The Sensitive Kind

In the debate over climate change one of the most misunderstood and misused terms is sensitivity. Climate sensitivity is usually defined as the change in global mean surface temperature following a doubling of atmospheric CO2 once equilibrium is reached. The concept seems simple but there is a catch: the definition of 'equilibrium', which depends on the timescale employed. As it turns out, the timescales that nature uses—which can encompass thousands and even millions of years—cannot be compared with the century long timescale used in climate models. A recent online article, published by Nature Geoscience, states that accurate prediction of Earth's future warming hinges on our understanding of climate sensitivity. Moreover, only by studying climate change in the past, the paleoclimate, identifying all the factors involved and how they interacted can our understanding of climate sensitivity be improved.

The reason people are interested in climate sensitivity is because it is a supposedly simple way of telling how fast the world will heat up because of human CO2 emissions. There are two basic ways of estimating climate sensitivity: using numerical climate models and studying climate change in the past. In “Where are you heading Earth?” Richard E. Zeebe, from the Department of Oceanography, University of Hawaii at Manoa, compares the two approaches and concludes that only by reconstructing Earth's climate history can we accurately predicting Earth's future warming. Unfortunately, different climate feedbacks operate on different timescales, greatly complicating the analysis. The author provides the following example:

For example, continental ice sheets respond slowly to changes in radiative forcing and their feedback on temperature may be ignored in the model-derived equilibrium climate sensitivity on a centennial timescale. However, the very same feedback is naturally part of the equilibrium climate sensitivity derived from palaeoclimate records in cases where the temporal data coverage extends beyond the characteristic response time of ice sheets. In this example, the climate sensitivities derived from models and from palaeodata are obviously not the same and comparing the two is like comparing apples and oranges.

If Models and paleodata are like apples and oranges, which source to trust? “Unfortunately, model-derived climate sensitivities are subject to large uncertainties,” Zeebe states. “This is not because climate models are flawed but simply because the climate system is complex and accurate predictions are inherently difficult.” While I agree that getting accurate predictions from a complex nonlinear system like a climate model is difficult I also believe the models themselves to be fundamentally flawed. This is proven every time a new missing factor is discovered or an existing mechanism is found to behave differently the previously assumed. Real world observations often show model assumptions to be false, and that qualifies as being flawed in my estimation.

Where does the author comedown on the model vs data question? “Studying past climates to estimate climate sensitivity inarguably has one great advantage over theoretical computer models: it is based on actual data,” he states. Indeed, the entire point of the article is to stress the importance of enhancing our knowledge of paleoclimate conditions. The problem is there's a dearth of proxy data.

The best data we have from prehistoric times is arguable ice core data from Antartica and Greenland. But that only goes back about 800,000 years, possibly less if recently discovered basal freezing is altering the deepest, and hence oldest, portions of the ice. For older periods the proxy data come from ocean floor sediments. “In fact, most of what we know today about the climate of the past few hundred million years is based on deep-sea archives,” states the author, who then proceeds to decry recent cutbacks in ocean core funding (he is, after all, an oceanographer).

Section of ice core coming out of drill. Credit: Kendrick Taylor, WAIS Divide.

Zeebe goes on to describe measurements taken around the time of the PETM—always a favorite among climate change researchers—pointing out that he and his coleagues “recently estimated the size of the PETM carbon input based on sediment records of deep-sea carbonate dissolution and showed that the subsequent rise in atmospheric CO2 alone was insufficient to explain the full amplitude of global warming.” The point here is not their conclusions or the comments of others regarding the new carbon release estimates, but rather the lack of comprehensive and reliable proxy data for paleoclimate research.

Ideal, of course, would be reconstructions of changes in past atmospheric CO2 concentrations based on direct proxy records to constrain carbon input and climate sensitivity — not only during the PETM but also during other climate episodes of the past. Although progress has recently been made to improve existing proxies for past atmospheric CO2 concentrations and seawater carbonate chemistry parameters10, the uncertainties are still significant, particularly in the more distant past. At present, it seems that key to improving the accuracy of palaeoclimate-sensitivity estimates is to both refine existing pCO2 proxies and encourage creative minds to develop new pCO2 proxies.

To that end, the author calls for the establishment of a monetary prize to promote the development of better paleodata: “I suggest establishing a prize in climate science, sponsors willing, for anyone who can find a reliable and accurate proxy for past atmospheric CO2 concentrations that works over timescales from millennia to hundreds of millions of years.” Perhaps Dr. Zeebe has his entry ready to go if such a prize is established (just kidding).

Zeebe is not alone in calling for better resolution proxy data to provide historical insights into past climate change. In a companion article, “Convergent Cenozoic CO2 history,” David J. Beerling and Dana L. Royer claim that it is time for systematic testing of proxies, “against measurements and against each other.” The Cenozoic era, the past 65 million years of Earth's history, experienced a wide range of large climate variations. These including the transition from an ice-free planet to the onset of the Pleistocene glacial–interglacial cycles, with a number of sudden climate shifts in between.

“A decade ago, efforts to reconstruct atmospheric CO2 levels during this era showed fundamental disagreements between different proxy indicators of atmospheric CO2 concentrations,” they state. “This was especially true for the first half of the Cenozoic, with discrepancies between proxies spanning a range from less than 300 ppm to more than 3,000 ppm.” Following recent revisions, atmospheric CO2 reconstructed from terrestrial and marine proxies is shown in the figure below.

While Zeebe is calling for developing new proxies, Beerling and Royer are proposing that existing proxies be refined and recalibrated. But developing proxies of atmospheric CO2 levels is a formidable interdisciplinary scientific challenge. Beerling and Royer describe the process:

The process begins with identifying a clear response in a biological or geochemical system to changes in atmospheric or oceanic CO2 concentrations. This response must be sufficiently large to be detected in the fossil or sedimentary record and it must persist in the fossil record without alteration at a later stage. If these conditions are met, the proxy can be calibrated against modern systems. Finally, the proxy must be shown to detect known changes in atmospheric CO2 concentrations over a time span also covered by independent reconstructions or records.

Each stage requires assumptions and introduces errors, making the process long, hard and fraught with danger (at least to data accuracy). “We recognize that it will not be easy to constrain Earth's CO2 history by proxy, but it is crucial to continue to reduce uncertainties,” the authors state. But they are nothing if not optimists, claiming that a “consensus” is being reached with regard to such data. One would think that the term consensus would be avoided by anyone in climate research, given the ill repute it has garnered in the global warming debate.

Evidently consensus is broadly defined in this case. Currently, estimates of Pliocene (5.332 million to 2.588 million years ago) CO2 levels by numerous methods agree with a difference of around 50 ppm. That is about half of the increase in current CO2 levels attributed to human excess. Deeper in time and the differences grow considerably. If climate is as sensitive as they say, this level of accuracy is still insufficient. “A twofold variation in estimates derived from the different techniques remains,” Beerling and Royer admit. “It raises legitimate concerns over the credibility of the estimates of ancient atmospheric CO2 concentrations.”

Are the climate science estimates getting better, is the historical data improving? Perhaps. But it is important to recognize that our current knowledge of paleoclimate remains spotty and filled with errors. So, if studying paleodata is superior to climate modeling in the elusive hunt for an accurate sensitivity reading, and the proxy data used to study paleoclimate is itself suspect, where does that leave climate science? Right where its critics have suggested, an immature science that really cannot make any trustworthy predictions about future climate change. That fact is something we all should be sensitive to.

Be safe, enjoy the interglacial and stay skeptical.

In the debate over climate

In the debate over climate change one of the most misunderstood and misused terms is sensitivity. Climate sensitivity is usually defined as the change in global mean surface temperature following a doubling of atmospheric CO2 once equilibrium is reached. That was new information for me.

Very interesting...

Miami-Dade County is at the forefront of understanding sealevel rise and its effects because most of the county is below 20 ft of elevation. Furthermore, Miami Beach residents need to sand bag their front entrances during extreme high tides. As sealevel rises, so do fresh groundwater levels, causing freshwater flooding in the interior of the county, underscoring that this is not just a coastal problem.

como hacer un ensayo

Land subsidence

There are many areas around the world where land subsidence is a problem. In cities like New Orleans, Venice and Mexico City the land is sinking and has been for centuries. Land can sink for tectonic reasons (Earth's crustal plates are always moving and colliding with each other) or because of ground water. Natural ground water flow can dissolve some rock formations, leading to collapse, and over pumping by humans can also cause the ground to settle and sink holes to open. There is a good article here and a more technical discussion here.

The point that most people miss is that people are more than capable of causing subsidence without acknowledging their culpability. And on the coast or an island, sinking land is easy to mistake for rising sea-level. This is what is happening to Tuvalu. On the other side of the coin, some areas are actually rising, like the coast of Alaska. My point is that one should be very careful before crying "rising sea-levels!"

Maximum possible sensitivity

The absolute maximum climate sensitivity for one century has to be limited to 0.257 degrees Celsius, contrary to estimates ranging from Arrhenius 5 degrees through the IPCC 3.2 down to .45 C. According to the Resilient Earth page 106, the COMET Project determined that 70% of TSI is absorbed by the Earth's climate and 30% radiates back out to space. If all the rest were held in by CO2 then the increase during the twentieth century would have been only 0.6 + 0.257= 0.857 C.

Maximum possible CO2 sensitivity

In my initial comment above I gave the maximum possible sensitivity to the whole greenhouse effect. Usually sensitivity is stated for CO2 alone and for a doubling of it rather than for one century. CO2 is only a fraction of the whole effect and anthropogenic CO2 is only about 3% of the total CO2. At the current rate of about 100 ppmv per century increase in total CO2 it would take three centuries to double. The human contribution for the whole three centuries may not be more than 0.257 degrees C.

Earth's core heat

Just how do these models factor in the Earth's core heat? I have been told that the temperature is in the neighborhood of 5,500 of degrees C that at about 12 kilometers the temperature is about 200 degrees C, and that at 4 kilometers (the TauTona Mine) the temperature is over 30 degrees C. There really is not that much insulation. In northern Vermont (10 miles from Canada) we had a water line from a spring head that ran over 1500 feet at a depth of less than 3 feet and NEVER froze up in the winter! Any mechanical engineer will tell you the surface of the earth has to be approximately the same temperature as the surrounding air - thus it is giving off heat to the air/water.

Supposedly the thickness of the Earth's crust, floating on this massive ball of molten rock and metal, would be less than the thickness of an egg shell if the Earth were reduced to that size. Well where does this heat go? It has to radiate outward and must be warming the earth. Place a few ounces of molten solder in a Styrofoam (or one that will take the heat) cup and see if you can pick it up. Additionally, there are numerous vents on the floor of the ocean (many, many more than on dry land), especially along the ridge line at the center of the oceans, spewing massive (and I mean humongous) amounts of water heated to 350-400 degrees C. That is quite a bit of thermal energy being dumped into the ocean. And scientists didn't even realize they were there when all of this AGW hype started. How do the factor in all of this heating that bypasses any insulating properties of the crust? How have the geologists taken into account these phenomenon into the actions that caused the end of the ice age?

Having lived on a farm I know that it only takes a very small amount of warm water from a spring under a lake to prevent the formation of ice on the top of the lake - with very low air temperatures. And, if there is no spring, then all it takes is a small air pump, like you would use in a larger home aquarium, to keep a water opening on the lake. Could the weight of the ice on the contents caused the formation of more hydrothermal vents which in turn caused the end of the ice age?

Surely you have been under a "radiant heater" at a loading dock or in a service garage. The air temperature can be well below zero, but you feel perfectly warm in shirt sleeves, no coat needed. The radiant heat is not heating the air it is heating the solid objects. So what is all of this bunk about the IR capture of CO2 multiplying the heating effect? In my mind it would block the IR heating effect, like the filters you place on the thermal guard windows, not enhance it. I think some models need remodeled.

Water:CO2 Heat Transfer Potential Comparison

Average Tropospheric Concentration (ppmv): H2O (vapor): 20,000 CO2: 390
Specific Heat (kJ/kg·K): H2O (vapor): 1.80 CO2: 0.85 Air (Dry): 1.00
Latent Heat of Vaporization/Condensation (kJ/kg): H2O: 2,270
Molecular Weight (g/mol): H2O: 18 CO2: 44 Air (Dry): 29
Bouyancy (MW Gas/MW Air): H2O (vapor): 0.62 CO2: 1.52

Heat Capacity: (Average Tropospheric Concentration) (Specific Heat) (Molecular Weight)
Heat Capacity Ratio: H20 (vapor):CO2 = 20,000 (1.80 ) (18) / 390 (0.85) (44) = 44.4
Water:CO2 Heat Transfer Ratio w/Water Condensing and 50 degrees K cooling: 20,000 [(1.80)(50) + 2,270] (18) / 390 (50) (0.85) (44) = 51,258

1. Greenhouses work by restricting convective heat transfer; earth's atmoshere is open to convection.
2. With local atmospheric water vapor ranging from near 0 to 4% (40,000 ppmv), water based heat transfer potential is extremely variable.
3. The buoyancy of warm moist air transports water in the vapor phase to the upper troposphere where heat released by water condensation is radiated to space.
4. Lack of phase change, low concentration and negative buoyancy make CO2 irrelevant to atmospheric heat transfer processes.
5. Solar input is variable with seasonal and solar cycles.

1. CO2 is irrelevant to Earth's climate (At current concentrations, water has 50,000 times the heat transfer potential of CO2)
2. CO2 is not a significant greenhouse gas on planets where water is present in large quantities and exists in at least two phases.
3. Solar Input and water in three phases control the Earth's Climate

1. At 1,000 ppm CO2 and 50 degees cooling, the Heat Transfer Ratio drops to 20,000:1 (and CO2 is still irrelevant).
2. As CO2 concentration increases, the molecular weight of dry air increases thus increasing the relative buoyancy of moist air and increasing the rate of convective cooling.

Proof That Carbon Based Climate Change is a Scam

The assumptions used to compare the heat transfer potential of water to CO2 are reasonably correct. Thus combining the published thermal properties of water and CO2 together with measured atmospheric concentrations it is shown with scientific certainty that the potential for carbon based climate change is too small to be of any significance. Unless some currently unknown magic property of CO2 exists that discounts this analysis, carbon based climate change is pure hokum.

There exist lies, damn lies, statistics and modeling, in order of increasing deceitfulness. In the Great Climate Debate, we have seen them all.

Not quite irrelevant

While I am not convinced that CO2 plays a primary role in regulating Earth's climate under the conditions currently present on our planet—as you said, water is much more important—there have been times when it was of great importance. I am speaking of the several “Snowball Earth” episodes that occurred prior to the Phanerozoic Eon. During the period from 850 to 635 million years ago, called the Cryogenian Period, there were at least two ice ages where Earth froze nearly completely over. With little or no open water and very low temperatures there was practically no gaseous H2O to help retain the Sun's warmth.

Indeed, indications are that only a massive build up of CO2 in the planet's atmosphere, caused by millions of years of volcanic eruptions, managed to break the frigid grip of those ice ages. Though it is not as important to our present day Holocene climate, CO2 may play an important part in the transition from glacial to interglacial conditions, acting as a positive feedback when the orbital cycles of the planet shift the climate back to warmer conditions. CO2 may not be the all powerful climate controlling daemon portrayed by climate change alarmists, but it does have its part to play in the complicated system that is Earth's climate.

As for the question of convection, planetary rotation establishes large scale circulation cells that greatly complicate simple convection. On planets with little atmosphere, like Mars, the effect of all greenhouse gases is reduced. On planets with thicker atmospheres, like Venus, the effect of CO2 can be overwhelming. This is partly because of pressure broadening the absorption band and partly because of the optical thickness of the overall atmosphere. But again, neither of these conditions apply to Earth.

Gaia Survives Even the Deep Freeze

Doug, That's a beautiful description of Gaia's recovery mechanism; almost as elegant as DNA, the ultimate creation. So long as water liquid to vapor and back to liquid phase change continues on a global scale, water rules the climate. This is where we are at now. So, keep on drilling, keep on mining and don't for a minute feel guilty about driving your SUV. If you really want to green the earth 1,600 ppm CO2 is the goal. Plants, both aquatic and terrestrial, will thank you. Keep up the truly scientific analysis. Stop the Dogma and ideology. Dan Fauth, Environmental and Civil Engineer, Durango, CO