JGR authors set the record straight.

Abstract

The Editors' Choice item “Climatology: hotter than ever” (9 Nov., p. 1245) about our paper published in the Journal of Geophysical Research ([1][1]) contains three misstatements that we wish to clarify. In the opening sentence, climate sensitivity is described as “a parameter used by climatologists to specify the increase in average global surface temperature in degrees Celsius as a consequence of doubling the concentration of atmospheric carbon dioxide.” Instead, climate sensitivity is the change in average global near-surface temperature (Δ T , °C) for a prescribed radiative forcing ( F , in units of watts per square meter), expressed as Δ T or λ = Δ T / F ([2][2]). It is practice to determine λ for general circulation models by performing a CO2 doubling simulation, with the resulting temperature change denoted by Δ T 2 x and l = Δ T 2 x / F 2 x . But climate sensitivity can also be determined for other forcings such as an increase in solar radiation. We have performed a suite of such simulations with our general circulation model for different radiative forcings and found that λ was virtually invariant ([3][3]). Also in the first paragraph, it is stated that “The Intergovernmental Panel on Climate Change [IPCC] range of likely values for climate sensitivity is 1.4 to 5.8°C, although the full range varies from 0.1 to 10.0°C.” These ranges are not for climate sensitivity, but for the temperature change in 2100 projected by the IPCC ([4][4]). Part of these ranges is due to the uncertainty in Δ T 2 x , given by the IPCC as 1.5°C ≤ Δ T 2 x ≤ 4.5°C ([4][4]), and part due to the uncertainty in future emissions. And lastly, the second paragraph begins, “In order to construct a probabilistic estimate for climate sensitivity, Andronova and Schlesinger analyze 16 different radiative-forcing scenarios with a simple climate model using, in each case, a doubling of carbon dioxide, but with various combinations of additional factors such as tropospheric ozone, anthropogenic sulfate aerosol, the Sun, and volcanoes.” We did not use a CO2 doubling. Rather, we used the time history of greenhouse gas radiative forcing, both alone and together with time histories of radiative forcing for the additional factors above. We estimated Δ T 2 x for each radiative forcing history. 1. [↵][5]1. N. G. Andronova, 2. M. E. Schlesinger , J. Geophys. Res. 106, 22,605 (2001). [OpenUrl][6] 2. [↵][7]1. M. E. Schlesinger, 2. N. G. Andronova , Encyclopedia of Global Environmental Change (Wiley, London, 2001), vol. 1, p. 301, 308. [OpenUrl][8] 3. [↵][9]1. M. E. Schlesinger 2. et al. , Technol. Forecasting Soc. Change 65, 167 (2000). [OpenUrl][10][CrossRef][11][Web of Science][12] 4. [↵][13]1. J. T. Houghton 2. et al. , Climate Change 2001: The Scientific Basis (Cambridge Univ. Press, Cambridge, UK, 2001). [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #xref-ref-1-1 View reference 1 in text [6]: {openurl}?query=rft.jtitle%253DJ.%2BGeophys.%2BRes.%26rft.volume%253D106%26rft.spage%253D22%252C605%26rft.atitle%253DJ%2BGEOPHYS%2BRES%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [7]: #xref-ref-2-1 View reference 2 in text [8]: {openurl}?query=rft.jtitle%253DEncyclopedia%2Bof%2BGlobal%2BEnvironmental%2BChange%26rft.volume%253D1%26rft.spage%253D301%26rft.atitle%253DENCYCLOPEDIA%2BOF%2BGLOBAL%2BENVIRONMENTAL%2BCHANGE%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [9]: #xref-ref-3-1 View reference 3 in text [10]: {openurl}?query=rft.jtitle%253DTechnol.%2BForecasting%2BSoc.%2BChange%26rft.volume%253D65%26rft.spage%253D167%26rft.atitle%253DTECHNOL%2BFORECASTING%2BSOC%2BCHANGE%26rft_id%253Dinfo%253Adoi%252F10.1016%252FS0040-1625%252899%252900114-6%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [11]: /lookup/external-ref?access_num=10.1016/S0040-1625(99)00114-6&link_type=DOI [12]: /lookup/external-ref?access_num=000165287700003&link_type=ISI [13]: #xref-ref-4-1 View reference 4 in text