Use Of Winds To Diagnose Long Term Temperature Trends – Two New Papers

There are two new papers in Nature Geosciences which report on the use of winds to assess the multi-decadal trends in tropospheric temperatures. The first paper with its brief summary is:

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

“There has been a strong disagreement between model predictions of troposphere warming and observations of temperature trends from radiosondes and satellites. However, when tropospheric temperature reconstructions are generated from thermal-wind measurements and the thermal-wind equation for 1970–2005, the results show a strong tropospheric warming trend, in agreement with model predictions.”

Allen and Sherwood further write in their paper that

We gridded wind data from 341 stations in the Integrated Global Radiosonde Archive23 to monthly means at 5×10 degrees (see Supplementary Information, Methods). Only 38 stations were available in the southern hemisphere, and only half of these would have been available before 1970. We thus consider two time periods, 1970–2005 and 1979–2005; the latter comprises the period of satellite observations, and has been the focus of previously published temperature trend discrepancies.

The second article is

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

where Thorne writes

“Uncertainty over tropical tropospheric temperature change has loomed large over the last two decades. Use of wind data to infer temperature change offers a new avenue of investigation”

I am pleased that these authors are using winds (specifically the change of wind with altitude – i.e. the “thermal wind relation“) to diagnose temperature trends within the troposphere.

However, this is not a “new avenue of investigation” as Peter Thorne erroneously claimed as, since not only have we published on this subject (with the Allen and Sherwood article only superficially mentioning our paper);

Pielke, R.A. Sr., T.N. Chase, T.G.F. Kittel, J. Knaff, and J. Eastman, 2001: Analysis of 200 mbar zonal wind for the period 1958-1997. J. Geophys. Res., 106, D21, 27287-27290

but the authors chose to ignore the conclusions of our paper and even to report that their method is new!

 We wrote in the abstract of the Pielke et al 2001 paper

The value of the analyses of the 200 mbar zonal winds is proposed as a particularly effective tool to assess variability and trends in atmospheric circulation. Using the thermal wind relation, the 200 mbar zonal wind results from the vertically integrated north-south temperature gradient between the Earth’s surface and 200 mbar. We found a tendency for the 200 mbar winds to become somewhat stronger at higher latitudes since 1958.”

Moreover,  Peter Thorne was among those who eliminated our recommendation to evaluate this issue in the 2007 CCSP report “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences”.

We reported on the abuse of the assessment process by several CCSP authors (including Peter Thorne) and the Chair of this Committee in 

Pielke Sr., Roger A., 2005: Public Comment on CCSP Report “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences”. 88 pp including appendices.

Specifically with respect to the use of winds to diagnose temperature trends, I made the recommendation that we ask the question

“What is the magnitude of the regional tropospheric layer-averaged temperature gradient annual- and season-averaged trends in the middle and higher latitudes as diagnosed from the horizontal winds using the thermal wind relation? How does this analysis compare with the layer-averaged temperature trends as computed with the available radiosonde and satellite data sets?”

Peter Thorne was among those who caused this recommendation to be excluded from the report, and now he introduces it in a Nature paper as a “new avenue”. This is a clear example where they excluded the value of using winds to diagnose long term temperature trends in the CCSP assessment report, yet subsequently took the idea and claimed it as their own. Very sad commentary on the state of climate science.

Even more importantly, on the science in their papers,  their use of the sparsely sampled radiosonde observed wind field  is not as accurate an evaluation as utilizing reanalyses which include radiosondes, but also have other sources of information such as satellite sounding information. We wrote in our Pielke et al 2001 paper with respect to the use of reanalyses,

“We emphasize that changes in the vertically averaged horizontal temperature gradient are a more appropriate circulation diagnostic (through the thermal wind relation) than changes in the horizontal temperature gradient at the surface. Analysis of winds as a tropospheric averaging technique is less affected by biases than temperature analyses and provides an effective method for assessing atmospheric variability and change. Because future shifts in wind regimes are likely under both natural and anthropogenically caused climate change, identifying the robustness of the simulated wind changes in many models and the monitoring of this quantity in observations is expected to become more important in coming years as a test of the predictive capability of climate change models and as one means for resolving the discrepancy between model simulations which show large upper tropospheric warming, and observations which show large surface warming but little change above the surface….”

Our peer reviewed paper, which documented a someone stronger zonal wind at 200 hPa at the higher latitudes also should have been discussed in the Nature Geosciences study. Selective use of peer reviewed papers is not science. [We will be submitting a new paper on this subject to address the science claims made in these two articles. A Climate Science weblog on the science in their paper will also be posted later this week.]

With respect to the current weblog, the deliberate neglect of the earlier research in the peer reviewed literature by the authors of the Nature Geosciences paper, as well as its exclusion in the 2007 CCSP report on reconciling surface and tropospheric temperature trends, shows the bias by certain members of the climate community that is used to promote their particular viewpoint on climate science. Science, however, must be open to all peer reviewed viewpoints.


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