La Nina

An Illustrated Guide to El Nino and La Nina and how they control climate

Bob Tisdale, author of Who Turned on the Heat?, has produced an excellent explanation of the solar-driven El Nino-La Nino events that arise in the Pacific Ocean and control global weather and climate on annual, decadal, and multidecadal time frames.

His long post contains 29 illustrations that take you through the process (three illustrations are reproduced below). Tisdale also provides explanatory text. I have read many papers on El Nino-La Nina (collectively called ENSO) and think Tisdale’s presentation is the most lucid and understandable explanation of the interplay between trade winds and ocean currents and their effects on ocean and air temperatures. It is aimed at the layman. Give it a look, read the whole post here.
A free preview of Tisdale’s book, in pdf format, is available here. The whole book is available for purchase here.

El Nino

ENSO neutral

La Nina

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Droughts in the Southwest put in perspective

The severe drought in Texas this year has fueled speculation that alleged human-caused global warming has somehow caused “unprecedented” conditions. But real research data show that the current drought is not unprecedented and is part of a natural cycle. There have been much more severe and persistent droughts in the past before humans began emitting signification amounts of carbon dioxide into the atmosphere. This post focuses on research from the University of Arizona and the Lamont-Doherty Earth Observatory of Columbia University.

From the University of Arizona and Arizona State University we have “A 1,200-year perspective of 21st century drought in southwestern North America.”

The Abstract reads in part:

A key feature of anticipated 21st century droughts in Southwest North America is the concurrence of elevated temperatures and increased aridity. Instrumental records and paleoclimatic evidence for past prolonged drought in the Southwest that coincide with elevated temperatures can be assessed to provide insights on temperature-drought relations and to develop worst-case scenarios for the future. In particular, during the medieval period, AD 900–1300, the Northern Hemisphere experienced temperatures warmer than all but the most recent decades. Paleoclimatic and model data indicate increased temperatures in western North America of approximately 1 °C over the long-term mean. This was a period of extensive and persistent aridity over western North America. Paleoclimatic evidence suggests drought in the mid-12th century far exceeded the severity, duration, and extent of subsequent droughts. The driest decade of this drought was anomalously warm, though not as warm as the late 20th and early 21st centuries. The convergence of prolonged warming and arid conditions suggests the mid-12th century may serve as a conservative analogue for severe droughts that might occur in the future. The severity, extent, and persistence of the 12th century drought that occurred under natural climate variability, have important implications for water resource management. The causes of past and future drought will not be identical but warm droughts, inferred from paleoclimatic records, demonstrate the plausibility of extensive, severe droughts, provide a long-term perspective on the ongoing drought conditions in the Southwest, and suggest the need for regional sustainability planning for the future.

This paper goes on to discuss the role of El Niño-La Niña cycles and sea-surface temperature, but the paper does not really address cause of the droughts. The theme of this paper is that past droughts are associated with warm periods and that continued warming may portend more severe droughts in our future. However, the authors partly contradict themselves by saying that the more severe droughts of the Medieval period occurred when the temperatures were cooler than the current warm period.

It seems we have a complex interplay of natural cycles which are not completely understood.

From Cornell, we have “The characteristics and likely causes of the Medieval megadroughts in North America.” and a very interesting graph:

Droughts in the west

  This graph shows that while the current drought is severe, it is much less severe than droughts during the Medieval Warm Period, a time before humans were emitting much carbon dioxide into the atmosphere.

The paper presents three conclusions:

1) The similarity of the spatial patterns suggests that the physical processes that caused the modern droughts also caused the medieval megadroughts.

2) The global atmosphere ocean conditions that currently cause modern droughts for a few years at a time were the prevailing ocean climate during the medieval period.

2) Despite the shift in the mean tropical ocean climate ENSO variability continued as now but oscillating about a colder mean state.

The authors also present an archaeological speculation:

The medieval megadroughts may also have left their signature on the human environment of the West. The great cliff cities in the four corners region of the West such as at Chaco Canyon and Mesa Verde were all abandoned towards the end of the drought. These societies were based on irrigated agriculture. Although there remains much debate about why these highly organized Indian societies collapsed, archaeologists are revisiting the idea that decades of dry conditions were part of the reason.

With both papers we see that data collection is one thing, interpretations are another.

See also:

Drought in the West

El Niño, bristlecone pines, and drought in the Southwest

EL NINO behavior, climate models predict opposite of what really happens

Obama parts the waters, sea level drops

During the presidential campaign, Barack Obama pompously declared that his presidency will be “the moment when the rise of the oceans began to slow and our planet began to heal.” (see statement on You-tube, link H/T to Marc Morano)

And lo! It has come to pass. The seas have receded from upon the land.

The European Space Agency’s Envisat monitoring, global sea level revealed a “two year long decline [in sea level] was continuing, at a rate of 5mm per year.”

NASA concurs. “While the rise of the global ocean has been remarkably steady for most of this time, every once in a while, sea level rise hits a speed bump. This past year, it’s been more like a pothole: between last summer and this one, global sea level actually fell by about a quarter of an inch, or half a centimeter.” But NASA blames it on La Niña rather than Obama power. There goes another Nobel prize.

 

The explanation from NASA:

Willis said that while 2010 began with a sizable El Niño, by year’s end, it was replaced by one of the strongest La Niñas in recent memory. This sudden shift in the Pacific changed rainfall patterns all across the globe, bringing massive floods to places like Australia and the Amazon basin, and drought to the southern United States.

Data from the NASA/German Aerospace Center’s twin Gravity Recovery and Climate Experiment (Grace) spacecraft provide a clear picture of how this extra rain piled onto the continents in the early parts of 2011. “By detecting where water is on the continents, Grace shows us how water moves around the planet,” says Steve Nerem, a sea level scientist at the University of Colorado in Boulder.

So where does all that extra water in Brazil and Australia come from? You guessed it–the ocean. Each year, huge amounts of water are evaporated from the ocean. While most of it falls right back into the ocean as rain, some of it falls over land. “This year, the continents got an extra dose of rain, so much so that global sea levels actually fell over most of the last year,” says Carmen Boening, a JPL oceanographer and climate scientist.

See also:

Sea Level Rising?

 

 

 

 

EL NINO behavior, climate models predict opposite of what really happens

The El Nino/La Nina cycle, more formally known as the El Nino/Southern Oscillation (ENSO) is an irregular cycle of sea surface temperature, atmospheric pressure, and wind direction in the tropical Pacific Ocean which has a profound affect on global weather. Both floods and droughts are associated with phases of ENSO.

ENSO2

 El Nino (warm phase)

In South America, this warm phase suppresses the normally cold upwelling currents that bring fish to the coasts of Peru and Ecuador. This phase brings unusually warm and wet weather during the South American winter.

In North America, El Nino brings warm, dry winters and wet summers to the northern region, and much wetter winters to the southwestern U.S. and northern Mexico.

Australia can experience droughts.

La Nina (cool phase)

In South America, La Nina brings drought to Peru and Chile but more rain to northern Brazil. In North America, La Nina brings above average precipitation to the north (hence our heavy snowfall during the winter of 2010-2011) and average to much below average precipitation to the southern U.S.

The influence of La Nina reaches Africa and produces more precipitation in south Africa and dryer conditions in equatorial Africa.

Climate models fail

Climate models, which are based on the assumption that carbon dioxide has a positive feedback, i.e., that carbon dioxide causes significant warming, make predictions on the behavior of ENSO. An analysis of those predictions versus what actually happened shows that the climate models predicted almost the exact opposite of what really happened.

Citation: McPhaden, M. J., T. Lee, and D. McClurg (2011), El Niño and its relationship to changing background conditions in the tropical Pacific Ocean, Geophys. Res. Lett., 38, L15709, doi:10.1029/2011GL048275

The abstract reads:

This paper addresses the question of whether the increased occurrence of central Pacific (CP) versus Eastern Pacific (EP) El Niños is consistent with greenhouse gas forced changes in the background state of the tropical Pacific as inferred from global climate change models. Our analysis uses high-quality satellite and in situ ocean data combined with wind data from atmospheric reanalyses for the past 31 years (1980–2010). We find changes in background conditions that are opposite to those expected from greenhouse gas forcing in climate models and opposite to what is expected if changes in the background state are mediating more frequent occurrences of CP El Niños. A plausible interpretation of these results is that the character of El Niño over the past 31 years has varied naturally and that these variations projected onto changes in the background state because of the asymmetric spatial structures of CP and EP El Niños.

In another paper:

Wolter, K. and Timlin, M.S. 2011. El Niño/Southern Oscillation behavior since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext). International Journal of Climatology 31: 1074-1087.

The researchers were able to extend analysis of ENSO events back to 1871 and found: “none of the behavior of recent ENSO events appears unprecedented, including duration, onset timing, and spacing in the last few decades compared to a full century before then.” Climate models predict that ENSO events should become more frequent and intense with global warming.

In other words, the climate model assumption of a positive feedback for carbon dioxide is wrong. And once again there is evidence that our carbon dioxide emissions have little actual effect on global temperature, and, there is still no physical evidence that carbon dioxide does have a significant effect. We, therefore, should not be basing policy decisions on flawed model scenarios.

ENSO is just one of several recognized oscillations driven by the sun and the earth’s position relative to the sun. To see other oscillations go here.

See Tisdales guide: An Illustrated Guide to El Nino and La Nina

See also:

A Basic Error in Climate Models

Climate Model Projections vs Real World Observations

Climate Data, Fact or Fiction

Natural Climate Cycles

NASA satellite data show climate models are wrong – again

Carbon Dioxide and the Greenhouse Effect

Humans and the Carbon Cycle

El Niño, bristlecone pines, and drought in the Southwest

While the Southwest is experiencing drought conditions, unusual flooding is occurring along the Mississippi River.  This is part of the natural La Niña cycle.

Research from the University of Hawaii’s International Pacific Research Center  has found an 1100-year correlation between El Niño-La Niña cycles and tree rings in bristlecone pines in the American Southwest.  This may allow better prediction of the cycles and a better understanding of past cycles and their implications.

El Niño and its partner La Niña, the warm and cold phases in the eastern half of the tropical Pacific,  play havoc with  climate worldwide. Predicting El Niño events more than several months ahead is now routine, but predicting how it will change  in a warming world has been hampered by the short instrumental record. An international team of climate scientists has now shown that annually resolved tree-ring records from North America, particularly  from  the US Southwest, give a continuous representation of the intensity of El Niño events over the past 1100 years and can be used to improve El Niño prediction.

Tree rings in the US Southwest, the team found, agree well with the 150-year instrumental sea surface temperature records in the tropical Pacific. During El Niño, the unusually warm surface temperatures in the eastern Pacific lead to changes in the atmospheric circulation, causing unusually wetter winters in the US Southwest, and thus wider tree rings; unusually cold eastern Pacific temperatures during La Niña lead to drought and narrower rings. The tree-ring records, furthermore, match well existing reconstructions of the El Niño-Southern Oscillation and correlate highly, for instance, with [oxygen 18] isotope concentrations of both living corals and corals that lived hundreds of years ago around Palmyra in the central Pacific.

The graph below shows the correlation.

El nino amplitude from tree rings

The tree rings reveal that the intensity of El Niño has been highly variable, with decades of strong El Niño events and decades of little activity. The weakest El Niño activity happened during the Medieval Climate Anomaly in the 11th  century, whereas the strongest activity has been since the 18th  century.

These different periods of El Niño activity are related to long-term changes in Pacific climate. Cores taken from lake sediments in the Galapagos, northern Yucatan, and the Pacific Northwest reveal that the eastern–central tropical Pacific climate swings between warm and cool phases, each lasting from 50 to 90 years. During warm phases, El Niño and La Niña events were more intense than usual. During cool phases, they deviated little from the long-term average as, for instance, during the Medieval Climate Anomaly when the eastern tropical Pacific was cool.

While correlation does not necessarily prove causation, these results are compelling.  Many factors such as temperature and amount of precipitation affect the width of tree rings.  The researchers say in this case, that precipitation is the controlling factor.  They rely on Liebig’s Law  which states that yield is proportional to the amount of the most limiting nutrient, and in the desert southwest, water is the limiting factor.

We are currently experiencing the La Niña phase which means a dry southwest and colder, wetter conditions in the north and mid-west.

For more background on drought see: Drought in the West.