From the Georgia Institute of Technology:
Looking at El Niño’s past to predict its future
The El Niño Southern Oscillation is Earth’s main source of year-to-year climate variability, but its response to global warming remains highly uncertain.
Scientists see a large amount of variability in the El Niño-Southern Oscillation (ENSO) when looking back at climate records from thousands of years ago. Without a clear understanding of what caused past changes in ENSO variability, predicting the climate phenomenon’s future is a difficult task. A new study shows how this climate system responds to various pressures, such as changes in carbon dioxide and ice cover, in one of the best models used to project future climate change.
“All of the natural climate fluctuations are in this model, and what we see is that the El Niño responds to every single one of these, significantly,” said Kim Cobb, an associate professor of Earth and Atmospheric Sciences at the Georgia Institute of Technology in Atlanta.
The El Niño-Southern Oscillation phenomenon controls how the climate changes in the tropics (and also influences weather patterns elsewhere, including the United States).
The study was sponsored by the National Science Foundation (NSF) and the Department of Energy (DOE). The study was published November 27 in the journal Nature.
In the study, researchers analyzed a series of transient Coupled General Circulation Model simulations forced by changes in greenhouse gases, orbital forcing, meltwater discharge and the ice-sheet history throughout the past 21,000 years. This is farthest in the past that this model has been run continuously, which required supercomputers at Oak Ridge National Laboratory and the National Center for Atmospheric Research to be dedicated to the simulation for months.
Some key findings of the new simulations of El Niño over the past 21,000 years:
- Strengthening ENSO over the current interglacial period, caused by increasing positive ocean-atmosphere feedbacks
- ENSO characteristics change drastically in response to meltwater discharges during early deglaciation
- Increasing deglacial atmospheric carbon dioxide concentrations tend to weaken ENSO
- Retreating glacial ice sheets intensify ENSO
“The model gives some very clear predictions that are very much in line with some of the best understandings of the physics controlling the El Niño system,” Cobb said. “It shows that this climate system in the model is sensitive to a variety of different natural climate changes that occurred over the last 21,000 years.”
In order to understand how El Niño responds to various climate forces, researchers test model predictions of past El Niño changes against actual records of past ENSO activity. Kim Cobb published several such records, including a large fossil coral dataset published in Science last year.
“The more we can close the loop between what this model says happened in the past and what the data say happened in the past, then we can project forward our improved understanding to understand future El Niño,” Cobb said.
This research is supported by the National Science Foundation, under award number NSFC41130105, and the Department of Energy, under award number MOST2012CB955200. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agencies.
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CITATION: Zhengyu Liu, et al., “Evolution and forcing mechanisms of El Niño over the past 21,000 years.” (Nature, November 2014). http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html
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Perhaps it is time to stop calling these studies of “how X responds to global warming” and say instead “projections of how X may respond to increased CO2”.
I can’t understand why they don’t allocate several months of data crunching to predicting changes in Wall Street. Seems to me the data are far more robust for matching with the past than climate, the potential profits are enormous and the potential fame is unlimited. What? They can’t? There are too many variables?
If they can’t forecast financial markets, what hope for climate?
Here’s the money shot:
“The more we can close the loop between what this model says happened in the past and what the data say happened in the past, then we can project forward our improved understanding to understand future El Niño,” Cobb said.”
In other words:
“The more we can model what our proxies think happened in the past the more funding we can get to do this again.”
So keep those grants acomin’ in, we gotta have ’em for super comp time and hey, let’s not ferget those proxy collectin’ trips to Borneo, East Africa, Palymyra. I mean dang it, that’s some beautiful country out there which we don’t got here in Georgia. All you kids and post docs, come on down y’all, we got the funds if you got the time! http://shadow.eas.gatech.edu/~kcobb/join/join.html .
Sign up today!!
Someone gave the famous career advice, “don’t quit your day job,” so they did this simulation. Next: 25,000 year simulation to predict the ENSO in 2100. It will convince China to ante up.
your Enso meter today is still between 05, and 1,00, while BOM Australia issued on December 2nd an El Niño alert;
can you please explain the difference in opinion?
Anyone familiar with a Lorenz Attractor from Chaos theory would have no trouble understanding how a comparatively simple system of equations/interactions could produce a result that seems to divide itself unpredictably (“chaotically”) between two incompatible, yet strangely similar regimes. Interestingly (and probably not coincidentally) Edward Lorenz developed this model while studying weather patterns.
Lorenz used just a few parameters – the Prandtl number representing the ratio of the fluid viscosity to its thermal conductivity (related to absolute humidity), the difference in temperature between the top and bottom of the system (surface and stratosphere), and the ratio of the width to height of the box used to hold the system (boundary conditions – he used a ‘box’ rather than a spherical shell for computational reasons).
The only real surprise is that why anybody who has ever heard a lecture on chaos theory would expect that ENSO could be predicted.
Well we in Oz are getting a lot of rain and storms, and if that is El Nino we welcome it. The farmers are happy.