Tag Archives: California Drought

Is the California Drought Over?

My friend Peter Gleick tosses this question aside and informs us that there are actually better questions. Is California having a wet year? How does the snowpack look? Are the reservoirs filling up? Will the groundwater recharge? Will the forests in the Sierra recover with all this precip? Will farmers get all the water they want this year? Will a wet year help the endangered salmon? Will governor Brown cancel the drought declaration? Can Californians stop conserving water and throw some on their lawn?

It turns out that the answer to most of these questions is not what you would assume unless you know a lot about California’s water. Hey, this would make a great facebook quiz! “Only 50% of Californians can answer all of these questions correctly. Take the quiz now!”

Anyway, read this: Gleick: Is the drought over? Wrong question!

Current Status of California Drought, and other matters: Interview with Peter Gleick

The latest episode of Ikonokast, the science podcast Mike Haubrich and I do, is now up. This is an interview with Pacific Institute’s Peter Gleick. We talk about the California drought (past, present, and future), Syria, virtual water, El Nino and climate science denialism.


Californians And Their Drought: New Poll

California voters feel increasingly squeezed by their drought, according to a new USC Donrslife/Los Angeles Times poll.

September 11, 2015 — As one of California’s most severe droughts on record continues to worsen, more than one in three state voters say the drought has had a major impact on them and the lives of their families, according to results from the latest USC Dornsife College of Letters, Arts and Sciences/Los Angeles Times Poll.

Thirty-five percent of California voters said the drought has had a major impact, 50 percent said it has had a minor impact, and 14 percent said it has had no impact at all, according to the poll. That’s an increase since last September, when the USC Dornsife/Los Angeles Times Poll showed 22 percent said the drought had had a major impact and 28 percent said it had no impact at all.

Overall, 92 percent of voters called the drought a “crisis or major problem,” with just 7 percent saying it was “minor or not a problem,” according to the poll. That’s a slight uptick since last September when the 90 percent of voters said the drought was a “crisis or major problem, according to the poll.

“Last year, Californians thought the drought was a problem for the politicans to handle,” said Dan Schnur, director of the USC Dornsife/Los Angeles Times Poll and director of the Unruh Institute of Politics of USC. “This year, it’s a daily challenge in our own lives.”

Among Latinos, 47 percent said the drought has had a major impact on their lives, the poll showed, with another 40 percent who said it’s had a minor impact.

California voters also strongly believe that the El Niño weather phenomenon forecasted to bring heavy rain this winter help the state’s water shortage and drought: 78 percent said El Niño will help, as opposed to 7 percent who said it will make no difference or make it worse, the poll showed.

Here’s a video:

The rest of the press release:

Voters are also increasingly less willing to pay higher water rates and bills to decrease water use, the poll showed.

When asked about a number of potential solutions to address the drought, 58 percent of voters said they would oppose increasing water rates and bills, as opposed to 38 percent who would favor it. In September 2014, voters opposed to raising water rates and bills, 51 to 44.

When asked to choose between two statements, 46 percent said they would be willing to pay higher water bills “to ensure a reliable, long-term water supply,” as opposed to 47 percent who said their water bills “are high enough” and are not willing to pay more to ensure the long-term water supply, the poll showed. In September 2014, the USC Dornsife/LA Times Poll showed 48 percent would pay more as opposed to 41 percent who believed their bills were high enough.

Voters gave high approval marks on water and drought issues to Gov. Jerry Brown – who in April issued an executive order calling for mandatory cuts in urban water use. Fifty percent of voters said they approved of the job being done by Brown on water and the drought, as opposed to 34 percent who said they disapprove. A year ago, the poll showed 39 percent of voters approved and 42 percent disapproved of the job Brown has done on water and the drought.

“Clearly as the state has put in the mandatory measures and implemented Gov. Brown’s policy, people are actually feeling this in their everyday lives. But California may be reaching the end of their rope in terms of the personal sacrifices they are making,” said Drew Lieberman, vice president of Democratic polling firm Greenberg Quinlan Rosner, part of the bipartisan team with Republican polling firm American Viewpoint that conducted the USC Dornsife/Los Angeles Times Poll.

Among the policy prescriptions most favored by voters: 95 percent favor both recycling more water and improving the state’s ability to capture storm water; 80 percent said investing in desalinating ocean water to make it suitable for household use; and 69 percent said build new dams and reservoirs.

But only 53 percent of voters said they favored requiring farmers and the agriculture industry to reduce water use. Voters were also unwilling to suspend environmental regulations that protect fish and wildlife to help address the drought, with 54 percent saying they oppose suspending environmental regulations and 42 percent saying they would favor it.

“Voters seem to have decided that they’re doing their share, there are other things that need to be done to impact the drought but it doesn’t need to affect the state’s other policy priorities,” Schnur said. “Voters are clearly concerned about the drought but tend to see it in isolation and not related to the state’s other policy challenges.”

When asked to choose between a pair of statements, 50 percent of voters said California should protect the environment, even if it hurts the water supply, as opposed to 34 percent who said the state should ensure the water supply even at the expense of the environment. In September 2014, 46 percent of voters said California should protect the environment and 37 percent said the state should ensure the water supply even if it harms the environment.

Californians were slightly opposed to allowing the government to impose fines of up to $10,000 for violations of water conservation rules, with 44 percent in favor and 49 percent opposed.

What (or who) is to blame for the drought?

When asked which factors were most to blame for California’s water supply problems, 90 percent said “not enough snow and rain,” followed by old delivery systems and not enough water storage (79%); Californians using too much water (78%); too much growth and development (72%); global climate change (69%); and environmental regulations (67%).

Sixty-five percent of voters said they blamed the agricultural industry, up from 54 percent a year ago, the poll showed. Support for requiring farmers to decrease water use jumped 16 percentage points over the September 2014 USC Dornsife/LA Times poll.

Latino voters were more likely than white voters to blame global climate change (76-65) and environmental regulations (76-62) for the state’s water supply problems.

“Given that a lot of these voters feel they’ve already made sacrifices, if other people had to take a further pinch they’d rather it be someone other than them. The agriculture industry is an easy victim to choose,” said David Kanevsky, research director of Republican polling firm American Viewpoint.

The latest USC Dornsife/Los Angeles Times Poll, the largest statewide survey of registered voters, was conducted Aug. 29 – Sept. 8 and includes a significant oversample of Latino voters as well as one of the most robust cell phone samples in the state. The full sample of 1,500 registered voters has a margin of error of +/- 2.8 percentage points.

California Drought Caused By Climate Change

Human released greenhouse gas pollution changes the climatic system through a variety of mechanisms. Trade winds and jet streams change their patterns of movement, and the distribution of moisture in the air changes, with precipitation either lacking more than usual or being more abundant than usual. The patterns of movement of major air masses and the increased bifurcation of air masses into more wet than usual and more dry than usual can result in long periods where region experiences excess precipitation or a lack of precipitation. When the latter happens, there can be a drought.

Increasingly, the California drought is being seen as an effect of climate change. Air masses that should have contributed precipitation in the form of mountain snow, which in turn feed the western ground water system, have been kept away. Increased temperature has increased evaporation. Other factors related to climate change have contributed. The result is an historic drought over California that shows at present no sign of stopping any time soon. There was hope that last winter there would be additional precipitation, and there was some, but not enough.

A paper just out in Geophysical Research Letters uses modeling and historic data to confirm that the current California drought is very likely an effect of climate change. The paper is “Temperature Impacts on the Water Year 2014 Drought in California“, by Shraddhanand Shukla, Mohammad Safeeq, Amir Aghkouchak, Kaiyu Guan, and Chris Funk. Here is the abstract, which is pretty self explanatory and understandable:

California is experiencing one of the worst droughts on record. Here we use a hydrological model and risk assessment framework to understand the influence of temperature on the water year (WY) 2014 drought in California and examine the probability that this drought would have been less severe if temperatures resembled the historical climatology. Our results indicate that temperature played an important role in exacerbating the WY 2014 drought severity. We found that if WY 2014 temperatures resembled the 1916-2012 climatology, there would have been at least an 86% chance that winter snow water equivalent and spring- summer soil moisture and runoff deficits would have been less severe than the observed conditions. We also report that the temperature forecast skill in California for the important seasons of winter and spring is negligible, beyond a lead-time of one month, which we postulate might hinder skillful drought prediction in California.

The caption for the graphic above is: “Percentiles of potential evapotranspiration (ETo) during WY 2014 with respect to 1979 to 2012 climatology.”

I find the ancillary finding of the lack of skill of temperature forecasts in California. One would expect low skill in forecast models that are designed under a given climatology, when that climatology shifts as it seems to have done.

Drought in California and Climate Change: They are linked

A paper just out now in PNAS by Noah Diffenbaugh, Daniel Swain, and Danielle Touma shows that “Anthropogenic warming has increased drought risk in California.” From the abstract:

… We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create ?100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm–dry conditions like those that have created the acute human and ecosystem impacts associated with the “exceptional” 2012–2014 drought in California.

Michael Mann and Peter Gleick have written a commentary for PNAS to accompany that research. The graphic at the top of the post is from that study. They note:

California is experiencing extreme drought. Measured both by precipitation and by run- off in the Sacramento and San Joaquin river basins, 10 of the past 14 y have been below normal, and the past 3 y have been the driest and hottest in the full instrumental record. A plot of temperature and precipitation anom- alies over the full instrumental record from 1895 through November 2014 shows that the 3-y period ending in 2014 was by far the hottest and driest on record (Fig. 1). As of the publication of this commentary, the state appears headed into a fourth consec- utive year of water shortfall, leading to massive groundwater overdraft, cutbacks to farmers, reductions in hydroelectricity gen- eration, and a range of voluntary and man- datory urban water restrictions.

A number of studies have examined the California drought to try to determine if it was “caused by” (or otherwise affected by) human greenhouse gas pollution. These studies vary in their level of attribution, but increasingly it is becoming clear that anthropogenic global warming has a very big hand in this.

Mann and Gleick tackle the problem of defining drought. There are multiple ways to do so, and they relate to different causes. The plethora of definitions and relevant variables allows for a given study to miss any global warming effect by picking certain factors and ignoring others. Studies that look mainly at inputs to the hydrological system (i.e., rainfall) tend to miss the output part of the equation, including evaporation, which is exacerbated by a warming climate. Mann and Gleick point out that the Diffenbaugh study adds significant weight to the idea that anthropogenic climate change has increased the frequency, magnitude, and duration of California’s droughts. Perhaps more importantly, the Diffenbaugh study suggests “the emergence of a climatic regime in which all future dry years coincide with warmer conditions.”

Gleick told me, “The scientific evidence showing the growing influence of climate changes on extreme events around the world, including the ongoing California drought, continues to pile up. The clearest piece of this is the record high, and increasing, temperatures, which directly influence the availability and demand for water, but there is also growing evidence that climate change is influencing pressure dynamics and atmospheric circulation patterns that either bring, or divert, water from the west coast of the United States.”

So, the current drought in California is linked to human induced climate change, and in the future, this will be a more common phenomenon than it has in the base, according to the best available science. But what about other effects of climate change? I asked Michael Mann about the relationship between California Drought and his recent study showing that we should soon be entering a period (over the next couple of decades) during which heat that has been hiding in the oceans will be leaving it’s watery milieu and joining us up here on the surface. He told me, “Here is the linkage I think is most relevant: the “faux pause”, in our recent study, was closely tied to the predominance of La Nina-like conditions in the tropical Pacific for a large part of the past decade, and these same conditions are closely linked with California drought (La Nina years tend to be drought years in California, while El Nino years tend to be wet years—though this doesn’t necessarily hold true for every single event). So one might imagine that a return to a greater tendency for El Nino-like conditions in the tropical Pacific over the next decade or two (which would spell an end to the “Faux Pause”) could actually be a mitigating effect as far as California drought is concerned. A bit counter-intuitive, but that’s best assessment here.”

California is clearly exceptional, but not in a good way: #Drought

The US Drought Monitor produces an assessment of drought conditions every week. The drought in California has taken a large jump over the last few days, with the highest category, “Exceptional,” jumping from 36.49% to 58.41%. At the start of the calendar year, that category was represented in California by 0%, so this is a continuation of an ongoing trend. The image above is the current map from US Drought Monitor.

I made a couple of other graphics that demonstrate the problem.

This is the percent area in California covered by severe to exceptional drought since the most recent time that this percentage was at zero, near the end of 2011.


And these two graphs show just the percentage of land area in California covered by Exceptional drought since the beginning of the US Drought Monitor’s data in 2000 to the present (upper graph) and the same information for the last year (lower graph).

Note the extreme uptick.

The drought monitor has a synopsis of the situation:

Increasingly, drought indicators point to the fact that conditions are not appreciably better in northern California than in central and southern sections of the state. In addition, mounting evidence from reservoir levels, river gauges, ground water observations, and socio-economic impacts warrant a further expansion of exceptional drought (D4) into northern California. For California’s 154 intrastate reservoirs, storage at the end of June stood at 60% of the historical average. Although this is not a record for this time of year—the standard remains 41% of average on June 30, 1977—storage has fallen to 17.3 million acre-feet. As a result, California is short more than one year’s worth of reservoir water, or 11.6 million acre-feet, for this time of year. The historical average warm-season drawdown of California’s 154 reservoirs totals 8.2 million acre-feet, but usage during the first 2 years of the drought, in 2012 and 2013, averaged 11.5 million acre-feet.

Given the 3-year duration of the drought, California’s topsoil moisture (80% very short to short) and subsoil moisture (85%) reserves are nearly depleted. The state’s rangeland and pastures were rated 70% very poor to poor on July 27. USDA reported that “range and non-irrigated pasture conditions continued to deteriorate” and that “supplemental feeding of hay and nutrients continued as range quality declined.” In recent days, new wildfires have collectively charred several thousand acres of vegetation in northern and central California. The destructive Sand fire, north of Plymouth, California—now largely contained—burned more than 4,000 acres and consumed 66 structures, including 19 residences.

Is the California Drought Caused By Climate Change, Or By Californians?

Possibly both.

Climate change certainly has a huge effect. Increased evaporation, decreased snowpack, the stalling of air masses that cause more drying and less wetting, which in turn is caused by changes in the jet stream, which in turn is caused by “Arctic Amplification,” an effect of global warming, are major causes of a three year drought coming hard on the heels of a decade of near-drought dry.

But also, Californian approaches to water management have been an issue. I recently learned that there are communities in California that don’t even have water meters on people’s houses. What the heck? A while back the state asked people to use less water. They didn’t. Just now, the California Water Board implemented a fine for overuse of water, and local communities are asking people to turn in their neighbors who do so.

Here is an interview on All In with Chis Hays of Peter Gleick of The Pacific Institute, on the drought and the response to it.

What is causing the California drought?

Peter Sinclair has tackled this difficult topic with an excellent video and informative blog post. The blog post is here, and I’ve pasted the video below.

This is a complicated issue. The water problem in California is obviously made worse by increased demands from population growth and expansion of agriculture. Under “normal” (natural) conditions, California and the American Southwest is fairly dry and can undergo extra dry periods. But climate change seems to be playing a role here as well. It appears that recent lack of rain in the region is the result of changes in atmospheric circulation that can be linked to anthropogenic global warming. Warm air also increases evaporation and decreases snow pack. When rain falls it tends more often to be in the form of heavy downpours, and thus, more runoff (not to mention landslides).

Peter also talks about Jacob Sewall’s model, ten years ago, that predicted the current situation as an outcome of reduced ice cover in the Arctic. Over at Significant Figures, Peter Gleick also talks about the California drought: Clarifying the Discussion about California Drought and Climate Change.

Photo Credit: Fikret Onal via Compfight cc

Other posts of interest:

Also of interest: In Search of Sungudogo: A novel of adventure and mystery, which is also an alternative history of the Skeptics Movement.

A Letter From John Holdren Regarding Roger Pielke Jr's Statements

The following is also found HERE on the White House web site. I provide it here without comment because it speaks for itself. But if you want more, check out “Global warming action: good or bad for the poor?” by John Abraham, and “Keeping The Carbon In The Ground Elsewhere: Developing Nations” by me.

Drought and Global Climate Change: An Analysis of Statements by Roger Pielke Jr

John P. Holdren, 28 February 2014


In the question and answer period following my February 25 testimony on the Administration’s Climate Action Plan before the Oversight Subcommittee of the U.S. Senate’s Committee on Environment and Public Works, Senator Jeff Sessions (R-AL) suggested that I had misled the American people with comments I made to reporters on February 13, linking recent severe droughts in the American West to global climate change. To support this proposition, Senator Sessions quoted from testimony before the Environment and Public Works Committee the previous July by Dr. Roger Pielke, Jr., a University of Colorado political scientist. Specifically, the Senator read the following passages from Dr. Pielke’s written testimony:

It is misleading, and just plain incorrect, to claim that disasters associated with hurricanes, tornadoes, floods or droughts have increased on climate timescales either in the United States or globally.

Drought has “for the most part, become shorter, less, frequent, and cover a smaller portion of the U.S. over the last century”. Globally, “there has been little change in drought over the past 60 years.”

Footnotes in the testimony attribute the two statements in quotation marks within the second passage to the US Climate Change Science Program’s 2008 report on extremes in North America and a 2012 paper by Sheffield et al . in the journal Nature, respectively.

I replied that the indicated comments by Dr. Pielke, and similar ones attributed by Senator Sessions to Dr. Roy Spencer of the University of Alabama, were not representative of main- stream views on this topic in the climate-science community; and I promised to provide for the record a more complete response with relevant scientific references.

Dr. Pielke also commented directly, in a number of tweets on February 14 and thereafter, on my February 13 statements to reporters about the California drought, and he elaborated on the tweets for a blog post on The Daily Caller site (also on February 14). In what follows, I will address the relevant statements in those venues, as well. He argued there, specifically, that my statements on drought “directly contradicted scientific reports”, and in support of that assertion, he offered the same statements from his July testimony that were quoted by Senator Sessions (see above). He also added this:

The United Nations Intergovernmental Panel on Climate Change found that there is “not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought.”

In the rest of this response, I will show, first, that the indicated quote from the US Climate Change Science Program (CCSP) about U.S. droughts is missing a crucial adjacent sentence in the CCSP report, which supports my position about drought in the American West. I will also show that Dr. Pielke’s statements about global drought trends, while irrelevant to my comments about drought in California and the Colorado River Basin, are seriously misleading, as well, concerning what is actually in the UN Panel’s latest report and what is in the current scientific literature.

Drought trends in the American West

My comments to reporters on February 13, to which Dr. Pielke referred in his February 14 tweet and to which Senator Sessions referred in the February 25 hearing, were provided just ahead of President Obama’s visit to the drought-stricken California Central Valley and were explicitly about the drought situation in California and elsewhere in the West.

That being so, any reference to the CCSP 2008 report in this context should include not just the sentence highlighted in Dr. Pielke’s testimony but also the sentence that follows immediately in the relevant passage from that document and which relates specifically to the American West. Here are the two sentences in their entirety (http://downloads.globalchange.gov/sap/sap3- 3/Brochure-CCSP–3–3.pdf):

Similarly, long-term trends (1925–2003) of hydrologic droughts based on model derived soil moisture and runoff show that droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the U.S. over the last century (Andreadis and Lettenmaier, 2006). The main exception is the Southwest and parts of the interior of the West, where increased temperature has led to rising drought trends (Groisman et al., 2004; Andreadis and Lettenmaier, 2006).

Linking Drought to Climate Change

In my recent comments about observed and projected increases in drought in the American West, I mentioned four relatively well understood mechanisms by which climate change can play a role in drought. (I have always been careful to note that, scientifically, we cannot say that climate change caused a particular drought, but only that it is expected to increase the frequency, intensity, and duration of drought in some regions ? and that such changes are being observed.)

The four mechanisms are:

  1. In a warming world, a larger fraction of total precipitation falls in downpours, which means a larger fraction is lost to storm runoff (as opposed to being absorbed in soil).

  2. In mountain regions that are warming, as most are, a larger fraction of precipitation falls as rain rather than as snow, which means lower stream flows in spring and summer.

  3. What snowpack there is melts earlier in a warming world, further reducing flows later in the year.

  4. Where temperatures are higher, losses of water from soil and reservoirs due to evaporation are likewise higher than they would otherwise be.

Regarding the first mechanism, the 2013 report of the IPCC’s Working Group I, The Science Basis (http://www.climatechange2013.org/images/report/WG1AR5_TS_FINAL.pdf, p 110), deems it “likely” (probability greater than 66%) that an increase in heavy precipitation events is already detectable in observational records since 1950 for more land areas than not, and that further changes in this direction are “likely over many land areas” in the early 21 st century and “very likely over most of the mid-latitude land masses” by the late 21 st century The second, third, and fourth mechanisms reflect elementary physics and are hardly subject to dispute (but see also additional references provided at the end of this comment).

As I have also noted in recent public comments, additional mechanisms have been identified by which changes in atmospheric circulation patterns that may be a result of global warming could be affecting droughts in the American West. There are some measurements and some analyses suggesting that these mechanisms are operating, but the evidence is less than conclusive, and some respectable analysts attribute the indicated circulation changes to natural variability. The uncertainty about these mechanisms should not be allowed to become a distraction obscuring the more robust understandings about climate change and regional drought summarized above.

Global Drought Patterns

Drought is by nature a regional phenomenon. In a world that is warming on the average, there will be more evaporation and therefore more precipitation; that is, a warming world will also get wetter, on the average. In speaking of global trends in drought, then, the meaningful questions are (a) whether the frequency, intensity, and duration of droughts are changing in most or all of the regions historically prone to drought and (b) whether the total area prone to drought is changing.

Any careful reading of the 2013 IPCC report and other recent scientific literature about on the subject reveals that droughts have been worsening in some regions in recent decades while lessening in other regions, and that the IPCC’s “low confidence” about a global trend relates mainly to the question of total area prone to drought and a lack of sufficient measurements to settle it. Here is the key passage from the Technical Summary from IPCC WGI’s 2013 report (http://www.climatechange2013.org/images/report/WG1AR5_TS_FINAL.pdf, p 112):

Compelling arguments both for and against significant increases in the land area affected by drought and/or dryness since the mid–20th century have resulted in a low confidence assessment of observed and attributable large-scale trends. This is due primarily to a lack and quality of direct observations, dependencies of inferred trends on the index choice, geographical inconsistencies in the trends and difficulties in distinguishing decadal scale variability from long term trends.

The table that accompanies the above passage from the IPCC’s report ? captioned “Extreme weather and climate events: global-scale assessment of recent observed changes, human contribution to the changes, and projected further changes for the early (2016–2035) and late (2081–2100) 21 st century” ? has the following entries for “Increases in intensity and/or duration of drought”: under changes observed since 1950, “low confidence on a global scale, likely changes in some regions” [emphasis added]; and under projected changes for the late 21 st century, “likely (medium confidence) on a regional to global scale”.

Dr. Pielke’s citation of a 2012 paper from Nature by Sheffield et al ., entitled “Little change in global drought over the past 60 years”, is likewise misleading. That paper’s abstract begins as follows:

Drought is expected to increase in frequency and severity in the future as a result of climate change, mainly as a consequence of decreases in regional precipitation but also because of increasing evaporation driven by global warming 1–3. Previous assessments of historic changes in drought over the late twentieth and early twenty-first centuries indicate that this may already be happening globally. In particular, calculations of the Palmer Drought Severity Index (PDSI) show a decrease in moisture globally since the 1970s with a commensurate increase in the area of drought that is attributed, in part, to global warming 4–5.

The paper goes on to argue that the PDSI, which has been relied upon for drought characterization since the 1960s, is too simple a measure and may (the authors’ word) have led to overestimation of global drought trends in previous climate-change assessments ? including the IPCC’s previous (2007) assessment, which found that “More intense and longer droughts have been observed over wider areas since the 1970s, particularly in the tropics and subtropics.”

The authors argue for use of a more complex index of drought, which, however, requires more data and more sophisticated models to apply. Their application of it with the available data shows a smaller global drought trend than calculated using the usual PDSI, but they conclude that better data are needed. The conclusion of the Sheffield et al . paper has proven controversial, with some critics pointing to the inadequacy of existing observations to support the more complex index and others arguing that a more rigorous application of the new approach leads to results similar to those previously obtained using the PDSI.

A measure of the differences of view on the topic is available in a paper entitled “Increasing drought under global warming in observations and models”, published in Nature Climate Change at about the same time as Sheffield et al. by a leading drought expert at the National Center for Climate Research, Dr. Aiguo Dai. Dr. Dai’s abstract begins and ends as follows:

Historical records of precipitation, streamflow, and drought indices all show increased aridity since 1950 over many land areas 1,2. Analyses of model-simulated soil moisture 3, 4, drought indices 1,5,6, and precipitation minus evaporation 7 suggest increased risk of drought in the twenty-first century. … I conclude that the observed global aridity changes up to 2010 are consistent with model predictions, which suggest severe and widespread droughts in the next 30–90 years over many land areas resulting from either decreased precipitation and/or increased evaporation.

The disagreement between the Sheffield et al. and Dai camps appears to have been responsible for the IPCC’s downgrading to “low confidence”, in its 2013 report, the assessment of an upward trend in global drought in its 2007 Fourth Assessment and its 2012 Special Report on Extreme Events (http://www.ipcc-wg2.gov/SREX/) .

Interestingly, a number of senior parties to the debate ? including Drs. Sheffield and Dai ? have recently collaborated on a co-authored paper, published in the January 2014 issue of Nature Climate Change, entitled “Global warming and changes in drought”. In this new paper, the authors identify the reasons for their previous disagreements; agree on the need for additional data to better separate natural variability from human-caused trends; and agree on the following closing paragraph (quoted here in full):

Changes in the global water cycle in response to the warming over the twenty-first century will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will probably increase, although there may be regional exceptions. Climate change is adding heat to the climate system and on land much of that heat goes into drying. A natural drought should therefore set in quicker, become more intense, and may last longer. Droughts may be more extensive as a result. Indeed, human-induced warming effects accumulate on land during periods of drought because the ‘air conditioning effects’ of water are absent. Climate change may not manufacture droughts, but it could exacerbate them and it will probably expand their domain in the subtropical dry zone.

Additional References (with particularly relevant direct quotes in italics)

Christopher R. Schwalm et al., Reduction of carbon uptake during turn of the century drought in western North America, Nature Geoscience, vol. 5, August 2012, pp 551–556.

The severity and incidence of climatic extremes, including drought, have increased as a result of climate warming. … The turn of the century drought in western North America was the most severe drought over the past 800 years, significantly reducing the modest carbon sink normally present in this region. Projections indicate that drought events of this length and severity will be commonplace through the end of the twenty-first century.

Gregory T. Pederson et al. , The unusual nature of recent snowpack declines in the North American Cordillera, Science, vol. 333, 15 July 2011, pp 332–335.

Over the past millennium, late 20 th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming that is due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.

Gregory T. Pederson et al., Regional patterns and proximal causes of the recent snowpack decline in the Rocky Mountains, US, Geophysical Research Letters, vol. 40, 16 May 2013, pp 1811–1816.

The post–1980 synchronous snow decline reduced snow cover at low to middle elevations by ~20% and partly explains earlier and reduced streamflow and both longer and more active fire seasons. Climatologies of Rocky Mountain snowpack are shown to be seasonally and regionally complex, with Pacific decadal variability positively reinforcing the anthropogenic warming trend.

Michael Wehner et al., Projections of future drought in the continental United States and Mexico, Journal of Hydrometeorology, vol. 12, December 2011, pp 1359–1377.

All models, regardless of their ability to simulate the base-period drought statistics, project significant future increases in drought frequency, severity, and extent over the course of the 21 st century under the SRES A1B emissions scenario. Using all 19 models, the average state in the last decade of the twenty-first century is projected under the SRES A1B forcing scenario to be conditions currently considered severe drought (PDSI<–3) over much of the continental United States and extreme drought (PDSI<–4) over much of Mexico.

D. R. Cayan et al ., Future dryness in the southwest US and the hydrology of the early 21 st century drought, Proceedings of the National Academy of Sciences, vol. 107, December 14, 2010, pp 21271–21276.

Although the recent drought may have significant contributions from natural variability, it is notable that hydrological changes in the region over the last 50 years cannot be fully explained by natural variability, and instead show the signature of anthropogenic climate change.

E. P. Maurer et al. , Detection, attribution, and sensitivity of trends toward earlier streamflow in the Sierra Nevada, Journal of Geophysical Research, vol. 112, 2007, doi:10.1029/2006JD08088.

The warming experienced in recent decades has caused measurable shifts toward earlier streamflow timing in California. Under future warming, further shifts in streamflow timing are projected for the rivers draining the western Sierra Nevada, including the four considered in this study. These shifts and their projected increases through the end of the 21st century will have dramatic impacts on California’s managed water system.

H. G. Hidalgo et al ., Detection and attribution of streamflow timing changes to climate change in the western United States, Journal of Climate, vol. 22, issue 13, 2009, pp 3838–3855, doi: 10.1175/2009JCLI2740.1.

The advance in streamflow timing in the western United States appears to arise, to some measure, from anthropogenic warming. Thus the observed changes appear to be the early phase of changes expected under climate change. This finding presages grave consequences for the water supply, water management, and ecology of the region. In particular, more winter and spring flooding and drier summers are expected as well as less winter snow (more rain) and earlier snowmelt.

California, Drought, Pineapple Express, Geological Imperative, Evacuations

If water had its way, this is what California would look like:

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Think about it for a second. Every single moment, currents of air move, slowly or rapidly, across every land surface on the planet. Anything loose gets blown slowly or rapidly, to lower places. Every now and then, in some places rarely and in other places commonly, liquid water falls from the sky on almost every land surface on the planet. Now and then, in certain limited areas, frozen water builds up to great heights, thousands of feet hight, and moves along, scraping deep hollows and grooves the size of big lakes out of these land surfaces. Now and then the earth shakes and stuff falls down. Most of the earth’s surface is ocean, only a small percentage is land. With all this blowing and washing and scraping away, you would think that all the stuff on the land would eventually end up in the ocean and all of the land would look like this:

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There are several reasons this does not happen. One is that mountain building happens because continental shelves push against each other. Another is that volcanoes occasionally spew ash, lava, and stuff out onto the land surface. Also, there is another, less often known about by the average person but incredibly important reason that the land does not look like this …

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Underneath the land there is melty-squishy-hot stuff that tends to push upwards a little bit almost everywhere, and a lot in some places, though it is usually pushed back upon by the weight of the land itself. If you remove a bunch of stuff from the surface of the continent, this pushing gets a bit of traction. So, if you have a big piece of continent with erosion happening all the time on the top, this pushing will happen from below, and the continent will not disappear below the surface of the sea. The Congo basin is probably an example of this. It rains a lot, there is constant erosion. So, the land surface across most of the Congo has been eroding for something like a couple or few hundred million years, at least, like it is now. As the surface is eroded away, the underneath slowly rises. So now, much of the Congo basin has deeply eroded rivers, and all the hills between the rivers are made of stuff that is like granite, the cooled down, hardened melty-squish-hot stuff. In fact, a lot of Africa is like that.

In California, the last calendar year was the driest one on record. California has been so dry over the last few years that it is nearly dried out. The reservoirs are puddles, the groundwater is a mystery, and the state is in a state of crisis. But today, the first Pineapple Express of the rainy season arrived, and dumped huge amounts of rain in parts of the state.

California is uplifted. Unlike Louisiana, Mississippi, and nearby areas, which are all very close to sea level, California stands up high over the ocean. When you head for the ocean from inland, depending on where you start, you may have to cross significant mountain ranges or linear arrangements of tall hills, and just before getting to the sea you will have your brakes on a lot of the time because you’ll be going down hill. The shoreline of California is roughly synonymous with the continental shelf, in contrast to other coastlines in the US where the shelf edge may be hundreds of miles out to sea.

The dry conditions over the last few years have resulted in a lot of fires on the hills in this hilly, uplifted country. The geological stuff underneath the surface in much of California is not like the deep hardened magma of the Congo, or for that matter, New Hampshire, Maine and the Maritimes. It is soft, to varying degrees. The top, exposed areas on those hills is made of rocks and dirt. When torrential rains flow over the surface, this material is held in place by a combination of plant roots and luck. The force of the rains is attenuated by the upper parts of the vegetation. But with the vegetation either burned off or dead(ish) from drought, or both, the water washes away the softer smaller particles, leaving the larger stones and rocks exposed, and rivulets start to form and erosional gullies deepen and widen. Meanwhile the ground soaks up water and becomes both loose and heavy at the same time. All these factors together constitute a step in the process of making California look, eventually, like this:

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And if your house, or the road to your house, or anything, is in the way, it will get washed down stream or buried under other stuff washing down stream. For this reason, evacuations are underway in parts of the Sunshine State.

There’s good news, though. Even though the forces of nature seem intent on making California eventually look like this:

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There are other forces of nature that are intent on making California look like this:

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That’s the good news. The bad news is that those other forces are, well, earthquakes.

Hey, how about this weather?

The drought in California is really bad. Bad enough that people are struggling to describe it.

weather</aPaul Douglas (below) suggests that this may be the biggest weather story of 2014, and the reason for that is food. They grow a lot of it in California, but those who developed this 21st Century breadbasket did so with too much hubris. Hubris about water, to be specific. It will be interesting to see if discussions about food prices turn into discussions about food availability, at least for certain kinds of food, as the non-growing season develops there.

People often equate California with other countries because it is so big and important. “If California was a country, it would be the Nth largest country that does XYZ.” It will be interesting to see how this trope works out should the drought continue (and by continue, I mean worsen, because a drought that continues is a worsening drought). “If California was a country, it would have an Arab Spring Uprising.” “If California was a country, it would require food aid from the UN.” “If California was a country it would be one of the largest suppliers of climate-related refugees in the world.” That sort of thing.

Meanwhile the Polar Vortex came to visit a few weeks ago and never really left. They should make a movie. “National Lampoon’s Polar Vortex.” The cold has stressed supplies of natural gas (exacerbated by a major pipeline explosion in Canada). Here in Minnesota there is a propane shortage. Brat on the weber is in danger as a thing.

The Vortex is connected to the drought, as both are caused by a configuration of major air masses also manifest as the meandering jet stream. And, with this comes also the parade of storms that have marched across the middle of the US and in some cases dumped snow where snow is usually not dumped.

The future is not rosy. There is no end in sight for the drought despite a smattering of snow and rain in the west. The Polar Vortex is expected to hang around for several more days, and then perhaps move on, but quite possibly to return not long after. There may be a major nor’easter in the Northeast this coming weekend.

Here’s Paul Douglas’s latest summary of the weather from his WeatherNation YouTube ChaNnel:

Graphic on California drought from: Historic January Drought Intensifies in California