Tuesday, October 18, 2016

GISS down 0.06°C in September

GISS is up from 0.97°C in August to 0.91°C in September. This compares with a larger fall of 0.12° in TempLS mesh, and contrasts with the small rise in the NCEP/NCAR index. It is still the warmest September in the record (just ahead of 0.90°C in 2014). It really hasn't cooled since May, and a record hot 2016 is ever more likely.

As I mentioned in the TempLS post, the dominant effect on recent changes is Antarctica. TempLS rose strongly in Aug, and dropped in Sep; GISS responded in the same way, but to about half the extent. I expect NOAA and HADCRUT to be less affected again.

I'll show the map comparisons below the fold. The updated comparison plots with 1998 are here

Friday, October 7, 2016

TempLS Surface temperature down 0.12°C in September

The Moyhu TempLS mesh index fell in September to 0.736°C, down from from 0.855°C in August. That still makes it the hottest September in the record. TempLS grid fell 0.04°C fro 0.785°C to 0.744°C. The recent ups and downs mainly relate to Antarctica, which was very cold in July, very warm (relatively) in August, and about normal (on average) in September. TempLS mesh followed this closely, while TempLS grid regards a lot of Antarctica as missing values, and so downweights the changes. This is reflected in the other indices - GISS and BEST rose like TempLS mesh, while NOAA (0.05°C) and HADCRUT changed mush less. I would expect GISS to also drop this month, but NOAA and HADCRUT maybe not.

In terms of regions, there isn't much unusual outside Antarctica. Siberia, Europe, E US and Alaska fairly warm, with just Australia on the cold side. I can vouch for that, though we were on the fringe of the cold region shown. With other indices, UAH lower trop was steady, while RSS rose by about 0.1. All seem set for a record warm 2016.

On housekeeping, Google says they are looking into the blogroll issues - still out.

The map is below the jump; report at the data page here.

Monday, October 3, 2016

Reanalysis index up 0.047°C in September

The Moyhu NCEP/NCAR index rose in September to 0.475°C, up from 0.428 in August. This brings it back to about the level of May. There was then a drop to June, followed by a gradual increase to now. This seems to be associated with ENSO-neutral conditions. And as usual recently, it was the hottest month of its kind in the record. Next month will test this trend of records, since Oct 2015 was very warm.

On other matters, I apologise for the absence of blogroll, search etc. Apparently Google Blogger has recalled them for repair. I'm told they should reappear soon.

Saturday, September 24, 2016

Twelve coin problem

Things are a bit quiet in climate blogging - so with a weekend coming I'll honor my ancient promise of diverting to some recreational math. I saw a few weeks ago a mention at Lucia's of the old twelve coin problem. Twelve coins, one of which is fake and of different weight to the others, and to be found with three weighings on a balance (Update: the usual spec, as here, is that you also have to say whether it is heavier or lighter). This first came to prominence in WWII, when it was said to have become a distraction to the war effort in places like Bletchley Park, leading to suspicions that it had been planted by the Germans. A suggested counter was for the RAF to drop it on Germany.

I first encountered it when I started University; it was posed in circumstances where I was expected to be able to solve it, and I was embarrassed. A year later, I went to a lecture on information theory (newish in those days). I was struck by the proposition, helpful in later years, that the information in a result was a function of prior uncertainty. So that is the clue - each weighing should be arranged so each of 3 outcomes was as near equally probable as could be managed, maximising prior uncertainty. Then I could solve it easily, and also versions with more coins.

The basic constraint is that in N weighings there are 3N possible outcomes, while with n coins, there are 2n situations to resolve, since only once coin is false, and could be heavy or light. So for 12 coins, there are 24 possibilities and 27 outcomes of 3 weighings, so it is tight but possible. An alternative to the equiprobable outcome method is a requirement that each weighing should be so that each outcome was resolvable with the remaining weighings.

When I saw it mentioned again, I started thinking of a constructive algorithm that would also prove feasibility for all cases where there were enough results to theoretically resolve. I had an idea of describing the proof, but then my other recent hobby of Javascript programming seemed it might help. So I've made an interactive version (below) with the information needed to solve.

Tuesday, September 20, 2016

CRUTEM (HADCRUT) versions are documented and accessible

I have encountered at WUWT ongoing complaints about HADCRUT 4 updates. It is currently in a thread here, but goes back to an earlier post here. The complaints typically say that the new versions always raise current anomalies, and suggest that they are poorly documented. In fact, the changes are extensively noted; see directory here.

In the earlier thread Tim Osborn commented here, to say mainly that the changes were due to changes (mainly additions) to station data, and listed the particular additions to HADCRUT 4.3. He also later made the important point that there is a good reason why the trends rise with new data. HADCRUT is a land/ocean set, but the empty cells are mainly on land, and the new data allows some of them to be filled. HADCRUT is an average by grid (area-weighted), in which cells without data are simply not included. That has the effect of assigning to them the global average, which is dominated by sea temp. If new stations assign to empty cells genuine land values, that will increase the trend, because land is warming more rapidly. HADCRUT had artificially low trends because of this missing value policy, as was remedied by Cowtan and Way (2013) - discussed here in a series of posts, with links here.

But another feature of HADCRUT transparency is insufficiently appreciated. For Ver 4, at least, they give a complete listing of station data for each version, with each station file documented. Here is a typical version file; it is for 4.4, but just change that URL to 4.2 or whatever you want. Each links to a zip file of the station data for that version (except for Poland), which has a URL like http://www.metoffice.gov.uk/hadobs/crutem4/data/previous_versions/ I'm spelling out the URL because if you click on it, it will immediately download about 18Mb. But again, you can edit for other versions.

I couldn't find, though, inventory files, except for 4.5. But it's easy enough to make them from the file headers. So I've done that, and placed the zipfile here (612 Kb). It has a csv file for each of 4.2-4.5, and the columns have 3 letter abbreviations meaning:
  • num - a unique HAD station number
  • nam - name of station
  • cou - country name
  • lat - latitude in deg
  • lon - longitude in deg
  • alt - altitude in m
  • sta - start year of data
  • end - end year
  • sou - source id code
UEA has an explanations file here, which is the best source I have found for the source id codes, but unfortunately it dates from 2012, and there is a new one pretty much with each new dataset that has come in. I'd be glad to hear of something more recent. It isn't really a problem, because the later numbers are in order of addition, so are easy to work out. Note that the files are in number order, but countries are not necessarily consecutive blocks.

So I thought I would just post this information, so that people who really want to know what HADCRUT is up to can look it up. I may in future produce a Google map.

Friday, September 16, 2016

Arctic ice freezing, Antarctic melting

As many have now noted, Arctic sea ice stopped melting rather abruptly after 6 September, and has lately been freezing quite rapidly. The pattern is quite similar to last year, but a few days earlier. In both JAXA and NSIDC the minimum was lower than 2007, but higher than 2012, so in secoind place (but in NSIDC, only just).

Meanwhile, more surprisingly, Antarctic ice has been melting strongly for six days, and now stands below the other years of this century at least, for this time. From the radial plot here, I'll show the NSIDC plots for recent days. The plot spans most of September.


The red curve is 2002. Orientation same as NH.

Thursday, September 15, 2016

Thermodynamics of climate feedback

I have been describing and responding to blog arguments about climate feedback and circuit analogies here and here. The arguments have continued, and they do provoke ideas. I'm going to write some down in this post.

The usual circuit analogy has surface temperature as voltage, and TOA flux as current. I showed in the first post that the feedback, including Planck, could be regarded as conductances. It's interesting to probe what this might mean. The units are watts/m²/K, which are actually the units of entropy/s/m². Does entropy make sense?

I wrote about entropy and atmospheric fluxes here and here. Sunlight (Q=240 W/m² global average after albedo) arrives, does things, loses the capacity to do work, and eventually leaves as thermal IR. It has accumulated entropy, or if you prefer, lost free energy. You might think that with a heat sink at 3K (space) the heat could go on doing work. But in fact you need a miniumum temperature to radiate that flux to space, which for Earth is about 255K (note 1). That constitutes a resistance. To get Q=240 W/m² to flow to space, you need 255K (voltage).

In our system, that resistance, inverted, is the Planck conductance, or feedback. It represents the entropy flux to space. It's really the maximum or optimal entropy flux for 240 W/m². In fact, emission to space comes from a rather large component at about 225 W/m², from GHGs, and some from the surface at average 288K (atmospheric window). We know uniform blackbody emission exports most entropy for a given flux, because any variation means that more entropy could be generated by transporting heat from the hotter parts to cooler.

This lies behind a supposed failing proclaimed in a WUWT post of Lord Monckton. The Planck feedback calculated for the Earth at 255K, the temperature for uniform BB emission of 240 W/m², is 3.75 W/m²/K, and Lord M thinks they erred by not using it. But its inadequacy has been long known, and I wrote in the previous post how Soden and Held (among others) did a thorough study with GCMs to get a value of about 3.2 W/m²/K. The difference is usually attributed to absorption in the atmosphere, but thermo gives an alternative viewpoint, which I find more useful. It is the entropy export reduced by the non-uniformity (sub-optimality) of apparent emission temperature.