Using Albatross' references, I put together Christy Crock #3: Internal Variability.  Alby, I tried emailing you a few days ago, but didn't hear back.  Anyway, when this is ready to post, I'll also make it into the rebuttal to "it's internal variability".  Let me know if you have any comments.

Sorry Dana!!  I infrequently check my gmail.  I should have, you did warn me for goodness' sakes....very distracted right now.  I'll have a look at this sometime this weekend.

No prob Alby.  The URL has changed from the one I emailed you, so check the link above when you have time.

Gonna have to address the AMO and PDO in this subject too won't you?

Hi Dana,

Have a few minutes here while Amy is in front of the radiation tube (aka TV).

Foster et al. (2010) also has a good discussion.  From Foster et al. (2010)

“It has been well known for many years that ENSO is associated with significant variability in global mean temper- atures on interannual timescales. However, this relationship (which, contrary to the claim of MFC09, is simulated by global climate models, e.g. Santer et al. [2001]) cannot explain temperature trends on decadal and longer time scales.

 In fact, the general rise in temperatures over the 2nd half of the 20th century is very likely predom- inantly due to anthropogenic emissions of greenhouse gases [IPCC, 2007].”

And 

“Jones [1989] found that roughly 30% of the variation in global annual mean surface temperature could be explained by the SOI over the period 1867-1988 (with the SOI leading temperatures by 6 months). Wigley [2000] found that the lower tropospheric warming trend over the 21 year period 1979-1999 increases from 0.15◦C/decade to 0.25◦C/decade after the joint impacts of ENSO and vol- canic aerosols are accounted for and removed. A related analysis by Santer et al. [2001] found trends of 0.210 to 0.25◦C/decade at the surface to 0.056 to 0.158◦C/decade in the lower troposphere, after the joint removal of both factors. Using Nin ̃o 3.4 region (170◦-120◦W, 5◦N-5◦S) sea surface temperature (SST) anomalies as an index of ENSO, Trenberth et al. [2002] found a residual global mean surface temperature trend of 0.4◦C over the period 1977-1998 after ENSO impacts alone are removed. More recently, Thomp- son et al. [2008] removed an estimate of global temperature variations associated with both ENSO and the so-called cold ocean/warm land or “COWL” pattern of extratropical tem- perature variation, and found a residual global mean surface warming of 0.4◦C over the 1950-2006 period.

In all of these previous analyses, ENSO has been found to describe between 15 and 30% of the interseasonal and longer-term variability in surface and/or lower tropospheric temperature, but little of the global mean warming trend of the past half century.”

IIRC, Tamino has undertaken a similar analysis removing the effects of solar, volcanoes and ENSO.  

I was wondering wether or not brief mention should be made of the several failed attempts by "skeptics" in the literature to attribute the warming over the past 130 years or so to natural cycles.  For example, McLean et al.  Someone will undoubtably bring up Spencer and Braswell (2008), so might be prudent to nip those ones (also 2010) before "skeptics" have a chance try and muddy the waters.  Maybe Barr Bickmore's analyses could come in useful here.

Was the offending statement made in Christy's written testimony or verbally during the hearing?  Reason that I ask is that he may have added some useful information in his written statement to back up his assertion, and that would be interesting to see, b/c it might dig him even deeper into his hole depending on what sources he cited or what reasoning he used.  I would track it down now, but i am pressed for time today...sorry.

Thanks Alby.  The quote is from Christy's verbal testimony, but I also looked over his written testimony, and he really didn't have any more details about internal variability there either.

Okay I added a section on PDO with references to Barry's 3 part series and the 'cooking a graph' post at RC.  I also added a discussion of Foster 2010.  It's getting pretty beefy - I wonder if this is detailed enough to be the Advanced rebuttal to 'internal variability'?

Hi Dana,

Just browsing the AMS journals to make sure we have not missing any significant papers and stumbled on this review paper from 2005 (I have emailed it to you and John).  They conclude that:

"The influence of external forcing is also clearly discernible in reconstructions of hemispheric-scale temperature of the last millennium. These observed climate changes are very unlikely to be due only to natural internal climate variability, and they are consistent with the responses to anthropogenic and natural external forcing of the climate system that are simulated with climate models. The evidence indicates that natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century, and that a large fraction of the warming over the last 50 yr can be attributed to greenhouse gas increases. Thus, the recent research supports and strengthens the IPCC Third Assessment Report conclusion that “most of the global warming over the past 50 years is likely due to the increase in greenhouse gases.”

Pretty much the opposite of what Christy is claiming.  Alas, they, like Christy, do not provide numbers....annoying.  

More interesting papers suggesting that the current warming is unusual and/or unlikely natural:

Zorita et al. (2008)

"We use a more simple approach to assess recent warming at different spatial scales without making explicit use of climate simulations. It considers the likelihood that the observed recent clustering of warm record-breaking mean temperatures at global, regional and local scales may occur by chance in a stationary climate. Under two statistical null-hypotheses, autoregressive andlong-memory, this probability turns to be very low: for the global records lower than p = 0.001, and even lower for some regional records."

Rybski et al. (2006)

"Accordingly, the hypothesis that at least part of the recent warming cannot be solely related to natural factors, may be accepted with a very low risk, independently of the database used."

Bertrand and van Ypersele (2002)

"Our results suggest that neither the individual responses nor the combined natural or anthropogenic forcings allow one to reproduce all of the recorded major temperature fluctuations since the latter half of the 19th century. They show that these temperature variations are the result of both naturally driven climate fluctuations and the effects of industrialization.

Since we've already got quite a few quotes in there, maybe we could just list these other papers arriving at essentially the same conclusion after the Wigley and Raper quote, before "Since prior studies have consistently shown that natural variability cannot account for the observed global warming trend..."?  That way we convey the consensus in the literature without having quote after quote after quote.

Hi Dana,

OK, finally reading the post.  Here are my thoughts as I go through, my comments/suggestions in blue:

1) "One of the most widely-circulated papers on natural variability is Swanson et al. (2009) which John has previously discussed."

Maybe elaborate "on the impact of natural variability on the global temperature record" or "on the impact of natural variability on 20th century climate change"  

2) "Swanson 2009"

Consider "Although Swanson et al. (2009)..."

3) "As you can see, over periods of a few decades, internal variability...."

This is a bit of a weak spot, b/c the "skeptic' will yell, well it was modelled and we know the models cannot reproduce internal climate variability.  Anyhow, to be clear, perhaps say "modelled internal variability".

4) "its short-term warming and cooling influences tend to average out"

Maybe, "its transient warming and cooling influences tend to average out in the long term, so...." 

5)  Maybe have a lead in sentence before DelSole?  How about "Here follows a short discussion of some key papers on the role of natural versus anthropogenic contribution to the observed warming."

6) ".....it cannot account for the 0.8°C warming that has been observed in the twentieth-century spatially averaged SST"

Period missing after "SST".

7) "Christy's statement that natural variability can account for the recent warming"

Maybe rub it in here, he definitely suggests 'all' the warming could be produced by natural excursions.  So how about "Christy's statement that natural variability can account for all the recent warming"

8) "it is consistent  for example"

Delete extra space between "consistent" and "for".

9)  "it begs the question,"

My grammar geek wife and father-in-law tell me that the correct phrase to use in this case is "it raises the question". Also, unless speaking about time, the sentence should ideally start with "Given that" or "Because"....sorry to be pedantic.

10) "..on what is Christy basing his claims..."

His "...his (unsubstantiated) claims to the contrary? 

11) "some unknown mechanism causes cloud cover to change"

Is he referring to an internal mechanism?  If so, maybe specify that.

12) "the current global warming"

We must be careful here.  By "current" does he mean the satellite record, instrument record, since 1970?

13) "such as the cooling upper atmosphere"

Maybe be more specific "..cooling stratosphere".  In meteorology we often talk of the upper troposphere as the "upper atmosphere" and some boundary layer guys/gals consider anything in the free atmosphere above the PBL to be the "upper atmosphere".

14) "and he higher rate of warming at night than during the day."

Should read "and the higher....".

15) "In order for internal variability to account for the recent warming,"

Again, probably safe to be specific as to which warming we are referring, I'm assuming the instrument record.

16) "But as discussed in Swanson 2009"

Swanson et al. (2009)

17) "This is a bit of a Catch-22 for Spencer's hypothesis; it effectively requires that climate sensitivity is simultaneously both low and high."

Gosh darn it Dana, you beat me to it.  This is "Spencer's great contradiction" that I was referring to earlier.  I was also thinking about his bizarre "internal climate forcing' allegedly explaining the warming, while he has also written blog posts in which he determines TCR to be +1.7 K for doubling CO2 based on his analysis of the UAH data following Pinatubo.  This is a logical fallacy, you can't argue that ECS is low, and at the same time demonstrate that TCR is =1.7 K (ECS of ~=2.5 K), and then also claim that the system is very sensitive to internal climate variability...ugh what a mess.  Maybe this requires a blog post of its own.

18) Maybe expand ENSO and PDO in the heading ["ENSO (El nino Southern Oscillation)"], where it is first introduced, and then no need to do so in the text. 

19) "Although he is very coy about the physical mechanisms behind his theory..."

I'm sure you meant to say "hypothesis' and not "theory".

20) "Further, as we  have previously discussed, PDO physically cannot..."

Extra space between "we" and "have".  Also, maybe say "..., like ENSO,the PDO physically cannot" 

21) "the oceans would cool as a consequence of warming surface air."

I'm a little uncomfortable with this statement-- it is not clear to me if the oceans warm the air or if the air warms the oceans. Also, to be clearer, perhaps say "as a consequence of them warming the overlying air"

22)  I think that we need to beef up the conclusion a tad.  Below is just my suggestion (my changes are bolded), feel free to edit:

"In conclusion, there is simply no supporting evidence or supporting science (physics?) behind Christy's unsubstantiated claim that the global warming observed during the instrumented record could all simply be attributed to internal variability.  Studies on the subject consistently show that internal variability does not account for more than ~0.3°C warming of global surface (and tropospheric?)  temperatures over periods of several decades.  Internal variability also tends to average out over longer periods of time, as has been the case over the past century, and cannot account for more than a small fraction of the observed warming over that time.  Spencer's hypothesis cannot account for numerous observed changes in the global climate that are unique to forcing from elevated GHGs, does not have a known physical mechanism, and there are simply better explanations for interactions between global temperature and cloud cover.

Dana @2:41 pm,

You are right Dana-- having read the piece adding the other quotes would probably make it a little too long and the message redundant.  One option is to simply add a sentence at an appropriate spot saying something like "Other research by Zorita et al. , Rybski et al. (2005) and Benett et al. (2005) has come to similar findings as Wigley and Swanson et al.".  And then to hyperlink to the respective abstracts.  Anyhow, not a deal breaker, just an idea.

Now off to bed for me.

Hi Dana,

Kate recently had a nice post here at SkS on this issue-- perhaps worth perusing.  I gave it a quick scan, and think that we have covered all the bases.  I do like the way she explains the importance of 'fingerprints':

"Firstly, the hypothetical natural cycle would have to explain the observed "fingerprints" of greenhouse gas-induced warming." 

In our essay, we could say, "Observations show that Spencer's hypothetical natural cycle does not explain the observed "fingerprints" of greenhouse gas-induced warming".

Someone ought to consolidate all the posts tackling natural variability, excluding my nominal contribution, some really good work has been done.

Lots of good comments there, Alby.  I think I incorporated them all.  We already had a similar statement about observed GHG 'fingerprints', but I also added a link to Kate's post in there.

I like the idea of doing an all-encompassing post on natural cycles and variability.  You could even throw in "it's the Sun" and "it's galactic cosmic rays" in there.  The main focus could be the fact that none of these natural effects can account for the GHG 'fingerprints', and physically they can't explain the observed warming.

I also like the idea of doing another post going more in depth into Spencer's contradiction.  Do you know where he said the transient sensitivity is 1.7°C?  That would really be a killer to his hypothesis.

Hi Dana,

No worries, you are welcome-- thanks for doing the lion's share on this.  

I informed you a bit about Spencer, he did look at Pinatubo, but his estimate of TCR was based on TSI data analysis.  The title, of course, is designed to appease the 'skeptics':

"Low Climate Sensitivity Estimated from the 11-Year Cycle in Total Solar Irradiance"

At the low end of the range stipulated in the literature maybe. I maintain that his analysis is an estimate of TCR and not EQS, but maybe I have that wrong.  Anyhow, a TCR of ~ +1.7 is not "low" in my books. 

It’s just occurred to me that Christy might not mean global warming is caused by internal variability. When he says “excursions that we’ve seen recently” he might be just referring to temperatures in the last decade or so.

No worries James, the questions phrased to him were specifically about long-term temperature trends.  Fortunately we've got the context of Christy's responses and the questions which elicited them on the record.