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Scientists' open letter to the Wall Street Journal re: Ridley and Peiser

Posted on 4 December 2015 by Guest Author

The following is an open letter from seven professors contributing to Climate Feedback, in response to an error-riddled Matt Ridley and Benny Peiser op-ed published in the Wall Street Journal.  For a point-by-point analysis of the op-ed, see this Climate Feedback post.

The opinion piece published in The Wall Street Journal by Matt Ridley and Benny Peiser (“Your Complete Guide to the Climate Debate” Nov. 27, 2015) is riddled with false statements, cherry-picked evidence and misleading assertions about climate science, according to an evaluation by a dozen scientists.

The article attempts to throw clouds of uncertainty around the hard facts about climate change that are agreed to by the scientific academies of every major country in the world and the vast majority of the world’s climate scientists. Here are just a few examples:

  •      The statement that the world has warmed at half the rate predicted in 1990 by the Intergovernmental Panel on Climate Change (IPCC) is false. The IPCC predicted that warming between 2015 and 1990 would be between about 0.35 and 0.60 °C. The actual temperature change during that period is 0.5 °C. The statement, besides being false, also ignores that the world has already warmed a total of 1 °C since the start of the industrial revolution, and that as temperatures continue to climb, we are headed into territory not seen in thousands of years. The assertion that the world has been warmer several times in the past 10,000 years is not supported by the most comprehensive temperature reconstructions, and ignores the fact that a continued temperature rise this century will rapidly take the world beyond any climate experienced in that 10,000 year period.
  •      The statement that there has been no increase in the frequency or intensity of storms, floods or droughts also is flat-out wrong. A recently-released UN study found that both the frequency and intensity of storms and floods has increased over the past decade, and that weather-related disasters are occurring at almost twice the rate as they did two decades ago. The authors also ignore the clear increases in the most deadly type of extreme events caused by climate change — heat waves.
  •      The claim that Antarctic ice is increasing is based on an isolated paper that has numerous uncertainties associated with it and is contradicted by many other observations. But more importantly, everywhere on Earth, it is clear we are losing ice and that we have likely already entered a period of major ice shelf retreat, with no mechanisms in sight to stop this retreat over the next hundreds to thousands of years. As University of Bristol Professor Jonathan Bamber has written: “West Antarctica has been losing mass at an increasing rate since the 1990s and that trend looks set to continue. The Greenland ice sheet has also been losing mass at an accelerating rate since around 1995. These trends at both poles are huge signals that are unequivocal and uncontested.”
  •      Finally, the assertion that the cost associated with warming “does not significantly deviate from zero until 3.5°C warming” is one that hardly any scientists or economists agree with, and is contradicted by the overwhelming weight of evidence showing that the adverse impacts from climate change will far outweigh the benefits.

Ridley and Peiser are correct that the challenge of decarbonizing the world is enormous. But obfuscation about strongly supported scientific facts is not the solution.


Prof. Roger Bales, University of California, Merced; Prof. Jonathan Bamber, University of Bristol; Prof. Anthony Barnosky, University of California, Berkeley; Prof. Mark Z. Jacobson, Stanford University;Prof. Steven Sherwood, University of New South Wales; Prof. Veerabhadran Ramanathan,University of California, San Diego; Prof. Eric Wolff, University of Cambridge

For more details about the scientists’ responses to claims made in this op-ed, please read our detailed analysis.

List of scientists who have contributed to this analysis:

Dr William Anderegg, Princeton University
Prof. Jonathan Bamber, University of Bristol
Prof. Anthony Barnosky, University of California, Berkeley
Dr Rasmus Benestad, The Norwegian Meteorological institute
Dr Alexis Berg, Columbia University
Dr Julien Emile-Geay, University of Southern California
Prof. Mark Z. Jacobson, Stanford University
Dr Twila Moon, University of Oregon
Prof. Steven Sherwood, University of New South Wales
Dr Victor Venema, University of Bonn
Dr Emmanuel Vincent, University of California, Merced
Dr Britta Voss, U.S. Geological Survey
Prof. Eric Wolff, University of Cambridge

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Comments 51 to 53 out of 53:

  1. #49 MA Roger. "you suggest there was "erroneous conversion from emissions to forcing" within the FAR scnarios. Could you expand on that comment?"

    1.  Errors in calculating concentrations that result from given emissions.

      I have not calculated the specific impact of this, but it appears that FAR overestimated the fraction of anthropogenic CO2 that would remain the atmosphere.

    2.  Errors in calculating radiative forcing for given concentrations  Is CO2 radiative forcing 3.7W/m2/doubling or is it 4.3W/m2/doubling.   Obviously, if one uses 4.3 (as did FAR) instead of 3.7 one calculates higher forcings than if one uses the currently accepted 3.7 number.

    3.  Ignoring aerosols.  Yes, FAR radiative forcing calculations completely ignored aerosols.   I have not caclulated the specific impact of this.  In 1990 the was uncertainty as to whether aerosols were even a positive or negative forcing:  "In view of the above uncertainties on the sign, the affected area and the temporal trend of the direct impact of aerosols, we are unable to estimate the change in forcing due to troposphenc aerosols. "  Page64 FAR WG1, forcing chapter. 


     The goal of governmental policies are to control emissions, since that is the human "input" to the ecosystem.  

    First, from emissions we make assumptions, and calculate concentrations.  Secondly, from those calculated concentrations we then calculate radiative forcings.  In a third step, from the radiative forcings we then calculate expected temperature changes.


    While it is instructive to ignore errors in the first two steps and then see if the calculations from forcings to temperature changes are correct, it sheds very little light on the overall accuracy of FAR predictions/projections.   This is particularly true since the FAR predictions are the output of a simple 2 box model.    While many seem to assume that the GCMs were used to make the FAR predictions, in reality they were done by an extremely simple two box model.  

    Provided that I get to choose my forcings, I can do a very accurate projection of global temperatures using a simple multiplier and a single exponential lag.  Even the two box model is overkill.   Of course, my projections become exceedingly accurate if I get to adjust the forcings to those observed, as others have done in their comments. 


    Some further details, .....

    A crude examination of assumed emissions vs project PPM CO2 leads me to believe that FAR assumed higher percentage of anthropogenic CO2 would remain in the atmosphere than actually remained.   I haven't bothered to see where the discrepancy comes from, but I did note that the FAR expected a "saturation effect" to take place which would lead to a rise in the percentage of anthropgenic CO2 remaining in the atmosphere  (about 1/2 stays in atmosphere and 1/2 is absorbed into biosphere and oceans).


    Another error is simply the radiative forcing formula used for CO2.   Yes, this is basic physics, but the consensus has changed as to the correct value.  For example, the TAR (2001) uses delta-F = 5.35ln(C/C0).  (This leads to the more often used 3.7W/m2/doubling of CO2)

    In 1990 the FAR used delta-F = 6.2ln(C/C0).  

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  2. Charlie A @51.

    You actually signal four objections to the FAR. Objecting to the abilities of the FAR climate models to provide anything useful does rather trump all that goes before. Do you feel the predictive abilities achieved by FAR to date are then just coincidental?

    But let us be "instructive" and begin by addressing initially your first point. The Airborne Fraction AF (as it is referred to these days) has remained remarkably steady over period of Atmospheric CO2 instrument data, something that wasn't that clear a quarter of a century ago. Another difficulty facing the FAR was the emissions from LUC which they greatly underestimated. Thus the numbers used to calculate the AF were not the ones we would use today and would indeed suggest a rising AF. However, these data problems do cancel each other out over initial decades.

    Also note that the FAR did not begin by defining emissions. That was not a part of the "Task A" brief required of WGIII whic was more to check that the climate forcings in their brief were realistic. Some of the numbers they considered were extreme by today's standards but those were generally averaged out of the final scenarios.

    Given this situation, your position on this first point is not clear. Are you then actually arguing that the scenarios, presumably specifically Scenario A is some form of straw man?

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  3. Charlie A @51 draws attention to three purported sources of "erroneous conversion from emissions to forcing", one of which (different estimate of radiative forcing relative to change of concentration) is valid and is discussed at 48 above.  It represents an 18% overestimate of FAR radiative forcing for change in concentration relative to current estimates for CO2 forcing, although less than that for all WMGHG.  It is the major factor as to why scenario B rather than scenario D is the closest relevant factor.

    To that valid concern, he adds two specious concerns.  The first is an assumed overestimate of the retained fraction of CO2 in the atmosphere.  However, the IPCC FAR BAU scenario represents a retained fraction of 55% of the specified emissions.  Those emissions are industrial emissions, as argued @48 above, for which the retained fraction on modern observations is also 55%.  The retained fraction would be too high if (and only if) the CO2 emissions specified in the scenarios were intended to be the combined industrial plus LUC emissions, a possibility contradicted by the fact that the states emissions in 1990 are well less than the combined emissions averaged over the preceding decade as specifice in the FAR.

    The second specious concern is that the model used for the prediction did not incorporate aerosols as a forcing.  That could be a valid concern if anthropogenic aerosol forcings increased significantly from 1990-2015.  Unfortunately I cannot test that, but from the IPPC AR5 Figure 8-18 (below), it can be seen that anthropogenic forcings in addition to WMGHG has decreased by 2.4%.  Furthermore, overall forcings have decreased relative to WMGHG as well.  The IPCC FAR included only anthropogenic WMGHG because rates of change in other anthropogenic forcings, and in natural forcings, was expected to be small relative to anthropogenic WMGHG, a supposition born out by AR5 data.


    Finally, Charlie A lets forth with a rhetorical cannard, suggesting we are comparing IPCC FAR predictions by applying their two box model to historical forcings.  Of course, nothing is further from the truth.  What we are doing is comparing historical forcings to the four IPCC scenarios to see which one most closely matches history.  That is what we are supposed to do.  That is the whole point of constructing different scenarios and generating a range of projections instead of just one prediction.

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