Monday, July 3, 2017

June NCEP/NCAR down 0.16°C

In the Moyhu NCEP/NCAR index, the monthly reanalysis average fell from 0.40°C in May to 0.241°C in June, 2017. This makes it the coolest month for nearly two years - since 0.164°C in July 2015. Even so, it was still the third warmest in the record for that index, though I comment caution in compare values decades, because of lack of homogeneity. It was only just behind 2013 (0.249) for second place. It's the first time for nearly two years that a month fell behind an earlier corresponding month other than 2016.

The main cool spot was Antarctica, and the main reason for the drop was that, as well, the Arctic dropped back to average, with Siberia mixed. Europe was warm.

in other (tropospheric) news, RSS has brought out a V4 version of TLT, described in a J Climate paper by Wentz and Mears here. I'll start using it for this month's reporting. I was actually wondering whether they would, since the trend seems to be more toward quoting TMT and TTT. AS has been the pattern with V4, the low trend that RSS V3.3 showed until recently, which gave rise to umpteen pause stories, has come closer to other records, mainly, they say, due to a revised diurnal correction. Here is their abstract:

A satellite-derived lower tropospheric atmospheric temperature dataset using an optimized adjustment for diurnal effects

Carl A. Mears and Frank J. Wentz
Remote Sensing Systems, 444 Tenth Street, Santa Rosa, CA, 95401

Temperature sounding microwave radiometers flown on polar-orbiting weather satellites provide a long-term, global-scale record of upper-atmosphere temperatures, beginning in late 1978 and continuing to the present. The focus of this paper is a lower-tropospheric temperature product constructed using measurements made by the Microwave Sounding Unit channel 2, and the Advanced Microwave Sounding Unit channel 5. The temperature weighting functions for these channels peak in the mid to upper troposphere. By using a weighted average of measurements made at different Earth incidence angles, the effective weighting function can be lowered so that it peaks in the lower troposphere. Previous versions of this dataset used general circulation model output to remove the effects of drifting local measurement time on the measured temperatures. In this paper, we present a method to optimize these adjustments using information from the satellite measurements themselves. The new method finds a global-mean land diurnal cycle that peaks later in the afternoon, leading to improved agreement between measurements made by co-orbiting satellites. The changes result in global-scale warming (global trend (70S-80N, 1979-2016) = °0.174 C/decade), ~30% larger than our previous version of the dataset (global trend, (70S-80N, 1979-2016) = 0.134C/decade). This change is primarily due to the changes in the adjustment for drifting local measurement time. The new dataset shows more warming than most similar datasets constructed from satellites or radiosonde data. However, comparisons with total column water vapor over the oceans suggest that the new dataset may not show enough warming in the tropics.

I have updated the data link in the source table.


  1. The same people who were thrilled to see UAH adjust the LT trend downwards in v6 are now furious that RSS has adjusted the trend upwards in v4. Clearly sauce for the goose is not good for the gander.

  2. At CargoCult Etc. I used to call the satellite surface temperature record garbage. Everything pointed to it being wrong. Gold standard my butt.

  3. July will be interesting for Niño 3.4. The models appear to be predicting a cooling. So far it has stayed in high neutral. The big number this month, to me anyway, will be 2nd quarter OHC.

    1. JMA's Nina prediction goes the same way:

  4. Thanks Nick for the reference to Mears & Wentz' new TLT product, I'm a bit lazy actually.

  5. According to Karsten Haustein's page, the 90N-60S area had actually a higher anomaly in June as in May, so all the cooling is due Antarctica.
    Since 2012 there is a series of very cool June and July in Antarctica, up to 3°C below the 1981-2010 reference period in this months there.
    If this is similar in the GISS, I expect 0.70 for June.