Climate Sensitivity

Climate Sensitivity Trending Down: Is A Climate Apocalypse Becoming Less Likely?


Global Warming

As I have reported earlier, several recent studies are suggesting that climate sensitivity, that is, the amount of warming in response to doubling the carbon dioxide content of the atmosphere by burning fossil fuels, is less than has been assumed by the U.N.'s Intergovernmental Panel on Climate Change. As noted earlier, the IPCC reported:

With regard to climate sensitivity, in 2007 the Fourth Assessment Report of the United Nation's Intergovernmental Panel on Climate Change (IPCC) estimated that "climate sensitivity is likely to be in the range of 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values." In IPCC parlance, likely means that there is a 66 percent probability that climate sensitivity falls between 2 and 4.5°C (3.6 to 8.1°F), with 3°C (5.4°F) as the best estimate.

Now a new paper in the Journal of Climate by statistician Nic Lewis suggests that "values substantially higher than 4.5°C" are unlikely and that any increase in average global temperature in response to doubled CO2 is likely to be constrained to a value of between 2.0°C and 3.6°C 1°C and 3.0°C.*

Over at the Cato Institute, climatologists Patrick Michaels and Paul Knappenberger have published a useful roundup of the latest studies on climate sensitivity. The chart below compares the various recent climate sensitivity ranges with the one assumed in the IPCC's latest draft of its Fifth Assessment Report (AR5).

roundup of climate sensitivity studies

Michaels and Knappenberger add:

Take special note of the new findings (and their mean) in relation to the black bar at the top labeled "IPCC AR5 Climate Models." Of the 19 state-of-the-art climate models used in the IPCC's newest Assessment Report (which is still in its draft form) exactly zero have an equilibrium climate sensitivity that is as low as the mean value of estimates from the recent literature included in our Figure.

Based on the collection of results illustrated in our Figure, the future climate change projections about to be issued by the IPCC are off by an average of a whopping 70 percent.

No wonder the IPCC is reluctant to lower their best estimate of the actual value of the earth's equilibrium climate sensitivity. If they did, they would be admitting that the collection of climate models they have chosen (there is choice involved here) to project the earth's future climate are, well, how should we put this, wrong!

It will be fascinating to see how the final version of the IPCC's Fifth Assessment Report ends up treating climate sensitivity. If climate sensitivity is in fact lower than many climate models assume, that means humanity has more time in which to respond to whatever man-made climate change is going to happen.

*Many thanks to commenter Greg F for pointing out my error in reporting.

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  1. What we need is comprehensive environmental legislation to control the economy NOW, before the problem vanishes entirely.

    1. Indeed, this is the greatest threat to climate science in our times.

    2. It's catastrophic climate-rate-of-change change.

  2. Does this mean the amount of Nobel Prize's they have will be revised downward too?

  3. "Is A Climate Apocalypse Becoming Less Likely?"

    No. It is just as likely as it ever was.

  4. Apocalypses are like a G-spot: Everyone thinks they know where they're gonna find it but the whole thing is just a myth.

    1. Until it happens. The Yellowstone caldera, for instance, is overdue for a blow.

      1. The Yellowstone caldera....yep...that is one hell of a G spot. Gaia is really working up to a squirter there.

        ( I will save y'all the trouble. This is why there are no female libertarians )

    2. Some time we need to have a talk FoE. The G spot is quite easy to find. Give me 50 random girls and I can find it 50 times in under a few seconds each.

      1. Yeah, I can find it too, but after the 3rd or 4th time, why bother?

        1. If you have to ask that question, I cant explain it to you.

  5. We libertarians ( Big L and little l ) are pathetic. Fucking pathetic.

    Margaret Mead, a proven fraud, and her Malthusian pals decide that the best way to reduce the population of the earth is to cook up a completely fabricated climate crisis to use as a pretense for legal and social changes. They say so openly and on the record. Then they start squawking about it as if in earnest. The press and academia fall to their knees and slurp their cocks frantically. Millions in the developed world fly into a panic over the impending DOOOOOOM. Billions are squandered on phoney baloney studies proving it to be so. Progressives latch onto it as their key to ultimate power. Al Gore, in spite of being batshit crazy, much?....a billion bucks off of a straight up con? Holeeeeey Shit.

    Why cant we pull off a stunt like that? Because we are pathetic?

    No, I think it is because no matter how you spin liberty, it always boils down to personal responsibility and paying your own way. Nobody wants to hear that shit.

    Where is Tony to tell me what a heartless bastard I am for not wanting to sacrifice several billion people to gaia and live in squalor under the boot heels of my betters?

    1. personal responsibility and paying your own way

      And that is exactly why so many people steer clear of libertarianism. It sucks having to take responsibility for your actions and earn what you want to have. It's much easier if someone else is to blame for your happiness or lack thereof.

    2. And they still haven't managed to reduce the population.

    3. Why cant we pull off a stunt like that? Because we are pathetic?

      Because we're not liars, frauds, and thieves like they are.

    4. Where is Tony

      Hah! We do miss him.

  6. We must have a world government take over the entire carbon economy to prevent Climate Non-Change. Science shows that the climate has been constantly changing over the entire history of Earth so we must act now to prevent Climate Non-Change.

    Al Gore is now standing by at the phone to receive your money to prevent Climate Non-Change. Have your carbon-free credit cards ready.

  7. Ron's description of results from Nic Lewis is a bit misleading. Nic Lewis posted a summary over at Bishop Hill .

    The F06 ECS PDF had a mode (most likely value) of 2.9 K (?C) and a 5?95% uncertainty range of 2.1 to 8.9 K. Using the same data, I estimate a climate sensitivity PDF with a mode of 2.4 K and a 5?95% uncertainty range of 2.0?3.6 K, the reduction being primarily due to use of an objective Bayesian approach. Upon incorporating six additional years of model-simulation data, previously unused, and improving diagnostic power by changing how the surface temperature data is used, the central estimate of climate sensitivity using the objective Bayesian method falls to 1.6 K (mode and median), with 5?95% bounds of 1.2?2.2 K. When uncertainties in non-aerosol forcings and in surface temperatures, ignored in F06, are allowed for, the 5?95% range widens to 1.0?3.0 K.

  8. GF: Didn't mean to be misleading. Will fix and amplify in the post. Thanks.

    1. NP Ron ... For the record, I didn't want to imply you did it with any malicious intent either.

  9. tarran had a great post in Ron's earlier article on climate change that pretty well sums up what's going on here.

  10. Is A Climate Apocalypse Becoming Less Likely?

    Yeah, how about a zero percent chance? I think that qualifies as "less likely".

  11. Now a new paper in the Journal of Climate by statistician Nic Lewis suggests that "values substantially higher than 4.5?C" are unlikely and that any increase in average global temperature in response to doubled CO2 is likely to be constrained to a value of between 2.0?C and 3.6?C 1?C and 3.0?C.

    A planet where multivariable systems do not behave with politically-convenient linearity?

  12. The real story is that doubling sensitivity has yet to converge on a single uncontroversial value, and that that failure to converge may signify that modeling is still in the course of evolving from art to science.

    For that very reason we should beware of Cato's incorrigable - and predictable - cherrypicking here- the range of sensitivity values in the peer reviewed literature is far broader than Michaels and Knappenberger suggest.

  13. Sounds liek a plan to me dude.

  14. I'll just leave this here, knowing that some will ignore it due to the source.

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