Tree rings open door on 1100 years of El Nino

May 27, 2011
El Niño amplitude derived from North American tree rings (blue) and instrumental measurements (red). The green curve represents the long-term trend in El Niño strength. Amplitudes above 1.0 indicate periods of strong El Niño activity, which occurred about every 50-90 years.

(PhysOrg.com) -- El Nino and La Nina, the periodic shifts in Pacific Ocean temperatures, affect weather around the globe, and many scientists have speculated that a warming planet will make those fluctuations more volatile, bringing more intense drought or extreme rainfall to various regions.

Now, scientists have used tree-ring data from the American Southwest to reconstruct a 1,100-year history of the cycle that backs up that assertion. The researchers found a 50-90-year cycle of waxing and waning El Niño intensity that shows that, when the earth warms, the acts up.
 
“Our work revealed that the towering trees on the mountain slopes of the U.S. Southwest and the colorful corals in the tropical Pacific both listen to the music of El Niño, which shows its signature in their yearly growth rings,” explains Jinbao Li, the paper’s lead author and a former PhD Student at Lamont-Doherty Earth Observatory.

The research, published May 6 in Nature Climate Change, will improve scientists’ ability to predict future climate and the effects of global warming, the scientists say. 
 

Bristlecone pines, such as this over 1,000-year-old tree in the Great Basin National Park, contributed to the tree ring record on El Niño. Credit: Gisela Speidel, IPRC

The temperature of the eastern tropical Pacific fluctuates between relative warm (El Niño) and relatively cold (La Niña) every 2 to 8 years, based on well-known instrumental records from the recent past. This is coupled with shifts in air surface pressure in the western Pacific – the Southern Oscillation. The patterns have a strong impact on the climate in many regions of the world, including the American Southwest: Warmer sea surface waters lead to relatively wetter winters there, while the cooler La Niña leads to drier ones.
 
Until now, scientists have not had a detailed enough record to see the longer term in the El Niño Southern Oscillation, or ENSO, spanning the past millennium. But tree ring samples taken from the U.S. Southwest provided a year-to-year account dating back 1,100 years. In those narrow cores, wider rings reflect wetter seasons and thinner rings the drier years.
 
The tree ring analysis corresponded several other records, including instrument readings for Pacific sea surface temperatures, isotope analysis of modern and relic corals from around the , and other climate reconstructions.

The record reveals an intriguing pattern: The variance between El Niño and La Niña becomes more pronounced in periods when the background temperature is warmer, and less so in cooler periods. The researchers found this cycle runs 50-90 years.

This connection between the overall temperature trend and the amplitude of the ENSO cycle could be interactive, with one enhancing the other. And that supports the idea that the continued warming of the climate may lead to enhanced ENSO variability and more extreme climate conditions around the globe.

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User comments : 11

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NotParker
2.3 / 5 (9) May 27, 2011
Wait ... El Nino has been warmer in the past?

Without Co2?

Who knew?
SteveL
5 / 5 (2) May 27, 2011
Don't be silly, there's always been CO2. I'd prefer if they would have told us were we are in that 50 - 90 year cycle.

It's hard to tell from such a small graph, but it looks like we are at the beginning of another 50 - 90 year El Nino warming cycle, and it looks like the cycles have been fairly moderate and have levelled off since about 1800 after a 700 - 800 year span of a pre-industrial warming trend.
Avitar
1.5 / 5 (8) May 27, 2011
That chart does not match with the Little Ice Age that began around 1306 and ended around 1850. Records in the American Mid-west and Europe both contain that temperature signature. If data from North America are not showing it your data methodology has to be suspect
ArtflDgr
2 / 5 (4) May 27, 2011
sure looks like the trend was warmer..
but it took 1000 years to go up one degree..

Dug
2 / 5 (4) May 27, 2011
"Until now, scientists have not had a detailed enough record to see the longer term fluctuations in the El Nio Southern Oscillation, or ENSO, spanning the past millennium." Really. Apparently, these guys don't see eye to eye to the ice core people who should see the same ENSO pattern, or don't the accept their results? Very interesting.
ted208
1.6 / 5 (7) May 28, 2011
It seems as if the CAGW CO2 theory will have to be scraped after all. El Nino has been warmer in the past with lower levels of CO2. that there is a recorded 50 - 90 year El Nino cycle. This all points to Cow methane (snarc) or simple the natural climate venerability/change as the climate history of the world changed thousands of time before mankind and will continue long after we are gone! Sadly there are powerful forces who want to ignore the relation ship of all the factors and mechanisms that affect our ever changing planet and it's becoming more obvious that CO2 plays only a minor role in a highly complexed climate system.
We would do better devoting the billions of dollars and wasted resources to dealing with the real challenges that face mankind,like pollution, over use of anti biotic's, over fishing, disregard for our rivers and oceans and most importantly over population, these are the real planet killers, and it will need a concerted effort to deal with them!
SteveL
4 / 5 (3) May 28, 2011
I don't know about in other countries, but when the USA stops funding via the tax code the propogation of an unlimited number of children, then I'll know they are actually interested in conserving our resources. Until then, it's just talk. When they modify the tax code to eventually bring the maximun deduction down to two children - I'll know they are serious because such an unpopular and "radical" change would cost many lawmakers their careers.
NotParker
2.3 / 5 (3) May 29, 2011
US Birthrate at record low:

"The birth rate, which takes into account changes in the population, fell to 13.5 births for every 1,000 people last year. That's down from 14.3 in 2007 and way down from 30 in 1909, when it was common for people to have big families."
SteveL
1 / 5 (1) May 30, 2011
I consider that very welcome news.
NotParker
3 / 5 (2) May 30, 2011
It will be fewer workers per retiree. Payroll taxes will have to rise a great deal for younger workers.

"The number of workers paying into [Social Security] was 5.1 per retiree in 1960; this declined to 3.3 in 2007 and is projected to decline to 2.1 by 2035.

Further, life expectancy continues to increase, meaning retirees collect benefits longer."
GSwift7
3 / 5 (2) Jun 02, 2011
I wonder which proxy series they used for this. I can't find any at NOAA that match the graph above.