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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Working out climate sensitivity from satellite measurements

What the science says...

Lindzen's analysis has several flaws, such as only looking at data in the tropics. A number of independent studies using near-global satellite data find positive feedback and high climate sensitivity.

Climate Myth...

Lindzen and Choi find low climate sensitivity

Climate feedbacks are estimated from fluctuations in the outgoing radiation budget from the latest version of Earth Radiation Budget Experiment (ERBE) nonscanner data. It appears, for the entire tropics, the observed outgoing radiation fluxes increase with the increase in sea surface temperatures (SSTs). The observed behavior of radiation fluxes implies negative feedback processes associated with relatively low climate sensitivity. This is the opposite of the behavior of 11 atmospheric models forced by the same SSTs. (Lindzen & Choi 2009)

Climate sensitivity is a measure of how much our climate responds to an energy imbalance. The most common definition is the change in global temperature if the amount of atmospheric CO2 was doubled. If there were no feedbacks, climate sensitivity would be around 1°C. But we know there are a number of feedbacks, both positive and negative. So how do we determine the net feedback? An empirical solution is to observe how our climate responds to temperature change. We have satellite measurements of the radiation budget and surface measurements of temperature. Putting the two together should give us an indication of net feedback.

One paper that attempts to do this is On the determination of climate feedbacks from ERBE data (Lindzen & Choi 2009). It looks at sea surface temperature in the tropics (20° South to 20° North) from 1986 to 2000. Specifically, it looked at periods where the change in temperature was greater than 0.2°C, marked by red and blue colors (Figure 1).


Figure 1: Monthly sea surface temperature for 20° South to 20° North. Periods of temperature change greater than 0.2°C marked by red and blue (Lindzen & Choi 2009).

Lindzen et al also analysed satellite measurements of outgoing radiation over these periods. As short-term tropical sea surface temperatures are largely driven by the El Nino Southern Oscillation, the change in outward radiation offers an insight into how climate responds to changing temperature. Their analysis found that when it gets warmer, there was more outgoing radiation escaping to space. They concluded that net feedback is negative and our planet has a low climate sensitivity of about 0.5°C.

Debunked by Trenberth

However, a response to this paper, Relationships between tropical sea surface temperature and top-of-atmosphere radiation (Trenberth et al 2010) revealed a number of flaws in Lindzen's analysis. It turns out the low climate sensitivity result is heavily dependent on the choice of start and end points in the periods they analyse. Small changes in their choice of dates entirely change the result. Essentially, one could tweak the start and end points to obtain any feedback one wishes.


Figure 2: Warming (red) and cooling (blue) intervals of tropical SST (20°N – 20°S) used by Lindzen & Choi (2009) (solid circles) and an alternative selection proposed derived from an objective approach (open circles) (Trenberth et al 2010).

Debunked by Murphy

Another major flaw in Lindzen's analysis is that they attempt to calculate global climate sensitivity from tropical data. The tropics are not a closed system - a great deal of energy is exchanged between the tropics and subtropics. To properly calculate global climate sensitivity, global observations are required.

This is confirmed by another paper published in early May (Murphy 2010). This paper finds that small changes in the heat transport between the tropics and subtropics can swamp the tropical signal. They conclude that climate sensitivity must be calculated from global data.

Debunked by Chung

In addition, another paper reproduced the analysis from Lindzen & Choi (2009) and compared it to results using near-global data (Chung et al 2010). The near-global data find net positive feedback and the authors conclude that the tropical ocean is not an adequate region for determining global climate sensitivity.

Debunked by Dessler

Dessler (2011) found a number of errors in Lindzen and Choi (2009) (slightly revised as Lindzen & Choi (2011)).  First, Lindzen and Choi's mathematical formula  to calculate the Earth's energy budget may violate the laws of thermodynamics - allowing for the impossible situation where ocean warming is able to cause ocean warming.  Secondly, Dessler finds that the heating of the climate system through ocean heat transport is approximately 20 times larger than the change in top of the atmosphere (TOA) energy flux due to cloud cover changes.  Lindzen and Choi assumed the ratio was close to 2 - an order of magnitude too small.

Thirdly, Lindzen and Choi plot a time regression of change in TOA energy flux due to cloud cover changes vs. sea surface temperature changes.  They find larger negative slopes in their regression when cloud changes happen before surface temperature changes, vs. positive slopes when temperature changes happen first, and thus conclude that clouds must be causing global warming.

However, Dessler also plots climate model results and finds that they also simulate negative time regression slopes when cloud changes lead temperature changes.  Crucially, sea surface temperatures are specified by the models.  This means that in these models, clouds respond to sea surface temperature changes, but not vice-versa.  This suggests that the lagged result first found by Lindzen and Choi is actually a result of variations in atmospheric circulation driven by changes in sea surface temperature, and contrary to Lindzen's claims, is not evidence that clouds are causing climate change, because in the models which successfully replicate the cloud-temperature lag, temperatures cannot be driven by cloud changes.

2011 Repeat

Lindzen and Choi tried to address some of the criticisms of their 2009 paper in a new version which they submitted in 2011 (LC11), after Lindzen himself went as far as to admit that their 2009 paper contained "some stupid mistakes...It was just embarrassing."  However, LC11 did not address most of the main comments and contradictory results from their 2009 paper.

Lindzen and Choi first submitted LC11 to the Proceedings of the National Academy of Sciences (PNAS) after adding some data from the Clouds and the Earth’s Radiant Energy System (CERES).

PNAS editors sent LC11 out to four reviewers, who provided comments available here.  Two of the reviewers were selected by Lindzen, and two others by the PNAS Board.  All four reviewers were unanimous that while the subject matter of the paper was of sufficient general interest to warrant publication in PNAS, the paper was not of suitable quality, and its conclusions were not justified.  Only one of the four reviewers felt that the procedures in the paper were adequately described. 

As PNAS Reviewer 1 commented,

"The paper is based on...basic untested and fundamentally flawed assumptions about global climate sensitivity"

These remaining flaws in LC11 included:

  • Assuming that that correlations observed in the tropics reflect global climate feedbacks.
  • Focusing on short-term local tropical changes which might not be representative of equilibrium climate sensitivity, because for example the albedo feedback from melting ice at the poles is obviously not reflected in the tropics.
  • Inadequately explaining methodology in the paper in sufficient detail to reproduce their analysis and results.
  • Failing to explain the many contradictory results using the same or similar data (Trenberth, Chung, Murphy, and Dessler).
  • Treating clouds as an internal initiator of climate change, as opposed to treating cloud changes solely as a climate feedback (as most climate scientists do) without any real justification for doing so. 

As a result of these fundamental problems, PNAS rejected the paper, which Lindzen and Choi subsequently got published in a rather obscure Korean journal, the Asia-Pacific Journal of Atmospheric Science. 

Wholly Debunked

A full understanding of climate requires we take into account the full body of evidence. In the case of climate sensitivity and satellite data, it requires a global dataset, not just the tropics. Stepping back to take a broader view, a single paper must also be seen in the context of the full body of peer-reviewed research. A multitude of papers looking at different periods in Earth's history independently and empirically converge on a consistent answer - climate sensitivity is around 3°C implying net positive feedback.

Last updated on 6 July 2012 by dana1981. View Archives

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Further viewing

Andrew Dessler explains in relatively simple and short terms the results from his 2011 paper:

Comments

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Comments 76 to 100 out of 220:

  1. Eric (skeptic) at 11:50 AM on 20 December, 2010 "What is the forcing effect of incrementally more CO2?" Eric, I believe the temperature increment is proportional to the forcing increment i.e. deltaT = sigma.deltaF [where sigma is the climate sensitivity in units of oC/(W.m^2)] so I guess the forcing scales as the ln of the [CO2] increment much the same as the temperature in my post #70 above. Does that seem right?
  2. Chris (RE: Posts 60 & 70), Those numbers are useless because they're all based on the assumption of a 3 C sensitivity to a doubling of CO2. You cannot start with a conclusion, assume it is correct, and then derive the specific numbers in support of it by simply back fitting calculations to your original assumption. How about you address the series of individual questions I laid out in post 61?
  3. RW1 (#73), yes, thanks, you were not referring to the last century and I thought you were. As for the difference at perihelion, my understanding is that the extra energy (14 W/m^2) falls on land masses in the NH winter which reflects away much of the extra energy (versus SH ocean which is a better absorber of solar energy). Hence the NH winter has a bit colder global average temperature than NH summer even though the energy from the sun is greater. If I am mistaken, someone will correct me.
  4. Alec Cowan at 12:04 PM on 20 December, 2010 yes, I see your point Alec!
  5. #76, chris, I think that assumes that "climate sensitivity" is a constant that can be subdivided like you are doing. My understanding is that sensitivity as it is defined here is the temperature response to a CO2 change of 280 to 560. It cannot be used for any other purpose in a linear fashion.
  6. In #80, I meant to say CS is a constant that can not be subdivided.
  7. Eric (RE: Post 78), Global average temperatures are about 3 C colder at perihelion because - yes, I think a lot of the increased power is reflected from off the ice and snow accumulations that occur in the NH winter in January. But most of the additional 14 W/m^2 at perihelion then still affects SH summer in January because at that time the SH is tilted toward the Sun.
  8. @RW1: "Those numbers are useless because they're all based on the assumption of a 3 C sensitivity to a doubling of CO2. You cannot start with a conclusion, assume it is correct, and then derive the specific numbers in support of it by simply back fitting calculations to your original assumption." That's not what has happened, here. Rather, multiple scenarios were proposed, and the one closest to reality (following observations) is the one that puts it in the 2-4.5C range. It is false to claim people decided that climate sensitivity was 3C, then tried to fiddle their calculations to make it fit. In fact, I'd say you're venturing dangerously close to accusations of conspiracy theories, there... Further reading: James Annan explains why sensitivity is at 3C. "Are you saying the response of CO2 is not logarithmic - but linear?" No, that's not what he's saying. Rather, he's (correctly) noting that your description of the logarithmic curve was too vague to be useful. Or perhaps you think all logarithmic scales are the same?
  9. #83, RW1, I agree, but the bigger point is that the hemispherical asymmetry makes it impossible to use the 14 W/m^2 change and the global average temperature change as a case for much of anything and especially your last two paragraphs in #14.
  10. #77: "You cannot start with a conclusion, assume it is correct, and then derive the specific numbers ..." Indeed. We have to test the calculations that derive from a set of assumption to see if they match observation. On that fundamental point, I have no doubt we all agree. No such assumptions went into the preparation of the graphic for #57. The plotted curves are straight from the literature of radiative forcing which is not under discussion here. However, in #63, "incrementally more CO2 is not linear - but logarithmic, which means each additional amount added only has about half of the effect of the previous amount," a major flaw in your thinking is revealed. The function deltaT = 5.35 lambda log (C/C0) flattens as C (ie, CO2) increases; this gives the impression that adding more CO2 will gradually not be as bad. What you've ignored is the fact that C is a function of time that is strongly concave up. As a result, both the first and second time derivatives of the deltaT function are positive: deltaT is an increasing function of C and C is an increasing function of time. So while each additional ppm of CO2 causes a smaller temperature increase, we are adding CO2 at a rate that forces deltaT as function of time to increase at an increasing rate. Referring back to the figure in #57, your 0.6 deg C sensitivity produces neither the correct temperature anomaly nor the correct rate of change. One must therefore conclude that the assumptions made to calculate 0.6C sensitivity are incorrect, taking those calculations with them.
  11. Eric (skeptic) at 12:29 PM on 20 December, 2010 I don't think that's right Eric. The climate sensitivity is defined by convention as the amount of warming at equilibrium resulting from a radiative forcing equivalent to a doubling of atmospheric [CO2]. But it can be (and is) used to determine the equilibrium temperature response expected from any change in forcing including that resulting from small increments of [CO2]. Clearly if the wealth of empirical data supports a climate sensitivity near 3 oC (say), then the warming contribution expected from a rise of [CO2] from 280 to 380 ppm (say), should be predictable within that climate sensitivity (according to the ln of the ratio of [CO2]s). It would be perverse to consider otherwise. Of course the climate sensitivity is obviously a shorthand estimate of a response in a complex world! So the climate sensitivity in a world with a certain amount of sea ice (say) will differ from that of a world with no sea ice (say), since the albedo feedbacks will differ. In the real world the "climate sensitivity" will likely "dance around" somewhat temporally and according to precise conditions. ----- O.K. I've just seen your correction so maybe my post doesn't quite address your point. But (re your correction), the climate sensitivity isn't being subdivided. We're considering the Earth's equilibrium temperature response to a forcing as parameterized within a single value of the climate sensitivity. What's being subdivided is the forcing and its response, not the CS! I suspect that we might be talking at cross purposes, btw! If you think I haven't addressed your point properly have another go and I'll try again in the morning.
  12. Eric (RE: Post 84), Why not? OK, so it's not about 14 W/m^2 net - but something less because the total albedo in January is greater than 0.3 you're saying?
  13. RW1, the 0.3 value may be an average over all seasons, but the effective albedo must be greater in January since the solar forcing is greater but the global average temperature is lower. My parenthetical statement about the SH oceans in #78 is probably incorrect. But my main point again is that your statement in #14 "That the global climate doesn't even appear to be phased by a 14 W/m^2 increase in radiative forcing, suggests the net feedback operating on the system as a whole is strongly negative - not positive,..." is not a logical conclusion. The reason why the global climate is not affected by the 14 W/m^2 is due to the differences between the hemispheres, not net global feedback.
  14. Eric (RE: Post 88), I agree that the difference between the hemispheres is one of the main reasons, but the whole climate is affected (i.e. about 3 C colder globally at perihelion - not just in the NH). Without the +14 W/m^2 at perihelion, the global average temperatures would probably be even colder in January than they are now. It should also be pointed out that global temperatures are actually 3 C warmer at aphelion in July when net incident solar power is about 14 W/m^2 less. My main point is the aggregate confluence of factors that actually determine global average temperatures don't appear to be even phased much by 14 W/m^2 increase in radiative forcing - an amount much larger than what would come from a doubling of CO2. The perihelion point aside, what then is so special about each 1 W/m^2 of increased power from CO2, that the system is all the sudden going to respond to it radically differently than it does each 1 W/m^2 of power from the original 238 W/m^2?
  15. Eric (RE: Post 88), That last paragraph in my post 89 should have read: The perihelion point aside, what is so special about each 1 W/m^2 of increased power from CO2, that the system is all the sudden going to respond to it radically differently than it does each 1 W/m^2 of power from the original 238 W/m^2 sourced from the Sun?
  16. The "radical" difference comes from the difference in the way the two hemispheres respond to the seasonal solar changes. There's no way to get away from that fact and it means that the global average temperature response to CO2 which is evenly distributed worldwide, has more effects in polar regions, etc, is going to be radically different. It's sort of like saying that a giant fire in one hemisphere is going to have the same effect as a lot of smaller fires adding up to the same amount of heat and smoke, but distributed worldwide. Clearly the effects on weather and thus temperature will be quite different in those two cases.
  17. Eric (RE: Post 91), Why would CO2 have more effect in the polar regions? The numbers I've used throughout are global average numbers.
  18. Because there is less water vapor in the polar regions so CO2 has a proportionally greater effect and so a change is CO2 would also have a greater effect than outside of polar regions. As for using average numbers, I'm not a big fan of those for many reasons, one of which is demonstrated in your #14 which didn't mention the large differences in seasonal responses between the hemispheres.
  19. Eric (RE: Post 93), Well yes, but the polar regions are also largely snow and ice covered, which means a lot of the incoming power is getting reflected back out (back through the CO2), so incrementally more CO2 in those areas won't do much at all. Also, if there is a global increase in temperature from CO2, there will likely be a global increase in water vapor. That should offset any increase in CO2 for areas in the polar regions not snow and ice covered - as far as water vapor/CO2 absorption overlap is concerned.
  20. @RW1: "My main point is the aggregate confluence of factors that actually determine global average temperatures don't appear to be even phased much by 14 W/m^2 increase in radiative forcing - an amount much larger than what would come from a doubling of CO2." Temperatures are very much affected by the seasonal effect - that's why we have seasons! The warming due to CO2 is in addition to the normal variations. That's why it matters. Also, RW1, by not responding to muoncounter at #85 you are ignoring a strong rebuttal to your argument. Are you conceding defeat?
  21. muoncounter (RE: Post 86), I now see the problem. When referring to the logarithmic response of CO2, I mean only the intrinsic radiative forcing response - not any theoretical increase in temperature in addition to the intrinsic response via potential feedbacks and so forth (i.e. a 3 C rise). The intrinsic increase in radiative forcing from a doubling of CO2 is 3.7 W/m^2. When I say we've already reached 70-80% of a doubling going from 300 to 380 ppm (or 280 to 380ppm), I mean 70-80% of 3.7 W/m^2 or about 2.6 to 2.9 W/m^2 of intrinsic forcing.
  22. muoncounter (RE: Post 85), I meant post 96 above to be in response to your post 85 (not 86).
  23. RW1 - No, CO2 at the poles will act like CO2 at the tropics - retaining a percentage of the thermal radiation at those locations. That's a bogus argument. As to water vapor - that's a feedback to any forcing, whether it's CO2 or solar or aerosol. It doesn't counteract CO2 forcing in itself. If you wish to argue for a cloud feedback, take it to the cloud sensitivity thread.
  24. archiesteel (RE: Post 95), I'm well aware that any CO2 warming will be in addition to, or on top of, the normal variations. I don't dispute this, and nothing I've written disputes it. Also, I know temperatures are affected by the seasons - I've written so multiple times in this thread. The +14 W/m^2 at perihelion is a global average addition - not isolated to just one hemisphere or the other.
  25. RW1 - Please keep in mind that the perihelion/aphelion cycle is just that - a cycle. Which means it goes down as well as up. The added greenhouse effect, on the other hand, is a long term increase in both perihelion and aphelion irradiance, a long term uncompensated change in total irradiance. And hence an energy imbalance. The climate response to shifts in overall irradiance appears to be (including ocean responses) at least 40 years for mid-length feedbacks, centuries for long-term (weathering) feedbacks. The perihelion and aphelion cycles average out over those time scales. CO2 does not.

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