We would like to thank Timo Hämeranta for alerting us to a new paper
Lean, Judith L., and David H. Rind, 2008. How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006. Geophys. Res. Lett., 35, L18701, doi:10.1029/2008GL034864.
The abstract reads
“To distinguish between simultaneous natural and anthropogenic impacts on surface temperature, regionally as well as globally, we perform a robust multivariate analysis using the best available estimates of each together with the observed surface temperature record from 1889 to 2006. The results enable us to compare, for the first time from observations, the geographical distributions of responses to individual influences consistent with their global impacts. We find a response to solar forcing quite different from that reported in several papers published recently in this journal, and zonally averaged responses to both natural and anthropogenic forcings that differ distinctly from those indicated by the Intergovernmental Panel on Climate Change, whose conclusions depended on model simulations. Anthropogenic warming estimated directly from the historical observations is more pronounced between 45°S and 50°N than at higher latitudes whereas the model-simulated trends have minimum values in the tropics and increase steadily from 30 to 70°N.”
In their Introduction, they write that
“Our results yield trends in the four individual global surface temperature components over the past 25, 50 and 100 years, augmenting the linear trends that IPCC reported in net global temperature for these same periods, and depicting the associated regional temperature trend patterns.”
There are several quite interesting statements in the article including
“Contrary to recent assessments based on theoretical models [IPCC, 2007] the anthropogenic warming estimated directly from the historical observations is more pronounced between 45°S and 50°N than at higher latitudes…”
“Climate models may therefore lack – or incorrectly parameterize – fundamental processes by which surface temperatures respond to radiative forcings.”
” None of the natural processes can account for the overall warming trend in global surface temperatures. In the 100 years from 1905 to 2005, the temperature trends produce by all three natural influences are at least an order of magnitude smaller than the observed surface temperature trend reported by IPCC .”
“In contrast with climate model simulations, the zonal surface temperature changes determined for natural (solar and volcanic) and anthropogenic influences from the historical surface temperature record do not increase rapidly from mid to high latitudes. Furthermore, since the temperature response to solar forcing occurs relatively rapidly (within months) with patterns that relate to existing tropospheric circulation patterns, the pathways likely involve dynamical motions not simply thermal processes that transfer heat to the deep ocean.”
The analysis presented in this paper provides an effective framework to seek to attribute reasons for long term climate trends. However, the use of the surface temperature data, with its range of uncertainties and biases; i.e. see
Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229
Lin, X., R.A. Pielke Sr., K.G. Hubbard, K.C. Crawford, M. A. Shafer, and T. Matsui, 2007: An examination of 1997-2007 surface layer temperature trends at two heights in Oklahoma. Geophys. Res. Letts., 34, L24705, doi:10.1029/2007GL031652.
is necessarily going to significantly alter their attribution study.
Climate Science recommends that a more robust study is for them to apply their analysis to the global average and regional pattern of tropospheric temperature variations and trends diagnosed in the UAH MSU and RSS MSU data, and in the upper ocean heat content data (see).