Saturday, August 15, 2020

GISS July global down by 0.03°C from June.

The GISS V4 land/ocean temperature anomaly was 0.89°C in July 2020, down from 0.92°C in June. That compares with a 0.039deg;C fall in the TempLS V4 mesh index. As with TempLS, Gistemp still had July tied with 2019 as the warmest July in the record. Jim Hansen's report is here.

As usual here, I will compare the GISS and earlier TempLS plots below the jump.

Here is GISS V4

And here is the TempLS V4 LOESS-based plot

This post is part of a series that has now run for seven years. The GISS data completes the month cycle, and is compared with the TempLS result and map. GISS lists its reports here, and I post the monthly averages here.
The TempLS mesh data is reported here, and the recent history of monthly readings is here. Unadjusted GHCN is normally used, but if you click the TempLS button there, it will show data with adjusted, and also with different integration methods. There is an interactive graph using 1981-2010 base period here which you can use to show different periods, or compare with other indices. There is a general guide to TempLS here.

The reporting cycle starts with a report of the daily reanalysis index on about the 4th of the month. The next post is this, the TempLS report, usually about the 8th. Then when the GISS result comes out, usually about the 15th, I discuss it and compare with TempLS. The TempLS graph uses a spherical harmonics to the TempLS mesh residuals; the residuals are displayed more directly using a triangular grid in a better resolved WebGL plot here.

A list of earlier monthly reports of each series in date order is here:

  1. NCEP/NCAR Reanalysis report
  2. TempLS report
  3. GISS report and comparison with TempLS


  1. I update my prediction for GISS temperature anomaly using data up to Jul20.
    JJA20 0.92+-0.05
    SON20 1.03+-0.14
    J-D20 1.05+-0.05
    DJF21 1.06+-0.23
    MAM21 1.03+-0.20

    Now the prediction gives a 89 % chance of a new record this year.
    Note that this may be on the high side if a La Nina develops, because it still does not use newer ENSO data yet (only old MEI).

  2. East Pacific warm water volume is now clearly in La Nina territory, which throws a spanner in the record hunt.

    Taking a simple approach of looking at 2016 as an analogous end-of-year descent into La Nina, first I take the TempLS estimate to suggest GISS August will be 0.85, then average September-December 2016 at 0.89. Assuming an underlying trend of 0.025C/yr that would suggest September-December 2020 should average about 0.99. That would produce a 2020 annual average of 1.03C. One thing I've noticed is that recent GISS estimates have tended to shift upwards as lagged data has come in over time, so it could happen that 2020 will not initially be above 2016 but will be a year or two later.

    That calculation assumes the developing La Nina does not deepen any further, but it could do. If it does then a 2020 record becomes <50% chance plus low chance of a record in 2021.

    In other milestone news, even with a strong La Nina it looks very likely 2020 will be the first non El Nino year to surpass 1998 in the UAH TLT record. A final wave goodbye to 1998 as a reference year?

  3. "Non El Nino year"? The extreme high anomalies from January to March looks a lot like an El Nino pattern, as predicted by the MetOffice: "The Met Office global temperature forecast suggests that 2019 will be close to record warmth due to climate change and the added effect of El Niño-related warming in the Pacific." ( )
    Also, the drop in anomalies from January to August in 2020 is as great as the corresponding drop in 2016, which very hard to explain without some sort of Nino effect - possibly this year also related to the record high IOD anomaly?? ( )

  4. They're calling the La Nina early, as it barely shows up on SOI time-series. But the Tropical Instability Wave (TIW) pattern is as clear as a bell on the map -- the thermocline is nearing the surface in the eastern Pacific and can thus directly observe the higher wavenumber solutions in addition to the ENSO standing wave dipole. TIW always has a wavelength of 1100 km, or one fully developed wave every 10 deg in longitude, like clockwork. Nothing chaotic, all predictable.