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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:

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Comments 476 to 483 out of 483:

  1. I'm a little confused... without seeing the paper, how can a temperature swing of 10-12˚C since from LGM to present, with an increase of CO2 from 180 to 280... less than a doubling... translate into a climate sensitivity of 2C, or even 3C? Is the paper saying that most of that change was the result of orbital forcings, or that the bulk of the change is so asymmetric compared to today that very little of that will be felt? Is there a link to an open copy of the paper anywhere?
  2. Schmittner et al 2011 propose three possible reasons for their low climate sensitivity, or which the first is low estimates for the difference in temperature between the current era and the LGM:
    "We propose three possible reasons why our study yields lower estimates of ECS2xC than previous work that also used LGM data. Firstly, the new reconstructions of LGM surface temperatures show less cooling than previous studies. Our best estimates for global mean (including grid points not covered by data) SAT and SST changes reported above are 30–40% smaller than previous estimates (21, 23). This is consistent with less cooling of tropical SSTs (–1.5 K, 30°S–30°N) in the new reconstruction (12) compared with previous datasets (–2.7 K) (24). Tropical Atlantic SSTs between 20°S–20°N are estimated to be only 2.4 K colder during the LGM in the new reconstruction compared to 3 K used in (23), explaining part of the difference between their higher estimates of ECS2xC and ΔSATLGM (–5.8 K)."
    If there estimates of LGM temperatures where equivalent to past values, that would increase their estimate of climate sensitivity by about 50%, giving a climate sensitivity of around 2.5 to 3.9 (lower median of 3.45). Therefore Schmittner et al presents us with a dilemma. If they are correct about temperatures then climate sensitivity is lower than previously thought, but the impact of a given change in temperature is also much greater than previously thought. Alternatively, if they are wrong about temperatures, then their estimate of climate sensitivity is a significant under estimate, and the data actually supports a higher climate sensitivity than currently expected. Of these two possibilities, the second seems more likely. If the impacts of temperature are greater (as with the first alternative), then surely the feedbacks for a given temperature change are also greater contrary to that hypothesis. However, as always, more study will be needed to resolve the issues raised. Whatever the outcome, this is not a paper that can be considered conclusive, and nor is it capable of a simple interpretation. Unless, of course, you are prepared to declare all other papers on this and related topics wrong by fiat, solely on the basis that this paper suits your prejudices.
  3. Sphaerica @476, I believe best estimates of the change in global temperature between the current era and the last glacial maximum are around 5 degrees C. Certainly that is the value Hansen uses in this calculation that appears to pop up in all of his papers of late: A link to a PDF of Schmittner et al can be found in my preceding post.
  4. If Schmittner et al 2011 low climate sensitivity depends on moderate warming from Last Glacial Maximum (LGM = peak glacial conditions) to the Altithermal (peak interglacial conditions), there will be debate among specialists. For example Shakun et Carison 2010 found a 4,9 K difference between the two periods. See also IPCC AR4 6.4.1.2 for a broader context on LGM.
  5. Perhaps the Schmittner et al sensitivity is low because their data are primarily sea surface temperatures: We combine recent syntheses of global sea surface temperatures (SSTs) from the Multiproxy Approach for the Reconstruction of the Glacial Ocean (MARGO) project and surface air temperatures over land based on pollen evidence, with additional data from ice sheets, land and ocean temperatures. The combined dataset covers over 26% of Earth’s surface (Fig. 1, top panel). In contrast to this balanced-sounding statement, the map in their Figure 1 reveals that there is actually very sparse data over land. Not surprisingly, their sensitivity is low because the find less cooling: Tropical Atlantic SSTs between 20°S–20°N are estimated to be only 2.4 K colder during the LGM in the new reconstruction compared to 3 K The MARGO 2009 results reveals an important caution, illustrated by this map: Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present.
  6. An interesting contribution from the Azimuth blog, including a link to the paper, this graph and a link to an interview with one of the authors.
  7. There is also an informative interview with Nathan Urban (second author of the Schmittner et al paper) at Planet3.org. He is not too happy about the way some so-called skeptics have used the graph shown in les's comment above, especially mentioning Pat Michaels. The interview also mentions the double-think of the so-called skeptics in general, because they can highlight and praise this paper as being something they find easier to believe in (because of the possibility of lower climate sensitivity); even though it also makes it very unlikely that Lindzen and Spencer are right with their claims that sensitivity is even lower, i.e. under 1. So, are Lindzen and Spencer now to be dismissed by the so-called skeptics ? As soon as pigs can fly...
  8. Can I recommend that we take discussion of Schmittner et al across to the new post discussing it?

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