Guest post by Dr. Roger Pielke Senior
Missing The Major Point Of “What Is Climate Sensitivity”
There is a post by Zeke on Blackboard titled Agreeing [See also the post on Climate Etc Agreeing(?)].
Zeke starts the post with the text
“My personal pet peeve in the climate debate is how much time is wasted on arguments that are largely spurious, while more substantive and interesting subjects receive short shrift.”
I agree with this view, but conclude that Zeke is missing a fundamental issue.
Zeke writes
“Climate sensitivity is somewhere between 1.5 C and 4.5 C for a doubling of carbon dioxide, due to feedbacks (primarily water vapor) in the climate system…”
The use of the terminology “climate sensitivity” indicates an importance of the climate system to this temperature range that does not exist. The range of temperatures of “1.5 C and 4.5 C for a doubling of carbon dioxide” refers to a global annual average surface temperature anomaly that is not even directly measurable, and its interpretation is even unclear, as we discussed in the paperPielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229.
This view of a surface temperature anomaly expressed by “climate sensitivity” is grossly misleading the public and policymakers as to what are the actual climate metrics that matter to society and the environment. A global annual average surface temperature anomaly is almost irrelevant for any climatic feature of importance.
Even with respect to the subset of climate effects that is referred to as global warming, the appropriate climate metric is heat changes as measured in Joules (e.g. see). The global annual average surface temperature anomaly is only useful to the extent it correlates with the global annual average climate system heat anomaly [most of which occurs within the upper oceans]. Such heating, if it occurs, is important as it is one component (the “steric component”) of sea level rise and fall.
For other societally and environmentally important climate effects, it is the regional atmospheric and ocean circulations patterns that matter. An accurate use of the terminology “climate sensitivity” would refer to the extent that these circulation patterns are altered due to human and natural climate forcings and feedbacks. As discussed in the excellent post on Judy Curry’s weblog
finding this sensitivity is a daunting challenge.
I have proposed definitions which could be used to advance the discussion of what we “agree on”, in my post
The Terms “Global Warming” And “Climate Change” – What Do They Mean?
As I wrote there
Global Warming is an increase in the heat (in Joules) contained within the climate system. The majority of this accumulation of heat occurs in the upper 700m of the oceans.
Global Cooling is a decrease in the heat (in Joules) contained within the climate system. The majority of this accumulation of heat occurs in the upper 700m of the oceans.
Global warming and cooling occur within each year as shown, for example, in Figure 4 in
Ellis et al. 1978: The annual variation in the global heat balance of the Earth. J. Geophys. Res., 83, 1958-1962.
Multi-decadal global warming or cooling involves a long-term imbalance between the global warming and cooling that occurs each year.
Climate Change involves any alteration in the climate system , which is schematically illustrated in the figure below (from NRC, 2005)
which persists for an (arbitrarily defined) long enough time period.
Shorter term climate change is referred to as climate variability. An example of a climate change is if a growing season 20 year average of 100 days was reduced by 10 days in the following 20 years. Climate change includes changes in the statistics of weather (e.g. extreme events such as droughts, land falling hurricanes, etc), but also include changes in other climate system components (e.g. alterations in the pH of the oceans, changes in the spatial distribution of malaria carrying mosquitos, etc).
The recognition that climate involves much more than global warming and cooling is a very important issue. We can have climate change (as defined in this weblog post) without any long-term global warming or cooling. Such climate change can occur both due to natural and human causes.”
It is within this framework of definitions that Zeke and Judy should solicit feedback in response to their recent posts. I recommend a definition of “climate sensitivity” as
Climate Sensitivity is the response of the statistics of weather (e.g. extreme events such as droughts, land falling hurricanes, etc), and other climate system components (e.g. alterations in the pH of the oceans, changes in the spatial distribution of malaria carrying mosquitos, etc) to a climate forcing (e.g. added CO2, land use change, solar output changes, etc). This more accurate definition of climate sensitivity is what should be discussed rather than the dubious use of a global annual average surface temperature anomaly for this purpose.
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Even more basically, it starts with the assumption that feedback is in fact positive for CO2. What if it isn’t?
In not too distant future graphics of the above type may have Geomagnetic field added, or at least I hope….
http://www.vukcevic.talktalk.net/NFC1.htm
Maybe someone is saying climate sensitivity when temperature sensitivity is intended?
What would be the collective climate science response to the statement, “It could be the that atmospheric sensitivity to CO2 is essentially zero?”
I believe that scientists measured and listed the following heat adsorption figures: 1) Oxygen = X, Nitrogen = X, yes they were very close to each other; CO2 = Y > X, a mixture of 20% O2 and 80% N2 was then measured and yielded a value VERY close to = Y.
I did NOT bookmark this article, but I believe it was published in Nature nearly a year ago. Has it since been debunked? Has it been buried? Is it totally unfounded? I would think this type of study would be central to resolving whether any Greenhouse gas theory around CO2 even applies? Science has the tools to quantify and repeat or discredit this type of thing – is anyone aware of any results?
Experts, more learned men/women than me and Faux-Mountebanks, all are welcome to reply! Dave
yabut if you put more joules into the ocean, it gets warmer. In any event, how are you going to measure those joules if not with a thermometer. (commieBob now ducks and hides under his desk) 😉
This is a much more rational way of looking at the issue. Thanks Roger.
Well I have been trying to discover for years, just who or what first described Climate Sensitivity in terms of its relation between teh global mean surface Temeprature, and the logarithm of the atmospheric CO2 abundance.
I was under the impression that this was a creation of the late Dr Stephen Schneider at Stanford..
I take a dim view of people who say that some relationship is “logarithmic”, unless they can demonstrate either by measurement or theory, that such a relationship is mainatained over at least several orders of magnitude (three min) of the variable whose logarithm tracks the other variable.
My point is simply that just because a relationship, is non-linear; does not automatically mean it is logarithmic. When somebody says it IS logarithmic, that to me means that a CO2 increase from 280 ppm to 560 ppm produces the same Temperature increase, as going from 1 ppm to 2 ppm. That IS alogarithmic relationship.
Mathematical curve fitting experimental data, to some function is a well practised art. In the Mauna Loa era, we have somewhat less than 1/3 of one doubling of the ML CO2 number, from 325 ppm to today’s 390 ppm.
That data can easily be fitted to an ordinary power series, over some restricted range, and to as accurate a fit to the data, as can say a logarithmic equation.
Usually one looks at logarithmic relationships; when some theoretical basis for believing it is logarithmic, exists, such as radioactive decay for example, or the Current-Voltage relationship of a Semiconductor diode junction at constant Temperature.
GHG absorptance of LWIR radiation has its roots in Beer’s Law relating the absorptance of chemical solutions to the molar concentration.
But one must not confuse optical absorptance with energy transmission.
The energy transmitted by an optically absorbing medium, can be orders of magnitude higher than (1-a) where (a) is the optical absoptance for some spectral region, and can have a Beer’s Law relationship.
That transmitted energy will likely be in a quite different spectrum, from that represented by the Beer’s law absorption.
This situation exists in the CO2 GHG absoption case. CO2 has well understood infra-red absorption spectra; but it is also well known that the absorbing CO2 molecule, seldom gets a chance to re-emit the photon that sent it to an excited state. The energy will become thermalized through molecular collisions that occur thousands of times faster than spontaneous emissions of the decay of the resonance absorption modes. and that energy simply raises the Temeprature of the main atmospheric gases. They in turn radiate a purely thermal (BB-like) continuum spectrum, that just happens to overlap the same range as the absorption band (of lines) for CO2.
That radiation is emitted isotropically from every level in the atmosphere, from the very surface to the end of the atmosphere, and only in the highest coldest rarest atmospheric regions does the CO2 get a chance to spontaneously emit its own characteristic band of frequencies. And at every level in the main body of the atmosphere, about half the emitted radiation is emitted upwards towards space, and half downwards to the surface. It matters not whether the surrounding layers are transmissive or absorptive. The transmitted portions of the spectrum, still travel about half in each direction, and the absorbed portions simply lead to a subsequenct emission of some thermal spectrum, that likelwise splits in two hemispheres.
Temperature, being an intensive variable, which means that it is possible to measure the temperature of the earth’s systems that vary with the seasons, the sun’s cycles, and orbital parameters etc. These would be the atmosphere, the oceans, the ice caps and the solid earth’s surface to a depth that changes with the seasons.
Possible yet difficult, so using the anomaly to measure the changes rather than the absolute is acceptable scientifiacally.
To replace that metric with a conglomeration of statistical measures, which it would probably be impossible to agree on which metrics to monitor in the data, seems without meric. Considering that finding longterm data trends for some of the suggested metrics, for example the geographic range of malaria carrying mosquitos, and agreeing on their validity, would be difficult.
What would the units be?
mosquito bite*hurricane * droughts per ppm CO2* rainforest acres cut down * solar variability
I mean we can track the changes in those variables, but to define climate sensitivity in terms of them is difficult.
If I am misunderstanding the point here then you can have my most sincere
Roseanna Roseannadanna
“never mind”
Roger Pielke:
Why do you think that it is an indirect measurement is an issue? There are plenty of quantities that get measured indirectly in meteorology, climate and other sciences. (More that get measured indirectly than not, I’d think.)
The question of interpretation (and utility which is really what you are driving at) depends on what you are planning on using the number for. We live in the surface layer, most of the land biosphere does too, so knowing how the temperature responds to CO2 does act as a proxy for the impact of CO2 emissions on humans (changes in growing seasons, shifts in dry belts etc).
Are there other numbers? Sure, and any policy maker needs to read further than just global mean temperature change.
You are right to say that there is perhaps too much fixation on CO2 sensitivity, but your more general definition of climate sensitivity could be quantified by including a list of global values, which would have to include global mean temperature, as well mean precipitation, mean ocean pH and so forth.
One question: Wouldn’t it be rather difficult to empirically demonstrate a cause-and-effect relationship between the broad definition of “weather statistics and other climate components” and “a climate forcing,” particularly on a global scale? I mean, we’ve yet to do that even where it comes to a single component, say heat content vs CO2.
You’re talking a lot of time and scientific shoe leather, which is fine by me, but I wouldn’t expect your definition to be embraced by the warmist camp anytime soon. They’re in too big a hurry.
I agree that global average annual temperature is not an incredibly useful metric of “climate” sensitivity, but only of temperature sensitivity. But, if one understand the implications of that temperature sensitivity, one can see the implications for the longer-term (but not daily) statistics of weather. For example, if we know that at 2 degrees C of global warming, we will get 7 to 10 C above the Arctic circle, than that also tells you to expect sea ice and permafrost to decline. This decline in sea ice has implications for atmospheric circulation patterns which of course affect longer-term weather patterns. What it comes down to is that experts can understand the potential implications of global temperature changes and thus sensitivity to GH gas increases measured in this manner can be very useful in making future potential scenarios based on that sensitivity. Those scenarios could be completely wrong of course, but they require some measurement of sensitivity to output anything at all.
I agree that OHC is the metric we should be using to measure the AMOUNT of global warming, assuming we can ever come up with a reliable way of measuring it. But the physical impacts of added heat (I hasten to add, if any) are felt at the land surface, which is where we humans and all the animals, trees, plants and crops we depend on live. So we can’t dismiss surface temperature as “almost irrelevant”. It’s the basic metric that measures the IMPACT of global warming, which is not the same thing as the amount. (And it’s also the more important. No one would care about global warming if it wasn’t going to do anything.)
Bishop Hill has an relevant post regarding climate forcings that quotes another blogger’s question to Freeman Dyson and his answer about important climate issues:
“1. What questions should intelligent lay-people be asking about climate, and to whom should these questions be directed?”
“Answer to your question”
“1. Both for humans and for wildlife, water is more important than temperature. Intelligent lay-people should be asking questions about water. What are the trends over the last hundred years for total rainfall, total water vapor in the atmosphere, total volume of ice on the continents, volume of fresh water in aquifers, distribution of droughts and floods, and last but not least, sea-level? Why did the Sahara change from green six thousand years ago to desert today? What are the implications for public health and natural ecology of the changes in flow and abundance of water?”
http://bishophill.squarespace.com/blog/2011/2/28/some-correspondence-with-freeman-dyson.html
I keep coming back to the fact that the IPCC altered a thermodynamic constant for CO2, bumping a 0.12 degree effect with doubling to 1.2—1.5 deg by multiplying the constant by 12-fold, all the while marveling at how consistent this constant had been while actually changing it at the same time – quite backhanded. Then, they used water vapor as a positive forcing factor to arrive at much higher values for warming with doubling, here, specifically pretending that atmospheric convection did not exist as part of a global heat engine, a powerful negative feedback machine.
Wh is so little made of this duplicity and fraud?
“Climate Sensitivity is the response of the statistics of weather (e.g. extreme events such as droughts, land falling hurricanes, etc), and other climate system components (e.g. alterations in the pH of the oceans, changes in the spatial distribution of malaria carrying mosquitos, etc)”
Hmmm. Changes in the spatial distribution of malaria may conceivably occur as a result of climate sensitivity, but the emphasis must be on the “may”. Certainly malaria has moved well southwards in Southern Africa since the mid ‘seventies, but without any detectable change in climate. The southern drift that has occurred can all be attributed to anthropological causes. The population has grown tremendously over that time period resulting in considerably greater movement of people and consequent greater carrying of the insect. Anti malaria preparations that worked unfailingly in the mid seventies are no longer nearly as effective. Governmental chemical actions to fight the the mosquito spread, have in some parts (Zimbabwe in particular) either become less effective or have broken down altogether.
I feel that the scientific community should avoid this type of bland statement, if for no other reason than that there will no lack of Governments who will happily claim compensation for the damage done to them by the West’s nasty CO2.
There is enough disagreement about the temperature variation and getting such obscure things involved like “land falling hurricanes” will only escalate the difficulty in defining what is going on.
Temperature should not be the problem that it, but the way it is used is a problem. Variations and trends in the different regions would be a better, but more complicated way. Most of the warming has been in the Arctic region. That is not a global effect, but the polar regions are important to climate.
Not sure what is the best way to define sensitivity, but less subjective is better than more subjective and weather events are very, very subjective.
Great post by dr. Pielke!
Carrick: Why do you think that it is an indirect measurement is an issue?
“Global mean temperature” is not only indirect, it’s also wrong. Even if we covered the earth with a grid of more than a billion temperature sensors of previously unmatched quality, the arithmetic mean of those readings would be a bad measure of “global warming”, since +10 C in the arctic corresponds to much less incremental athmospheric heat content than +10C in the tropics.
Dr. Pielke,
I agree with you that the surface temperature response to doubling CO2 (e.g. standard climate sensitivity) is not a full description of the effects of a climate forcing, but rather a limited subset of those effects. However, discussing how the full effects (which are characterized by even more uncertainty than sensitivity itself) should be communicated to the public and policy makers is a separate issue from what our best understanding of the science says about climate sensitivity as generally defined. It hardly amounts to a wittily alliterative “zinger” on my part that I referred to the current notion of climate sensitivity, rather than your more encompassing definition. Even were we to broaden the definition, we would still need a term for the surface temperature response to forcings, as it is important piece to the puzzle.
Judy Curry’s weblog article Spatio-temporal chaos is exactly what I have been looking for for years!
I am glad that someone like Judy Curry has expressed so well the unavoidable facts about chaotic systems and how they relate to climate.
I have to take exception to the semi-definition of Climate Change. There is the persistent predication that the Climate is static, and as a consequence, any alteration of this stasis constitutes “Climate Change”. The climate is not static; climate is a complex of events that isn’t even in equilibrium, let alone static. Acknowledging and accepting “climate change” as a definable, measurable paremeter is a mugg’s game, and we’ve already been beat to death with it. There is NO universally agreeable definition for climate change that has any useful scientific value whatsoever.
Thanks for the feedback that has been sent. I have just two further comments here. First, while ocean heat content requires the measurement of temperature, it also includes mass so that the proper unit of global warming (Joules) can be calculated. This is not true with the two dimensional analyses of surface temperatures which are used to calculate global averge surface temperature anomaly. There is no mass associated with this determination of heat.
Secondly, even with respect to surface temperature, it is a flawed metric. For example, what height is this temperature measured at (e.g. the surface, 2m etc). This matters in terms of the anomaly values that are computed as we have shown, for example, in our recent paper
Steeneveld, G.J., A.A.M. Holtslag, R.T. McNider, and R.A Pielke Sr, 2011: Screen level temperature increase due to higher atmospheric carbon dioxide in calm and windy nights revisited. J. Geophys. Res., 116, D02122, doi:10.1029/2010JD014612.
http://pielkeclimatesci.files.wordpress.com/2011/02/r-342.pdf
There is the issue that anomalies in absolute humidity alter the anomalies in temperature even if the total heat of a volume of air does not change, as we showed in our paper
Pielke Sr., R.A., C. Davey, and J. Morgan, 2004: Assessing “global warming” with surface heat content. Eos, 85, No. 21, 210-211.
http://pielkeclimatesci.wordpress.com/files/2009/10/r-290.pdf
These are just two of a number of issues with this data set. We can add all of the seminal work that, Joe Daleo, Anthony Watts and surface project volunters have done on the quality of the siting, as well as the failure of the land part of the surface temperature record to clearly define how they massage the data in order to create what they call a “homogenized” analysis.
We will have more to report on the surface temperature data set soon. My recommendation, however, is to scrap the use of surface temperatures to indirectly diagnose global warming and replace with upper ocean heat content change which is a direct measure of climate system heat changes.
Until the temperatures get above the Holocene Optimum everything we are talking about is within normal variation with or without CO2.
Zeke’s problem is formulating “climate change sensitivity” in terms laid out by the IPCC authorities.
In an important sense, Zeke is parsing a different problem from the narrower one Pielke, Sr., attacks above. Zeke and Lucia’s friends attempt to declare and decide on the range of probable and improbable problems pertinent to climate change science. Zeke hopes to move beyond debate to zero-in on genuine scientific problems; this makes agreement (or “consensus”) a priority before progress can be made.
Yet all of this is highly speculative, dependent upon the context of one’s selective knowledge of the literature, and besides the point of genuine scientific criticism. “How many angels can dance on the head of a pin” theology speculations, but dressed up as science. Furthermore, Zeke shows us that Linzen’s lessons about the corrupt fatuities of climate science have not yet been learned by his cohorts. (SEE “Climate Science – is it currently designed to answer questions,” Nov 2008) Instead, they must be papered over and denied as genuine problems.
This is not science, but politics IPCC-style, plain and simple.
It is striking that the level of water vapor in the upper atmosphere (300mB level) has dropped steadily and substantially (20+%) in the past60 years: http://www.climate4you.com/ see the greenhouse gases section, yet there has been no effort afaik to evaluate either the causes or the consequences of this change.
At a minimum, it seems inconsistent with the idea of increasing CO2 raising the atmospheric water vapor level.
More generally, if this kind of change in the Earth’s primary greenhouse gas has so little measurable effect, why would a comparable change in a vastly less abundant trace gas make a difference?
R Gates: you said “I agree that global average annual temperature is not an incredibly useful metric…” You made up a new term there. Perhaps you meant global average temperature anomaly?
I would ask for support for “For example, if we know that at 2 degrees C of global warming, we will get 7 to 10 C above the Arctic circle,…” but your answer is probably climate models. Are those the same models that predicted that AO would increase? The ones that were trumpeted as validated when AO was increasing in the 90’s And now that AO is decreasing, those models are quietly tossed aside for new speculations that ice loss causes negative (decreased) AO? Bottom line: your claim is an unknown. The decline in sea ice was a well known prediction in the 90’s yet those models predicted the opposite of what is now happening.