Tree Rings Provide 1100 Year El Nino Cycle

This is very instructive.  We see specific confirmation of the warmperiod as been a period of low El Nina activity that is finally followed by adecline to the little Ice Age that appears more and more precipitous thanoverly gradual.  I come back to understandingthat we get an abrupt temperature drop every eleven hundred years or so whichinforms us that we are looking at a complete comparable with this data.

Again the important event is thedrop in temperature that then takes most of three centuries to reversefully.  The actual causation is likely tobe an unstable aberration of the Antarctic currents dumping a major shot ofcold waters into the Atlantic system. The evidence suggests a sudden but brief event that then takes threehundred years to overcome.

It actually makes  great deal of sense as that acts as anadjustment switch for the global climate itself and allows everything to goback to some form of equilibrium until it needs adjustment 1100 years later.  Thus the Holocene has and will never actuallygo off the tracks.

Tree rings tell a 1,100-year history of El Nino

by Staff Writers

Manoa HI (SPX) May 10, 2011

Bristlecone trees, such as this over a thousand-year-old tree in the Great Basin National Park, contributed to thetree-ring record on El Nino. Credit: Image courtesy International Pacific Research Center

http://www.terradaily.com/reports/Tree_rings_tell_a_1100_year_history_of_El_Nino_999.html

El Nino and its partner La Nina, the warm and cold phases in the eastern halfof the tropical Pacific, play havoc with climate worldwide. Predicting El Ninoevents more than several months ahead is now routine, but predicting how itwill change in a warming world hasbeen hampered by the short instrumental record.

An international team of climate scientists has now shown that annuallyresolved tree-ring records from North America, particularly from the USSouthwest, give a continuous representation of the intensity of El Nino eventsover the past 1100 years and can be used to improve El Nino prediction inclimate models.

The study, spearheaded by Jinbao Li, InternationalPacific ResearchCenter, University of Hawai'iat Manoa, is published in the May 6 issue of Nature Climate Change.

Tree rings in the USSouthwest, the team found, agree well with the 150-year instrumental seasurface temperature records inthe tropical Pacific. During El Nino, the unusually warm surfacetemperatures in the eastern Pacific lead to changes in the atmosphericcirculation, causing unusually wetter winters in the US Southwest, and thuswider tree rings; unusually cold eastern Pacific temperatures during La Ninalead to drought and narrower rings.

The tree-ring records, furthermore, match well existing reconstructionsof the El Nino-Southern Oscillation and correlate highly, for instance, withd18O isotope concentrations of both living corals and corals that livedhundreds of years ago around Palmyra in the central Pacific.

"Our work revealed that the towering trees on the mountain slopesof the US Southwest and the colorful corals in the tropical Pacific both listento the music of El Nino, which shows its signature in their yearly growthrings," explains Li. "The coral records, however, are brief, whereasthe tree-ring records from North America supply us with a continuous El Ninorecord reaching back 1100 years."

The tree rings reveal that the intensity of El Nino has been highly variable,with decades of strong El Nino events and decades of little activity. Theweakest El Nino activity happened during the Medieval Climate Anomaly in the11th century, whereas the strongest activity has been since the 18thcentury.

These different periods of El Nino activity are related to long-termchanges in Pacific climate. Cores taken from lake sediments inthe Galapagos Islands, northern Yucatan, andthe Pacific Northwest reveal that theeastern-central tropical Pacific climate swings between warm and coolphases, each lasting from 50 to 90 years.

During warm phases, El Nino and La Nina events were more intense thanusual. During cool phases, they deviated little from the long-term average as,for instance, during the Medieval Climate Anomaly when the eastern tropicalPacific was cool.

"Since El Nino causes climate extremesaround the world, it is important to know how it will change with globalwarming," says co-author Shang-Ping Xie.

"Current models diverge in their projections of its futurebehavior, with some showing an increase in amplitude, some no change, and someeven a decrease. Our tree-ring data offer key observational benchmarks forevaluating and perfecting climate models andtheir predictions of the El Nino-Southern Oscillation under globalwarming."

Citation: Jinbao Li, Shang-Ping Xie, Edward R. Cook, Gang Huang,Rosanne D'Arrigo, Fei Liu, Jian Ma, and Xiao-Tong Zheng, 2011: Interdecadalmodulation of El Nino amplitude during the past millennium. Nature ClimateChange.