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Uncertainty Is Not the Basis for Investment

Posted on 22 February 2012 by jg

Warren Meyers, writing in Forbes magazine (Forbes 2/9/12), argues that breaking the theory of AGW into three parts undermines the potency of the often cited 97% consensus (Science, 03 December 2004):

Part 1) doubling CO2 induces global warming of 1 degree C.
Part 2) CO2-based warming will be amplified by feedback effects.
Part 3) the results will be bad for civilization.

Meyers argues that the 97% consensus is valid for part 1, but breaks down when parts 2 and 3 stand apart. Yet, his support for this censensus breakdown diverges from what a careful reading of the climate change literature would offer. He also takes on the more difficult position of proving negatives, and so additional information from the peer-reviewed literature should move his conclusions toward the conservative direction. (By "conservative," I mean, if you have a mild interglacial that has been conducive to civilization and prosperity, don't mess with it.)

Before celebrating our agreement on Part 1, it should be noted that 1C per doubling of atmospheric CO2 may be an underestimate and that 1.2 C may be more accurate (Hansen and Sato). Whether the value is 1 or 1.2, this is no small change for two reasons:

1) we are near 1C already, leaving little breathing room, and

2) Hansen makes a plausible case that ice core climate reconstructions have overestimated the ultimate warmth of the previous interglacials, thus we had less breathing room than we may have counted on if we are to preserve our mild interglacial climate.  

Since Meyers' article is published in Forbes business magazine, perhaps I can compare this to financial investment: Have my advisors thoroughly apprised me of the risks before I invest in a warmer Earth? Do I want to be cautious (overestimating the risks) or daring (underestimating or disregarding the risks)? Think of risks as Earth's feedback effects, Meyers' Part 2.

On Part 2, that CO2-induced warming is accompanied by feedbacks, Meyers and I diverge on our reading of the scientific literature and on where to apply caution or engage in risk.

Meyers: "IPCC assumed that strong positive feedbacks dominated" and "catastrophic global warming advocates are wrong to over-estimate our understanding of these feedbacks"

The IPCC did not assume. It summarized the body of scientific literature which, using many different lines of evidence over many different time frames, concluded that the empirical evidence overwhelmingly suggests that warming induces positive feedbacks (see also Skeptical Science, Climate Sensitivity). A look at the palaeoclimate record reinforces this:

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These data show a repeating pattern: Global cooling walks a gradual pace (blue arrow), often taking four times as long to reverse the onset of warming (red arrow). Thus, warming related feedbacks are more abrupt, and should be more disturbing to anyone looking for a safe, long-term investment. 

A good investor would try to understand why risk-associated changes occurred. E.g., why did global climate snap out of a glacial era and create warm interglacials? Orbital changes in tilt and precession (Huybers, Nature, 08 Dec 2011) offer likely destabilizing triggers. The onsets (gray highlights) of the past four interglacials coincide with orbital changes that brought an increase of sunlight (red) to the northern hemisphere while the global sunlight (black) changed little.

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The black line represents total mean insolation and is important in understanding Earth's portfolio of warming-related feedbacks. These data show that Earth is extremely sensitive to changes that merely redistribute energy, in this case, by warming the northern hemisphere. There was fractional net gain in total energy (less that 1 W/m2), yet interglacials occurred with rapid onset. To get Biblical: Warming begets warming. If a long slow wobble (precession) was sufficient for Earth's feedbacks to raise the global temperature 8-12 degrees, we should be cautious, wary, risk-adverse of a global disturbance of 1 degree C, as this one degree disturbance occurs on top of an interglacial.

Meyers also underestimates another significant risk in Earth's feedback portfolio, how clouds will respond to warming.

Meyers: "On the other hand, water evaporated by rising temperatures may form more clouds that shade the Earth and help to reduce temperatures. Whether future man-made global warming is catastrophic depends a lot on the balance of these effects."

Meyers has missed an opportunity to point out that scientists are studying the cloud and water vapor angles (e.g., Dessler, 2010; Dessler and Sherwood, 2009). According to Schmidt et al. (Journal of Geophysical Research, 2010), clouds account for approximately 25% of the greenhouse effect. So, while Meyer cites the cooling effect of clouds, he fails to mention 25% of the greenhouse warming effect.

And what is the current understanding of clouds? Dessler (Science, 10 Dec. 2010) demonstrates that the cloud feedback effect over 2000 – 2010 has been slightly positive, 0.54 +/- 0.74 W/m2, and thus "a small negative feedback effect is possible but one large enough to cancel the climate's positive feedbacks is not supported" -- Dessler. This, however, is not a resolved issue, so a conservative interpretation is that as far as we know, clouds do not appear to be a negative feedback needed to counter warming, and it's too early to used clouds as a variable to dismiss the impact of global warming.

The other key feeback that Meyers omits is the water vapor feedback. Per Dessler and Sherwood (Science, 20 February 2009), "the water vapor feedback is is virtually certain to be strongly positive, with most evidence supporting a magnitude of 1.5 - 2.0 W/m2 per degree of warming."

So, considering clouds are neutral, and water vapor feedback well-established, I think the risk is most succinctly put by Meyers's own words:

Meyers: "Whether future man-made global warming is catastrophic depends a lot on the balance of these effects"

Hence, Meyers has framed the question to answer itself, but not yet put in all the data.

Risk could be swept aside if we had reason to believe that rising CO2 levels were not affecting Earth's energy budget. To this effect, Meyers makes his most flawed claim: that the missing heat from Earth's energy budget has not been found in the oceans. In fairness, it's difficult to say something isn't happening. It means he has to survey all the literature for lack of proof, and then monitor for new developments. In this case, current research is finding the missing heat in the oceans (NOAA) where it has the potential to create and sustain a new climate regime, one that may not mesh with our immense investments in water storage, agricultural, transportation and coastline infrastructure.

It's probably not necessary to critique Meyers's part 3, that warming must be bad, for our difference over part 2 is sufficient. However, in looking at the future, we should ask whether we want to be risk prone or risk averse. Skeptical Science has covered this topic (See "It's not bad"). Warming creates feedbacks that amplify warming. And, the data show that warming increases atmospheric CO2, likely through thawing of high latitude permafrost, changes in how the ocean absorbs or stores CO2, and changes in soil chemistry. Reconstructions of temperatures and CO2 levels from ice cores support this.

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We are near one degree over Holocene and should expect feedbacks. If nothing else, the risk-adverse among us must admit that we are charting new territory. Earth's CO2 portfolio has been spiked by humanity's ingenuity. The level we've reached, 390 ppm, departs from any level pulled from 800,000 year ice, and yet current trends project concentrations to rise to 600 ppm in 70 years (Four degrees and beyond). Would you invest in this planet without a better understanding of what is happening?

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UPDATE: In response to comments, I've removed an illustration comparing CO2 and temperature over the past 160,000 years (See Eric's comment 25 and my comment 34). In it's place I've added this chart from the IPCC Fourth Assessment Report showing plausible surface temperatures from various emissions scenarios.

Figure SPM.5 from IPCC AR4. Scenarios for GHG emissions from 2000 to 2100 (in the absence of additional climate policies) and projections of surface temperatures relative to 1980–1999. (See link for full description of the chart.)  

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Comments 51 to 52 out of 52:

  1. Taking one of Meyers points
    "Rising temperatures may increase evaporation and therefore the amount of water vapor in the air, thus adding powerful greenhouse gasses to the atmosphere and accelerating warming."

    This seems to be a common misunderstanding about what drives the water vapour feedback. Increased temperatures most certainly are likely to increase evaporation but that isn't necesarily the driver of increased water vapour in the atmosphere.

    Evaporation is happening all the time, so water vapour levels in the atmosphere would just keep rising unless something counter-balances them. That something is precipitation. So if evaporation increases precipitation needs to increase.

    However, if there were increased atmospheric temperatures alone, without any increase in evaporation we would still get increased water vapour in the atmosphere. The reason is driven by cloud formation. Clouds need the air to be nearly saturated before they can form. The water vapour content of the atmosphere where the clouds might form needs to be around the maximum possible content for that temperature - its saturation point. Clouds don't form unless the air essentially is saturated.

    So if the air is warmer then its saturation water level is higher - it can hold more water before it reaches its limit. So just the act of increasing the air temperature means the air has to hold more water before cloud formation becomes possible. And since evaporation keeps adding water to the atmosphere until precipitation is high enough to balance it, in warmer air this drives water vapour levels up. And this doesn't require increased evaporation to occur. Just that current evaporation levels be continued.

    Imagine a tank with water being pumped into it. The pump is evaporation. And the tank fills with water until it reaches its capacity. The tank is like the atmosphere and its volume is the saturation limit. Once full, the tank starts to overflow and balnce is struck. The overflow is precipitation.

    So we increase the height of the tank, increasing what it can hold. This is the equivalent of increasing the air temperature so it can hold more water. The same flow rate from the pump will still eventually fill this larger tank and overflow it. If the pump runs faster the tank fills faster and then the overflow is greater. But the amount of water in the tank doesn't change because it isn't the flow rate that matters (evaporation) it is the height of the tank (air temperature)
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  2. How is Myers point, as quoted in #51 a denier point? It would seem to be true (as refined by Glenn Tamblyn). What am I missing?
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  3. Albatross, thanks for breaking it all down. On (1), I agree with Meyer although CAGW should be qualified as CAGW by 2100 and I believe we will have adequate technological fixes for all potential consequences well before that. (2) The plant growth data is ambiguous, specifically we don't the proportion of natural uptake of our CO2 by extra plant growth versus oceans. But it is mostly oceans and we continue to eliminate forests net, so I do think Meyer has a valid point here. (3) My answer starts here (quick summary: water vapor distribution is what matters, not C-C)

    (4) If one assumes nothing within the models, then there is no consensus on sensitivity. For example "An intercomparison of 14 atmospheric general circulation models, for which sea surface temperature perturbations were used as a surrogate climate change, showed that there was a roughly threefold variation in global climate sensitivity." http://www.sciencemag.org/content/245/4917/513.short I would argue the IPCC researchers assumed nothing in their research but that the uncertainty was downplayed in the final summary reports.

    (5) I believe there is some short term negative feedback, probably by clouds and likely by increased convection. There are also plenty of short term positive feedbacks, water vapor, ice cover, etc. Long term the clouds are still unknown, but probably don't matter, feedbacks will be mostly positive. In short, no homeostatis.

    (6) You are correct. OHC rises have not stopped but I would point out that the deep ocean is a giant heat sink and since heat content appears to be rising there, that heat is not a warming factor for time intervals of interest. If that water does in fact return, it will cool the atmosphere.

    (7) You are correct. The rise in atmospheric temperature and OHC has slowed but there are two very good explanations for it: ENSO and a recent deep solar minimum. Same with (8), a sloppy statement by Meyer. He should have said: Before 1940, the increase in temperature is believed to have been caused mainly by two factors: 1. Increasing solar activity; and 2. Low volcanic activity (as eruptions can have a cooling effect by blocking out the sun).

    (9) Meyer is oversimplifying but we should have seen more system warming (OHC plus atmosphere). As I said in response to (7), the two major explanations of the lull in warming are ENSO and solar, but the solar minimum was very recent (2008) and ENSO would have transferred heat from the atmosphere to the ocean in greater quantities than we hav seen. So he is basically correct, but didn't explain it well.

    (10) Meyer is not correct IMO. The atmospheric rise is about 0.3C or a bit more since 1979 against a rise in CO2 from 335 to 390, for a sensitivity of 2C. Although the slowing of OHC rise makes a case for lower sensitivity, the observed temperature rise demonstrates some positive feedback.

    (11) Meyer's point is valid. The models are tuned to the atmospheric temperatures using anthropogenic aerosol parameters (not measurements) and crudely calculated natural aerosols. In addition, "...simulations with the GISS GCM for the first indirect effect (with sulfates, sea salt, and OC aerosols) with a minimum CDNC = 10 cm−3 was −2.1 W m−2, whereas that for CDNC = 40 cm−3 was −1.1 W m−2. This difference of 1 W m−2 is quite large and regionally can change the surface temperature response from a positive to a negative, as shown in Figure 3." (http://www.atmosp.physics.utoronto.ca/people/lev/ESSgc2/14892396.pdf)

    (12) I do not agree with you. My statements were about a specific issue which has now been addressed in the OP. I didn't give evidence for low sensitivity in this thread, I have addressed it in dribs and drabs here and there. Sensitivity also depends on exogenous factors, for example solar as I pointed out here
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  4. I have a question on this point about coming out of the ice ages:
    "If a long slow wobble (precession) was sufficient for Earth's feedbacks to raise the global temperature 8-12 degrees, we should be cautious, wary, risk-adverse of a global disturbance of 1 degree C, as this one degree disturbance occurs on top of an interglacial."

    Surely a disturbance of 1 degree C on top of an interglacial is a lot less dangerous than a disturbance of 1 degree C on top of an ice age?

    It seems to me that the conditions that prevailed on the Earth as it started to come out of the ice age were very different to those now (during an interglacial).

    The primary positive feedback driving the 8-12C of temperature rise was the melting of the summer ice and snow at low latitudes and consequent dramatic fall in albedo. The sunlight reflected from snow at 40-59N is much greater than that reflected from snow at the 60-90N. Hence melting at low latitudes causes a bigger reduction in the amount of light energy reflected back to space than the same area of melting at high latitudes.

    Once all but the polar ice caps remained the albedo stabilised, there was dramatically less summer ice and snow to melt and the positive feedbacks reduced - hence the warming came to an end.

    We cannot assume that the dramatic positive feedback affects that brought us out of an ice age still apply when there is no low latitude summer ice and snow to melt.
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  5. Hi Matthew. I agree with you. My original post was deficient in that I didn't provide an estimate of expected warming. I was focussing on the point that feedbacks are well-established and that we cannot dismiss risk by dismissing feedback effects. About 10 hours ago I added a range of IPCC projections to the end of my post to represent likely outcomes.
    I think a 3 to 4 deg C warmer world has a unique set of risks that I could never cover in a single post. The effect of permafrost melting, drying out of peat lands, changes to forests, increased seasonal drying of soils, changes in ocean currents and sea level are likely to play roles in a warmer world. This is why I cited the Four Degrees collection.
    To go farther back in time, consider hyperthermals, sudden onsets of warming that occurred on top of an already warmer world than what we have today (e.g., first have of the cenozoic). Though the climate proxies documenting these are much older, I believe their existence is well-established, and therefore what we don't know about hyperthermals should also equate to risk.
    thank you,
    jg
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  6. Eric (skeptic) I'm glad that you spell "Meyer" correctly. Others please follow Eric's example.

    Matthew @ 54, I think you are on the right track but you forgot CO2. Note that as land and sea warm for the reasons you describe, atmospheric CO2 increases. You can figure out why it might in about a minute.
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  7. I simply followed Albatross's example, it is obvious that Albatross spent some time reading and digesting Meyer's material.
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  8. There is a sentence that struck me as odd in the article:
    "Even more important for scientists (since the oceans are a much larger heat reservoir than the atmosphere) is the fact that the new ARGO floating temperature stations have measured little or no increase in ocean heat content since they were put in service in 2003."

    This contradicts what I see in OHC graphs presumably using ARGO data:
    and


    Since he is depending on level ocean temperature to cast doubt on global warming, this seems like a real problem.
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  9. SB

    As we noted in recent posts here and here, Ocean Heat Content is the big ticket item, the dog that wags the tail. And since it is still rising, it completely slam-dunks the 'its stopped warming meme'

    So a real problem for Meyer and the view he puts up? Thats an understatement.
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  10. actually thoughful @ 52,
    "Protect yourself at all times." That's the first rule of boxing.
    It's true that Meyer mentions a possible water vapor feedback, but this is just to set you up. Read on and see that he delivers blow after blow against it (for a scientifically unsophisticated audience).

    http://www.forbes.com/sites/warrenmeyer/2012/02/09/understanding-the-global-warming-debate/print/

    If a climate change denier says the sky is blue, go outside and check.
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  11. Glenn Tamblyn @ 51, I see your point. It's worth noting though that in the atmosphere there is not the straight line from evaporation to condensation to precipitation that happens in a closed jar. The column of air above an area may on average contain about 25mm, about an inch of water (if it all rained out). After a rain the air is still damp, missing only about 7 mm of the 25 it might have had. At the same time, over an inch of rain may have fallen. What's going on? You might enjoy this paper which starts out "Why does it rain?"
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  12. One other comment while I'm on the subject: We use the expression "The air holds water" but this is not quite right. Air is mainly oxygen and nitrogen and these do not "hold" H2O. From the point of view of a water molecule breaking free of the liquid surface, air is virtually empty space. The equilibrium vapor pressure depends on temperature. The space in a closed jar with some water at the bottom will contain the same amount of water in the absence or presence of air.
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  13. Pete @61,

    That Trenberth et al. (2003) paper that you linked us to is great, one of my favourites!
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  14. Eric @53,

    Thanks for your point-by-pint reply. I still have some issues with your responses, such as citing a 20 plus year old modelling paper @#4. But I do not have time right now to address those concerns/issues.

    It seems though that we are in agreement that Meyer was either wrong or sloppy or too simplistic on numerous key points.
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  15. Pete @61. Agreed. The real world is more complex that my example. My point is that their is an underlying driver for water vapour increase that does not depend on increased evaporation.
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