anthropogenic warming."


The figure below shows that the 2000–2018 drought was on a megadrought-like trajectory throughout its development. In the absence of anthropogenic climate trends, 2000–2018 would still rank among the 11 most severe prolonged droughts in the reconstruction (dark blue line in Fig. 3), but anthropogenic warming was critical for placing 2000–2018 on a trajectory consistent with the most severe past megadroughts. These results are robust regardless of the drought metric used or whether only forested areas are considered (fig. S15).






Fig. 3 Development of the most severe 19-year droughts since 800 CE.

Time series of cumulative SWNA summer soil-moisture anomalies for the 20 prolonged droughts with the most-negative 19-year soil-moisture anomalies. The drought periods analyzed here begin 18 years before the most-negative 19-year anomaly. The dark blue line shows 2000–2018 cumulative anomalies after removing CMIP5 multimodel mean climate trends. The shaded regions represent 95% confidence intervals for the four reconstructed megadroughts shown with the light colored lines.

 

The Data all came from the NOAA website, don't need a 4 year college education to publish a paper for that since most climate researcher already know this and know where to find it.

How come you didn't know?

You are embarrassing when you write this way.

Here go try it for yourself... NOAA LINK It is really easy and safe too, heck cave children can do it.....

 

Already saw that, again YOU keep missing the point, it has happened a number of times in the past and below 300 PPM too, CO2 isn't the cause of droughts.

 

The baloney gets promoted all the time but ZERO evidence that CO2 is driving it, you are so brainwashed by the CO2 mantra.

and this irrational claims built on dozens of models.... ha ha ha... you are so charmed by them,

Meanwhile ALL the rest of the country is getting wetter since 1970..... which is completely ignored.

CO2 is warmist/alarmist bogeyman, it is so irrational when its effect on the "heat" budget is very small.

Pathetic.