Limits on CO2 Climate Forcing from Recent Temperature Data of Earth by David H. Douglass and John R. Christy, 2008

There is an important and informative new paper on the role of the radiative forcing of CO2 on the climate system. It is

Douglass, D.H., and J.R. Christy, 2008: Limits on CO2 Climate Forcing from Recent Temperature Data of Earth. Energy and Environment, accepted.

The abstract reads

“The global atmospheric temperature anomalies of Earth reached a maximum in 1998 which has not been exceeded during the subsequent 10 years. The global anomalies are calculated from the average of climate effects occurring in the tropical and the extratropical latitude bands. El Nino/La Nina effects in the tropical band are shown to explain the 1998 maximum while variations in the background of the global anomalies largely come from climate effects in the northern extratropics. These effects do not have the signature associated with CO2 climate forcing. However, the data show a small underlying positive trend that is consistent with CO2 climate forcing with no-feedback.”

This is an excellent paper which provides a new perspective on the role of CO2 as a radiative climate forcing.

There is one statement in the paper that should be clarified

“The atmospheric CO2 is well mixed and shows a variation with latitude which is less than 4% from pole to pole [Earth System Research Laboratory. 2008]. Thus one would expect that the latitude variation of delta T from CO2 forcing to be also small”

The actual radiative forcing is not as small as indicated from 4% value. We have explored this issue in two Climate Science weblogs; i.e.

Relative Roles of CO2 and Water Vapor in Radiative Forcing

Further Analysis Of Radiative Forcing By Norm Woods

While much smaller than the effect of the more heterogeneous climate forcings {as we reported for example, in

Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974,

it is larger than 4% since i) the temperatures within the atmosphere vary latitudinally, and ii) the higher water vapor levels in the lower latitudes reduces the fraction of absorption that can be attributed to CO2.

The conclusions of the Douglas and Christy paper, however, are not altered by this issue, and all of us should look forward to objective scientific scrutiny of their study [after all, that is the scientific method].

The paper should be required reading for all climate scientists, and the conclusions tested to order to build confidence or to refute their findings. Climate scientists who ignore this paper (as seems to be a frequent policy by some) must mean that they agree with the science in the Douglas and Christy paper, but elect to ignore it since it conflicts with their narrow perspective of the dominance of the radiative effect of human-added CO2 as an anthropogenic climate forcing. Of course, ignoring peer reviewed papers, is not the scientific method.

[ADDED 10am EDT: I have been informed that the journal Energy and Environment is not scientifically peer reviewed nor in any citation index. Unfortunately, this significantly diminishes the impact of this very important paper. While the publication process is a difficult road for research that differs from the IPCC type perspective, papers must stll be submitted and published in peer reviewed journals that appear in science citation indexes].

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