North American drought worst in 500 yearsBrent Herbert 23 Jun 2004 23:49 GMT
North American drought worst in 500 years
According to the U.S. Geological Survey, the current drought in the West of North America is the worst that has occured in the last 500 years, with water flow levels at close to half those of the drought in the dirty thirties of the previous century.
According to the report Climatic Fluctuations, Drought, and Flow in the Colorado River
The early 21st century drought is the most severe in terms of flow deficit in more than a century. The current drought also has produced the lowest flow period in the record, with an average of only 5.4 MAF for 2001-2003. In contrast, the drought of the Dust Bowl years between 1930 and 1937 produced an average of 10.2 MAF. The predicted inflow into Lake Powell for 2004 is 49% of the long-term average (5.6 MAF), which indicates that the early 21st century drought is on-going.
North American droughts are linked to the global climate system, linked to both oscillations in the Pacific and the Atlantic Oceans. When the Atlantic Ocean is cooler this typically corresponds to wetter conditions in the American west, while a warmer Atlantic corresponds to drought and decreased water flow in the West. Changes in the Atlantic (as measured by the AMO) interact with the PDO (ENSO, oscillations in the Pacific between El Nino and La Nina conditions) to affect climatic conditions on the North American continent in a complex pattern that is hard to predict and not fully understood.
The recent drought, referred to here as the early 21st century drought, has its origins in several global-scale atmospheric and oceanic processes that reduce delivery of atmospheric moisture to the Colorado River basin.
ENSO reflects an oscillation between two basic states of the ocean. The warm phase (negative SOI), called the El Niño, involves warming of the eastern tropical Pacific Ocean off the coast of Peru. The warm water spreads northward in the eastern North Pacific Ocean off the west coast of the United States. The cold phase (positive SOI), called La Niña, is the opposite, resulting in a cooling of the water off western North America.
Although the Atlantic Ocean is downstream from the moisture-delivery sources to the Southwest, warm conditions indicated by positive AMO are indicative of drought, for example the Dust Bowl of the early 1930s During positive AMO conditions, atmospheric flow is shifted to deliver less moisture to the continental United States.
Correlation between drought conditions and the PDO and AMO
The graphic above shows the relationship that exists between drought conditions and the AMO (the X axis from left to right along the bottom) and PDO (the y axis from top to bottom). Wetter than normal conditions are shown as blue spots while drought conditions are mapped as red spots, and as the graph indicates their is a correlation between rises in Atlantic Ocean temperature (towards the right of the graph) and the occurence of drought in the North American West (the red dots). The change in temperature on the graph displays a variation of two degrees in Atlantic Ocean temperature and the corresponding drought conditions on the North American continent.
Sea Surface Temperature Anomaly June 2004
The map above shows the temperature anomaly for the Atlantic Ocean, with the shades from orange to red showing water than is from 2 to 5 degrees warmer than the normal average. It is the persistence of this warming of the ocean, also in evidence by the rapid shrinking of the Arctic ice caps during the previous decade, that has scientists concerned that the drought currently gripping the North American west could persist for decades into the future. The dire consequences of such a future are obvious, with many tens of millions of Americans living in inhospitable deserts and semi-desert regions such as California, and dependant on river water that is continuing to deplete, and with ground water levels at dangerously low levels due to decades of nonsustainable use of nonrewable resources (a characteristic of the modern economic system, focused as it is on quarterly results and profits). The effects ripple across the continent as water levels in the Great Lakes continue to drop, and barge traffic on the Mississippi carries half loads to avoid scraping bottom. Battles are already beginning as businesses and cities demand the draining of protected wet land habitats to release more water into river system, and businesses rush to book what threatens to be a shortage of trucks if shipping becomes impossible on the nations waterways.
It turns out to be the case that current water management agreements in the west rely on water flow statistics gathered in the 1920s, and this period was one of the wettest on record with the highest recorded stream flows. What this implies is that it is not possible to continue using water at the rates established during what was actually a peak flow period during a time of record low water flow rates. The problem is made worse by the fact that North America has a depleted ground water crisis, making major urban areas and large scale desert agriculture even more dependant on depleted rivers and watersheds.
Tree-ring reconstructions of Colorado River flows provide a longer-term flow record that can be used to assess drought frequency. One of the most important conclusions from dendrochronology is that the period from 1906 through 1930, which was partially used to determine flow allocations under the Colorado River Compact, was likely the highest period of runoff in 450 years.
The decade with the lowest annual flow volume (averaging about 9.71 MAF) reconstructed using dendrochronology occurred from A.D. 1584-1593 (Meko and others, 1995). For comparison, the 10-year period of 1995 through 2004 (2004 is a predicted volume) produces an average annual flow volume of 9.9 MAF (not corrected for upstream diversions or use). Similarly, the lowest 5-year average using tree rings is 8.84 MAF (A.D. 1590-1594), compared with 7.11 MAF from 1999 through 2003. These comparisons suggest that the current drought may be comparable to or more severe than the largest-known drought in 500 years.
If the primary control on drought in the Colorado River basin is the AMO, then drought conditions might continue for several decades owing to the persistence of SST warming in the Atlantic Ocean.
What this suggests is that a future of global warming, resulting in the warming of the Atlantic, along with flooding caused by the melting arctic ice caps could also bring a state of permanent drought to the American west.
West drought may be worst in 500 years, experts say .... The drought gripping the West could be the worst in 500 years, with effects in the Colorado River basin even worse than during the Dust Bowl years, scientists at the U.S. Geological Survey say. "That we can now say with confidence," said Robert Webb, lead author of the report released yesterday. "Now I'm completely convinced." The drought has produced the lowest flow in the Colorado River on record, with an annual average flow of only 5.4 million acre-feet at Lees Ferry, Ariz., during the period 2001-2003, adjusted for the effect of Glen Canyon Dam. By comparison, during the Dust Bowl years, between 1930 and 1937, the annual flow averaged about 10.2 million acre-feet, the report said.
According to the report the west had its highest river flow in almost 500 years during the years 1905 to 1922, when an agreement was reached on sharing the water resources that each state would receive under the Colorado River Compact. Under the present circumstances it is obvious that the compact will need to be renegotiated with tough fights ahead between large urban areas dependant on the water and huge agricultural interests and related multinational corporations with a large stake in continued usage of the areas water resources at current levels.
The political implications of the drought are already being recognized, and probably the worst is yet to come, as feuding interest groups battle for what water is left (or desperate politicians find temporary relief in depleting the already low ground water levels, in the hope that it will rain before to much damage is done).
Western governors to meet on debilitating drought ... Drought conditions in parts of the West are the worst in 500 years, and Western governors will meet today with federal climate officials to assess conditions and discuss what steps can be taken to prepare for what could be a dire summer in terms of crops, wildfires and drinking water. The drought in the Colorado River Basin, which is the main water supply for seven states and the big metropolitan areas of Los Angeles, Phoenix and Las Vegas, is probably as bad or worse than the basin's biggest drought in 1590-94. The U.S. Geological Survey, which studied rings on trees among other things, says that the flow of the Colorado River the past two years was barely half that of the Dust Bowl in the 1930s.
The problem is compounded with this spring having been the third warmest on record, depleting the snow pack, the long term drought monitor remains unchanged, with more drought in the forecast, and the city of Las Vegas close to declaring a drought emergency in the next few months, and the Weather Service predicting above average heat over the west for this summer, along with below average rain, and more drought.
Drought Monitor for June 2004
The Rocky Mountain ecosystem is the hardest hit
along with the western plains.
The Darker the color, the more severe the drought
Visible Greenness for June 2004
Visible Satellite, source for the Visual Greenness Graphic
Darker in the East, Pale in the West
The drought is impacting the forests and the Rocky Mountain eco-system very hard. According to the Rocky Mountain Area Predictive Services in their seasonal report for 2004 (pdf)
Due to long-term drought, the entire RMA (Rocky Mountain Area) is potentially at risk for an above average fire season; however, potential is greatest for above average fire activity across portions of the Northern and Southern Front Range of Colorado, Ute/Mesa Verde, Uncompahgre, West Northwest Colorado Plateau, North Central Colorado Mountains, portions of southern Wyoming, and the western mountains of Wyoming.
Much of last summer, fuels were at or near critical levels throughout many portions of the RMA due to below normal precipitation, above normal temperatures and the extended drought. At times the Energy Release Components (ERCs) were setting or very near record historic highs, which indicated the potential for extreme fire behavior. Combining the warm, dry fall of 2003, most notably in Colorado and Wyoming, and the continued long-term drought in 2004, fuels will likely remain stressed during this season, unless above average precipitation amount and duration is received; that scenario is not expected to occur this year.
Fire Danger Graphic, June 2004
Yellow - High, Red Extreme
Most of the danger area is in the Rocky Mountains
Tree Mortality caused by beetle infestations
The Grey area was not surveyed.
White Shows the survey area and red indicates trees killed by beetles.
Beetles have been killing drought stressed trees in large numbers in recent years, and this indicates that record breaking fires will be burning in the forests in a few years time, as the needles drop, and the dead trees dry and fall over, creating a dangerous fuel situation. The entire RMA ecosystem was not surveyed by the results in the surveyed areas is indicative of the wide spread damage caused by these beetles over the entire area. Drought stressed trees are unable to resist beetle attacks, and over a period of years, bettle infestations and high tree mortality lead to extreme forest fires. According to the RMA Predictive Services Report,
Insect infestations are becoming a fuels issues in the RMA. Ips Beetle, Spruce Beetle, Douglas fir Beetle and Mountain Pine Beetle infestations are occurring in Colorado and a Spruce Beetle epidemic has been reported on the Shoshone National Forest in Wyoming. The main infestation showing on the map in the Black Hills of South Dakota is Mountain Pine Beetle. While dead needles are present on the trees that have been killed by the bugs, an aerial fuels problem exists, which may contribute to crown fire initiation leading to larger fires. After a few years, the needles will fall off, contributing to the fuel bed on the ground. Eventually, the dead trees will fall over significantly adding to the heavy dead fuel loading of the area, which may lead to potential control problems of fires in those areas.
The same warming of the Atlantic which has created the worst drought in a millenia in the Western North American continent, and which is melting the polar ice caps at the fastest rate in history since the late 1990s, has also been causing major climate change to begin in North Africa, with the disappearance of the Sahara desert underway. The melting glaciers also began to disappear at an accelerated rate during the late 1990s, around the same time that the arctic ice cap began to melt at a rate twenty times faster than previously, and at this same time the Sahara desert began to retreat and the North American continent was plunged into the worst drought in 500 years. Anyone of these events taking place in isolation could be considered just a spell of strange weather, but taken together they point to rapid climate change which is currently underway on planet earth, now, not in 50 or 100 years. (I often hear people going into denial on this point, even though the evidence is there, but I suppose that is understandable, because it sounds horrible, and 50 or 100 years sounds better.) You can add onto this fact that the global climate system is incredibly sensitive (for example, as noted above, just a swing of two degrees in the temperature of the Atlantic has dramatic effects on the North American West). As well rapid, sudden climate change is the historical norm. Never, in history, has climate every changed slowly over a long period of time, but it always changes suddenly, typically over a ten year period. One of the criticism aimed at modern climate change modeling computer software is that these systems model climate change as taking place gradually over an extended period of time, when the historical record indicates that climate change takes place suddenly, with an exponential rate of increasing change, once a critical threshold has been crossed.
The pattern over the Sahara has been a year of normal rains, followed by a year of record breaking rains, followed by a year of normal rains, and then another year of record breaking rains as the desert begins to retreat and the savannah pushes northward. (See the page Africa's deserts are in retreat, according to New Scientist magazine for a report on a recent scientific survey conducted in 2002, which concluded that the Sahara has been retreating 'and no one noticed.'). Last year the record breaking rains brought flooding to the Sahel as raging rivers in the region came within one inch of bursting their banks, and brought with it the ominous threat of famine in North Africa, as the crops of millions of subsistence farmers were clustered around the banks of swollen raging rivers. Last years threatened plague of locusts did not materialize, but it looks like this year will be the year of the locust. Rainfall has been increasing and breaking previous records on the Sahel, which borders the Southern Sahara, since late 1990s. Last years rains flooded parts of the region and led to large, record breaking harvests, and ironically it is these rains and these large harvests that have been setting the stage for a plague of the dreaded North African Locust. At its worst, a plague of these locusts can cover one fifth of the earth, and affect the food security of one tenth of the world's population. In 2002 the locusts crossed the Mediterranean and attacked vine yards and the famous tomatoe fields of Italy, and at its height a plague of North African locusts can devestate crops as far afield as the Indian subcontinent. The monsoon season on the Southern Sahara has just begun. Last years heavy monsoons pushed the hot summer air of a summer on the Sahara north into Europe resulting in tens of thousands of deaths, as well as creating both record breaking harvests (which thankfully escaped the threat of destruction by flooding) but at the same time created the preconditions for a plague of locusts. So then as the monsoon season begins the world once again faces potential humanitarian crises, including possible flood related famine, which seems likely to occur one of these years, a plague of locusts, also leading to famine, and the deaths of poor people in Europe to poor to afford air conditioning, especially the elderly, who die of heat stroke.
According to the FAO Sahel report
The rainy season has started following its normal pattern in the Sahel. Seasonal rains commenced in late April or May in southern Burkina Faso, Chad, Mali, Niger and the extreme south-east of Senegal. Seed availability is generally adequate following the 2003 record harvest.
Desert locusts are posing a serious threat to agricultural production this year across the Sahel...control operations continue to be hampered by insufficient resources... The Desert locust situation should be closely monitored this year. Although the situation remains calm so far, adult groups and swarms are likely to arrive from Northwest Africa in summer.
(In Mauritania) the Locust situation is very serious. Swarms have started to form in the north and the centre, where considerable damage to crops is reported in oases and pastures. From about mid-June onwards, a substantial number of adult groups and swarms from Northwest Africa are expected to move to the important cereal producing south. Control operations continue to be hampered by lack of resources. According to official estimates, US$6 million are needed to treat about 500 000 hectares infested.
Currently it is still early in the year, and so it is to soon to know whether or not the monsoons will be as severe, or even more severe, than they were last year, leading to flooding, and even more deaths in Europe. If the pattern from the past repeats itself, it may be that this year will be calm, followed by a disaster next year, as once again the rains break all records and flooding, heat stroke, and famine are the inevitable result. The signs are all there, and the world has the rare opportunity to prepare for a humanitarian crisis ahead of time, but given how the FAO can't even raise 6 million for locusts, I don't feel particularly optimistic, in particular during the post Reagan-Thatcher era of deregulation, and lax enviromental enforcement combined with tax give-aways to corporate share holders, and welfare and humanitarian cuts for everyone else.
But everything comes and goes, and every thing falls sooner or later, it is just kind of unfortunate that the Reagan-Thatcher era has to end in a series of worsening disasters such as those developing on the earth, but so be it...I mean, after all, when you are on top of the world, and everything is marching to your tune, you do wind up taking the full share of the blame for what happens to place when that day comes when the bucket of hot tar and the wheel barrow full of feathers comes around...Just a thought, to encourage people to think long term about these things, and realize that even in the worst of times, or perhaps in particular during the worst of times, they is always a bright side to even the worst sounding sorts of things...After all, another world is possible, but sometimes you have to let other people take you there, even if the route they choose isn't your first choice, and they don't seem to understand where they are going...have a nice day...
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