Friday, February 23, 2007

Climate model self destructs in El Nino conditions

God does not play dice.
Albert Einstein

The IPCC the international convention on advanced computer games for followers of Nostrodamus tell us they can predict the climate for the next 50-500 years using advanced computer algorithms.

In reality they cannot predict 10 months in advance. James Hansen the director of the Nasa Goddard Institute for Space Studies distributed the following paper in march 2006 predicting a super el Niño for 2006-2007.

The interesting title tells us all.

Early model predictions of global warming proved accurate,the Pacific Ocean seems charged for a potential super-El Nino,and global temperature is poised to reach record,perhaps dangerous,levels.

by James Hansen, Makiko Sato, Reto Ruedy, Ken Lo, David Lea and Martin Medina-Elizalde
DRAFT March 29, 2006

SUPER EL NINO IN 2006-2007? We suggest that an El Nino is likely to originate in 2006 and that there is a good chance it will be a "super El Nino", rivaling the 1983 and 1997-1998 El Ninos, which were successively labeled the "El Nino of the century" as they were of unprecedented strength in the previous 100 years (Fig. 1 of Fedorov and Philander 2000). Further, we argue that global warming causes an increase of such "super El Ninos". Our rationale is based on interpretation of dominant mechanisms in the ENSO (El Nino Southern Oscillation) phenomenon, examination of historical SST data, and observed Pacific Ocean SST anomalies in February 2006.

In the "normal", La Nina, phase of ENSO the east-to-west trade winds push warm equatorial surface waters far to the west such that some of the warmest SSTs on the planet are located in the West Pacific Warm Pool. In this normal state the thermocline is shallow in the East Pacific near the coast of South America, where upwelling of cold deep water occurs, and deep in the West Pacific (Fig. 2 of Cane 2005). Associated with this tropical SST gradient across the Pacific is a longitudinal circulation pattern in the atmosphere, the Walker Cell, with generally rising motions and heavy rainfall in the West Pacific and sinking motions and drier conditions in the East Pacific. This Walker circulation enhances upwelling in the East Pacific, causing a powerful positive feedback, the Bjerknes (1969) feedback, which tends to maintain the La Nina phase, as the temperature gradient and the resulting higher pressure in the East Pacific support east-to-west trade winds.

This normal state is occasionally upset when, by chance, the east-to-west trade winds slow down, allowing the warm water piled up in the west to slosh back in the direction of South America. If the chance fluctuation is large enough, the Walker circulation breaks down and the Bjerknes feedback loses power. As the east-to-west winds weaken, the Bjerknes feedback works in reverse, and warm waters move more strongly toward South America, reducing the thermocline tilt and cutting off the upwelling of cold water along the South American coast. In this way a classical El Nino is born.

Given the high degree of chaos in weather and climate, there is great variability among El Niño’s and some arbitrariness in the definition of when one has occurred. Enough time since the preceding El Nino needs to elapse for the West Pacific to "recharge" with warm water and for the thermocline to regain its strong tilt such that it is deep in the West Pacific and approaches the surface near South America. An El Nino has the best chance of forming in Northern Hemisphere spring, when the Intertropical Convergence Zone (ITCZ) is close to the equator, SST is a maximum, and equatorial upwelling is weakest. Thus, as Mark Cane (priv. comm.) has stated, once the West Pacific is recharged, we can think of Mother Nature as "rolling the dice" each spring to see if there will be an El Nino.

Unfortunately the dice landed on snakes eyes

Summary: The 2006/07 El Niño has ended
The 2006/07 El Niño has ended. All the main ENSO indicators show that neutral conditions have returned to the Pacific Basin. Along the equator, sea-surface temperatures are cooling rapidly and have been below their El Niño thresholds for about a month now. The Trade Winds have mostly been close to or somewhat stronger than normal since December, the SOI has been neutral for three of the past four months and central-western Pacific cloudiness is close to average. Computer models indicate further cooling in the Pacific, with a La Niña not out of the question (see third paragraph).


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