Statistical analysis shows pattern consistent with pre-industrial temperature swings, study concludes
From McGill University’s Shaun Lovejoy
Statistical analysis of average global temperatures between 1998 and 2013 shows that the slowdown in global warming during this period is consistent with natural variations in temperature, according to research by McGill University physics professor Shaun Lovejoy.
In a paper published this month in Geophysical Research Letters, Lovejoy concludes that a natural cooling fluctuation during this period largely masked the warming effects of a continued increase in man-made emissions of carbon dioxide and other greenhouse gases.
The new study applies a statistical methodology developed by the McGill researcher in a previous paper, published in April in the journal Climate Dynamics. The earlier study — which used pre-industrial temperature proxies to analyze historical climate patterns — ruled out, with more than 99% certainty, the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate.
In his new paper, Lovejoy applies the same approach to the 15-year period after 1998, during which globally averaged temperatures remained high by historical standards, but were somewhat below most predictions generated by the complex computer models used by scientists to estimate the effects of greenhouse-gas emissions.
The deceleration in rising temperatures during this 15-year period is sometimes referred to as a “pause” or “hiatus” in global warming, and has raised questions about why the rate of surface warming on Earth has been markedly slower than in previous decades. Since levels of greenhouse gases have continued to rise throughout the period, some skeptics have argued that the recent pattern undercuts the theory that global warming in the industrial era has been caused largely by man-made emissions from the burning of fossil fuels.
Lovejoy’s new study concludes that there has been a natural cooling fluctuation of about 0.28 to 0.37 degrees Celsius since 1998 — a pattern that is in line with variations that occur historically every 20 to 50 years, according to the analysis. “We find many examples of these variations in pre-industrial temperature reconstructions” based on proxies such as tree rings, ice cores, and lake sediment, Lovejoy says. “Being based on climate records, this approach avoids any biases that might affect the sophisticated computer models that are commonly used for understanding global warming.”
What’s more, the cooling effect observed between 1998 and 2013 “exactly follows a slightly larger pre-pause warming event, from 1992 to 1998,” so that the natural cooling during the “pause” is no more than a return to the longer term natural variability, Lovejoy concludes. “The pause thus has a convincing statistical explanation.”
The methodology developed in Lovejoy’s two recent papers could also be used by researchers to help analyze precipitation trends and regional climate variability and to develop new stochastic methods of climate forecasting, he adds.
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The paper:
“Return periods of global climate fluctuations and the pause”, Shaun Lovejoy, Geophysical Research Letters, published online July 14, 2014. DOI: 10.1002/2014GL060478
Abstract
An approach complementary to General Circulation Models (GCMs), using the anthropogenic CO2 radiative forcing as a linear surrogate for all anthropogenic forcings [Lovejoy, 2014], was recently developed for quantifying human impacts. Using preindustrial multiproxy series and scaling arguments, the probabilities of natural fluctuations at time lags up to 125 years were determined. The hypothesis that the industrial epoch warming was a giant natural fluctuation was rejected with 99.9% confidence. In this paper, this method is extended to the determination of event return times. Over the period 1880–2013, the largest 32 year event is expected to be 0.47 K, effectively explaining the postwar cooling (amplitude 0.42–0.47 K). Similarly, the “pause” since 1998 (0.28–0.37 K) has a return period of 20–50 years (not so unusual). It is nearly cancelled by the pre-pause warming event (1992–1998, return period 30–40 years); the pause is no more than natural variability.
Preprint paper here:
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“Natural variabiity” does not explain anything – it merely demonstrates the inability of climate science to understand how climates work.
Thx DBS that strikes the Guardian off my reading list.
The most significant thing about the “pause” is not that temperatures are not increasing, but that climate models did not predict it, and, therefore, the long term trend must not be as steep or dangerous as alarmists have tried to scare the public into believing it is. The paper is arguing a straw man.
What Bob T said.
One really has to wonder how much longer “natural variation” “pauses” “global warming” for before they’ll admit they could be wrong.
No Felix you give it up. For what % of the Earths history do we have “records” for (irregardless of the quality) and how big was the magnitude of your new Record warmth relative to the norm? Come on now show us your stuff, inquiring minds want to know.
Ric Werme
“we can measure CO2, we can determine the (wrong) climate sensitivity the delta-T for a doubling of CO2”
There is no such physical property called “Climate sensitivity” it is not really a thing… the “delta-T for a doubling of CO2” is based on no physical premise which can effect a planets climate, anymore than natural variability does or does not effect the climate.
A doubling of CO2 under static conditions and quantities do not control the climate of those static conditions. This would be like first proving a static condition, and then using it to prove that a static condition is a variable influence on another even greater variable. Do you see the physical problem?
Sparks:
Right on!
This entire CAGW scam was concocted from the brief global warming trend experienced from 1980 to 1998…
This is hilarious, because the 1980~1998 warming trend is identical to the warming trend from 1913~1940, which even the IPCC admits could not have been caused by CO2 induced warming.
The IPCC asserts that CO2 was only at sufficient levels from 1950 to have caused any global warming, however, from 1950~1979, global temperatures had a FALLING trend…
The temperature trend from 1850 to 2013 is just 0.05C/decade and the Central England Temperature data shows the temperature trend from 1659 to 2013 is, drum roll please…….. 0.05C/decade…
Almost all of the 0.75C of warming from 1850 is simple natural variation, with only about 0.2C of the total possibly contributable to CO2 induced warming with the most likely outcome of around 0.5C of total CO2 induced warming by 2100… (Lindzen Choi et al.)
Why are we still wasting $trillions on this CAGW scam? Almost all of the warming since the end of Little Ice Age can ONLY be attributed to natural variation.
For the CAGW hypothesis to reach its minimum projected warming of 3C by 2100, the global warming trend would need to be around 0.3C/DECADE starting from tomorrow and to hold this trend for the next 8.6 decades…. That AIN’T going to happen.
Rather than giving excuses, the CAGW grant grubbers need to provide firm criteria required to nullify the CAGW hypothesis. Using the Scientific Method and the rules of statistics, if hypothetical projections exceed their 95% confidence intervals, then the CAGW needs to be run through the shredder. We’re already on the cusp of meeting this standard criteria for nullification:
http://www.drroyspencer.com/wp-content/uploads/CMIP5-73-models-vs-obs-20N-20S-MT-5-yr-means1.png
The world is getting sick and tired of hearing the dog-ate-my-warming excuses. NONE of CAGW’s projections are even CLOSE to matching reality: OHC, global warming trend, extreme weather incidence, sea level rise, ocean pH, ad nauseam.
I will look at the paper later, it may show that the recent hiatus is consistent or caused by natural variability but to show that CO2 has something to do with the warming it has to also show that the warming from 1980 to 1998 is not consistent with natural variability. If it does not consider variability from 1910 to 1976 the analysis is incomplete.
Felix says:
July 21, 2014 at 5:36 pm
If a recent month is the warmest on record, it says nothing about whether the cause is CO2 or natural variability.
There is a point where confirmation bias crosses over the line into just plain clueless, agenda driven crap. We appear to have passed that point.
The climate obsessed travel full circle: If it gets warmer, it is a climate crisis. If it gets cooler, it is a climate crisis. If it is natural fluctuation, it is a cliamte crisis.
The climate obsession turns critical thinking into circular reasoning. No reflection on the idea that if ‘natural fluctuation’ can mask what as recently as 1998 was a “planetary emergency”, then perhaps the emergency was not really so uniquely dangerous.
No reflection on the idea that if a world ending process was underway, it should not be so difficult to actually measure.
So, as I understand it, the “pause” is now longer than the “rise”. The models correctly modelled the rise, usually by hind-cast i.e. they fitted the known temperature record at that time.
Now that the models are in forecast mode they are proving to be more and more inaccurate. I suggest we develop some new models that fit the current hind-cast and then see how they look going forwards. In other words; throw away the old models, figure out what was missing, add that in and then start again.
If these people are that confident that they now know what the “natural variability” factors are; they should incorporate them into the models and then publish their findings. Instead it seems that are happy to “explain” that it’s natural variability without incorporating that into a model and make new predictions. To my mind this is equivalent to rearranging the deck chairs on the Titanic.
norah4you says:
July 21, 2014 at 6:30 pm
I recall hanging on to a copy, but it’s packed away from remodeling.
Does anyone know if Steve McIntyre ever took a look at Shaun Lovejoy’s previous paper? I find the claim that Lovejoy’s statistical analysis ruled out the possibility global warming is just a natural fluctuation in the earth’s climate with 99.9% certainty to be impossible. The pre-industrial temperature proxies that he used in his analysis have too many uncertainties to allow anywhere near that kind of accuracy. It would be nice to have McIntyre analyze Lovejoy’s statistical analysis.
Ah. The old principle of pausible deniability….
“variations in pre-industrial temperature reconstructions”, i.e. variations of adjustments to arrive at a preferred end state.
Epic Fail.
Felix
Now try looking at the satellite records.
I do, though, love the way in which you chaps jump from “climate is multi-decadal” to “hottest month on record” without pausing to think about what you are saying.
I’m not sure how much time I want to waste looking at Dr. Lovejoy’s paper. I wasted a bukuload last time around and walked away with the impression that either the man knew he was playing games with assumptions in statistics or that he wasn’t as good with applied statistics as he thought (1).
So I haven’t read the paper. Maybe I’ll look at it this week. My question goes like this; if we’ve only been pumping large amounts of CO2 into the atmosphere for about 100 years now, how can you tell the difference statistically between a pause and warming that just isn’t there? What would it look like statistically if there were a percent or two change in cloud cover?
I suspect there are more games being played with assumptions here.
(1)- Dr. Lovejoy’s maths are way better than mine. This said, I listened to the opinions of people with better stat skills than me. Caveat emptor.
Mark Bofill:
You ask the apt question of “how can you tell the difference statistically between a pause and warming that just isn’t there?” My answer is that one can hope to tell the difference when this question is posed statistically. To pose it statistically is not accomplished by Dr. Lovejoy’s paper. This paper replaces a statistical description by the paper’s Equation 1.
To pose this question statistically is to identify the set of independent events underlying the associated model. This set is not identified by Lovejoy’s paper.
So nature conspired to “hide the rise”? Diabolical. Are there emails?
Dave N said:
‘One really has to wonder how much longer “natural variation” “pauses” “global warming” for before they’ll admit they could be wrong.’
For the core group of environmental alarmists, I fear the answer is… til the end of time.
Ken L.:
Climatologists extend the period in which they’ll not admit that they are wrong to the end of time through applications of the equivocation fallacy: through the use of equivocal language they avoid making statements that are susceptible to being proved false. Details are presented in my peer-reviewed article at http://wmbriggs.com/blog/?p=7923 .
Goldie:
Thanks for sharing. A barrier to throwing out the old models and replacing them with new models is that with rare exceptions the arguments made by global warming models are not falsifiable. Under the scientific method of investigation we throw out models that have been falsified. Here, even though the models exhibit error, they are not falsifiable. The falsifiability of a model is dependent upon the existence of the underlying statistical population. With rare exceptions, there is no such population.
Dr Love joy,
” a natural cooling fluctuation of about 0.28 to 0.37 degrees Celsius since 1998 — a pattern that is in line with variations that occur historically every 20 to 50 years,”
Absolutely correct and now you may be able to show that the warming between 1978 and 1995 or thereabouts was caused by recovery from a variation.
You see natural variations go both ways as well.
Cheers
Roger
http://www.thedemiseofchristchurch.com
Middle of winter here in Sydney. Feeling cold as i left for work at 3.00 am . Apparently i was actually hot, its just that it was being masked by the cold.
The IPCC has never produced a chart showing natural variability above 0.1C over any period of time. Now Lovejoy comes along and says it might be up to 0.37C.
Sorry, you guys are a bunch of fake scientists making stuff up as you go along and re-writing history as you go along. When does this hypocrisy end.
So could the “natural variation” cause the temperatures to rise quicker than expected OR does this work only one way for the alarmists?
Does he clarify how the 0.3C of warming between 1980-2000 was ruled out as [not] natural with 99% certainty… yet he proposes cooling of 0.3C between 2000-2014, which he asserts was completely natural?