This paper suggests that the CMIP5 models’ (which IPCC relies upon) predicted US SW temperature sensitivity to the GHG has been significantly overestimated by about a factor of two.
Imprint of the Atlantic multi-decadal oscillation and Pacific
decadal oscillation on southwestern US climate: past, present,
and future
Petr Chylek • Manvendra K. Dubey • Glen Lesins • Jiangnan Li • Nicolas Hengartner
Abstract
The surface air temperature increase in the southwestern United States was much larger during the last few decades than the increase in the global mean. While the global temperature increased by about 0.5 °C from 1975 to 2000, the southwestern US temperature increased by about 2 °C. If such an enhanced warming persisted for the next few decades, the southwestern US would suffer devastating consequences. To identify major drivers of southwestern climate change we perform a multiple-linear regression of the past 100 years of the southwestern US temperature and precipitation. We find that in the early twentieth century the warming was dominated by a positive phase of the Atlantic multi-decadal oscillation (AMO) with minor contributions from increasing solar irradiance and concentration of greenhouse gases.
The late twentieth century warming was about equally influenced by increasing concentration of atmospheric greenhouse gases (GHGs) and a positive phase of the AMO. The current southwestern US drought is associated with a near maximum AMO index occurring nearly simultaneously with a minimum in the Pacific dec- adal oscillation (PDO) index. A similar situation occurred in mid-1950s when precipitation reached its minimum within the instrumental records. If future atmospheric concentrations of GHGs increase according to the IPCC scenarios (Solomon et al. in Climate change 2007: working group I. The Physical Science Basis, Cambridge, 996 pp, 2007), climate models project a fast rate of southwestern warming accompanied by devastating droughts (Seager et al. in Science 316:1181–1184, 2007; Williams et al. in Nat Clim Chang, 2012).
However, the current climate models have not been able to predict the behavior of the AMO and PDO indices. The regression model does support the climate models (CMIP3 and CMIP5 AOGCMs) pro- jections of a much warmer and drier southwestern US only if the AMO changes its 1,000 years cyclic behavior and instead continues to rise close to its 1975–2000 rate. If the AMO continues its quasi-cyclic behavior the US SW temperature should remain stable and the precipitation should significantly increase during the next few decades.
Discussion and conclusion
A multiple linear regression analysis of the twentieth century US SW climate suggests a strong oceanic influence on both the southwestern US temperature (from the AMO) and precipitation (from the PDO and AMO). About a half of the recent (post 1975) US SW warming trend can be attributed to the anthropogenic influences of increasing atmospheric concentration of greenhouse gases and aerosol variability (GHGA), with the remaining half being due to a positive phase of the AMO. The US SW precipitation has been dominated by oceanic influences (PDO and AMO) with no direct effect due to anthropogenic greenhouse gases and aerosols (GHGA). This of course does not exclude a possibility that the GHGA affects the AMO and PDO.
To estimate the future US SW climate evolution using the regression model we need to make an assumption concerning the future AMO behavior. The situation that we consider most likely is the repetition of a cyclic behavior that was observed during the twentieth century (Schle- singer and Ramankutty 1994) as well as during the previous hundreds of years (Delworth and Mann 2000; Gray et al. 2004; Chylek et al. 2011, 2012). The regression model with a continuing AMO cyclic behavior suggests a stable temperature close to its present level and increasing precipitation within the next two to three decades.
A rising AMO index at the rate comparable to its 1975–2005 increase would bring harsh climatic conditions to the southwestern US. Projected temperature would increase by 2050 by about 2 °C above the current level (a warming similar to that predicted by the ensemble mean of the CMIP5 simulations) and precipitation would decrease by an additional 30 % compared to the current conditions. A strong warming and severe drought predicted on the basis of the ensemble mean of the CMIP climate models simulations (Seager et al. 2007; Williams et al. 2012) is supported by our regression analysis only in a very unlikely case of the continually increasing AMO at a rate similar to its 1970–2010 increase.
There is substantial evidence to support future AMO cyclic behavior. Instrumental records of central England temperature (Tung and Zhou 2013), tree rings (Delworth and Mann 2000; Gray et al. 2004) and ice core analysis (Meeker and Majewski 2002; Chylek et al. 2011, 2012; Henriksson et al. 2012) demonstrate the existence of the AMO cycles for many hundreds and possibly thousands of years when anthropogenic influences were negligible. Ice core analysis suggests a shorter AMO quasi-period- icity (about 20 years) during the Little Ice Age and a longer periodicity in the Medieval Warm Period (Chylek et al. 2012). Atmosphere–Ocean coupled climate models (Metha and Delworth 1995; Griffies and Bryan 1997; Delworth and Knutson 2000; Dong and Sutton 2001; Wei and Lohmann 2012; Mahajan et al. 2011; Henriksson et al. 2012; Yang et al. 2013; Escudier et al. 2013; Zanchettin et al. 2013) as well as simplified conceptual ocean models (Frankcombe and Djikstra 2011), or sta- tistical harmonic models (Humlum et al. 2011; Mazzarella and Scafetta 2012; Scafetta 2012) suggest a future per- sistent AMO like multi-decadal oscillation. Based on this evidence of the past behavior we expect the AMO to retain its cyclic behavior during the twenty-first century with a cycle length of 60–70 years.
It seems that the AMO index may have reached its peak around 2005 and started to turn downward (Fig. 4) but still in a positive AMO phase. Within a few years we should be able to see more clearly if this was a real turning point or only a temporary pause.
Fig. 4 a Instrumental era AMO (black), and three considered cases of its future projection: [1] repetition of the 65 year cycle (blue), [2 ] a constant at the present AMO value (green), and [3] continuation of the 1975–2010 increasing trend (red). b Regression reconstruction of the US SW temperature (black), and three different projections of the US SW temperature ([1], [2], [3]) based on the three considered AMO future projections. The observed US SW temperature (SWT gray) and the CMIP5 ensemble mean (yellow) with the RCM4.5 pathway are also shown. All data are the 5 year moving means. c 95 % confidence level (thin lines) for regression model and cases [1] and [3] of the temperature projection
The US SW temperature and precipitation are strongly influenced by the AMO and PDO. The fact that the CMIP simulations ensemble mean can reproduce the 1970–2010 US SW temperature increase without inclusion of the AMO (the AMO is treated as an intrinsic natural climate vari- ability that is averaged out by taking an ensemble mean of individual simulations) suggests that the CMIP5 models’ predicted US SW temperature sensitivity to the GHG has been significantly (by about a factor of two) overestimated.
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Received: 21 February 2013 / Accepted: 26 August 2013
© The Author(s) 2013. This article is published with open access at Springerlink.com Paper: Chylek et all ClimDyn_US_SW (PDF)
h/t to Dr. Roger Pielke Sr.
Sounds about right to me. One point five instead of IPCC climate sensitivity mid-point of three (after latest lowering).
Cheylek has also done excellent climate sensitivity work (satellite and paleo), concluding ECS is at or below 2. This new study contains similar results to an earlier USGS study linking regional US drought to the AMO and PDO. That study covered all of CONUS, not just the SW. McCabe et. al., PNAS, 2004. So there are lots of reasons to think this is good solid climate science of the sort that the IPCC and the CAGW crowd ignore at their peril.
Huh. It’s almost like large scale quasi-periodic thermal disequilibriums would be correlated with other quasi-periodic thermal disequilbriums.
“However, the current climate models have not been able to predict the behavior of the AMO and PDO indices.”
Yes well, that’s because climastrologists have approached the climate in the manner in the of Newton approaching planetary orbits. That crafty old dodger started with the small irrelvancies like Einstein’s Relativity before moving on to the larger scale effects. As everyone knows the obvious is too obvious to recognize.
Upshot about misprediction of the AMO and PDO, is that the models can start putting better error bars on things. Might not be better at misprediction, but at least there will be a better knowledge of how soon they get out of whack and how badly. Otherwise known as, the same thing Weather Forecasters do for 5-day models.
Here are 3 AMO reconstructions going back to 1700
http://www.vukcevic.talktalk.net/AMO-recon.htm
if you can workout you way out of this spaghetti
“The fact that the CMIP simulations ensemble mean can reproduce the 1970–2010 US SW temperature increase without inclusion of the AMO (the AMO is treated as an intrinsic natural climate variability that is averaged out by taking an ensemble mean of individual simulations) suggests that the CMIP5 models’ predicted US SW temperature sensitivity to the GHG has been significantly (by about a factor of two) overestimated.”
The sensitivity of climate models being too high by a factor of 2 seems to have become a common conclusion.
Nothing new here.
NOAA have been saying for a while that AMO warm phase leads to droughts/heatwaves in the Mid West and South West.
Recent research suggests that the AMO is related to the past occurrence of major droughts in the Midwest and the Southwest. When the AMO is in its warm phase, these droughts tend to be more frequent and/or severe (prolonged?). Vice-versa for negative AMO. Two of the most severe droughts of the 20th century occurred during the positive AMO between 1925 and 1965: The Dustbowl of the 1930s and the 1950s drought. Florida and the Pacific Northwest tend to be the opposite – warm AMO, more rainfall.
Natural variation? Who’d have thunk?
http://www.aoml.noaa.gov/phod/faq/amo_faq.php
From the Grauniad no less.
http://www.theguardian.com/environment/2013/oct/13/the-basking-shark-returns-british-waters
Bob, yup. And to be numerate about it using the amplifier feedback version of ECS sensitivity (Lindzen British House of Commons early 2012 testimony available on his website), the IPCC S=3 means f=0.67.
Now the overstated UTrH constant thing (AR4 8.6.3.1 and black box 8.1 as I recall) doubles sensitivity according to the IPCC from the “grey world” Stefan-Boltzmann law S= 1.2 that even Lindzen accepts (pure black body theory is 1.0). So that by itself gives an overstated water vapor f=0.5. By subtraction IPCC positive cloud feedback is implicity f=0.17. (ignoring all other really minor contributions to feedbacks).
Now many lines of observational evidence say actual cloud feedback is neutral or slightly negative.
Many other lines of evidence say that although UTsH increases, it increases at only about 2/3 of what Clausius-Clapeyron requires for constant UTrH. So f=0.67 minus 0.17 for neutral cloud feedback minus ([1-2/3]*0.5) for overstated positive water vapor feedback is an f=0.33, which using Lindzen’s amplifier S=1/(1-f) equation yields an observational S=1.5 after rounding. IPCC overstated by 2x. QED.
Except here I have given the main physical reasons actually imbedded in the GCMs versus observations. The derivation is also in my book published last year that includes the supporting observational evidence, plus lots of other ways to estimate an ECS lower by up to half than the IPCC estimate of 3. Some of this was also posted last year courtesy of Dr. Judy Curry.
Regards
“A strong warming and severe drought predicted on the basis of the ensemble mean of the CMIP climate models simulations (Seager et al. 2007; Williams et al. 2012) is supported by our regression analysis only in a very unlikely case of the continually increasing AMO at a rate similar to its 1970–2010 increase.”
These equivocations are tiring. The CMIP have already been thoroughtly falsified, invariably being away to hot. It wouldn’t be support for CMIP if we had an unlikely “continually increasing AMO rate. It would only further strengthen your thesis re the AMO!!! Nothing can save the CMIP models now. Sheesh.
1) this conclusion is not surprising; a simple extension of teleconnection theory but on longer time frames. Joe Bastardi has been discussing this idea for years
2) it would be surprising if other NH cyclical events aren’t tied to the AMO /PDO cycles as well.
3) it begs the question of what other even longer natural cycles have yet to be recognized (ie century or longer cycles) in the climate data
4) it also begs the question of once these natural cycles are removed from the total signal, how much of any signal remains that can attributed to CO2 / AGW ?
5) I am looking forward to cooler & wetter conditions over the next several decades
Also, they leave out what, to me, would represent a fair probability case that the SW US temp would DECLINE with a declining AMO if the AMO has otherwise had this affect on past temps. People from the CAGW camp come up with alternatives to the strong CO2 place in climate but can’t seem to let it go. Comon, the ECS is 1.0 or less already and likely further constrained by negative feedbacks.
Bob, btw. I believe the reasons for the overstated positive water vapor feedback and the wrong sign cloud feedback are both related to Lindzen’s previously ‘discredited’ adaptive iris hypothesis about Tstorms in the tropics. Willis Eschenbach has recently done more than anyone else IMO to show that Lindzen’s idea was probably right, even though he could not marshal the observational facts to prove it back in 2000. Willis appears to have take major strides toward having done so this year, despite Dr. Spencer’s rather petulant recent objections.
Now, you couple those errors to the ocean cycle changes you, Dr. Curry, and others have been pointing out, and one has a rather complete refutation of the IPCC, plus a rather complete alternative observed climate explanation using no GCM models at all.
Rud Istvan says:
October 13, 2013 at 2:33 pm
“This new study contains similar results to an earlier USGS study linking regional US drought to the AMO and PDO”
Paul Homewood says:
October 13, 2013 at 3:07 pm
“Nothing new here.
NOAA have been saying for a while that AMO warm phase leads to droughts/heatwaves in the Mid West and South West.”
Jeff L says:
October 13, 2013 at 3:37 pm
“1) this conclusion is not surprising; a simple extension of teleconnection theory but on longer time frames. Joe Bastardi has been discussing this idea for years”
Wow, a lot of people jumped all over Willis for coming up with something even more different and well presented than his predecessors. This looks like Chylek is simply writing it all down. I don’t have any problem with this – maybe it gathers bits and pieces together. But hey, sauce for goose and gander.
Chylek et al. paper is very good.
Note that this paper highlights both the quasi 60 year and 20 year oscillations (for centuries).
Which are two of the 6 major oscillations that make the astronomical harmonic climate model.
see details in:
Scafetta, N. 2013. Discussion on climate oscillations: CMIP5 general circulation models versus a semi-empirical harmonic model based on astronomical cycles. Earth-Science Reviews 126, 321-357.
http://www.sciencedirect.com/science/article/pii/S0012825213001402
and in my other papers:
http://people.duke.edu/~ns2002/#astronomical_model
Gary, Anthony’s thread style does not allow immediate topical responses. But if you will look up above on this thread, you will see I credited both Lindzen and Eschenbach, while trying to explain the underlying physics. Most interesting.
One may note:
1) Regarding where this paper states: “This of course does not exclude a possibility that the GHGA affects the AMO and PDO.”
More likely more relevantly, it does not exclude a possibility than a greater external forcing affects the AMO and PDO. For example, a definition of the AMO [index] is temperature averaged over the North Atlantic minus global mean temperature. High-latitude areas by the poles warm more than the equator or the rest of the world average during times of high solar warming (Medieval Warm Period, Holocene Climate Optimum, Modern Warm Period, etc.). So such means that, indirectly practically about by definition, the AMO will usually be higher when solar activity is higher.
The depicted pattern in the AMO index is not identical to but mostly a lot like the pattern in solar activity over that timeframe. Compare to plots in http://img176.imagevenue.com/img.php?image=81829_expanded_overview_122_424lo.jpg
There may be a significant independent component of the AMO, separate from the part relatively directly from external solar/GCR forcing; there definitely seems to be so with the ENSO, at least (as well as with shorter-term weather oscillations). However, splitting it out would be complicated.
2) CAGW movement type models never reconstruct any lengthy past history accurately without creative and unique adjustment of aerosol values used as a fudge factor; that is why models of widely varying sensitivities supposedly all accurately reconstruct the past (different made-up assumed historical values used for each) but fail in future prediction, like they didn’t predict how global average temperatures have been flat to declining over the past 15 years.
3) Unless very unusually different from the temperature data sources commonly used by publications like this, the reported Southwestern U.S. temperature history has probably been fudged towards the hockey stick version depicted, rather than twin peaks in the 20th century, in a similar manner to U.S. average temperature history (examples in the prior link, comparing versus older sources before they were rewritten).
And, so correspondingly, the conclusion that half of the late 20th century warming was from GHGs is hardly likely to be supported once taking into account the above, especially since generally non-fudged temperature data has much less warming to account for in the first place.
While I will refrain from certainty on the Southwestern U.S. in particular (due to not having focused on investigating how much it may differ from the U.S. average), the big picture for the global average over the past century is as Dr. Shaviv notes at http://www.sciencebits.com/CO2orSolar … that:
““One can actually quantify empirically the relation between cosmic ray flux variations and global temperature change, and estimate the solar contribution to the 20th century warming. This contribution comes out to be 0.5 +/- 0.2 C out of the observed 0.6 +/- 0.2 C global warming (Shaviv, 2005)”
EDIT to prior post (hit submit too fast):
Annoying typo:
“More likely more relevantly it does not exclude” … “a possibility than”
should be a possibility that.
One last typo fix: The earlier reference to a definition of the AMO
being “temperature averaged over the North Atlantic minus global mean temperature” means, of course, a definition of the AMO index.
Well it seems the SW drought has kind of gone into remission over the past 90 days;
http://water.weather.gov/precip/index.php?yday=1381665600&yday_analysis=0&layer%5B%5D=0&layer%5B%5D=1&layer%5B%5D=4&timetype=RECENT&loctype=STATE&units=engl&timeframe=last90days&product=per_normal&loc=conus
Since they submitted this paper in February….
Regarding projections for the AMO, this may interest, although still in a test phase it projects a .5C decline over the next few years. Extract from a blog at No Tricks Zone.
“Project MiKlip first result shows cooling North Atlantic
The most interesting project among them is the Midterm Climate Prognoses project (MiKlip) described on Page 6 of the Federal Ministry of Education and Research (BMBF) bulletin. Page 6 shows the above chart and poses the question: “How warm is it going to be in 10 years? Business and policy need reliable climate forecasts.”
The bulletin adds that “in business and politics there is an increasing need for reliable forecasts for climate developments in the range of years up to a decade.”
And to fulfill that midterm need the German government is funding the MiKlip 10-year forecasting system, which comprises 60 individual research projects. Excerpts from page 6:
It is mainly about computer simulations that use recorded measurement data. … The MiKlip projects have been taking place since spring 2012. The first tangible results are expected to be available in September 2014. … Compared to the long-term scenarios, the results should be more exact. … The model will not deliver a forecast such as the weather at a specific location in a few years. Instead it looks more at the probable mean temperature in Europe in a certain month.””
http://notrickszone.com/2013/10/13/explosive-max-planck-institute-initial-forecast-shows-0-5c-cooling-of-north-atlantic-sst-by-2016/
more model bullshit….reminiscent of the medieval theologians arguments about how many angels could dance on the head of a pin…or the ever more complicated epicycles of the ptolemaic astronomers….there is no salvation in computer models…on the other hand well shaped human models models can make you very happy.!!
Typo…!
[Where? What should be checked? What is the correction? Mod ]
Bookmarked! Thanks to all who added the extra background information.
Smoothing the datasets before running the regression increases the autocorrelation between the input variables. I’m surprised the reviewers did not consider this an important factor.
What do people reckon is the position of multicentennial oscillation indices?? At a maximum after 200 years coming out of the Little Ice Age?? Still with a further rise to come?? Starting to descend??
When people do models about ‘sensitivity to carbon dioxide’ do they model changes in total forest area/total photosynthetic surface area?? I’m sure that the more trees and photosynthetic organisms there are out there, the better they will be at mopping up the Carbon Dioxide and hence the less sensitive temperature will be to carbon dioxide.
So, the theory would go: alarmists would see their interests allied to the logging companies, since their doomsday scenarios would be most likely to come true if you chopped down all the forests. Skeptics should be best aligned with tree planting organisations, save the forests groups etc etc, since in that situation, the effects of carbon dioxide would be most effectively mitigated.
Anyone wonder how the two groups will think about that little analysis??
Well????
Rud Istvan said:
“Now, you couple those errors to the ocean cycle changes you, Dr. Curry, and others have been pointing out, and one has a rather complete refutation of the IPCC, plus a rather complete alternative observed climate explanation using no GCM models at all”
Already done:
http://www.newclimatemodel.com/new-climate-model/
This is all fine and good .. but my hat remains off to David Archibald … the only guy with the guts to predict that temperature is actually going to go DOWN. Seems every “prediction” I see with solar or ocean, or combined, or based on whatever, has the comming 30 years down as a “pause”. Temps may drop just a little bit. That tells me there is ZERO predictive skill in any of it, because they are too chicken to walk out on a limb and predict something different from the status quo … that is, increased CO2 will continue to warm the planet, and thus, any natural variation will just cause a “pause” like we saw between 1950 and 1975.
Archibald on the other hand, says it is about to get cold. .. that means global cooling. .. that means it doesn’t matter how much CO2 is floating around .. it won’t matter, because it doesn’t contribute significantly to global temperature outside of its mimiscule contribution to the overall 33C greenhouse adjustment.
So it’s highly likely AMO reversal will end the threat. GHGA has no discernable effect.