Monday, April 14, 2014

March GISS Temp up by 0.25°C

GISS has posted its March estimate for global temperature anomaly, and it has risen from 0.45°C in February to 0,70°C in March. That balances the drop from January to February.

The TempLS comparison is murky this month, because of GHCN errors that I described here, here and here. My original estimate was a rise of 0.27°C, but after correcting a sign reversal at Sarh in Chad, that rose to 0.31°C. Then I found that NORD ADB in Greenland had September data instead of march; removing that brought the estimate back to 0.23°C. Then I found that other Greenland stations were also affected, and removing them all made the final estimate also a rise of 0.25°C. But I had little faith in it.

The comparison maps are below the jump.

Saturday, April 12, 2014

More GHCN QC errors

My previous post was on some specific problems in the March GHCN data (monthly TAVG QCU). At this stage that data is newly posted, and while the errors should not have passed QC, they will probably be corrected. I imagine that Greenland, for example, will be sorted once the CLIMAT form comes in.

But I'm finding data points going back, which should have been eliminated by QC. It seems there may be a general failure.

Significant GHCN errors in March 2014

Every month I run my least squares program TempLS on the data from GHCN V3 TAVG QCU and ERSST, when enough stations have reported, to estimate the month's temperature. A few days ago I posted for March. I found a substantial rise of 0.27°C.

As luck would have it, I had recently upgraded my program for showing the spatial pattern using spherical harmonics. So when the picture looked a bit strange, I checked and rechecked my revisions.

But in trying to analyse a spurious-looking cool spot in central Africa, I discovered that FORT-ARCHAMBAULT (now Sarh) in Chad had reported a very surprising -31.6°C. That was clearly a sign error, and fixing it removed the cool spot and raised the global average to 0.31°C. I traced the sign error to the CLIMAT form submitted by Chad.

The reason it had such a large effect is that it is an oasis in a data desert, and is weighted to represent a large area.

There was also an oddity with the map which was a very hot spot over N Greenland. When I looked into that, I found the March average at NORD ADB (81°N) was 4.3°C. It's usually about -30. This time I found that OGIMET says that no forms for March had been submitted.

So I looked further, and it appears that the data from September 2013 has been re-entered in the GHCN V3 QCU file for March 2014. Naturally this has a huge effect. Just omitting NORD ADB brought the global back to 0.23°C. But there were 5 Greenland stations, all with March averages of more than 4°C.

So I don't now have a reliable March estimate. I may calculate one without Greenland, but I think I'll wait for the errors to be fixed.

FWIW, with Greenland removed, the March average anomaly is 0.559°C, a rise of about 0.25°C. Almost back to where I started. But Greenland is important here.
Denmark has the same problem. 19.3°C in Copenhagen, March 2014! This time the March data is from July 2013.

Thursday, April 10, 2014

TempLS global temp unknown (yet) in March

Update  12/4. I have discovered another big error in GHCN for March, which makes all my estimates unreliable. See next post.

TempLS showed a large rise from February to March, more than balancing the large drop to February. The global average anomaly rose from 0.305°C to
0.616°C. The satellite indices showed little movement.

Update 11/4. As you'll see below the jump, there has been a little excitement this month, caused by what seems to be an error in GHCN. I originally posted a rise of 0.27°C and showed a plot with a huge cool spot in Central Africa. It turns out that FORT-ARCHAMBAULT Lat 9.10 Lon 18.40 is in GHCN as having a -31.6°C average in March. This station reports infrequently, but March 1998 and 1999 were both 31.5°C. Looks like a sign error. Assuming that, the global mean rises by 0.04°C, and the cold spot in the map goes away. This place is influential because there's not much other data in the region.
Update;  Here is the CLIMAT form submitted by Chad for Sarh (formerly FORT-ARCHAMBAULT). It shows -31.6°C.

Friday, April 4, 2014

Active viewer for Neukom et al proxies

A current paper in Nature from a long list of authors, including Neukom, Gergis and Karoly, on Southern Hemisphere proxies, is attracting attention. It's emphasis is on inter-hemispheric comparisons. The paper is here, the extensive SI here, and the data here. A press release is here.

There are critical posts at WUWT (here and here) and at Climate Audit.

So far I don't have an opinion on the study itself. But as with previous studies by Marcott et al and Pages2K, I have posted an active viewer, which gives easy access to plots and metadata. It's below the jump.

Wednesday, April 2, 2014

WebGL code: shaded grids and maps

In a previous post, I described a generic specification for a WebGL representation of continuum data on a spherical Earth that you can rotate like Google Earth. Examples were cited. The idea was to separate out the task of geometry specification from the nuts and bolts of WebGL (which were hidden). But you still had to specify the geometry.

In this post, I want to simplify three common tasks:
  • Drawing a shaded plot of gridded data.
  • Specifying a palette (there's a default for grid shading).
  • Adding a world map (just coast outlines)

It's reduced to the extent where you have to simply supply the gridded data as a comma separated list. In the example below, you can enter it by pasting into a text box, and press the "Plot New" button.

To enter a world coast outline map, just define an object with new type MAP. Nothing else required. I have also added a "title" attribute of an object. If supplied, the title will appear top left. It can be any HTML (including plain text).

Saturday, March 22, 2014

Paleo plotting - new draft climate plotter

In the previous post, in response to a challenge posed by Gavin at Real Climate for better ways of visualizing Phanerozoic climate data, I showed an interactive plot mechanism which could allow the user to easily vary the time scale in a single plot environment. The mechanics really come from the Moyhu climate plotter, and I've been meaning to work up a new version of that (and it's time to update with 2013 data).

A limitation in the V2 plotter was a restriction to annual data, and it generally covered the instrumental period. This reduced the data size, which is of some importance if all the data has to be downloaded. It also facilitates post processing - eg combining or smoothing series.

In V3 I've allowed all kinds of time data. I can overcome the size p[roblem by using XMLHTTPrequest, so only requested data is downloaded. And to allow the user to easily go from a century timescale to decade (for monthly data) or million years, I need to upgrade the user controls. Also to show monthly data, I will need an automatic updating system.

I'm posting a draft version here. It doesn't yet have request download, though download times are reasonable. And a lot of the post-processing doesn't yet work. Smoothing and regresion are patchy, and the calculate facility will probably go. But the basic plotting should work, and I'd be interested in comments, especially of datasets to include.