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The summary for policymakers of the Intergovernmental Panel on Climate Change sixth assessment reports synthesis

7 Apr 2023 by rasmus 60 Comments

The summary for policymakers of the Intergovernmental Panel on Climate Change (IPCC) sixth synthesis report was released on March 20th (available online as a PDF). There is a recording of the IPCC Press Conference – Climate Change 2023: Synthesis Report for those who are interested in watching an awkward release of the report.

It strikes me that the IPCC perhaps assumes that everyone is climate literate and are up to speed on climate change. While many journalists clearly got the message, expressed through news reports though e.g. the Guardian and Washington Post, I doubt that relevant leaders were swayed. One problem may be that journalists do not carry as much weight as scientists. 

[Read more…] about The summary for policymakers of the Intergovernmental Panel on Climate Change sixth assessment reports synthesis

Filed Under: Climate Science, Communicating Climate, IPCC

Serious mistakes found in recent paper by Connolly et al.

29 Nov 2022 by rasmus

Guest post by Mark Richardson who is a Research Scientist in the Aerosol and Clouds Group at NASA’s Jet Propulsion Laboratory, California Institute of Technology. All opinions expressed are his own and do not in any way represent those of NASA, JPL or Caltech.

Should scientists choose to believe provably false things? Even though that would mean more inclusive debates with a wider range of opinions, our recent paper Richardson & Benestad (2022) argues no: “instead of repeating errors, they should be acknowledged and corrected so that the debate can focus on areas of legitimate scientific uncertainty”. We were responding to Connolly et al., who suggested that maybe the Sun caused “most” of the warming in “recent decades” based on a simple maths mistake. 

[Read more…] about Serious mistakes found in recent paper by Connolly et al.

References

  1. M.T. Richardson, and R.E. Benestad, "Erroneous use of Statistics behind Claims of a Major Solar Role in Recent Warming", Research in Astronomy and Astrophysics, vol. 22, pp. 125008, 2022. http://dx.doi.org/10.1088/1674-4527/ac981c

Filed Under: Climate Science, Featured Story, Instrumental Record, Scientific practice, skeptics, statistics, Sun-earth connections

New misguided interpretations of the greenhouse effect from William Kininmonth

1 Oct 2022 by rasmus

I have a feeling that we are seeing the start of a new wave of climate change denial and misrepresentation of science. At the same time, CEOs of gas and oil companies express optimism for further exploitation of fossil energy in the wake of Russia’s invasion of Ukraine, at least here in Norway.

Another clue is William Kininmonth’s ‘rethink’ on the greenhouse effect for The Global Warming Policy Foundation. He made some rather strange claims, such as that the Intergovernmental Panel on Climate  Change (IPCC) allegedly should have forgotten that the earth is a sphere because “most absorption of solar radiation takes place over the tropics, while there is excess emission of longwave radiation to space over higher latitudes”. 

[Read more…] about New misguided interpretations of the greenhouse effect from William Kininmonth

Filed Under: Climate modelling, Climate Science, Communicating Climate, Greenhouse gases, IPCC, Scientific practice, skeptics Tagged With: climate change, co2, greenhouse warming

Unforced Variations: Jun 2023

2 Jun 2023 by group 14 Comments

This month’s open thread on climate topics.

Filed Under: Climate Science, Open thread, Solutions

Evaluation of GCM simulations with a regional focus.

31 May 2023 by rasmus 6 Comments

Do the global climate models (GCMs) we use for describing future climate change really capture the change and variations in the region that we want to study? There are widely used tools for evaluating global climate models, such as the ESMValTool, but they don’t provide the answers that I seek.

I use GCMs to provide information about large-scale conditions, processes and phenomena in the atmosphere that I can use as predictors in downscaling future climate projections. I also want to know whether the ensemble of GCM simulations that I use provides representative statistics of the actual regional climate I’m interested in. 

[Read more…] about Evaluation of GCM simulations with a regional focus.

Filed Under: Climate modelling, Climate Science, Featured Story, statistics Tagged With: CMIP5, CMIP6

CMIP6: Not-so-sudden stratospheric cooling

21 May 2023 by Gavin 72 Comments

As predicted in 1967 by Manabe and Wetherald, the stratosphere has been cooling.

A new paper by Ben Santer and colleagues has appeared in PNAS where they extend their previous work on the detection and attribution of anthropogenic climate change to include the upper stratosphere, using observations from the Stratospheric Sounding Units (SSUs) (and their successors, the AMSU instruments) that have flown since 1979.

[Read more…] about CMIP6: Not-so-sudden stratospheric cooling

References

  1. B.D. Santer, S. Po-Chedley, L. Zhao, C. Zou, Q. Fu, S. Solomon, D.W.J. Thompson, C. Mears, and K.E. Taylor, "Exceptional stratospheric contribution to human fingerprints on atmospheric temperature", Proceedings of the National Academy of Sciences, vol. 120, 2023. http://dx.doi.org/10.1073/pnas.2300758120

Filed Under: Climate modelling, Climate Science, Featured Story, Greenhouse gases, Instrumental Record, Sun-earth connections Tagged With: CMIP6, SSU

Unforced variations: May 2023

1 May 2023 by group

This month’s open thread on climate topics. Please be succinct, courteous and on point.

Filed Under: Climate Science, Open thread, Solutions

A NOAA-STAR dataset is born…

23 Apr 2023 by Gavin 55 Comments

What does a new entrant in the lower troposphere satellite record stakes really imply?

At the beginning of the year, we noted that the NOAA-STAR group had produced a new version (v5.0) of their MSU TMT satellite retrievals which was quite a radical departure from the previous version (4.1). It turns out that v5 has a notable lower trend than v4.1, which had the highest trend among the UAH and RSS retrievals. The paper describing the new version (Zou et al., 2023) came out in March, and with it the availability of not only updated TMT and TLS records (which had existed in the version 4.1), but also a new TLT (Temperature of the Lower Troposphere) record (from 1981 to present). The updated TMT series was featured in the model data comparison already, but we haven’t yet shown the new TLT data in context.

[Read more…] about A NOAA-STAR dataset is born…

References

  1. C. Zou, H. Xu, X. Hao, and Q. Liu, "Mid‐Tropospheric Layer Temperature Record Derived From Satellite Microwave Sounder Observations With Backward Merging Approach", Journal of Geophysical Research: Atmospheres, vol. 128, 2023. http://dx.doi.org/10.1029/2022JD037472

Filed Under: Climate Science, Featured Story, Instrumental Record Tagged With: AMSU, climate change, MSU, NOAA STAR, RSS, UAH

Unforced Variations: Apr 2023

1 Apr 2023 by group

This month’s open thread on climate topics (no joke).

Filed Under: Climate Science, Open thread

Some new CMIP6 MSU comparisons

16 Mar 2023 by Gavin

We add some of the CMIP6 models to the updateable MSU [and SST] comparisons.

After my annual update, I was pointed to some MSU-related diagnostics for many of the CMIP6 models (24 of them at least) from Po-Chedley et al. (2022) courtesy of Ben Santer. These are slightly different to what we have shown for CMIP5 in that the diagnostic is the tropical corrected-TMT (following Fu et al., 2004) which is a better representation of the mid-troposphere than the classic TMT diagnostic through an adjustment using the lower stratosphere record (i.e. TMT_{corr} = 1.1 TMT - 0.1 TLS).

[Read more…] about Some new CMIP6 MSU comparisons

References

  1. S. Po-Chedley, J.T. Fasullo, N. Siler, Z.M. Labe, E.A. Barnes, C.J.W. Bonfils, and B.D. Santer, "Internal variability and forcing influence model–satellite differences in the rate of tropical tropospheric warming", Proceedings of the National Academy of Sciences, vol. 119, 2022. http://dx.doi.org/10.1073/pnas.2209431119
  2. Q. Fu, C.M. Johanson, S.G. Warren, and D.J. Seidel, "Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends", Nature, vol. 429, pp. 55-58, 2004. http://dx.doi.org/10.1038/nature02524

Filed Under: Climate modelling, Climate Science, Featured Story, Instrumental Record Tagged With: CMIP6, Corrected-TMT, MSU

How not to science

5 Mar 2023 by Gavin

A trip down memory lane and a lesson on scientific integrity.

I had reason to be reviewing the history of MSU satellite retrievals for atmospheric temperatures recently. It’s a fascinating story of technology, creativity, hubris, error, imagination, rivalry, politics, and (for some) a search for scientific consilience – worthy of movie script perhaps? – but I want to highlight a minor little thing. Something so small that I’d never noticed it before, and I don’t recall anyone else pointing it out, but it is something I find very telling.

The story starts in the early 90’s, but what caught my eye was a single line in an op-ed (sub. req.) written two decades later:

… in 1994 we published an article in the journal Nature showing that the actual global temperature trend was “one-quarter of the magnitude of climate model results.”McNider and Christy, Feb 19th 2014, Wall Street Journal

Most of the op-ed is a rather tired rehash of faux outrage based on a comment made by John Kerry (the then Secretary of State) and we can skip right past that. It’s only other claim of note is a early outing of John Christy’s misleading graphs comparing the CMIP5 models to the satellite data but we’ll get back to that later.

First though, let’s dig into that line. The 1994 article is a short correspondence piece in Nature, where Christy and McNider analyzed MSU2R lower troposphere dataset and using ENSO and stratospheric volcanic effects to derive an ‘underlying’ global warming trend of 0.09 K/decade. This was to be compared with “warming rates of 0.3 to 0.4 K/decade” from models which was referenced to Manabe et al. (1991) and Boer et al. (1992). Hence the “one quarter” claim.

But lets dig deeper into each of those elements in turn. First, 1994 was pretty early on in terms of MSU science. The raw trend in the (then Version C) MSU2R record from 1979-1993 was -0.04 K/decade. [Remember ‘satellite cooling’?]. This was before Wentz and Schabel (1998) pointed out that orbital decay in the NOAA satellites was imparting a strong cooling bias (about 0.12 K/decade) on the MSU2R (TLT) record. Secondly, the two cited modeling papers don’t actually give an estimated warming trends for the 1980s and early 90s. The first is a transient model run using a canonical 1% increasing CO<sub>2</sub> – a standard experiment, but not one intended to match the real world growth of CO2 concentrations. The second model study is a simple equilibrium 2xCO2 run with the Canadian climate model, and does not report relevant transient warming rates at all. This odd referencing was pointed out in correspondence with Spencer and Christy by Hansen et al. (1995) who also noted that underlying model SAT trends for the relevant period were expected to be more like 0.1-0.15 K/decade. So the claim that the MSU temperatures were warming at “one quarter” the rate of the models wasn’t even valid in 1994. They might have more credibly claimed “two thirds” the rate, but the uncertainties are such that no such claim would have been robust (for instance, just the uncertainties on the linear regression alone are ~ +/-0.14 K/dec).

This image has an empty alt attribute; its file name is mcnider55-253x600.png
Replication of the Christy and McNider calculation and figure from 1994 but using the UAH v5.5 data.

But it gets worse. In 2014, McNider and Christy were well aware of the orbital decay correction (1998), and they were even aware of the diurnal drift correction that was needed because of a sign error introduced while trying to fix the orbital decay issue (discovered in 2005). The version of the MSU2R product at the beginning of 2014 was version 5.5, and that had a raw trend of -0.01 K/decade 1979-1993 (+/- 0.18 K/dec 95% CI, natch). Using an analogous methodology to that used in 1994 (see figure to the right), the underlying linear trend after accounting for ENSO and volcanic aerosols was…. 0.15 K/dec! Almost identical to the expected trend from models!

So not only was their original claim incorrect at the time, but had they repeated the analysis in 2014, their own updated data and method would have shown that there was no discrepancy at all.

Now in 2014, there was a longer record and more suitable models to compare to. Models had been run with appropriate volcanic forcings and in large enough ensembles that there was a quantified spread of expected trends. Comparisons could now be done in a more sophisticated away, that compared like with like and took account of many different elements of uncertainty (forcings, weather, structural effects in models and observations etc.). But McNider and Christy chose not to do that.

Instead, they chose to hide the structural uncertainty in the MSU retrievals (the TMT trends for 1979-2013 in UAH v5.5 and RSS v3.3 were 0.04 and 0.08 +/- 0.05 K/dec respectively – a factor of two different!), and ignore the spread in the CMIP5 models TMT trends [0.08,0.36] and graph it in a way as to maximise the visual disparity in a frankly misleading way. Additionally, they decided to highlight the slower warming TMT records instead of the TLT record they had discussed in 1994. For contrast, the UAH v5.5 TLT trends for 1979-2013 were 0.14± 0.05 K/dec.

But all these choices were made in the service of rhetoric, not science, to suggest that models are, and had always been, wrong, and that the UAH MSU data had always been right. A claim moreover that is totally backwards.

Richard Feynman often spoke about a certain kind of self-critical integrity as being necessary to do credible science. That kind of integrity was in very short supply in this op-ed.

References

  1. J.R. Christy, and R.T. McNider, "Satellite greenhouse signal", Nature, vol. 367, pp. 325-325, 1994. http://dx.doi.org/10.1038/367325a0
  2. F.J. Wentz, and M. Schabel, "Effects of orbital decay on satellite-derived lower-tropospheric temperature trends", Nature, vol. 394, pp. 661-664, 1998. http://dx.doi.org/10.1038/29267
  3. J. Hansen, H. Wilson, M. Sato, R. Ruedy, K. Shah, and E. Hansen, "Satellite and surface temperature data at odds?", Climatic Change, vol. 30, pp. 103-117, 1995. http://dx.doi.org/10.1007/BF01093228

Filed Under: Climate modelling, Climate Science, Featured Story, Instrumental Record, Scientific practice Tagged With: John Christy, MSU, Satellite temperature

Unforced variations: March 2023

1 Mar 2023 by group

This month’s open thread. Antarctic sea ice anyone?

Filed Under: Climate Science, Open thread

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