Climate Sensitivity Higher Than We Thought, Researchers Find

JR:  There’s been a lot of confusion this year on how sensitive the climate is to greenhouse gases (see Media Misleads On Flawed Climate Sensitivity Study: Avoiding “Drastic Changes Over Land” Requires Emissions Cuts ASAP).  Given all the media attention given to one (flawed) study, a little attention to other studies seems worthwhile.


by Rolf Schuttenhelm, reposted from Bits of Science

An international research group led by Gothenburg University looked at the impact of organic aerosol feedbacks on climate sensitivity

It serves to show individual climate sensitivity studies are never conclusive but add up bits of fresh understanding to an already enormous pile of data and knowledge.

Right in the middle of that pile is the IPCC. Should the entire pile shift or change shape – rest assured, then the official IPCC climate sensitivity range [now around 3 degrees Celsius for a doubling of atmospheric CO2] will do the same in their 2013 climate report.

The new Swedish climate sensitivity research has just been published (PDF) in Atmospheric Chemistry and Physics, the open-access journal of the European Geosciences Union.

The authors argue that climate sensitivity could be ‘greater than previously believed’ because in the initial phases of the current CO2-induced warming plant life has emitted larger amounts of precursor gases that lead to the formation of reflective or blocking* secondary organic aerosols (SOA) in the atmosphere, thereby acting as a negative climate feedback, and masking part of the ‘warming’ that’s occurring underneath.

Because of the increased production of organic aerosols the sensitivity of our Holocene climate system to a doubling of the atmospheric CO2 concentration can not simply be extrapolated** from the observed temperature rise, but would in fact be higher.

Of course we would also like to know if an increase in organic aerosols leads to climate cooling, can we count on this aerosol increase to continue as we keep emitting ever more climate-warming greenhouse gases? The new study shows the chemical processes involved in the formations of SOAs favour higher temperatures. But as the aerosol precursor gases are a by-product of plant growth, let’s not ignore plants too live in ecosystems – and yesterday we learned ecosystems will change dramatically under continued climate change. So perhaps the answer is no, and this cooling is just as temporary as the thermal of the oceans, and warming will increase just about at the point where our planet’s many positive climate feedbacks from the ecological carbon cycle will start to pick up. Doesn’t this only confirm the theoretical nature of ‘climate senstivity’? At some point it will in fact be the icecaps, and indeed your backyard thermometer that will do a much better job at explaining what is going on…

— Rolf Schuttenhelm is a climate analyst at MeteoVista and a Science Writer for Bits of Science, where this piece was originally published at Bits of Science.

[*) These SOAs are also more important to cloud formation than previously thought, other recent research shows – but such ‘organic clouds’ may in fact only complicate the climate story further, as clouds may be positive feedbacks to our planet’s warming. Lead author Kent Salo of Gothenburg University summarises this complexity as follows: “Particles in the atmosphere basically have a cooling effect on the Earth, and they affect cloud formation. The greater the number of particles in the air, the greater will be the number of cloud droplets. This affects the lifetime of the clouds and the amounts of precipitation, and consequently, the climate. Today, we do not have a fundamental understanding of how SOA particles are formed and the properties they have, despite them being an important component of, for example, climate models.” So basically they cool and elsewhere they may at least interfere with precipitation patterns, but no one is really sure to what effect.]

[**) Noteworthy at this point is that there are many other reasons why climate sensitivity should not be derived from that temperature graph – most notably the fact that our planet’s warming is a much delayed response to the rise of atmospheric greenhouse gases – because of the large thermal mass of our oceans. It is estimated that delay could be about 4 decades, which implies the current warming is the effect of combined emissions up to around 1970, which have about doubled since – inevitable future warming.]

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7 Responses to Climate Sensitivity Higher Than We Thought, Researchers Find

  1. Leif says:

    I’ll believe Corporations are “People” when they take responsibility for their mess and pay to clean it up.

    Like every other “person” in the world is “supposed” to do. You know, that “do unto others” story…

  2. Merrelyn Emery says:

    Four decades. Oh dear!

    But part of me is not surprised at all – when one practices systems thinking (and the Earth is a system), one is automatically very suspicious of anything that looks remotely like a linear extrapolation, ME

  3. Rabid Doomsayer says:

    The Milankovitch cycles are so very gentle and yet result in massive swings in and out of ice ages. What we have done is a much more violent change in forcing, so yes I think we have significantly underestimated sensitivity.

    The huge lags in the paleo record cannot be counted on now. The sheer magnitude of what we are doing must inevitably result in a quicker climatic response. We have seen how fast the icebox melts when we apply a candle, now we expect the icebox to melt at the same rate when we apply a blowtorch.

  4. Mike Roddy says:

    It’s nice to see this kind of discussion, and Cox’ work is apparently holding up. The physics of particulates is fairly straightforward.

    This is not the case for plant life on earth. In the boreal, for example, one would expect slightly higher growth rates from elevated CO2 and longer growing seasons, increasing sequestration. On the other side is ecosystem degradation, leading to damaged forests, including fires, insects, and inability to move ranges quickly enough. A sick ecosystem switches from a sink to a source.

    My New Year’s wish is to see CP address these very complex biological interactions. The information that we have is incomplete, and global extrapolations difficult. This must be addressed in greater detail, however, in spite of all of the obstacles.

  5. Solar Jim says:

    Tombstone in graveyard:

    Here Rests Humanity – Climate Impacts Were “Worse Than Previously Thought”
    “Greater Than Previously Believed”
    “No One Saw This Coming”
    “No Way, Dude. 1970?”

  6. EDpeak says:

    “A doubling of co2 will cause X degrees of warming” is itself a simplification

    Even more narrowly “a doubling from 280 to 560ppm will cause X degrees of warming” still doesn’t have one single answer, it seems to me, as explained below.

    Granted, all scientific statements are only models, approximations of reality, and resorting to such simplifications is necessary for science or we’d never move forward since we can’t morel 100% of everything perfectly..and even more so some level fo simplification is needed for having a public debate


    It surely matters HOW the doubling happens, even if we restrict to doubling from 280ppm to 560ppm (since doubling from 1ppm to 2ppm or even 50ppm to 100ppm may not cause the same X in “increase by X degrees”)

    Why? For one thing, the RATE of increase.

    If this is an order or magnitude (or more) faster than past rates of increase, that could mean we warm by Y degrees where we’d otherwise warm by X degrees.

    Right now we are warming about 60 times faster than the fastest rate of co2 change observed in the previous 800,000 years, quote:

    “The “scary thing”, he added, was the rate of change now occurring in CO2 concentrations. In the core, the fastest increase seen was of the order of 30 parts per million (ppm) by volume over a period of roughly 1,000 years. “The last 30 ppm of increase has occurred in just 17 years. We really are in the situation where we don’t have an analogue in our records”


    I could give other examples where “the value of X depends on the HOW of the co2-doubling” like: did ALL of it happen by methane release and co2 release in the arctic? A silly example on one level since it’s not even close to true that all of the extra co2 and methane (and methane later converted into co2) from the Arctic..but obviously if 0% versus 100% of the extra 280ppm of going from 280ppm to 560ppm happened that way versus in other ways, the amount of arctic feedbacks triggered may not be the same in one scenario versus another…you can add your own examples of how and why the value of X will depend on how the extra 280ppm is released.

    But going just back to the main serious example I gave, even if true that “all other things being equal, a doubling from 280ppm to 560ppm causes 3C warming” then it’s NOT necessarily true that you get only 3C of warming if the 280-to-560 doubling comes about 60 times more rapidly than even the most-extreme-fastest previous rates of co2 increase found in the 800,000 year record reviewed in the above bbc story.. (the 2006 publication of the EPICA ice cores)

    We are also higher in co2 levels than anytime in about the last 15,000,000 years, but not sure how many times faster “Than any previous time in the pst 15m years” we’re increasing..but “how many times faster is the rate of increase than any previous time in the last 800k years?” is answered in the above, and, all other things being equal, it’s a fair guess (and a prudent assumption under Precautionary Principle) to prepare oneless for it causing perhaps _more_ than a 3 degrees C increase, due to the extreme nature of the _rate_ of co2 increase, by geological standards…

    We’re not just playing with fire, we’re playing with fire with our faces, and our children, right near the flames edge..if the fire suddenly expands, trouble!

  7. Mulga Mumblebrain says:

    Needless to say the denialists, and the Murdoch pathocracy in particular, are running a hard line that climate sensitivity is lower than expected, that the Communist watermelon ‘alarmists’ have been lying, in order to achieve through the ‘climate change conspiracy’ what they could not achieve in the Cold War, ie the destruction of capitalism and forcing Rupert to get a real job yada, yada, ya bloody da. I seem to recall Lomborg running that line, but perhaps it’s just a dyspeptic hallucination caused by something I ate.