AGW Observer

Observations of anthropogenic global warming

Papers on tropical troposphere hotspot

Posted by Ari Jokimäki on September 6, 2009

This list contains papers on the tropical troposphere hotspot. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (January 2, 2012): Fu et al. (2011) added.
UPDATE (September 21, 2010): McIntyre & McKitrick (2009) removed (it didn’t pass peer-review) and McKitrick et al. (2010) added.
UPDATE (January 4, 2009): Addendum for Douglass et al. (2008) added, thanks to kse for pointing this out, see the comment section below.
UPDATE (December 24, 2009): Fu et al. (2004) and Steiner et al. (2009) moved to global troposphere list. Some of the papers are still in both lists.
UPDATE (December 24, 2009): Sherwood et al. (2008) added and final publication links to Bengtsson & Hodges (2009) added.
UPDATE (September 23, 2009): Steiner et al. (2009) added, thanks for John Cook for pointing this out (see the comment section below). McCarthy et al. (2008) added.
UPDATE (September 13, 2009): Bengtsson & Hodges (2009?) added.

On the warming in the tropical upper troposphere: Models versus observations – Fu et al. (2011) “IPCC (Intergovernmental Panel on Climate Change) AR4 (Fourth Assessment Report) GCMs (General Circulation Models) predict a tropical tropospheric warming that increases with height, reaches its maximum at ~200 hPa, and decreases to zero near the tropical tropopause. This study examines the GCM-predicted maximum warming in the tropical upper troposphere using satellite MSU (microwave sounding unit)-derived deep-layer temperatures in the tropical upper- and lower-middle troposphere for 1979–2010. While satellite MSU/AMSU observations generally support GCM results with tropical deep-layer tropospheric warming faster than surface, it is evident that the AR4 GCMs exaggerate the increase in static stability between tropical middle and upper troposphere during the last three decades.” Fu, Q., S. Manabe, and C. M. Johanson (2011), On the warming in the tropical upper troposphere: Models versus observations, Geophys. Res. Lett., 38, L15704, doi:10.1029/2011GL048101. [Full text]

Panel and multivariate methods for tests of trend equivalence in climate data series – McKitrick et al. (2010) “We explain panel and multivariate regressions for comparing trends in climate data sets. They impose minimal restrictions on the covariance matrix and can embed multiple linear comparisons, which is a convenience in applied work. We present applications comparing post-1979 modeled and observed temperature trends in the tropical lower- and mid-troposphere. Results are sensitive to the sample length. In data spanning 1979–1999, observed trends are not significantly different from zero or from model projections. In data spanning 1979–2009, the observed trends are significant in some cases but tend to differ significantly from modeled trends.” Ross McKitrick, Stephen McIntyre, Chad Herman, Atmospheric Science Letters, Article first published online: 17 SEP 2010, DOI: 10.1002/asl.290. [Full text]

On the evaluation of temperature trends in the tropical troposphere – Bengtsson & Hodges (2009) “A series of model experiments with the coupled Max-Planck-Institute ECHAM5/OM climate model have been investigated and compared with microwave measurements from the Microwave Sounding Unit (MSU) and re-analysis data for the period 1979-2008. … When forced by analysed sea surface temperature the model reproduces accurately the time-evolution of the mean outgoing tropospheric microwave radiation especially over tropical oceans but with a minor bias towards higher temperatures in the upper troposphere. … We have also compared the trend of the vertical lapse rate over the tropical oceans assuming that the difference between TLT and TMT is an approximate measure of the lapse rate. The TLT–TMT trend is larger in both the measurements and in the JRA25 than in the model runs by 0.04–0.06 K/decade. Furthermore, a calculation of all 30 year TLT–TMT trends of the unforced 500-year integration vary between ±0.03 K/decade suggesting that the models have a minor systematic warm bias in the upper troposphere.” [Full text]

Robust Tropospheric Warming Revealed by Iteratively Homogenized Radiosonde Data – Sherwood et al. (2008) “Results are presented from a new homogenization of data since 1959 from 527 radiosonde stations. … The troposphere warms at least as strongly as the surface, with local warming maxima at 300 hPa in the tropics” [Full text]

Toward Elimination of the Warm Bias in Historic Radiosonde Temperature Records—Some New Results from a Comprehensive Intercomparison of Upper-Air Data – Haimberger et al. (2008) “Both of the new adjusted radiosonde time series are in better agreement with satellite data than comparable published radiosonde datasets, not only for zonal means but also at most single stations. A robust warming maximum of 0.2–0.3K (10 yr)−1 for the 1979–2006 period in the tropical upper troposphere could be found in both homogenized radiosonde datasets.” [Full text]

Consistency of modelled and observed temperature trends in the tropical troposphere – Santer et al. (2008) “Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to human-caused increases in well-mixed greenhouse gases (GHGs). We revisit such comparisons here using new observational estimates of surface and tropospheric temperature changes. We find that there is no longer a serious discrepancy between modelled and observed trends in tropical lapse rates. … Our results contradict a recent claim that all simulated temperature trends in the tropical troposphere and in tropical lapse rates are inconsistent with observations. This claim was based on use of older radiosonde and satellite datasets, and on two methodological errors: the neglect of observational trend uncertainties introduced by interannual climate variability, and application of an inappropriate statistical consistency test.” [Full text]

Warming maximum in the tropical upper troposphere deduced from thermal winds – Allen & Sherwood (2008) “Climate models and theoretical expectations have predicted that the upper troposphere should be warming faster than the surface. Surprisingly, direct temperature observations from radiosonde and satellite data have often not shown this expected trend. However, non-climatic biases have been found in such measurements. Here we apply the thermal-wind equation to wind measurements from radiosonde data, which seem to be more stable than the temperature data. … Warming patterns are consistent with model predictions except for small discrepancies close to the tropopause.” [Full text]

Assessing Bias and Uncertainty in the HadAT-Adjusted Radiosonde Climate Record – McCarthy et al. (2008) “This paper presents an automated homogenization method designed to replicate the decisions made by manual judgment in the generation of an earlier radiosonde dataset [i.e., the Hadley Centre radiosonde temperature dataset (HadAT)]. … Using climate model data to simulate biased radiosonde data, the authors show that limitations in the homogenization method are sufficiently large to explain much of the tropical trend discrepancy between HadAT and estimates from satellite platforms and climate models. … Previous assessment of trends and uncertainty in HadAT is likely to have underestimated the systematic bias in tropical mean temperature trends.” [Full text]

A comparison of tropical temperature trends with model predictions – Douglass et al. (2008) “We examine tropospheric temperature trends of 67 runs from 22 Climate of the 20th Century model simulations and try to reconcile them with the best available updated observations (in the tropics during the satellite era). Model results and observed temperature trends are in disagreement in most of the tropical troposphere, being separated by more than twice the uncertainty of the model mean.” [However, they ignored the observation uncertainties, see Santer et al. above and this RealClimate article.] [Full text] [Addendum]

Utility of Radiosonde Wind Data in Representing Climatological Variations of Tropospheric Temperature and Baroclinicity in the Western Tropical Pacific – Allen & Sherwood (2007) “Wind data show a slowing of the midlatitude jets in the Maritime Continent region since 1979, indicating that tropical thicknesses and temperature have increased less than those poleward of 25°N/S. This pattern is consistent with Microwave Sounding Unit temperature trends in the region but is exaggerated south of the equator in trends obtained directly from the temperature data. … These results support the use of the wind field as a way of overcoming heterogeneities in the temperature records in the monitoring of climate change patterns.” Allen, Robert J., Steven C. Sherwood, 2007, J. Climate, 20, 5229–5243. [Full text]

Tropical vertical temperature trends: A real discrepancy? – Thorne et al. (2007) “The uncertainty of inter-satellite calibration implied by available MSU T2 (mid-troposphere) estimates (σ = 0.035K) is much greater than that required to adequately resolve the trend (σ < 0.01K), or the amplification behaviour (implied amplification range ±0.95).”

Ozone, water vapor, and temperature in the upper tropical troposphere: Variations over a decade of MOZAIC measurements – Bortz et al. (2006) Provides another dataset for the tropics (by in situ aircraft samples), including water vapor and ozone measurements. “The decade of MOZAIC in situ measurements now available provides unique insights into the composition and processes of the upper tropical troposphere. In this analysis of temperature, water vapor, and ozone at flight cruise levels in the tropics, we find greater seasonal variability for all three parameters in the South (0–20°S) than in the North (0–20°N) Tropics.” [Full text]

The Vertical Structure of Temperature in the Tropics: Different Flavors of El Niño – Trenberth & Smith (2006) Discusses the strong role of El Niño on tropical temperatures. [Full text]

Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences – Karl et al. (2006) Report about temperature trends in stratosphere and in troposphere. [Full text of chapter 1]

Satellite-derived vertical dependence of tropical tropospheric temperature trends – Fu & Johanson (2005) “For the tropical troposphere’s response to greenhouse forcing, GCMs predict a positive temperature trend that is greater than that at the surface and increases with height [e.g., Hansen et al., 2002]. … Tropical atmospheric temperatures in different tropospheric layers are retrieved using satellite-borne Microwave Sounding Unit (MSU) observations. We find that tropospheric temperature trends in the tropics are greater than the surface warming and increase with height. Our analysis indicates that the near-zero trend from Spencer and Christy’s MSU channel-2 angular scanning retrieval for the tropical low-middle troposphere (T2LT) is inconsistent with tropical tropospheric warming derived from their MSU T2 and T4 data.” [Full text]

Amplification of Surface Temperature Trends and Variability in the Tropical Atmosphere – Santer et al. (2005) Highlights the problematics of the issue, and also notes the role of El Niño in tropical temperature variability. “On multidecadal time scales, tropospheric amplification of surface warming is a robust feature of model simulations, but it occurs in only one observational data set. Other observations show weak, or even negative, amplification.” [Full text]

Closely related

The Radiative Signature of Upper Tropospheric Moistening – Soden et al. (2005) “Climate models predict that the concentration of water vapor in the upper troposphere could double by the end of the century as a result of increases in greenhouse gases. Such moistening plays a key role in amplifying the rate at which the climate warms in response to anthropogenic activities, but has been difficult to detect because of deficiencies in conventional observing systems. We use satellite measurements to highlight a distinct radiative signature of upper tropospheric moistening over the period 1982 to 2004. The observed moistening is accurately captured by climate model simulations and lends further credence to model projections of future global warming.” [Full text]

There are a lot of papers discussing troposphere temperature trends from the global perspective. Those papers are not on the list above, but have their own list:

Papers on tropospheric temperatures

20 Responses to “Papers on tropical troposphere hotspot”

  1. Curious said

    Great compilation, thanks a lot!

    I think an index would be very helpful (at least with the paperlists). It could be linked in the “Pages” section.


  2. Ari Jokimäki said

    Thanks for the suggestion. An index page has been in my plans, but I thought first to post some posts to include to the index page. But I guess it’s about time to do it, so you can expect it in a few days.

  3. Curious said

    It’s already there! Thanks a lot again!
    Your compliations are really good, I added your site to my resources list on AGW. 🙂

  4. Ari Jokimäki said

    Well, when you suggested it, I decided to do it right away so I don’t forget. Besides, the index page is also helpful to me for browsing around here.

  5. John Cook said

    New paper: Atmospheric temperature change detection with GPS radio occultation 1995 to 2008 – Steiner (2009)
    Existing upper air records of radiosonde and operational satellite data recently showed a reconciliation of temperature trends but structural uncertainties remain. GPS radio occultation (RO) provides a new high-quality record, profiling the upper troposphere and lower stratosphere with stability and homogeneity. Here we show that climate trends are since recently detected by RO data, consistent with earliest detection times estimated by simulations. Based on a temperature change detection study using the RO record within 1995–2008 we found a significant cooling trend in the tropical lower stratosphere in February while in the upper troposphere an emerging warming trend is obscured by El Niño variability. The observed trends and warming/cooling contrast across the tropopause agree well with radiosonde data and basically with climate model simulations, the latter tentatively showing less contrast. The performance of the short RO record to date underpins its capability to become a climate benchmark record in the future.

  6. Ari Jokimäki said

    Thanks, John. I added it, and I also added McCarthy et al. (2008). Curiously, I was just yesterday browsing new papers in journals, including GRL, but I missed this one. It perhaps wasn’t in the list yet, but I don’t know if I had paid much attention to it anyway because the title doesn’t really say that they are studying the “hotspot”. 🙂

  7. Ari Jokimäki said

    I added Sherwood et al. (2008). It’s more about the whole tropophere, but I included it here as they do have nice tropical troposphere hotspot in their data (as witnessed by their figure 6).

  8. kse said

    I think that you should include the replay from Douglass to the critique about the version of ROABCORE:


    and possibly link to a paper pointing out the problems with ERA-40 and its implications to reanalyses:


  9. Ari Jokimäki said

    (In case you’re wondering, I fixed the link presentations in your post, they weren’t showing properly, because of missing HTML tags.)

    Thanks. Douglass et al. doesn’t seem to be published yet, but I added it anyway.

    Sakamoto & Christy don’t seem to be discussing the hot spot issue specifically (at least based on the abstract), so I didn’t add it.

  10. kse said

    (Eh… I hope that some day I’ll learn how to use these different tagging styles in each blog service…)

    It is true that Sakamoto & Christy do not discuss about the hot spot issue. However, their paper supports Douglass et. al. doubts about ERA-40 and thus ROABCORE 1.3-4. Furthermore, that paper nullifies (at least partially) some of the critique expressed in Santer et. al. (2008).

    So, if we combine Sakamoto & Christy and McIntyre & McKitrick (2009) (bad data + poor analysis), is there anything concrete left in Santer et. al (2008)?

  11. Ari Jokimäki said

    I removed McIntyre & McKitrick (2009) because it didn’t pass peer-review, and I added McKitrick et al. (2010).

  12. Ari Jokimäki said

    I updated this list (checked links, etc.). Soden et al. (2005) now has full text link.

  13. New paper:
    Tropospheric temperature trends: history of an ongoing controversy (Thorne et al 2010)
    Changes in atmospheric temperature have a particular importance in climate research because climate models consistently predict a distinctive vertical profile of trends. With increasing greenhouse gas concentrations, the surface and troposphere are consistently projected to warm, with an enhancement of that warming in the tropical upper troposphere. Hence, attempts to detect this distinct ‘fingerprint’ have been a focus for observational studies. The topic acquired heightened importance following the 1990 publication of an analysis of satellite data which challenged the reality of the projected tropospheric warming. This review documents the evolution over the last four decades of understanding of tropospheric temperature trends and their likely causes. Particular focus is given to the difficulty of producing homogenized datasets, with which to derive trends, from both radiosonde and satellite observing systems, because of the many systematic changes over time. The value of multiple independent analyses is demonstrated. Paralleling developments in observational datasets, increased computer power and improved understanding of climate forcing mechanisms have led to refined estimates of temperature trends from a wide range of climate models and a better understanding of internal variability. It is concluded that there is no reasonable evidence of a fundamental disagreement between tropospheric temperature trends from models and observations when uncertainties in both are treated comprehensively.

  14. Ari Jokimäki said

    Thanks Jesús! As this is more general paper on tropospheric temperatures, I added it to the list of tropospheric temperatures. I actually did a Finnish news article on this paper, but I have been lazy in adding the new papers to these lists.

  15. Ari Jokimäki said

    I added. Fu et al. (2011).

  16. barry said

    Ari, did you move all these papers to the list on tropospheric temps? A note to that effect, with a link, would be good. Unless there is something wrong with my browser, I only see two papers here.

  17. Ari Jokimäki said

    All papers are still here, and I also see them with my browser. I checked the file and there shouldn’t be any special characters that would cut the list after two papers. If you still have the problem, it would be good if you could pinpoint the exact point where the list ends for you.

  18. barry said

    I see the updates at the top, Fu et al 2011 and Mckitrick et al 2010, indluding the abstracts, and that’s where the list stops. Below is a screenshot.

    I’m using firefox browser on Windows 7 Ultimate

  19. Ari Jokimäki said

    Ok, thanks. It should work now, I changed the URL to McKitrick et al. full text. For some reason the original link made the page cut there with Firefox, but not with IE.

  20. barry said

    Yep, fixed. 🙂

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