Ross McKitrick: The flaw in relying on worst-case climate modelling

Posted: June 24, 2020 by oldbrew in alarmism, climate, Critique, modelling, Temperature

Credit: Wikipedia

H/T The Global Warming Policy Forum (GWPF).

Or relying on any climate modelling, some might say given its current tendency toward overheated predictive mediocrity.
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The purpose of global climate policy is to get us from the dangerous upper end of the forecast range down to the safe bottom end. In fact, we are already there.

Whenever you read a media story about how we’re heading toward catastrophe if we continue operating “business as usual” — i.e., if we don’t slash carbon emissions — the reports are almost always referring to a model simulation using RCP8.5.

And you can bet that nowhere in the story will they explain that RCP8.5 is an implausible worst-case scenario that was never meant to represent a likely base case outcome, or that scientists have begun castigating its usage as a prediction of a doomed business-as-usual future.

The term RCP8.5 refers to a greenhouse gas emissions scenario often used by scientists for climate model projections. You might never have heard of RCP8.5 but you have definitely heard of forecasts based on it.

Listening to the politicians who make the strongest pleas for radical climate action, it is clear that their fears for the future are driven by RCP8.5 scenarios, yet it is also clear that they have no idea what it is or what is wrong with it.

RCP stands for “Representative Concentration Pathways,” or projections of how much carbon dioxide (CO2) will accumulate in the atmosphere due to fossil fuel use over the coming century.

The United Nations’ Intergovernmental Panel on Climate Change (IPCC) generated a set of four RCP scenarios a decade ago, attaching to each a number indicating how much “radiative forcing” (a measure of global warming potential) each one generates.

RCP2.6 refers to a benign, low-end emission scenario with correspondingly minimal radiative forcing. In the middle are RCP4.5 and RCP6.0, and at the top end is RCP8.5, a scorcher that predicts historically unprecedented increases in global CO2 emissions.

To appreciate how implausible RCP8.5 is, consider its coal use trajectory.

Continued here.

  1. cognog2 says:

    To me the basic flaw in all these models is omission of a proper analysis of the influence of the thermodynamic behaviour of water in the climate, where large energies are transmitted up through the atmosphere into the clouds and beyond to space irrespective of the GHG Effect. The result being an overestimate of the Global Sensitivity value.

  2. ivan says:

    The problem with all those models is;
    a) they do not model the atmosphere.
    b) if they put garbage in they always get garbage out.
    c) politicians rely on unknown drips under pressure to tell them what to think.

    There isn’t one of those models that stands up to comparison with real world measurements yet most people are so brainwashed that they believe them, even people that should know better.

  3. oldbrew says:

    Headline chasing has distorted the thinking of some climate researchers.

  4. tom0mason says:

    Ivan said — “The problem with all those models is;
    a) they do not model the atmosphere.”
    Yes indeed there is more to weather and climate than just averaged temperature.
    Long term but chaotic changes in atmospheric humidity and pressure affect the climate. As does long term jet-streams’ intensities and movements.

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