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| Data sources: UAH v6, UAH v5.6 and RSS |
UAH v6 is now a touch cooler than RSS and the trend isn't as steep. However v6 beta lines up better with RSS for the last couple of years.
You can read about it on Roy Spencer's blog - I've archived his description of the changes here.
That's weird. Spencer says it took them 3 years of work. So what have they been doing the rest of those 9 years? Waiting for a divine intervention?
ReplyDeletePPP
You mean they *adjusted* the data? the horror!
ReplyDelete"most of the software has been rewritten from scratch" - now that one can find the source code as of 2011, it can be said that rewriting it from scratch was probably a good idea. And a fairly painful process given the rather primitive state of the previous code. It should make it a lot easier for them to move forward in the future, though (assuming they've done a good job of rewriting it).
ReplyDeleteBTW this is yet another round of futzing UAH (though much more major than previous futzing, at least in regard to having rewritten the entire program) that vindicates the general impression that RSS's results have consistently been more robust than UAH's.
ReplyDeleteEven when UAH showed significantly more warming in recent years than RSS :)
Here's Spencer, in 2011:
ReplyDeleteAnyway, my UAH cohort and boss John Christy, who does the detailed matching between satellites, is pretty convinced that the RSS data is undergoing spurious cooling because RSS is still using the old NOAA-15 satellite which has a decaying orbit, to which they are then applying a diurnal cycle drift correction based upon a climate model, which does not quite match reality. We have not used NOAA-15 for trend information in years…we use the NASA Aqua AMSU, since that satellite carries extra fuel to maintain a precise orbit.
Now UAH v6 beta is *cooler* than RSS, which is extremely puzzling.
Somehow that never gets brought up when the fake skeptics trumpet the "pause" using the RSS data...
DeleteIt's a red flag indeed. No mention of those misgivings now. Let's go with spurious cooling, at least until Spencer releases his paper and refs.
DeleteV6 has some major changes from V5.6, in particular going from a multiple angle view calculation to one based on combinations of multiple channels in the same view for tropospheric temperatures, the LT or TLT that is the basis for most of the arguments regarding temperature records. With very large resulting changes in regional trends, particularly the US and the Arctic (where the recent trend is almost a factor of 2x smaller than in 5.6).
ReplyDeleteIf the UAH group has done their job well, the correlation with RSS may indicate issues with our understanding of upper tropospheric warming. If they haven't, and it may be a while before UAH releases the code for the beta V6, then there will be more nonsense from deniers.
Regardless, I predict that the climate denialati will trumpet this beta result just as much as they decried the recent Cowtan and Way temperature data which indicated larger trends than other records. And with complete blindness of the irony in clinging to "untested science" while complaining about every new paper supporting the science behind AGW...
Already done
DeleteI hadn't bothered to check the yammerheads, but you're entirely correct. Already done.
DeleteKR
DeleteWith very large resulting changes in regional trends, particularly the US and the Arctic (where the recent trend is almost a factor of 2x smaller than in 5.6).
That is... troubling. Polar amplification is apparently strongly expressed in Arctic surface temperatures so far as they are known. This beta really does worry me. But no doubt it will be subjected to considerable scrutiny by the expert community.
The hell it will, they are going to hide the cheese (the code) as long as they can and longer. Everybunny should hammer Dr. Roy on this and questions should be asked in Congress. How are Rabetts going to have any faith in the UAH hocus pocus without a good auditing?
DeleteExcept that UAH was pre-emptively gutted:
ReplyDeletehttp://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/mar/25/one-satellite-data-set-is-underestimating-global-warming
Perhaps with the latest changes UAH is no longer an outlier wrt tropical TMT trend?
ReplyDeleteWeng et al. (2014) Uncertainty of AMSU-A derived temperature trends in relationship with clouds and precipitation over ocean
ReplyDeleteMicrowave Sounding Unit (MSU) and Advanced Microwave Sounding Unit-A (AMSU-A) observations from a series of National Oceanic and Atmospheric Administration satellites have been extensively utilized for estimating the atmospheric temperature trend. For a given atmospheric temperature condition, the emission and scattering of clouds and precipitation modulate MSU and AMSU-A brightness temperatures. In this study, the effects of the radiation from clouds and precipitation on AMSU-A derived atmospheric temperature trend are assessed using the information from AMSU-A window channels. It is shown that the global mean temperature in the low and middle troposphere has a larger warming rate (about 20–30 % higher) when the cloud-affected radiances are removed from AMSU-A data. It is also shown that the inclusion of cloud-affected radiances in the trend analysis can significantly offset the stratospheric cooling represented by AMSU-A channel 9 over the middle and high latitudes of Northern Hemisphere.
A question: why aren't other groups doing their own satellite data set, rather than just Spencer and Christy?
ReplyDeleteRSS is doing just that, but they are dependent upon the same small set of satellite measurements (microwave emissions from oxygen proportional to temperature) as UAH. Their processing is, however, different, as is their determination of data quality for the various instruments.
DeleteThere have been other examinations of the data and algorithms used to derive temperature, such as the work from Stephen Po-Chedley and Qiang Fu, who have discussed potential (and primarily cooling) biases in the UAH data, but in essence everyone is working from the same primary data.
Actually, that's not entirely correct - in addition to microwave sounders there are (as discussed by RSS) other upper atmosphere temperature measures such as radiosondes, IR sounders, and GPS radio refraction, but each has different challenges with sampling coverage, sensitivity to clouds, changing instruments, and length of observations. It's difficult to draw direct comparisons.
DeleteOne point that hasn't been mentioned yet, is the elimination of the first 2 kilometers of air, the atmospheric boundary layer, from the lower troposphere, which might be accurate by textbook, in version 6 beta. In Roy Spencers blog article he writes about reducing the influence of "earths surface skin layer " temperature to LT temperatures, which sounds harmless enough, but means leaving a gap between measurement by thermometer and satellite msu starting at 2 kilometers up to 8 kilometers high. The LT of version 6 beta has become quite a different thing and should be regarded as such.
ReplyDelete"Earths surface skin layer"? Sounds like a bit of a contradiction for where a lot of weather happens. Plus how does that then relate to air temperature over the ocean, I am aware GIS etc "fudge" the sea surface air temperature a bit, but the fudge seems reasonable.
ReplyDeleteI did challenge some deniers a while back to demonstrate to me the lower troposphere estimates were a reasonable proxy for surface temperatures but I never got a response. So I guess I will just wait for a paper or two to be published.