From Penn State: Slowdown of global warming fleeting
By A’ndrea Elyse Messer
UNIVERSITY PARK, Pa. — The recent slowdown in the warming rate of the Northern Hemisphere may be a result of internal variability of the Atlantic Multidecadal Oscillation — a natural phenomenon related to sea surface temperatures, according to Penn State researchers.
“Some researchers have in the past attributed a portion of Northern Hemispheric warming to a warm phase of the AMO,” said Michael E. Mann, Distinguished Professor of Meteorology. “The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily.”
According to Mann, the problem with the earlier estimates stems from having defined the AMO as the low frequency component that is left after statistically accounting for the long-term temperature trends, referred to as detrending.
“Initial investigations into the multidecadal climate oscillation in the North Atlantic were hampered by the short length of the instrumental climate record which was only about a century long,” said Mann. “And some of the calculations were contaminated by long-term climate trends driven or forced by human factors such as greenhouse gases as well as pollutants known as sulfate aerosols. These trends masqueraded as an apparent oscillation.”
Mann and his colleagues took a different approach in defining the AMO, which they report online in a special “Frontier” paper in Geophysical Research Letters. They compared observed temperature variation with a variety of historic model simulations to create a model for internal variability of the AMO that minimizes the influence of external forcing — including greenhouse gases and aerosols. They call this the differenced-AMO because the internal variability comes from the difference between observations and the models’ estimates of the forced component of North Atlantic temperature change. They found that their results for the most recent decade fall within expected multidecadal variability.
They also constructed plausible synthetic Northern Hemispheric mean temperature histories against which to test the differenced-AMO approaches. Because the researchers know the true AMO signal for their synthetic data from the beginning, they could demonstrate that the differenced-AMO approach yielded the correct signal. They also tested the detrended-AMO approach and found that it did not come up with the known internal variability.
The detrended approach produced an AMO signal with increased amplitude — both high and low peaks were larger than in the differenced-AMO signal and in the synthetic data. They also found that the peaks and troughs of the oscillation were skewed using the detrending approach, causing the maximums and minimums to occur at different times than in the differenced-AMO results. While the detrended-AMO approach produces a spurious temperature increase in recent decades, the differenced approach instead shows a warm peak in the 1990s and a steady cooling since.
Past researchers have consequently attributed too much of the recent North Atlantic warming to the AMO and too little to the forced hemispheric warming, according to the researchers.
Mann and his team also looked at supposed “stadium waves” suggested by some researchers to explain recent climate trends. The putative climate stadium wave is likened to the waves that go through a sports stadium with whole sections of fans rising and sitting together, propagating a wave around the oval. Random motion of individuals suddenly becomes unified action.
The climate stadium wave supposedly occurs when the AMO and other related climate indicators synchronize, peaking and waning together. Mann and his team show that this apparent synchronicity is likely a statistical artifact of using the problematic detrended-AMO approach.
“We conclude that the AMO played at least a modest role in the apparent slowing of warming during the past decade,” said Mann. “As the AMO is an oscillation, this cooling effect is likely fleeting, and when it reverses, the rate of warming increases.”
Others working on this project were Byron A. Steinman, postdoctoral fellow in meteorology, and Sonya K. Miller, programmer/analyst, meteorology, Penn State
The National Science Foundation supported this work.
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The paper:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL059233/abstract
WUWT post on the stadium wave: http://wattsupwiththat.com/2013/11/30/climate-stadium-waves-and-traffic-waves/
“The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily.”
Please correct me if i’m wrong….But I thought the AMO was in a possitive phase now. I thought it wasn’t going nebeative until around 2020.
^negative
It seems to me that every time the temp goes up it is CAGW.
When it stops, levels out, or dips, it is from “natural” causes
I thought it was a “faux pause”, but now it’s a “fleeting pause”. Maybe it’s a fleeting faux pause or a faux fleeting pause.
Steinar Midtskogen says:
The AMO has a period of about 70 years.
I’m not sure we know enough about the AMO to conclude that it’s really cyclic and not just a random walk. That the AMO peaked in the 90s, however, completely defies common sense.
Has anyone found any non-paywalled information on how Mann defines his “true AMO” index?
I cannot believe anybody is giving this guy ANY attention after the Hockey Stick Fraud…He has been soundly debunked totally by Steve Mcyintyre
“Initial investigations into the multidecadal climate oscillation in the North Atlantic were hampered by the short length of the instrumental climate record which was only about a century long,” said Mann.
But he believes anthropogenic warming since 1950 is solid?
“They also constructed plausible synthetic Northern Hemispheric mean temperature histories against which to test the differenced-AMO approaches.”
I am not sure the author of this piece has a clue what science is given the first quote and the second statement I clipped out, offered in the same article…. and we the taxpayers paid for it?
Our winter might have been too much for MM.
Mann is right — “The Pause” is fleeting — much like his so called “warming” — a warming of little consequence.
We should always acknowledge the truth — no matter who utters it.
The earth has been here several Billion years. It will survive Dr Mann, his Mann-made warming, his fellow-travelers and much else besides.
No matter how many times Mann saws off the limb on which he perches, you look up and he’s still sitting in the tree. This tree is either magical or imaginary.
No pause in warming. Slow down in warming. The pause in warming is likely fleeting.
He is walking very slowly toward the truth.
Interesting how he calls a 17 1/2 year halt a “10-year slowdown”, which is “temporary”, partly due to the AMO. Funny how he “forgets” PDO as well. Both AMO and PDO are now in the cooling phase, and that means we’ll be cooling for at least another 20 years. You can smell the desperation and fear in these prison-bound climate shysters.
Quote:
“They call this the differenced-AMO because the internal variability comes from the difference between observations and the models’ estimates of the forced component of North Atlantic temperature change.”
There is no internal variability, the “forced” phase of the AMO is its cold phase, e.g. from 1965 to 1995 where the heat content of the northern north Atlantic Ocean was declining:
http://i35.tinypic.com/28vsnzq.png
The warm phase from 1995 is simply declines in solar plasma forcing, causing an increase in negative AO/NAO episode frequency and intensity, a more southerly jet stream track, and increased poleward warm sea water transport. The whole thing is a negative feedback with a large overshoot, and is responsible for a significant proportion of the rise in global mean surface temperature since 1995.
Quote:
“We conclude that the AMO played at least a modest role in the apparent slowing of warming during the past decade,” said Mann. “As the AMO is an oscillation, this cooling effect is likely fleeting, and when it reverses, the rate of warming increases.”
Apparently it caused the warmest decade on record, and it is behaving as it should do. That is to give a sharp step up in global mean temp as poleward sea water transport is increased, followed by a leveling off in temp, because the external solar forcing is reduced. With increased solar forcing, the AMO will return to its cold phase, which is very unlikely while solar activity is at such low values (as in the 1880/90’s).
The use of the word “pause” is symptomatic of how the AGW lobby torture the language, and of their circular logic.* They should call it a “cessation” or a “stop”. If the world resumes a warming trend later on then, and only then, can it be called a pause.
“Fleeting” is another interesting word. If 17 years is “fleeting”, what would we call the period from 1980 to 1997 when the globe really did warm?
* For those that don’t know, circular logic means assuming what you set out to prove.
“They compared observed temperature variation with a variety of historic model simulations to create a model for internal variability of the AMO that minimizes the influence of external forcing — including greenhouse gases and aerosols. They call this the differenced-AMO because the internal variability comes from the difference between observations and the models’ estimates of the forced component of North Atlantic temperature change.”
Apparently, Mann wants to be recognized as the greatest practitioner of the Alarmist Method. That method is to combine some statistical manipulation of some data with some scenarios created on computer models until there is a result that supports Alarmist Dogma. The final touch is that all this creativity is presented as science.
How long must we be abused by such nonsense. Results of model runs are not data. Models are not data. Therefore, comparisons between model runs and data are worthless.
As I understand it, the ‘warming’ period was 22 years and it stopped 17.5 years ago. That means that the ‘pause’ is currently running at 79.5% of warming for longevity. Of course, it all depends where the pause is taken from, some people say it’s been 20 years…
I would like to know what the Penn State students think of this. Because if they are buying into this absolutely abysmal excuse for science, then Penn State will be graduating absolutely worthless scientists.
Claude Harvey says:
April 9, 2014 at 5:15 am
It’s magical, Claude. It’s the same one he got the tree ring cores from.
I thought Dr. Mann was a tree guy?
Does he think he may have lost his hockey stick somewhere in the Atlantic?
cn
hmmmm
Differenced-AMO. What next? Upsided downeded detrendeded homogenizeded spliceded tree rings-ed? Sounds like they massaged-ed that data till it sang “the tune”.
Oh wait…Mann already did the treed one.
“… Mann and his team show that this apparent synchronicity is likely a statistical artifact of…”
Well he is a specialist in these artifacts so he could be right. He took a good course from Steve M about such artifacts.
Re: Harry Passfield says:
April 9, 2014 at 6:22 am
“It’s magical, Claude. It’s the same one he got the tree ring cores from.”
Of course! I’d forgotten his ability to sort through thousands of trees and find that handful of “magical hockey-stick trees”. Hockey-stick tree limbs are immune to the effects of gravity! I wonder if “pause trees” are so endowed?
“Synthetic data” in my world is called pencil whipping.
It’s good to see Mr. Mann producing solid science again! Oh, wait….
“Mann and his colleagues took a different approach”…
So does my father-in-law when it comes to navigating. He’ll tell you the absolute best route to take, based on the fact that the drove there 20 years ago, and you haven’t.
Yes, he is now invariably late for things…