As usual, the Global Warmers have used their religious zeal to attach causality for a natural disaster to “Global Warming”.
The two are quite unconnected and even less connected to anything done by humans.
How can we know this?
Because of all the history of prior, much larger, droughts.
An example article:
Droughts show global warming is ‘scientific fact’
NASA researcher’s study ‘reframes the question,’ UVic professor says
The Associated Press Posted: Aug 4, 2012 10:49 PM ET
The relentless, weather-gone-crazy type of heat that has blistered the United States, Canada and other parts of the world in recent years is so rare it can’t be anything but man-made global warming, according to a new statistical analysis from a top American scientist.
The research by a man often called the “godfather of global warming” says that, from the 1950s through the 1980s, the likelihood of such sweltering temperatures occurring was rarer than 1 in 300. Now, the odds are closer to 1 in 10, according to the study by James Hansen. The NASA scientist says that statistically, what’s happening is not random or normal, but pure and simple climate change.
“This is not some scientific theory,” Hansen told The Associated Press in an interview. “We are now experiencing scientific fact.”
This drought is not “unprecedented”. Heck, it isn’t even unusual. The Mississippi River record low level was in 1988. There have been major floods recently too. Anyone remember 2011 flooding? (It, too, was not unprecedented or unusual. Check out the 1927 flood for comparison.)
So I went looking for a history of flow rate in the Mississippi as a decent indicator of aggregate precipitation in the entire drainage basin. I didn’t find it. Instead I found something I liked more. A much longer series.
There are many readable articles in the set of pages linked to this one:
I’m going to just load up a set of graphs from those articles in one sweeping series here along with selected text quotes. I think that gives the sense of it better than piecemeal one article at a time or needing to click back and forth.
The 500 Year Perspective
Notice that the last half of the 1500′s were mighty dry…
I also note in passing that the “Dust Bowl” drought of the 1930s has not been matched. We are not having a “Dust Bowl” now. No matter what airport tarmac thermometer fantasies dance in Hansen’s head…
Looking at the “Colorado Plains” red line you can see the dustbowl spike down, though the 1950′s look to have been worse in the Southwest of New Mexico (green line). I also just have to note that here they are using tree rings to measure water, not temperature. So a wag would have to ask “Which is it?” but I’m much more confident that they found trees in places that are sensitive to water. (The text described some of the locations and it does look like water is the limiting factor).
A gridded network of tree-ring reconstructions of Palmer Drought Severity Index (PDSI) for the last 300 years has been used to create a set of maps of the spatial pattern of PDSI for each year, back to AD 1700. This set of maps enables an assessment of the droughts of the 20th century compared to droughts for the past 300 years. An inspection of the maps shows that droughts similar to the 1950s, in terms of duration and spatial extent, occurred once or twice a century for the past three centuries (for example, during the 1860s, 1820s, 1730s). However, there has not been another drought as extensive and prolonged as the 1930s drought in the past 300 years.
Longer records show strong evidence for a drought that appears to have been more severe in some areas of central North America than anything we have experienced in the 20th century, including the 1930s drought. Tree-ring records from around North America document episodes of severe drought during the last half of the 16th century. Drought is reconstructed as far east as Jamestown, Virginia, where tree rings reflect several extended periods of drought that coincided with the disappearance of the Roanoke Colonists, and difficult times for the Jamestown colony. These droughts were extremely severe and lasted for three to six years, a long time for such severe drought conditions to persist in this region of North America.
So we get a couple of ’50s like droughts per century. Gee… on in the ’50s and one 1/2 century later is, er, absolutely normal.. and the ’30s drought is the ‘unprecedented’ one in recent history. But what about earlier?
The 2000 Year View
Here we see a 2000 year perspective. What does it show? That recent droughts, even the ’30s megadrought, are not very big and certainly not “unprecedented”.
Even the 1550′s era megadrought is a piker compared to the first 1000 years or so.
Per the reasoning of Hasen et. al. we’d have to conclude that there was “unprecedented global warming” from 0 A.D. to 1200 A.D. then followed massive Global Cooling.
Fluctuations in lake salinity records, inferred from fossil diatom assemblages, were reconstructed for Moon Lake, North Dakota. Different kinds of diatoms favor more or less saline conditions, so an analysis of the types of diatoms found in the layers of lake sediment can be used to reconstruct variations in salinity. The changes in salinity are a reflection of drought variability in this region over the last 2000 years. The sediments were sampled at an average interval of 5.3 years, and radiocarbon and lead- 210 dates provided age control. The gap in the record from the early 17th to the early 18th century is due to loss of data from the core drying out.
One of the notable features about this paleodrought proxy is the abrupt shift in the data about A.D. 1200. This record raises the possibility that different, relatively stable drought “states” or “modes” may have existed over the past 2,000 years. The graph on the right shows a marked shift between high and low salinity conditions around A.D. 1200, suggesting a change in general drought characteristics about this time. Before A.D. 1200, this record indicates regular and persistent droughts, specifically pronounced during the years of A.D. 200-370, A.D. 700-850, and A.D. 1000-1200. In sharp contrast with the period prior to ca. A.D. 1200, the current mode of drought appears relatively wet and free of truly severe drought.
These research results suggest that the current mode of drought variability encompassing the modern instrumental record is not representative of the full range of drought variability displayed in this record. It is important to note that similar lake sediment records for this part of the northern Great Plains do not all reflect the shift in variability at AD 1200, so additional investigations are needed to confirm such a shift. The mechanisms for major shifts in drought variability in the past are not understood, and currently, there is no explanation of a climatic process that could lead to a mode change.
So any large drought now, even one vastly longer and stronger could simply be a return to the ‘regime’ of the past. A regime change driven by things we do not understand and don’t know. Our present drought is absolutely normal, and frankly relatively wet when compared to even just 1000 years ago.
But that’s just one lake… So let’s look at New Mexico to round out the view:
Extraordinarily long-lived trees have been found growing in the El Malpais volcanic field of west-central New Mexico. Although it seems incongruous to find long-lived trees growing in the seemingly harsh environment of these relatively recent (3,000-115,000 years) lava fields, there are good reasons why these trees exist in this area. The lava flows have created kipukas (isolated areas of original substrate and vegetation surrounded by more recent lava flows) that have escaped disturbances such as fire, grazing, logging, and agricultural practices, because of their isolation. The lava field also appears to trap and retain moisture in this otherwise arid environment, creating a habitat favorable to tree growth.
The oldest living tree found at this site is a 1274-year old Douglas-fir, the oldest known tree of this species in North America. Samples from this and other old trees were augmented with subfossil wood, from logs and remnants of living trees, to generate a 2129-year tree-ring chronology extending back to 136 BC.
Not only are the El Malpais trees old, but they are sensitive to precipitation and thus, excellent recorders of past rainfall. The chronology was used to reconstruct annual precipitation for northwestern New Mexico for the past two millennia, as shown in the graph on this page (the units are standard deviation from the mean). The top graph shows the reconstruction for the years 1700-1992. The 1950s drought was the most severe drought 20th century drought in this region, but when viewed in the context of the past three centuries, it appears to be a fairly typical drought. However, when the 1950s drought is compared to droughts for the entire reconstruction, back to 136 BC (bottom graph), it is clear that the 1950s drought is minor relative to many past droughts. A number of the severe droughts of the past spanned several decades, the most recent occurring in the second half of the 16th century.
It’s pretty clear from this graph that from about 1800 on has generally been a very abnormally wet period, and fairly consistently so. It is that wetness that is “unusual”, not the present drought. Even the extreme New Mexico drought of the ’50s is small in comparison to the prior 2000 years; being substantially the same as the “normal” from 800 A.D. to 1400 A.D.
We can now also use these two as ‘bookends’ for the geography. Not some ‘local thing’ at all, but prolonged dryer times reaching from New Mexico to Moon Lake North Dakota.
A similar dry time shows up in Bristle Cone Pines in California in this short page:
In this study, 7979 years of annual (July-June) precipitation were reconstructed from bristlecone pine in the White Mountains of eastern California. The graph to the right shows a comparison between the instrumental (in blue) and reconstructed (in red) precipitation records. The reconstruction documents the occurrence of eight multi-decadal droughts, with the two most recent centered on A.D. 924 and A.D. 1299. The graph below shows the record since AD 1. The occurrence of these two droughts is validated by an independent lake-level record from the neighboring Sierra Nevada Mountains. The timing of coinciding low lake levels from the Mono Lake record (Stine 1994) is shown by the yellow bars. Droughts of this character, were they to occur today, would clearly have a devastating impact. Future work will focus on expanding the multi-millennial record of drought from tree rings and determining forcing mechanisms for these droughts.
Moving down to the Mayan area, we find a ‘megadrought’ too. This graph is in years B.P. Before Present. So about 800 A.D. or 1200 B.P. they had a great drought, right on top of that long dry period in the USA.
Going way back to deeper past time, we find that 3000 B.P. to 7000 B.P. were very wet. So by Hansen’s reasoning, we had massive “global warming” from 3000 B.P. to 1200 B.P. causing a megadrought? No doubt due to all those Mayan SUVs and coal power plants…
Originating in the Yucatan Peninsula, the ancient Maya civilization occupied a vast area of Mesoamerica between the time period of 2600 BC and 1200 AD. Constructing thousands of architectural structures and developing sophisticated concepts surrounding the disciplines of astronomy and mathematics, the Maya civilization rose to a cultural florescence between the years of 600 to 800 AD. Although this prosperity reigned for nearly two centuries, the Maya civilization met with misfortune between the years of 800 and 900 AD.
During this time period, known by archaeologists as the Classic Collapse of the Maya civilization, many southern cities were abandoned and most cultural activities ceased. The Maya, never able to regain their cultural or geographical prominence, were assimilated into other Mesoamerican civilizations until the time of the Spanish Conquest in 1530 AD.
The cause of the collapse of the Classic Maya civilization represents one of the great archaeological mysteries of our time, and has been debated by scholars for nearly a century. Some scientists theorize that the paleoclimate of the region was not only different than the present day climate, but the natural climate variability of the past could have included a period of intense drought that occurred in conjunction with the Classic Maya Collapse.
Scientists reconstructed the past climate of the Maya civilization by studying lake sediment cores in the Yucatan Peninsula. In closed basin lakes, the ratio of 18O to 16O in lake water is controlled mainly by the balance between evaporation and precipitation. The 18O to 16O ratio of lake water is recorded by aquatic organisms, such as gastropods and ostracods that precipitate shells of calcium carbonate (CaCO3). Scientists can measure the 18O to 16O ratio in fossil shells in sediment cores to reconstruct changes in evaporation/precipitation through time, thus inferring climate change.
Looking even deeper back in time, we find a pattern of repeating longer term swings from wet to dry.
Changes in types of pollen found in lake sediment layers provide information about hydroclimatic (i.e., both climatic and hydrologic) variability in central North America during the mid-Holocene (~ 8,000-6,000 years ago). Pollen analyses from lakes in the northern Great Plains suggest a mid-Holocene shift from grasslands to vegetation dominated by weedy annuals, whereas charcoal evidence indicates persistent decade-to-century scale drought cycles at this time (Grimm et al. 1999). The diagram to the right shows the changes in grass (Poaceae, in green) and weedy annuals (Ambrosia-type, in red) in the mid-Holocene for Kettle Lake, North Dakota. When weedy annuals are more prevalent, relative to grasses, episodic droughts are indicated. This diagram also shows charcoal found in the lake sediments, which is a sign of fire. In the Great Plains, higher fire frequency occurred under wet conditions when more fuel, needed by fire, was produced. A lack of fire, and a decrease in charcoal, correspond to drier conditions. The far lefthand columns show changes in minerals in the sediments which correspond to wetter (aragonite) and drier (other minerals) conditions. Taken together, the greater relative amounts of weedy annual pollens, and smaller amounts of charcoal and aragonite define periods of drought (indicated by horizontal yellow bars).
So looks to me like they are saying the graph covers about 650 years. There are 4.5 drought cycles. I make that about 144 years each, but it could easily reach the 179 year solar cycle range. Looking at the Struvite peaks, it look like they would make it a roughly 350-400 year cycle. Rather like that sub-period of Bond Events that we saw reflected in other data. ( 1500 / 750 / 375 periods and sub-periods showing up in historical events).
Back at that pollen article:
At the subcontinental scale, relationships between modern climate and pollen were used to reconstruct the climate of the past from fossil pollen. Past distribution of fossil pollen have been used to generate estimates of past climate conditions in eastern North America (Webb et al. 1998.) One such map of eastern North America (shown to the right) indicates regional increases and decreases in annual precipitation 6,000 years ago, relative to today’s conditions. The southeastern United States was up to 20% wetter than it is today, but much drier conditions prevailed from the Great Lakes to the Northeast, and from central Canada south to Louisiana. Accompanying these decreases in precipitation was an increase of 1 to 2 degree centigrade in mean July temperature in central North America.
Golly, we’re supposed to worry about “Global Warming” of fractional degrees C and here we have historical evidence of natural variations of up to 2 C. I make that nature at about 4 x the power…
How about up in Minnesota?
The distribution of the vegetation present in Minnesota today reflects both north-south and east-west climate gradients (figure to the right), and identifies this as an important region for studies of past drought and climate variability. Lakes sediments from Elk Lake, in the headwaters region of the Upper Mississippi Basin (northeastern Minnesota), record variations in climate and other environmental factors over time scales of years to millennia. Elk Lake sediments are layered in varves, which make it possible to reconstruct information on climate variability with annual resolution. Sediment cores taken from the lake bottom have been used to generate a regional record of aridity based on the chemical, sedimentological, and biological characteristics of the sediments. Changes in varve thickness as well as the abundances of wind-blown quartz-rich silt and clay (quartz values increase under dry conditions), or the sodium from plagioclase feldspar (under dry conditions, retained in soil until washed or blown into lakes) are indicative of regionally wet and dry conditions. Increases in the remains of the diatom Aulacoseira indicate windy conditions, commonly accompanying increased aridity.
The Elk Lake record, spanning almost 11,000 years, shows that conditions were warmer, drier, and windier between 8000 and 6000 year ago as inferred from increases in varve thickness, sage pollen, quartz abundance, sodium levels, and the diatom Aulacoseira (figure to the right). Similar changes in the sediment composition between 4800 and 4300 years ago are indicative of another interval of dry conditions. The subsequent decrease in varve thickness, sage pollen, quartz abundance, sodium levels, and Aulacoseira, reflects an overall trend to moister conditions from 4000 to 1000 years ago. High amplitude changes in sediment composition over the last 1500 years are also interpreted to reflect a number of shorter but equally severe intervals of dry conditions (see Dean, 1997 for details on this work).
Golly… So it was HOTTER and DRYER 6-8 thousand years ago (ending of the 8.2 Kiloyear event) than now… Again 4300-4800 years ago. Gee, almost like it was a 4000 ish year cycle. ( 1500 x 3 = 4500 so perhaps supercycles of the Bond Event period?) Then we’ve got 4000 years of getting cooler and more wet to about 1000 years ago (and we saw above that the last 1000 years has been even wetter with less total drought tendency).
Overall this just confirms what we’ve seen in other geologic contexts.
The exit from the last Ice Age Glacial had ‘overshoot’ to the hot side about 6000 years B.P. and we’ve been on a generally cooling trend since. It is not exceptionally hot now. It is barely getting close to what it was during the prior warm cycles ( MWP, Roman Warm Period, etc.) when civilization flourished. We are still in a long term cooling trend and we have not warmed as much as prior cycles. Next turn is down, to the cold side, and it will go further and colder than in the last 8000 years or so.
This drought is not exceptional. Heck, it isn’t even notable on a 2000 year scale and is substantially nothing in a 10,000 year context. It doesn’t even rise to the level of the 1930s.
Heck, we even had sand dunes wandering the central USA:
The semi-arid Great Plains is covered by >100,000 km2 of eolian (wind blown) deposits which contain evidence for episodes of dune formation, or reactivation of old dunes, over the past 10,000 years. The region of multiple sand dunes and eolian deposits across the central United States (figure on this page) is currently stabilized by vegetation. However, analyses of sediments within sand dunes (stratigraphic records) and the shapes of the dunes (geomorphic records) provide information about multiple past droughts, which resulted in the removal of vegetation, and the movement and accumulation of eolian sand. Accumulations of eolian sediment and formation of dunes occurs when there is adequate sediment supply, when winds exceed the speed needed to move particles of sand, and when there is a lack of stabilizing vegetation or landforms. On the Great Plains, there is adequate sediment supply. Wind strength is already sufficient in much of the Great Plains to move silt and sand, and create widespread active dunes. When a decrease in moisture results in a reduction of vegetation cover below a threshold (~30% decrease in rainfall), dunes can once again become active.
The combination of integrated geomorphic and stratigraphic studies and advances in dating techniques has lead to an enhanced understanding of the timing and location of Holocene (the last 10,000 years) eolian activity on the Great Plains. The data indicate that relatively moist conditions, leading to landscape stability and soil development, were repeatedly interrupted by eolian deposition during periods of drought. Despite the uncertainties associated with the preservation of soil horizons (i.e., the mixing of sediments within a dune) or in correlating dune deposits across the Great Plains, there is regionally consistent evidence for activation of dune systems between 8,000 and 5,000 years ago. Although not as spatially coherent, evidence also indicates the occurrence of a number of drought-related dune formation events in the past 1500 years.
The figure to the right [...] , from the work of Forman and Munyikwa, shows the spatial distribution and extent of stabilized dune fields (in brown) in the North American Great Plains. Superimposed on this map are 15 time series for the last 10,000 years with evidence for episodes of dry and moist conditions (LS denotes landscape stability, DR denotes dune reactivation. HW denotes high water level, LL denotes low water level).
Until we have sand dunes wandering the west, until we have a giant dust bowl that makes the ’30s look like small time drying, any drought is well inside natural variability.