Associate Professor Kim Cobb’s Obsession…Ignores 95% Of Climate Models Running Too Hot

Cobb_GATechWhat About Climate Change?
By Ed Caryl

In last week’s on-line issue of the Georgia Tech Alumni Magazine (Volume 90, Number 4), Judith Curry and Kim Cobb contributed their thoughts on the issue of climate change in two short essays.

Photo: Kim Cobb; source: Georgia Tech.

These essays were obviously intended to oppose each other. As one would expect, Ms. Curry wrote a low-key, well reasoned opinion piece urging caution and a measured approach to a more efficient use of our energy resources. She emphasized the considerable uncertainty in climate science:

The climate has always changed and will continue to change. […]

There is growing evidence that the climate is less sensitive to adding greenhouse gases than has been predicted by climate models.  Solar variability, volcanic eruptions and long-term ocean oscillations will continue to be sources of unpredictable climate surprises.”

On the other hand, Ms. Cobb has NO doubt that disaster is at hand, and dismisses those who disagree with a wave of the hand. For example:

Nobody with any knowledge on the subject denies that carbon dioxide (CO2) derived from the burning of fossil fuels is measurably warming the planet.”

“Measurably”? Ms. Cobb, could you share that measure with us? Even the IPCC can’t decide this measure plus or minus 100%. That isn’t a measure! That is a wildly adventurous guess.

As Judith Curry implies, the measure of climate sensitivity is declining almost with each new paper on the subject. Even the IPCC acknowledges that. Studies based on data place climate sensitivity somewhere between zero and one degree. Only papers based on models put the number higher, all with huge uncertainty ranges. KC says:

Nobody denies that the risks of climate change will accelerate as greenhouse gas emissions accelerate.”

To that breath-taking statement I have a question. What are the “risks” of climate change? So far, those risks seem to be fewer hurricanes, fewer tornados, warmer winters, longer growing seasons, enhanced crop growth due to higher CO2 levels, and warmer nights due to urban heat islands. Those “risks” will also accelerate IF emissions accelerate. Emissions from the US and the EU are falling along with their economies. Emissions are rising and will rise in the developing countries as they pull their citizens out of energy poverty. Both the drivers of increased emissions and the chief “risks” all seem good things. Reduced emissions often result in bad things.

The down-side seems restricted to sea-level rise. For most of the world, subsidence and uplift govern local sea level and these factors have nothing to do with climate change. For the rest, if we judge from the past, 17 cm of sea level rise in the next 100 years should not be a big problem. For island nations, coral growth easily keeps pace. Cobb claims:

And nobody denies that, given the long lifetime of CO2 in the atmosphere, the climatic response of our current emissions will play out over the lifetimes of our children and our grandchildren. They will inherit our generation’s climate debt, and its accrued interest, potentially in the form of irreversible impacts.”

“Long lifetime”? I wonder if she is as worried about the national debt? Each year only about half of the human carbon emissions remain in the atmosphere. This is called the CO2 “airborne fraction”. In the long term this fraction is falling (See Figure 3 in this link) as emissions increase, because the biosphere is greening and pulling out increasing amounts of CO2. With CO2 “half-life” at one year, if global emissions decrease, within a few years CO2 content in the atmosphere would begin falling. Then those “irreversible” positive impacts that I describe in my previous paragraph would begin to disappear. According to Cobb:

It is equally likely that future impacts will be less than or greater than those projected by climate models.”

Ms. Cobb has evidently not seen a comparison of the climate models and data. So far, 95% of the models are running too hot compared to real measurements. This is obviously not “equally likely”. The models have failed to predict reality, and will continue to fail because they are written with an over-estimation of warming due to CO2. Future impacts will be far less than the climate models indicate.

Ms. Cobb is an alarmist. All her opinions are biased by that alarm. Her lack of skepticism makes her resemble more an end-of-world preacher rather than a thoughtful scientist.


21 responses to “Associate Professor Kim Cobb’s Obsession…Ignores 9521 Of Climate Models Running Too Hot”

  1. Ed Caryl

    “Adventurous” I was trying to think of an A word…

  2. Eduardo Ferreyra

    People have long forgotten about Dr. Sherwwod Idso great paper (Idso 1998 and 2000) “CO2-induced global warming: a skeptic’s view of potential climate change” downloadable in .pdf format from:
    ABSTRACT: Over the course of the past 2 decades, I have analyzed a number of natural phenomena that reveal how Earth’s near-surface air temperature responds to surface radiative perturbations. These studies all suggest that a 300 to 600 ppm doubling of the atmosphere’s CO2 concentration could raise the planet’s mean surface air temperature by only about 0.4°C. Even this modicum of warming may never be realized, however, for it could be negated by a number of planetary cooling forces that are intensified by warmer temperatures and by the strengthening of biological processes that are enhanced by the same rise in atmospheric CO2 concentration that drives the warming. Several of these cooling forces have individually been estimated to be of equivalent magnitude, but of opposite sign, to the typically predicted greenhouse effect of a doubling of the air’s CO2 content, which suggests to me that little net temperature change will ultimately result from the ongoing buildup of CO2 in Earth’s atmosphere. Consequently, I am skeptical of the predictions of significant CO2-induced global warming that are being made by state-of-the-art climate models and believe that much more work on a wide variety of research fronts will be required to properly resolve the issue

    1. David Appell

      Sherwood is already badly wrong, just looking at the data from the 20th century, which shows ECS ~ 2 C, surely low because we can’t quantify aerosol cooling for that time period.

      Learn to think for yourself.

      1. David Johnson

        Learn to think for YOURSELF

  3. John F. Hultquist

    The first “crisis” I remember was the build-a-fallout-shelter one.
    Since then there have been many other things from the “drive 55” (save gas) to the “Whip Inflation Now” (WIN) buttons.
    This is getting old.
    Regarding Kim Cobb — I remember Ronald Reagan’s response (1984) when asked about his age. Reagan remarked, “I am not going to make age an issue of this campaign. I am not going to exploit, for political purposes, my opponent’s youth and inexperience,”
    I look forward to Ms. Cobb’s views when she is an emerita full professor.

    1. David Appell

      You think the potential for nuclear war is “getting old?” How many thousands of them are on the planet now? And in the hands of whom, exactly?

      Wow, is that scary.

      1. DirkH

        David, are you saying that Western governments are acting irresponsibly by fearing a hypothetical and minor warming 100 years in the future while ignoring the need for nuclear bombshelters?

  4. DirkH

    Well that looks like the dole then for Mrs. Cobb, once the USA becomes incapable of feeding the load of scoundrels they currently suffer under, which I expect to happen in 2015… USA currently burns through Japan’s retirement money, as nobody else buys their newly issued debt anymore. Nobody needs treasuries to pay for oil anymore, thanks to new arrangements and low oil price; the petrodollar flows back to USA now, only Japan has been given the order to absorb excess treasuries… destined to be the intermediary bagholder, the buffer that stands between the USA and the abbyss.

    Low oil price is a Russian weapon…

  5. JB

    Could someone inform Ms Cobb that the level of CO2 in the atmosphere was 760 ppm (nearly double what it is now) when Antarctica froze over. Glasshouses with CO2 levels of 1100 ppm still require heating during winter. No sign of runaway greenhouse effect there.

  6. David Appell

    Ed: I’m curious if you know what this means — ‘climate models solve a boundary value problem, not an initial value problem…..’

    1. Ed Caryl

      David, I know what it means, and I agree. So far, reality is increasingly outside the bounds of the climate models. Each time the initial values are reset, reality wonders outside those boundaries again. Those that ignore history are doomed to repeat it.

  7. PeterK

    David Appell: You remind me of a sniper who wears coke bottle glasses and every time you fire off a shot, you are blown right out of the tree that you are sitting in. You add no value to anything that is being discussed.

    1. David Johnson

      Now that is funny!

  8. Richard111

    For anyone who believes we might control climate by controlling CO2 production please read the link…

    “”• The Science magazine reports that termites annually generate more than twice as much carbon dioxide as mankind does burning fossil fuels. One termite species annually emits 600,000 metric tons of formic acid into the atmosphere, an amount equal to the combined contributions of automobiles, refuse combustion and vegetation. “”

  9. Mervyn

    About Kim Cobb’s statements:

    “Nobody with any knowledge on the subject denies that carbon dioxide (CO2) derived from the burning of fossil fuels is measurably warming the planet.”

    “Nobody denies that the risks of climate change will accelerate as greenhouse gas emissions accelerate.”

    “And nobody denies that, given the long lifetime of CO2 in the atmosphere, the climatic response of our current emissions will play out over the lifetimes of our children and our grandchildren. They will inherit our generation’s climate debt, and its accrued interest, potentially in the form of irreversible impacts.”

    Notice the language of certainty in relation to a field of science loaded with so much uncertainty. This language of Cobb is the classic language of propaganda not science.

    What is of most concern here, is that Kim Cobb is an associate professor. God help the university students!!!!

  10. Loodt Pretorius

    I see that Kim omitted to state that …nobody denies that witches float when dunked into water…

    Her beliefs are at the same level of fanaticism as that of the Salem witch hunters, and need I add, just as dangerous.

    1. Graeme No.3

      I think Kim Cobb is well suited for the role of a certain type of “scientist”.

      Ignorant of the basics of climate science. She is apparently unaware of higher temperatures at lower CO2 levels several times in the Holocene, let alone in previous interglacials. Nor does she seem to want to know about P. Jones (Uni. East Anglia) admission that the rate of temperature rise 1975 to 1995 was the same as previous rises 1850-1885 and 1920-1935 (apologies if I’ve got the exact years wrong).

      Nor is she able to produce any evidence that CO2 has warmed the planet or caused rising numbers of “climate catastrophes”. Then there is her basic assumption that any rise in temperature will be bad for humans, although the increasing likelihood of the reverse could well be.

      And I guess it would be pointless querying her on solar variability, oceanic cycles etc. Hardly an advertisement for american education.

  11. cementafriend

    The problem with both professors at Georgia Inst of Tech is that neither has sufficient knowledge of engineering science particularly Thermodynamics and Heat Transfer. If they had knowledge of the work of Prof Hoyt Hottel at MIT (such as described in Perry’s Chemical Engineering handbook or Mark’s Mechanical Engineering Handbook), if they had any experience and knowledge of the analogies in Transport Phenomena and the use of dimensional analysis and dimenionless numbers they might begin to realise that AGW (or IPCC’s idea of climate change) is just a political scam.
    David Appell above has demonstrated many times in the past and again above that he has no knowledge of engineering science and that he is unable to understand simple data. He must have been brainwashed in the Al Gore school of trolling. The public will eventual learn that Al Gore is full of lies as they did with that crook Bernie Madoff.

  12. Ross McLeod

    Can anyone please tell me if there is any real evidence supporting the ability of back radiation from the atmosphere to increase the temperature of the Earth’s surfaces when all the radiation budgets show the flux from the atmosphere is the result of a hotter surface radiating more than the atmosphere.

    I find it hard to reconcile the algebraic manipulations involving these simplistic sums of radiation fluxes.

    Just as an example consider 2 values from Trenberth et al Energy Budget of 396 surface radiation versus 333 back radiation.

    Surely the question here is does the 333 back radiation supply energy capable of increasing the surface temperature or does it merely replace some of the energy lost by the surface thus delaying its radiative cooling effect ?

    As much of this is based upon the Stefan-Boltzmann equation I cannot see how back radiation of 333 W/sqm can increase the temperature of a surface already radiating 396 W/sqm.

    The Stefan-Boltzmann equation provides very little information about radiation fluxes. On the other hand Planck’s equation is considered to provide a complete description of a radiative flux.

    Further the SB equation can be derived as the integral of Planck’s equation over all wavelengths ( or frequency or whatever variable is chosen) and as such represents the area under a particular temperature curve.

    Armed with this information you can plot Planck curves for the temperatures represented by these radiative flux values assuming blackbody approximations.

    So plotting 333 W/sqm =~276.8 K versus 396 W/sqm = ~289.1 K yields 2 curves which indicate to my way of thinking it is impossible for a radiative flux of 333 W/sqm to increase the temperature of a surface already emitting 396 W/sqm.

    This seems to me to be a fair analysis of the information presented as the Energy Budget is supposedly modelling terrestrial temperatures.

    The only method whereby a lower flux value such as 333 W/sqm can supply extra energy is if the flux is the result of radiation emitted by a significantly hotter source attenuated by inverse square reduction.

    We know this is not the case for terrestrial radiation and certainly not due to the atmosphere.

    I have also plotted the photon flux curves and again the 333 W/sqm curve is not only lower in intensity than the 396 W/sqm curve but in both plots the 396 W/sqm curve shows high energy photons emitted that the 333 W/sqm curve does not emit.

    Most University lectures on the “greenhouse effect” use a, to my mind ridiculous, assumption that you simply add the solar radiation value of as often quoted 239.7 W/sqm to 239.7 W/sqm back radiation to arrive at 479.4 and then they say this equals sigma T^4.

    But plot these claimed sums and you see that no sum of radiative fluxes involving terrestrial temperatures produces Planck curves that equal sigma T^4 !!

    You also see that there is little overlap of the inverse square law modified Planck curve for the solar radiation with terrestrial radiation.

    To my mind summing these two distinctly different values is nonsense !

    So can someone please explain why I should accept the simple algebraic manipulations involving radiation fluxes are correct when the results do not correlate with Planck curves.

    Remember the SB equation is intimately related to Planck’s equation.

    The worst example of the inappropriateness of algebraic manipulation involves confusing P(net) – the difference of 2 legitimate fluxes with a REAL radiative flux as I see all the “greenhouse effect” supporters doing all the time.

    Again plotting Planck curves shows this is just plain wrong !

    I do not pretend to know how to combine radiation fluxes BUT unless someone knows another method of describing a radiation flux besides Planck’s equation they need to explain why all of their algebra fails to produce a viable Planck curve !

    If the manipulations do not produce a viable Planck curve then the result CANNOT be equal to sigma T^4.

    Can someone explain why I am wrong on this ?

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