Global warming and unforced variability: Clarifications on recent Duke study

RealClimate.org ^ | May 13, 2015 | by Patrick Brown and Wenhong Li

[Oldeconomybuyer]

We recently published a study in Scientific Reports titled Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise. Our study seemed to generated a lot of interest and we have received many inquires regarding its findings. We were pleased with some of coverage of our study but we were disappointed that some outlets published particularly misleading articles.

In our study, we created an alternative statistical estimate of unforced variability that was derived from reconstructed and instrumental surface temperature records corrected for external forced changes. We then used this new estimate of unforced variability to aid in our interpretation of observed global mean temperature variability since 1900.

We found that unforced variability is large enough so that it could have accounted for multidecadal changes in the rate-of-increase of global average surface temperature over the 20th century. However, our estimate of unforced variability was NOT large enough to account for the total warming observed over the 20th century. Therefore, our results confirm that positive radiative forcings (e.g., from human-caused increases in greenhouse gas concentrations) are necessary in order for the Earth to have warmed as much as it did over the 20th century.

The results of our study indicate that multidecadal changes in the rate of global warming can indeed be attributable to unforced variability and thus the climate system may be more like panel-b than panel-a. This means that the accelerated warming over the last quarter of the 20th century would not ipso-facto require an acceleration in the forced component of warming. Instead, this accelerated warming could have come about due to a combination of anthropogenic forcing and unforced variability.

[Oldeconomybuyer]

[MortMan]

Using estimates to validate a model.

What happened to science?

[cuban leaf]

http://wattsupwiththat.com/2015/05/12/22-very-inconvenient-climate-truths/

[Da Coyote]

I’venot seen the actual math, but my firsi impression would be to give them a C-.

Been teaching at grad and undergrad level for 30+ years. These folks would never get through some real physics and enginnering curricula.

[GOPJ]

They’ve gussied up the words to sound ‘scientific’ - liberal elite reporters who can’t do math will be impressed.

[Lake Living]

I know I’m probably giving them too much credit but I wonder if the IPCC and all the other government pushers of global warming don’t know and understand point #5 in the 22 Inconvenient Climate Truths?

5. The changes of the Mean Global Temperature are more or less sinusoidal with a well defined 60 year period. We are at a maximum of the sinusoid(s) and hence the next years should be cooler as has been observed after 1950. (discussion: p. 12)

That way any phony attempts (now) to reduce temperatures by these charlatans could be used to say, “See... it’s working! (Therefore give us all your money and give Us the power and we will save you.). The longer the pause, and possible reversal of temps, the higher pitched and unhinged the alarmists message becomes. They must know we’re on them. Hee, hee!

[driftless2]

"what about science"

What!!!...you're demanding some kind of hard proof/evidence???!!?? Are you a lunatic or something? ..../s

[The_Reader_David]

We found that unforced variability is large enough so that it could have accounted for multidecadal changes in the rate-of-increase of global average surface temperature over the 20th century. However, our estimate of unforced variability was NOT large enough to account for the total warming observed over the 20th century. Therefore, our results confirm that positive radiative forcings (e.g., from human-caused increases in greenhouse gas concentrations) are necessary in order for the Earth to have warmed as much as it did over the 20th century.

Having looked at the actual paper, I would claim they can conclude nothing of the sort: they assume that the excess "forced variability" is due to human greenhouse gas emissions on the basis of considering only volcanic aerosols, solar irradiance and human greenhouse gas emissions as possible sources of external forcing. They have omitted variation in cosmic ray flux (as modulated by solar magnetism) as a driver of cloud formation, soot emissions changing the albedo of the Arctic (but not Antarctic) ice pack, and (of necessity) all the unknown unknowns that bear on the earth's climate.

We were still coming out of the Little Ice Age (caused by changes in cosmic ray flux -- the most important cause they omit consideration of) in the early part of the 20th century.

The school of climatology based on astrophysics and planetary motion can easily make models that match data back millions of year. The school of climatology based on general circulation models of the earth's atmosphere struggles to make models that work on the scale of centuries or even decades.

The sun is blank. No spots. Winter is coming.

[Pietro]

"The sun is blank. No spots. Winter is coming."

That's what I'm worried about.

[spokeshave]

Life will become short, cold and brutish....

[sand88]

Do you know that realclimate.org is a far-left site funded by the evil Soros.

I have watched this site for years. It has many very well educated utterly EVIL mathematicians and utterly EVIL so-called scientists who directly attack "real" science by publishing articles filled with high-sounding B.S.

This site professes to be real science by real scientists but it is nothing but part of the leftist totalitarian's push to impose absolute control.

[sand88]

Please see my post#11. realclimate.org is one of the most evil sites on the web.

It is run by very smart leftists who use their intellect in the pursuit of pure evil.

They publish papers filled with high-sounding research. It is all lies and distortions.

They use their sophisticated sounding research to smear EVERY SINGLE paper and author who does "true" science.

realclimate.org is pure propaganda.

[bert]

The data is so large that science can’t actually grasp the variation of the variables

the real issue however is not that there has been some warming but what caused the warming

[Pete from Shawnee Mission]

David; Thank you for your analysis. I do not have the training in statistics to read the paper. I have heard of comic ray effect on cloud formation. (Smaller the particle, the greater the number of cosmic rays, the greater the cloud development I think?)

Your analysis coincides with the grade school general Science that I was taught in the 1960s, that we were in an interglacial warming period and at some point it would start to cool and we could expect new continental ice sheets to form and start racing down from the north! (Oh Canada!) I do not recall if they discussed causation, we did discuss sun spots and 11 year cycles.

I have a lot of respect now for the science taught in my grade school and high school.

[Steve_Seattle]

A few weeks ago my local newspaper featured a story claiming that researchers had found the FIRST EVER experimental evidence (evidence not based on computer models) that increased CO2 levels were related to global warming. What jumped out at me was the admission that this was the FIRST empirical evidence, even though we have been told for years that "the science is settled."

As for the research itself, my layman's mind struggled to understand it, but there were several red flags. The claimed energetic effect of the increased CO2 was so infinitesimally small that it was hard to see how it could be "driving climate change." And I noticed that the effect was not measured in units of TEMPERATURE, but of some other scientific unit (I forget which).

If I recall, the claimed energetic effect of the increased CO2 was roughly equivalent to the energy expended in snapping your fingers once every ten years, and this effect was said to apply to every square yard of the earth's surface.

[The_Reader_David]

Indeed, which I why I actually followed the link to the paper published in Nature and gave a critique of the actual scientific paper, not the propagandistic puff-piece about it from realclimate.org.