Comments On The Science In The Nature Paper By Allen and Sherwood

On Monday, Climate Science documented the inapprorpriate credit that Robert Allen and Steve Sherwood, and in a separate article, Peter Thorne, took for introducing the use of the “thermal wind” to diagnose tropospheric temperatures.  Today’s weblog briefly overviews several of the science mistakes in their papers, with additional ones to follow in our submitted paper.

The two Nature papers are:

Warming maximum in the tropical upper troposphere deduced from thermal winds
Robert J. Allen & Steven C. Sherwood Published online: 25 May 2008; | doi:10.1038/ngeo208

Atmospheric science: The answer is blowing in the wind; P. W. Thorne Published online: 25 May 2008; | doi:10.1038/ngeo209

The mistakes in their analyses include:

  • The use of models to “prove” a relationship

Allen and Sherwood write

“This method has recently been found to recover regional climatic temperature fluctuations accurately, even in the deep tropics, where the Coriolis force approaches zero, a finding we test further here using climate models.”

While climate models are valuable tools they cannot prove anything! They are just hypotheses as to how the climate system works. The authors ignore peer reviewed papers that support the analyses of the temperature trends using the UAH MSU data

There are several papers that document the robustness of the UAH MSU and the RSS MSU data that were completed independently of the UAH research group. These include

Randall, R. M., and B. M. Herman (2007), Using Limited Time Period Trends as a Means to Determine Attribution of Discrepancies in Microwave Sounding Unit Derived Tropospheric Temperature Time Series, J. Geophys. Res., doi:10.1029/2007JD008864, in press,

where it is written in the abstract that

Comparison of MSU data with the a reduce RATPAC radiosonde dataset indicates that RSS’s method (use of climate model) of determining diurnal effects is likely overestimating the correction in the LT channel. Diurnal correction signatures still exist in the RSS LT time series and are likely affecting the long term trend with a warm bias”

and

Chase, T.N., R.A. Pielke Sr., J.A. Knaff, T.G.F. Kittel, and J.L. Eastman, 2000: A comparison of regional trends in 1979-1997 depth-averaged tropospheric temperatures. Int. J. Climatology, 20, 503-518

where the text states

“This study examines regional temperature trends during the period 1979–1997 from the Microwave Sounding Unit (MSU) 2r satellite measurements and compares them with the same trends in depth-averaged tropospheric temperatures derived from the National Center for Environmental Prediction (NCEP) reanalysis, in an attempt to determine whether regional trends exist which are larger than known inhomogeneities in the data. Large, statistically significant regional trends were found in both the NCEP and the MSU data that are of both signs and have larger magnitude than documented biases in the data. The datasets have overall agreement on the location and strength of these significant regional trends at mid and high latitudes but agreement decreases in the tropics.

A global annual average of the significant regional trends with larger amplitudes than reported data biases and areally weighted over the globe yields 0.02°C over the 19-year period of the record in the MSU 2r Version C dataset, and 0.05°C/ 19 years in the NCEP data in the 1000–500 mb layer. Increasing the bias threshold by as much as five times still results in an average cooling in both datasets.”

The NCAR/NCEP Reanalysis has more information than is used in the Allen and Sherwood radiosonde study and thus is a more accurate analysis

Allen and Sherwood, and Thorne, fail to recognize that radiosonde data is used to adjust the NCAR/NCEP Reanalysis, and as a result agree with the radiosondes where the data is consistent and provide a physically consistent diagnosis of the temperature and winds elsewhere. The close correspondence between the radiosondes and the reanalysis approach was studied in detail in

Davey, C., R.A. Pielke Sr., and T.N. Chase, 2008: Annual and seasonal tropospheric temperature trend comparisons of radiosonde and reanalysis data at regional scales. Nat. Wea. Dig., in press

where the abstract reads in part

With the current widespread interest in anthropogenic climate change, many studies have investigated tropospheric temperature trends. These studies have used data from various satellite, reanalysis, and radiosonde sources. Of those studies that have been conducted comparing temperature trends between data sets, few have focused on the differences between radiosonde and reanalysis trends. Since radiosonde data are input for reanalyses, the two data sets could be expected to agree well with each other, but this is not guaranteed since the reanalyses utilize other information such as winds. These comparisons are needed in light of existing uncertainty over the use of current reanalyses in climate trend research. Our study compares linear tropospheric temperature trend estimates for radiosonde and reanalysis data, both annually and seasonally, at land-based sites in the Americas and Australasia/Oceania from 1979-2001. The average radiosonde trends generally fell in between the average reanalysis trend values and indicate that reanalyses are indeed useful for climate trend analysis.”

The procedure to adjust the reanalysis frequently is discussed in

Pielke Sr., R.A., T.N. Chase, with input from J. Christy, and T. Reale, 2004: Scientific Comment on R-278 and R-278a

where Tony Reale, a NOAA expert on this issue wrote

“I am not so familiar with reanalysis techniques, etc, but can certainly address NESDIS sounding products. John is essentially correct; each week the coefficients (measurement vs. radiosonde temperature) for producing both the first guess and retrieval solution are updated.”

Reale, Anthony L., 2001: NOAA operational sounding products from advanced-TOVS polar orbiting environmental satellites. NOAA Technical Report NESDIS 102, U.S. Dept of Commerce, Washington, DC, 57 pp.

This issue is investigated formerly in the paper

Ming Cai and Eugenia Kalnay: 2005 Can Reanalysis Have Anthropogenic Climate Trends without Model Forcing? Journal of Climate Volume 18, Issue 11 (June 2005) pp. 1844–1849 Vol. 18, No. 11, pp. 1844

where the abstract says in part

“Here it is merely proven mathematically that using a frozen model in a reanalysis does not cause significant harm to the fidelity of the long-term trend in the reanalysis.”

These issues will be updated through 2007 in our new paper, and other problems with their study will be described. It is clear, however, that their exclusion of other research on trends has resulted in a flawed analysis. 

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