How much out of whack is the UAH temperature data set? (Revamped)

POSTSCRIPT: See postscript below (added 7:09 pm Monday 7 June 2013 AEST)

UPDATE: See addendum below (added 10:27 pm Friday 7 June AEST)


Has the day of reckoning arrived?

I see that Anthony Watts has a post up on WUWT with a chart from Roy Spencer and John Christy that compares UAH data to CMIP5 model runs.  It's titled: Climate modeling EPIC FAIL – Spencer: ‘the day of reckoning has arrived.’

Roy Spencer has the same article on his blog, but the comments are dominated by hard-core deniers (like "Cohenite" - an Australian lawyer who is one of the more extreme and obnoxious deniers with nothing to say and who uses a lot of words to say it). I gave up trying to glean anything useful from the discussion there.  Needless to say there's almost nothing useful in the comments on WUWT.  (I noticed the Roger Pielke Sr had piled on in his usual clumsy fashion.)

I originally miscontrued the WUWT article and charts as referring to global surface temperatures. However, in the comments below, Ryan pointed out my error.  The examples on WUWT are only for the tropics and only for the mid-troposphere in the tropics.  I was going to leave my post with all the edits as is, but it's too messy.  So I've revamped it.

Here is the chart posted on WUWT. (Click to enlarge.)

I found this paper by Stephen Po-Chedley and Qiang Fu that seems to be more or less on topic, though it appears to be discussing the difference between tropical upper troposphere and lower middle troposphere.  They indicate it's not known if it's the models or the data.  The paper also references other papers on the topic, so it seems to be a well-known issue at least as it relates to the tropical upper troposphere relative to the lower-middle troposphere.  Here are some excerpts  (my bold and para breaks):

Recent studies have examined tropical upper tropospheric warming by comparing coupled atmosphere–ocean global circulation model (GCM) simulations from Phase 3 of the Coupled Model Intercomparison Project (CMIP3) with satellite and radiosonde observations of warming in the tropical upper troposphere relative to the lower-middle troposphere. These studies showed that models tended to overestimate increases in static stability between the upper and lower-middle troposphere.

We revisit this issue using atmospheric GCMs with prescribed historical sea surface temperatures (SSTs) and coupled atmosphere–ocean GCMs that participated in the latest model intercomparison project, CMIP5. It is demonstrated that even with historical SSTs as a boundary condition, most atmospheric models exhibit excessive tropical upper tropospheric warming relative to the lower-middle troposphere as compared with satellite-borne microwave sounding unit measurements. It is also shown that the results from CMIP5 coupled atmosphere–ocean GCMs are similar to findings from CMIP3 coupled GCMs.

The apparent model-observational difference for tropical upper tropospheric warming represents an important problem, but it is not clear whether the difference is a result of common biases in GCMs, biases in observational datasets, or both.

And more here from the same paper.  Seems to me Christy and Spencer need to be a bit cautious or they might end up with egg on their faces.  I notice Christy and Spencer have stuck a couple of balloons in their charts, so what they might be doing is a blog justification, saying their satellite readings are accurate.  However this paper was written in the knowledge that radiosonde data also differs from the models:

The effect of internal uncertainty related to the dataset construction is large (Christy et al 2003, Zou et al 2009, Mears et al 2011), so it is possible that the differences between GCMs and observations are byproducts of the merging procedure for satellite observations. It is unclear why the interannual amplification ratio should be different from the decadal amplification ratio, but MSU observations show less amplification on decadal time scales (figure 4). We also note that NOAA T24 has larger upper-middle tropospheric warming compared to RSS and UAH (tables 1 and 2) and that other analyses that use temperature trends derived from wind measurements have found that historical tropical tropospheric warming is largely consistent with GCM results (Allen and Sherwood 2008). In general, the comparison of model and observed trends over a relatively short time period has large uncertainties, so some of the discrepancy noted here may also be related to the length of the datasets.

Brian over at Eli Rabett's place also speculated about the above paper and the accuracy of the UAH temperature data set back when it first came out.

In the comments BBD points out that UAH is similar to surface-based data series for the tropics.

This is a bit off topic, but RealClimate had an article "Verification of regional model trends" only a short while ago. It's worth a read.  Basically the models are getting better but are still not reliable for many things at the regional level.  Here is an excerpt:

All these studies reach similar conclusions. For temperature: the ensemble is reliable if one considers the full signal, but this is due to the differing global mean temperature responses (Total Climate Responses, TCR).

When the global mean temperature trend is factored out, the ensemble becomes overconfident: the spatial variability is too low. For annual mean precipitation the ensemble is also found to be overconfident. Precipitation trends in 3-month seasons have so much natural variability compared to the trends that the overconfidence is no longer visible.

Addendum

What game is John Christy playing?

It's worth reading the comments below.  For example, BBD has pointed out that Christy compared his tropical mid-troposphere data with the most extreme scenario, RCP 8.5 among other useful observations. Wotts up with that blog made an interesting comment about questions raised by David Appell.

John Christy seems to be playing a game.  Maybe it was a reaction to the above paper and maybe to the 97% consensus paper and the Marcott et al study also.

What game is Roy Spencer playing?

While Spencer is playing the conspiracy theorising game (à la Lewandowsky), whining on his blog:

Hundreds of millions of dollars that have gone into the expensive climate modelling enterprise has all but destroyed governmental funding of research into natural sources of climate change. For years the modelers have maintained that there is no such thing as natural climate change…yet they now, ironically, have to invoke natural climate forces to explain why surface warming has essentially stopped in the last 15 years!

Forgive me if I sound frustrated, but we scientists who still believe that climate change can also be naturally forced have been virtually cut out of funding and publication by the ‘humans-cause-everything-bad-that-happens’ juggernaut. The public who funds their work will not stand for their willful blindness much longer.

First, as Barry Bickmore demonstrates, it's ridiculous to suggest that any climate scientists, whether a 'modeler' like him or anyone else, maintains there is no such thing as natural climate change.  How does he think scientists have worked out what forces and feedbacks affect climate?  It's just as ludicrous to suggest any particular aspect of climate studies are rejected on the basis of whether it is a 'natural' force or a 'supernatural' force :D  Okay - maybe a study with the objective of determining how God influences climate wouldn't get much of a hearing.  Spencer discounts the entire field of climate science if he thinks 'natural forces' aren't the basis of it all.  Whether it's the way greenhouse gases affect climate, studies of clouds, oceans, the biosphere or any other aspect.  All of it is "natural".  What is arguably unnatural is the way humans are affecting the 'natural' climate by digging up carbon and putting it into the air at such a fast rate. Probably more in a single year than one or two supervolcanoes would emit.

Not only that, but one has to ask Roy Spencer, just what do his satellites cost the taxpayer?  What about the salaries of himself and John Christy and any offsiders they may have, their administrative support and corporate overheads, and all their accommodation, equipment, conference attendances, travel allowances and the like?

Chart Comparisons

I've put together some charts comparing UAH near surface** to UAH mid-troposphere** and GISTemp**.  Click to see larger versions.

1. Northern Hemisphere

2. Southern Hemisphere

3. Tropics - note GISTemp tropics is 24N-24S, whereas I believe UAH is 30N to 30S, but I'm not sure about that.

I can't say much about them except to note that UAH in the southern hemisphere in particular (and the tropics to a lesser extent) has much greater extremes than does GISTemp (1979-83, 1998-99, 2008 and 2010).  This surprises me, because I would have thought the southern hemisphere ocean would have modified the swings a great deal.  In fact if you look at the southern hemisphere overall, UAH looks to be quite a bit different to GISTemp.  

Also, the early years in UAH don't accord with GISTemp very well in the tropics or the southern hemisphere.

PS I'm not in a position to know how accurate UAH data is over time.  However the suggestion that Christy used RCP 8.5 on purpose, and possibly when it's not appropriate to run it back to a single point and aligning it with the UAH point, is persuasive.

I also note that in all three of the above charts, in the early part and in 1979 in particular, GISTemp is quite a bit lower than UAH, whereas in later years they line up better.  Thus UAH temps haven't risen as much since 1979 as the surface-based instrumental record.  What Christy did was align the model mean with the first UAH temperature data point (1979).  If those first satellite calculations were in fact lower (with a similar trend to the land-based records), then the UAH temperatures would line up with the model means more closely.  That again suggests the comparison that Christy makes may be invalid. (Sou 7:09 pm Mon 10 June 2013 AEST.)

**Data sources: GISTemp, UAH mid-troposphere, UAH near surface