Reposted from Dr. Roy Spencer’s Blog
June 25th, 2020 by Roy W. Spencer, Ph. D.
Those who defend climate model predictions often produce plots of observed surface temperature compared to the models which show very good agreement. Setting aside the debate over the continuing adjustments to the surface temperature record which produce ever-increasing warming trends, let’s look at how the most recent (CMIP6) models are doing compared to the latest version of the observations (however good those are).
First, I’d like to explain how some authors get such good agreement between the models and observations. Here are the two “techniques” they use that most annoy me.
- They look at long periods of time, say the last 100+ years. This improves the apparent agreement because most of that period was before there was substantial forcing of the climate system by increasing CO2.
- They plot anomalies about a common reference period, but do not show trend lines. Or, if they show trends lines, they do not start them at the same point at the beginning of the record. When you do this, the discrepancy between models and observations is split in half, with the discrepancy in the latter half of the record having the opposite sign of the discrepancy in the early part of the record. They say, “See? The observed temperatures in the last few decades nearly match the models!”
In the following plot (which will be included in a report I am doing for the Global Warming Policy Foundation) I avoid both of those problems. During the period of strongest greenhouse gas forcing (since 1979), the latest CMIP6 models reveal 50% more net surface warming from 1979 up to April 2020 (+1.08 deg. C) than do the observations (+0.72 deg. C).
Note I have accounted for the trends being somewhat nonlinear, using a 2nd order polynomial fit to all three time series. Next, I have adjusted the CMIP time series vertically so that their polynomial fit lines are coaligned with the observations in 1979. I believe this is the most honest and meaningful way to intercompare the warming trends in different datasets.
As others have noted, it appears the CMIP6 models are producing even more warming than the CMIP5 models did… although the KNMI Climate Explorer website (from which all of the data was downloaded) has only 13 models archived so far.
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Since 2015 guess what the global T anomaly is… based on 14.0°C baseline zero: Exactly 0.0°C based on over 60000 continuous worldwide observation sites. Use down arrow to see graph and data sources.
http://temperature.global/
I’m finding the problem with this site is that in a way it is too good; meaning that with so many new posts each day within a couple of days most discussions stop.
Discussions like this one I think are most important and productive as it seems some people who can explain the view from within climate science are joining in, but either because of the above, or other reasons frustratingly there seem to still be questions raised in these sorts of discussions they haven’t answered or issues not adequately discussed.
Perhaps it could be more productive if:
A) Such important discussions weren’t so quickly lost in the forest of other posts so participants don’t disappear before clarifying or answering questions.
B) Some sort of summary added, periodically updated that summarises important points raised, the answers or conclusion, indicating if that issue can be closed, and listing important questions not adequately answered or discussed.
I know this may sound like a lot of work, but hopefully it could mean such discussions are much more productive, forcing answers and acting as a reference. My initial thought is a page showing, say the latest 6 important discussions, an archive as they drop off into various categories, but keep them open so the discussion can continue and if enough good new information or questions raised show them on another page showing the top 3 or 4 that need to be looked at again so hopefully people with suitable knowledge will add relevant comments, answers, etc.
Unfortunately too much of this is over my head or comments too short for me to adequately understand otherwise I’d attempt the kind of summary I mean. Similarly I’m struggling with summarising or deciding what I think are the important questions that need to be addressed by someone, and I may have missed the answers.
QUESTIONS NEEDING ANSWERS or more discussion?
1) The validity of using average temperature.
2) The validity of using temperature as proxy for energy.
3) The 2005 step.
Probably more than that.
The IPCC was originally set up to assess the risks of anthropological CO2 emissions. Had the IPCC concluded that there was insignificant risk it would have been closed down . It is not surprising therefore that high risks were found and that subsequent findings provide increasing support for this conclusion. Neither is it surprising that any challenge to this position would be rigorously suppressed and ignored.
Conspiracy theory or not, there is little doubt that there is a strong conflict of interest here.
Thanks for pointing that out Charles. But you are still dead wrong when asserting that CO2 has been forcing the climate instead of the climate forcing the CO2 increase if any, as the 100 ppm rate of increase over 60 years fits very well with the reduction in the eccentricity of Earth’s orbits over the next 10,000 years or so increasing the speed of Earth’s rotation to conserve angular momentum. Detrending of the annual Mauna Loa CO2 values actually shows how they relate to the Jupiter and Saturn orbital cycles.