Tree Rings Tell a 1,100-Year History of El Niño

[A-L-E-X]

http://www.scienceda...Science+News%29

Tree Rings Tell a 1,100-Year History of El Niño

ScienceDaily (May 6, 2011) — 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 in climate models.

The study, spearheaded by Jinbao Li, International Pacific Research Center, University of Hawai'i at Manoa, is published in the May 6 issue of Nature Climate Change.

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 δ18O isotope concentrations of both living corals and corals that lived hundreds of years ago around Palmyra in the central Pacific.

"Our work revealed that the towering trees on the mountain slopes of the US 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 Li. "The coral records, however, are brief, whereas the tree-ring records from North America supply us with a continuous El Niño record reaching back 1100 years."

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 Islands, 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.

"Since El Niño causes climate extremes around the world, it is important to know how it will change with global warming," says co-author Shang-Ping Xie. "Current models diverge in their projections of its future behavior, with some showing an increase in amplitude, some no change, and some even a decrease. Our tree-ring data offer key observational benchmarks for evaluating and perfecting climate models and their predictions of the El Niño-Southern Oscillation under global warming."

This research was funded by the National Science Foundation, National Oceanic and Atmospheric Administration, Japan Agency for Marine-Earth Science and Technology, National Basic Research Program of China, and the National Natural Science Foundation of China.

[BethesdaWX]

Yeah I read this earlier today, a good study. I'm pleased with the results.

Tree-Ring Data are good farily good proxies regarding precipitation, so I don't see a problem in that regard. Of course I'm only 18, but you get the point.

But, since trees grow Faster When they Are Young (would be in the first 10-15% of the data), how do they Correct for this? If they're using these 1000yr old trees for the study, that would have to be done accurately.

These statements below are key to the AGW debate, though.

"""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 Islands, 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""".

Not regarding temperature change in the past 300 years, they are (or should be) referring to the PDO, IPO, and QDO cycles in the Pacific Ocean, and depending on how they all align, you can get longer or shorter phases I'd confidently think, since the climate system is Chaotic piece of work.

So the results are pleasing from my point of view.

[Clifford]

The link above is broken.

This should work.

http://www.sciencedaily.com/releases/2011/05/110506093107.htm

Obviously the spacing between the rings decreases as the tree ages.

I'm sure there is an algorithm to compensate, but it is probably best to compare nearby rings, perhaps 10 or 20 years of successive rings. So you would compare difference between pairs of nearby rings.

Purely solar driven temperature differences between the Medieval Warm Period and the Marauder Minimum would be interesting when looking at the global climatological impacts on El Nino/La Nina.

However, assuming the Greenhouse Gas Hypothesis, a planet warmed by greenhouse gases would not be the same as a planet warmed by increased solar activity. In particular, a planet warmed by greenhouse gases may warm the poles more than tropical areas, and may cause more nocturnal warming than diurnal warming.

[BethesdaWX]

However, assuming the Greenhouse Gas Hypothesis, a planet warmed by greenhouse gases would not be the same as a planet warmed by increased solar activity. In particular, a planet warmed by greenhouse gases may warm the poles more than tropical areas, and may cause more nocturnal warming than diurnal warming.

Well, to compare solar warming with AGW can be tricky, because Solar Magnetism is the major driver of low-level Cloud Cover (source to change),(long term), which, decreases in GCC would warm the Surface faster than the LT since the surface is what would take higher incoming SW once below the cloud deck. AGW implies that 1)....Both Poles should be warming equally, and 2), the LT should be warming faster than the Surface, since it is re-emitted LW radiation.

Coincidentally, Solar warming During the MWP Hit the Arctic 50-100 years before the Antarctic, not at equal timeframes either. The solar Max during the MWP was not nearly as strong as our current max based on 10/BE & C10 concentrations, which have always been a direct link to not only Solar, but Global Cloud Cover.

The proxy of 10/BE can only go into the 1980's at this point, but it finds that GCC then was lower than it ever was in the past 1300yrs. And as little as a 3% decrease in GCC over 100yrs can equate to ~ 0.5C increase. Oceans absorb the extra incoming SW radiation, as less is reflected back, and more is absorbed into the climate system.

Depending on the speed of equilibrium, the amount of warming that manifests could be very high or very low. We know its happened before, and past history is repeating itself it seems.

[WeatherRusty]

Well, to compare solar warming with AGW can be tricky, because Solar Magnetism is the major driver of low-level Cloud Cover (source to change),(long term), which, decreases in GCC would warm the Surface faster than the LT since the surface is what would take higher incoming SW once below the cloud deck. AGW implies that 1)....Both Poles should be warming equally, and 2), the LT should be warming faster than the Surface, since it is re-emitted LW radiation.

Coincidentally, Solar warming During the MWP Hit the Arctic 50-100 years before the Antarctic, not at equal timeframes either. The solar Max during the MWP was not nearly as strong as our current max based on 10/BE & C10 concentrations, which have always been a direct link to not only Solar, but Global Cloud Cover.

The proxy of 10/BE can only go into the 1980's at this point, but it finds that GCC then was lower than it ever was in the past 1300yrs. And as little as a 3% decrease in GCC over 100yrs can equate to ~ 0.5C increase. Oceans absorb the extra incoming SW radiation, as less is reflected back, and more is absorbed into the climate system.

Depending on the speed of equilibrium, the amount of warming that manifests could be very high or very low. We know its happened before, and past history is repeating itself it seems.

Two areas of dispute here.

AGW does not imply that both poles should warm equally, most of the warming in the northern polar region is due to the ice albedo feedback, a mechanism not nearly as pronounced in the south. Warmer ocean currents can also penetrate deep into the northern polar regions, while the same can not occur near the south beyond the coastal regions.

Only in the tropics should the mid troposphere be warming faster than at the surface. The anticipated "hot spot" is a consequence of water vapor feedback which is most pronounced in the tropics.