El Nino – La Nina and Megadrought

(Survival manual/ 1. Disaster/El Nino – La Nina and Megadrought)

The El Nino – La Nina Southern Oscillations (ENSO) alternate quasi-periodically across the tropical Pacific Ocean on average every five years, but over a period which varies from three to seven years. ENSO causes extreme weather such as floods, droughts and other weather disturbances in many regions of the world.

Periodicity
Between 1950 and 1997, El Ninos were present 31%, La Ninas 23% of the time, and about 46% of the period was in a neutral state. El Nino and La Nina occur on average every 3 to 5 years. Based on the historical record, the interval between events has varied from 2 to 7 years. Since 1975, La Ninas have been only half as frequent as El Ninos, therefore, a La Nina episode may, but does not always
follow an El Nino. La Nina conditions typically last approximately 9-12 months, but some episodes may persist for as long as two years.

 1.  EL Nino
El Niño’s Are Growing Stronger, NASA/NOAA Study Finds
ScienceDaily (Aug. 27, 2010) — A relatively new type of El Niño, which has its warmest waters in the central-equatorial Pacific Ocean, rather than in the eastern-equatorial Pacific, is becoming more common and progressively stronger, according to a new study by NASA and NOAA.

El Niño, Spanish for “the little boy,” is the oceanic component of a climate pattern called the El Niño-Southern Oscillation, which appears in the tropical Pacific Ocean on average every three to five years. The most dominant year-to-year fluctuating pattern in Earth’s climate system, El Niños have a powerful impact on the ocean and atmosphere, as well as important socioeconomic consequences.
They can influence global weather patterns and the occurrence and frequency of hurricanes, droughts and floods; and can even raise or lower global temperatures by as much as 0.2 degrees Celsius (0.4 degrees Fahrenheit).

During a “classic” El Niño episode, the normally strong easterly trade winds in the tropical eastern Pacific weaken. That weakening suppresses the normal upward movement of cold subsurface waters and allows warm surface water from the central Pacific to shift toward the Americas. In these situations, unusually warm surface water occupies much of the tropical Pacific, with the maximum ocean warming remaining in the eastern-equatorial Pacific.

Since the early 1990s, however, scientists have noted a new type of El Niño that has been occurring with greater frequency. Known variously as “central-Pacific El Niño,” “warm-pool El Niño,” “dateline El Niño” or “El Niño Modoki” (Japanese for “similar but different”), the maximum ocean warming from such El Niño’s is found in the central-equatorial, rather than eastern, Pacific. Such central Pacific El Niño events were observed in 1991-92, 1994-95, 2002-03, 2004-05 and 2009-10. A recent study found many climate models predict such events will become much more frequent under projected global warming scenarios.

Graphic above pasted from <http://www.eoearth.org/article/El_Ni%C3%B1o,_La_Ni%C3% B1a_and_the_southern_oscillation>

Our understanding of the processes responsible for the development of El Niño is still incomplete. Scientists are able to predict the future development of an event by noting the occurrence of particular weather precursors. Researchers also now have a pretty complete understanding of the global weather effects caused by the formation of an El Niño (see Figure 5).

2.   La Nina
La Niña is essentially the opposite of an El Niño. During a La Niña, trade winds in the western equatorial Pacific are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific. La Niñas change global weather patterns and are associated with less moisture in the air, resulting in less rain along the coasts of North and South America. They also tend to increase the formation of tropical storms in the Atlantic.

“For the American Southwest, La Niñas usually bring a dry winter, not good news for a region that has experienced normal rain and snowpack only once in the past five winters,” said Patzert.

 La Niña causes mostly the opposite effects of El Niño. La Niña causes above average precipitation across the North Midwest, the Northern Rockies, Northern California, and in the Pacific Northwest’s southern and eastern regions. Meanwhile there is below average precipitation in the southwestern and outheastern states.

La Niñas occurred in 1904, 1908, 1910, 1916, 1924, 1928, 1938, 1950, 1955, 1964, 1970, 1973, 1975, 1988, 1995, 1998-99, 2008, 2010-11.

Recent occurrences
The strength of the La Niña made the 2008 hurricane season one of the most active since 1944; there were 16 named storms of at least 39 mph (63 kph), eight of which became 74 mph or greater hurricanes. The Gulf of Mexico holds about 27 percent of the U.S.’s oil and 15 percent of its natural gas, the U.S. Department of Energy reports. This makes La Niña and hurricanes serious business.

According to NOAA, El Niño conditions have been in place in the equatorial Pacific Ocean since June 2009, peaking in January-February. Positive SST anomalies are expected to last at least through the North American Spring as this El Niño slowly weakens.

3.  Megadrought Ancient megadroughts preview warmer climate -study
By Deborah  Zabarenko, 2/24/2011, WASHINGTON, Feb 23 (Reuters Life!) –
“Ancient mega droughts that lasted thousands of years in what is now the American Southwest could offer a preview of a climate changed by modern greenhouse gas emissions, researchers reported on Wednesday.

The scientists found these persistent dry periods were different from even the most severe decades-long modern droughts, including the 1930s “Dust Bowl.” And they determined that these millennial droughts occurred at times when Earth’s mean annual temperature was similar to or slightly higher than what it is now. These findings tally with projections by the U.N. Intergovernmental Panel on Climate Change and others, according to study author Peter Fawcett of the University of New
Mexico. The results were published in the current edition of Nature.

“The IPCC model suggests that when you warm the climate, you’ll see extended droughts in this part of the world and this is what the paleo record seems to be telling us,” Fawcett said in a telephone interview. “When you’ve got past temperatures that were at or above today’s conditions, conditions got drier.”

The U.S. Southwest has seen steep population growth over the last century, with population increasing by 1,500 percent from 1900 to 1990, according to the U.S. Geological Survey. The total U.S. population grew 225 percent over the same period.

The settlement of this area depended, as all human settlements do, on access to water. There would clearly be less water available in a megadrought.

Earth’s orbit and greenhouse emissions
Megadroughts in the past were caused by subtle changes in the Earth’s orbit around the Sun, which were also responsible for periodic ice ages. If these orbital changes were the only influence on the
planet’s climate, Earth should be heading into a cool period, Fawcett said in a telephone interview.

However, recent temperature statistics indicate that is not the case. The decade that ended last year was the hottest since modern record-keeping began in 1880. The previous decade, 1991-2000, was next-warmest and 1981-1990 was third-warmest.

Emissions of climate-warming greenhouse gases including carbon dioxide help trap heat near Earth’s surface and could be influencing the natural orbital cycle that would dictate a cooling period.

To figure out just how long these megadroughts lasted, and what happened during them, scientists took samples from a dried lake bed in northern New Mexico called the Valles Caldera. They analyzed these sediments for biochemical signs of drought, ranging from which trees and shrubs grew and how much calcium was in the cracked mud in the dried lake bottom.

Looking at records going back more than a half-million years, they also developed a technique to determine temperature in the ancient past by looking at signs left by soil bacteria, Fawcett said.

The fats in the walls of these bacteria change their structure in response to temperature changes, he said, and act like a “tape recorder” for antique temperatures. (Editing by Eric Walsh)
Pasted from <http://www.msnbc.msn.com/id/41739225/ns/business->

4.  Mega-drought threat to US Southwest
Quirin Schiermeier
The Dust Bowl — the seven-year drought that devastated large swathes of US prairie land in the 1930s — was the worst prolonged environmental disaster recorded for the country. But a study of the American Southwest’s more distant climatic past reveals that the catastrophic drought was a mere dry spell compared to the ‘mega-droughts’ that were recurring long before humans began to settle the continent.

The findings, reported in a paper in Nature this week, add to concerns that the already arid region might face quasi-permanent drought conditions as climate continues to warm.

The team, led by Peter Fawcett, a climate scientist at the University of New Mexico in Albuquerque, reconstructed the region’s climate history using geochemical indicators from an 82-metre-long lake sediment core from the Valles Caldera in northern New Mexico. Analysis of climate and vegetation proxies, such as pollen and carbon-isotope ratios, suggests that the Southwest experienced abrupt and surprisingly pronounced climate shifts during warm periods of the Pleistocee, including transitions to extended dry periods that lasted for hundreds or even thousands of years.

 5.  Reliving the past
If today’s climate repeated past patterns, the southwestern United States might move into a wetter and cooler phase. Such a transition happened at one point during the so-called Marine Isotope Stage (MIS) 11, an interglacial period around 400,000 years ago that shows some striking parallels with the Holocene, our current warm period. This seems to have roughly advanced to the point at which the climate in MIS 11 began to switch to a less arid one.

Earth’s orbit and axial tilt during the unusually long MIS 11 stage was similar to orbital conditions during the Holocene, which scientists think will last longer than most Pleistocene warm periods.

But for all the similarities, the climate during MIS 11 was unperturbed by human activity. This time around, rising greenhouse-gas concentrations driven by human activity will very likely override any natural cooling trend. Scientists fear that the Southwestern climate may in fact switch to an extended dry mode such as the ones that occurred during particularly warm Pleistocene periods.

“We won’t know for sure if it happens again until we get there,” says Fawcett. “But we are certainly increasing the possibility of crossing a critical threshold to severe and lasting drought conditions.”

Sudden shifts in carbon isotopes and lowered total organic carbon in the sediment record suggest that grasses and shrubs that depend mostly on summer rain died out during extended Pleistocene droughts. This is surprising, says Fawcett, because summer monsoon rainfall was thought to become more intense in a warmer climate. That summer rain was in fact strongly reduced, or had almost stopped, suggests that regional climate patterns must have shifted radically when Pleistocene temperatures crossed a threshold.

“The scary thing is that we seem to be very close to this point again,” he says.

 6.  A dry future
The Southwest has experienced significant reductions in rainfall during the last decade, causing freshwater reservoirs and groundwater to fall to unusually low levels. Colorado River flows recorded at Lees Ferry, Arizona, from 2000 to 2009 are the lowest on record.

Climate models suggest that the region will in future become even drier as atmospheric circulation patterns change and subtropical dry zones expand towards the poles2.
“The drying we expect for the twenty-first century is entirely the result of increased greenhouse forcing,” says Richard Seager, a climate researcher at the Lamont-Doherty Earth Observatory in Palisades, New York. “Any natural variations in orbital forcing and incoming sunlight will hardly have a noticeable role in the near future.”

A 10–15% reduction in rainfall is enough to cause severe drought in the region, he says. Meanwhile, debate continues among scientists whether a transition to quasi-permanent dry conditions is imminent or already underway, and to what extent global warming has increased the risk of drought.

“A signal of anthropogenic drying is emerging, but it is still small,” says Seager. “I’d expect that by mid-century the human signal will exceed the amplitude of natural climate variability. Then we can safely say that the Southwest has entered a new climate stage.”
[Chart: Drought in American west]

“The climate system clearly has the capacity to get ‘stuck’ in drought-inducing modes over North America that can last several decades to a century or more,” Seager and colleagues wrote in an article published in 2009.

The researchers also point out that the megadroughts occurred without any intervention from human beings. So they could well happen again. It’s also very possible that human-caused warming could bring a return to megadroughts by inducing the same climatic conditions that appear to have been associated with them in the past.

Given projected increases in demand for water on the river, and a 20 percent reduction in its annual flow by 2057 due to climate change, there would be a nearly 10-fold increase in the chances that lakes Mead and Powell would become depleted.
Pasted from <http://www.cejournal.net/?p=4924&gt;

7.  Higher Water Shortage Risks in One Third of US Counties Due to Climate Change: NRDC Report
21 July 2010, Tree Hugger.com, by Matthew McDermott,  http://www.treehugger.com/files/2010/07/higher-water-shortage-risks-one-third-u-s-counties-climate-change.php#ch02

A new report from the National Resources Defense Council paints a really dry and thirsty picture in a world warmed by climate change: More than 1100 counties in the United States face higher risks of water shortages by 2050, with more than 400 of these placed at extremely high risk.

14 States At Extreme Risk
Tetra Tech, which did the report for NRDC, used publicly available water use data and climate change models to examine water withdrawals versus renewable water supply. The result was that 14 states face extreme to high risk to water sustainability, or are likely to experience limitations in the water
supply. This is a 14-fold increase from previous estimates.

Parts of Arizona, Arkansas, California, Colorado, Florida, Idaho, Kansas, Mississippi, Montana, Nebraska, Nevada, New Mexico, Oklahoma, and Texas all are in this latter category–with the Great Plains and Southwest states singled out as places where “water sustainability is at extreme risk.”

Arid Western States’ Water Use Already Unsustainable
Stats on water use as a percentage of available precipitation clearly illustrate the problem: In the eastern US generally less than 5% of precipitation is withdrawn; in the majority of the western US water withdrawals are under 30% of precipitation. But in the arid areas of the states mentioned in the report (particularly in California, Texas and the desert Southwest), withdrawals top 100% of available precipitation.

In the Ogallala Aquifer, stretching from Nebraska to Texas and supplying about 30% of all the water used for farmland irrigation in the country, unsustainable water withdrawals have led to the aquifer dropping by more than 100 feet in many places. In fact The Nature Conservancy, whose scientists contributed research for the report, points out that some studies show the aquifer drying up in as little as 25 years.

As previous studies have indicated, the effect of these water shortages and patently unsustainable water use trend on agricultural production is pronounced. NRDC cites 2007 data to show that the value of crops raised in the 1100 counties at risk exceeded $105 billion.

Strong Climate Action by Congress Can Help
Dan Lashof, director of NRDC’s Climate Center:This analysis shows climate change will take a serious toll on water supplies throughout the country in the coming decades, with over one out of three U.S. counties facing greater risks of water shortages. Water shortages can strangle economic development and agricultural production and affected communities.

As a result, cities and states will bear real and significant costs if Congress fails to take the steps necessary to slow down and reverse the warming trend. Water management and climate change adaptation plans will be essential to lessen the impacts, but they cannot be expected to counter the effects of a warming climate. The only way to truly manage the risks exposed by this report is for Congress to pass meaningful legislation that cuts global warming pollution and allows the U.S. to exercise global leadership on the issue.

[The jury has delivered its verdict: Look for increasing drought during the next few decades. The drought is not a temporary climatic anomaly, but a global change in climatic conditions that will persist  for several centuries. -Mr Larry]

8.  Understanding Your Risk and Impacts: Economic Impacts
2006-2011, The National Drought Mitigation Center, University of Nebraska, Lincoln.
http://www.drought.unl.edu/risk/economic.htm
http://www.drought.unl.edu/index.htm
Costs and losses to agricultural producers:

  • Costs and losses to agricultural producers Annual and perennial crop losses [wheat and other grains]
  • Damage to crop quality [reduced yield]
  • Income loss for farmers due to reduced crop yields
  • Reduced productivity of cropland (wind erosion, long-term loss of organic matter, etc.) {late in oil decline making fertilizer very expensive]
  • Insect infestation [late in the oil decline]
  • Plant disease
  • Wildlife damage to crops
  • Increased irrigation costs [during a spreading and  increasingly severe  megadrought]
  • Cost of new or supplemental water resource development (wells, dams, pipelines)
  • Costs and losses to livestock producers
  • Reduced productivity of rangeland
  • Reduced milk production
  • Forced reduction of foundation stock
  • Closure/limitation of public lands to grazing
  • High cost/unavailability of water for livestock
  • Cost of new or supplemental water resource development (wells, dams, pipelines)
  • High cost/unavailability of feed for livestock
  • Increased feed transportation costs
  • High livestock mortality rates
  • Disruption of reproduction cycles (delayed breeding, more miscarriages)
  • Decreased stock weights
  • Increased predation
  • Range fires
  • Loss from timber production
  • Wildland fires
  • Tree disease
  • Insect infestation
  • Impaired productivity of forest land
  • Direct loss of trees, especially young ones
  • Loss from fishery production
  • Damage to fish habitat
  • Loss of fish and other aquatic organisms due to decreased flows
  • General economic effects
  • Decreased land prices
  • Loss to industries directly dependent on agricultural production (e.g., machinery and fertilizer manufacturers, food processors, dairies, etc.)
  • Unemployment from drought-related declines in production
  • Strain on financial institutions (foreclosures, more credit risk, capital shortfalls)
  • Revenue losses to federal, state, and local governments (from reduced tax base)
  • Reduction of economic development
  • Fewer agricultural producers (due to bankruptcies, new occupations)
  • Rural population loss
  • Loss to recreation and tourism industry
  • Loss to manufacturers and sellers of recreational equipment
  • Losses related to curtailed activities: hunting and fishing, bird watching, boating, etc.
  • Energy-related effects
  • Increased energy demand and reduced supply because of drought-related power curtailments
  • Costs to energy industry and consumers associated with substituting more expensive fuels (oil) for hydroelectric power
  • Water Suppliers
  • Revenue shortfalls and/or windfall profits
  • Cost of water transport or transfer
  • Cost of new or supplemental
    water resource development
  • Transportation Industry
  • Loss from impaired navigability of streams, rivers, and canals
  • Declinein food production/disrupted food supply
  • Increase in food prices
  • Increased importation of food (higher costs)

[The lists above speak of reduced agricultural production, rapidly accelerating input costs due to the decline in world petroleum production, stress on agricultural producers-fewer farmers, less land, less product—and much higher U.S. food prices, as a percentage of net income, hence much less discretionary income, less ability to develop a finacial cushion, and a lower quality of life. Add to this the hunger/ socially driven measures some foreign countries may be willing to undertake in these circumstances and we will likely see regional wars; one theater of broad damage might be on American soil. The lists also  speaks quietly about a global and US overpopulation on a diminishing resource base. As every ecologist knows, when  a population has exceeded its resources, its numbers must adjust to a level that is sustainable. Mr Larry]

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