Tuesday, June 15, 2021

GISS May global temperature up by 0.04°C from April.

The GISS V4 land/ocean temperature anomaly was 0.80°C in May 2021, up from 0.76°C in April. This small rise is similar to the 0.012°C increase reported for TempLS. Jim Hansen's report is here.

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

Sunday, June 6, 2021

May global surface TempLS up 0.012°C from April.

The TempLS mesh anomaly (1961-90 base) was 0.67°C in May, up from 0.658°C in April. It was cool relative to recent Mays, although 2018 and 2015 were a little cooler.. The NCEP/NCAR reanalysis base index rose more - 0.089°C. However, it did not rise much in April, when TempLS did.

Cold patches in W Europe and Eastern US have been talked about. Also cold in India and N Canada. But it was warm in central Russia and much of the Arctic. Also in N Africa and the Middle East.

Here is the temperature map, using the LOESS-based map of anomalies.


 
As always, the 3D globe map gives better detail.

Friday, May 14, 2021

GISS April global temperature down by 0.14°C from March.

The GISS V4 land/ocean temperature anomaly was 0.74°C in April 2021, down from 0.88°C in March. This is similar to the 0.165°C decrease (now 0.134) reported for TempLS. Jim Hansen's report is here.

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

Wednesday, May 5, 2021

April global surface TempLS down 0.165°C from March.

The TempLS mesh anomaly (1961-90 base) was 0.608°C in April, down from 0.773°C in March. That takes away much of the rise in March, and goes back to about the level in Dec/Jan, though warmer than February. It was the coolest April since 2013. The NCEP/NCAR reanalysis base index did not rise as much in March, and so did not fall in April, rising just 0.016°C. Again, April was about the level of Dec/Jan.

Many Moyhu readers will have experienced the cold patches, which were in Eastern US (also Alaska and NW Canada), Europe and most of Australia. There was also a cold band through Afghanistan/China. N Africa, S America, NE Canada and NW Siberia (and much of Arctic) were warm; Antarctica was cold.

Here is the temperature map, using the LOESS-based map of anomalies.


As always, the 3D globe map gives better detail.

Monday, May 3, 2021

CMIP6 comparing TOS with observed SST, and blended TOS/TAS with GISSlo

This post is a sequel to my recent post, which reviewed a claim by Dr Roy Spencer that the new round of CMIP6 modelling gave warming in the 1979-2020 period twice what was observed. One of the issues was that he had used TAS (surface air) instead of TOS (sea surface) to compare with observed SST. The data source he used, KNMI, does not at present have CMIP6 TOS results, so nor did I.

However, Gavin Schmidt noted that there was a new repository at University of Melbourne which had more results available, including TOS. This is a useful repository in which a lot of averaging is pre-done. The supporting paper by Nicholls et al is here. And indeed, it does have currently TOS results from 13 models, and also a wider range of TAS.

This makes it possible for me to update the plots of the last post, which used TAS restricted to ocean (following Roy), which I adjusted using the difference trend from CMIP5. But it also makes it possible to calculate the correct blend of TOS/TAS to match the commonly quoted land/ocean observed indices.

In 2015, Cowtan, Hausfather et al published a paper in which the noted that comparisons of modelled and observed frequently compared modelled TAS with observed land/ocean, which is not like with like. They created a blended CMIP5 set using TAS on land and TOS at sea. It makes a considerable difference. I do something similar here, but for the rather limited set posted so far.

CMIP6 and TOS

There are 10 models that provide TOS results, and this time I plot just the first for each model type. They are normalised so that the 1979-1983 average is zero, for each month. The result is


As before, the CanESM results, of which there are two, are clearly the most rapidly warming. If you exclude them, the observed is in the centre of the modelled range. For comparison, here is my previous plot in which I showed TAS with a trend adjustment from CMIP5 TAS/TOS:

Blending TOS/TAS to compare with observed land/ocean.

As said above, CMIP TAS results are often compared with modelled land/ocean, with much the same problems as in Roy Spencer's usage. Cowtan et al (2015) derived a combined TOS/TAS for CMIP5. They did a cell by cell calculation of the blend. I think it is arithmetically equivalent to use the posted land average TAS with TOS, provided the weighted combination uses the same land/sea mask to calculate areas as it did to average the temperature subsets. In this case, I used the areas that were provided with the TAS/TOS data (in the header), so I hope that is true. If not, it won't make a big difference. The land fraction was 0.287.

Update 5 May 2021. I made an error in the initial post; I used the wrong column blended with  sea TAS instead of land TAS. It makes a considerable difference, although the relative position of GISS is as originally described. The old plot is  <a href="https://s3-us-west-1.amazonaws.com/www.moyhu.org/2021/05/blend1.png">here</a>. The zip file linked below has been updated.

I blended always TOS/TAS runs that had the same variant number, although that common value may vary from model to model. Again, I chose one blend from each model, and compared with GISS land/ocean:

Again, the CanESM results warm fastest, and GISS sits on the warm side of the other results. For comparison, I plotted what would happen using TAS global alone, as is often done


Even excluding CanESM, it now appears that modelled results run warmer than GISS. They are also a lot more variable. It is important to compare with the blend.

Data posted

I have posted a zipped csv file here, with blends for 102 runs from 1850 to 2101, with a readme file and some headers. Update 5 May 2021. I made an error in the initial post, see above. The file has been updated.









Thursday, April 29, 2021

No, global warming is not 50% of what CMIP6 models predict.

The title is a reference to a post by Dr Roy Spencer titled
"An Earth Day Reminder: “Global Warming” is Only ~50% of What Models Predict"
It was reposted at WUWT here. I commented at both places.

The title is somewhat misleading; the post treats a subset of SST (sea surface temperature), not global warming, and does not deal with a supposed failure of a prediction, but a possible discrepancy in SST in the years 1979-2020, as modelled in the latest round (CMIP6). Here is Dr Roy's main plot:





It isn't true, and the reasons are to do with the fact that only a small subset of CMIP6 results have yet appeared. Roy (and I) use the results posted by KNMI Explorer. The two key data problems are
  • Roy is using  near surface air temperatures (TAS) restricted to ocean. The CMIP version of SST is TOS, not yet posted for CMIP6. Both were posted for CMIP5 (see below), but TOS came later. I'll look at the CMIP5 results, and show how TOS and TAS differ considerably. CMIP5 TOS is quite close to observation in 1979-2020.
  • Although 68 simulations have been published for TAS, as used by Roy, 50 of those came from one model, CanESM5. This does weight the results toward high warming in that period (and others); if removed, the CMIP6 results are fairly consistent with CMIP5.

CMIP5 results for TOS and TAS, and compared with observations.

I have used the CMIP5 results for RCP4.5. The scenario should not matter for historic data, where the forcings are known. They have some influence in the years since about 2011.

Here is a graph of results:



I have given both the 60S-60N and 90S-90N results from CMIP5; Roy uses the former, which does avoid sea-ice complications. Like Roy, I have normalised so that the 1979-1983 average of all series are zero. For the trends, I have used an AR(1) model, since the residuals are clearly highly autocorrelated. HADSST3 is from here and NOAA SST from here. The multi-model means are as supplied by KNMI. There are a couple of things to unpack here
  • The correct CMIP5 set to compare is TOS 90S-90N, and that is quite close to HADSST3; the trend is 0.14°C/decade, vs 0.135 for HADSST3, with the difference much smaller than the σ's. NOAA SST is lower, but still well within the CI range.
  • TAS, as used by Roy for CMIP6, is substantially higher at 0.197°C/dec. However, Roy used the latitude range 60S-60N, for which TOS and TAS are closer.
So CMIP5 matched observed SST very well in this time range.

CMIP6 TAS data limitations

As said, posting of CMIP6 results is at a very early stage. For each scenario of TAS there are 68 simulations, but 50 are from the model CanESM5. In the following plot, analogous to Roy's above, I have shown the ssp585 Can results in faint blue, with other CMIP6 TAS (ocean 60S-60N) results in red. I have shown HADSST3 and NOAA SST for comparison.



Removing CaanESM5 does not change the profile very much, but does radically change the multi-model mean (not shown). But again, these are TAS results, and in CMIP5, there was a 0.022°C/decade trend differential for TOS. If that is subtracted here, we get



It is now clear that the observed results are well within the model range, being only a little below average.

Conclusion

The difference between modelled and observed is far less than Roy Spencer claims. For CMIP5, using the right model variable TOS, there is very little difference. And adjusting for the TOS-TAS difference in CMIP6, and being wary of the excessive weight given to one model, the observed SST is well within the model range.

















Wednesday, April 14, 2021

GISS March global up by 0.22°C from February.

The GISS V4 land/ocean temperature anomaly was 0.88°C in March 2021, up from 0.66°C in February. This increase is similar to the 0.252°C increase reported for TempLS. Jim Hansen's report is here.

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