“Simpson's Law” and the Spectral Cancellation of Climate Feedbacks

We spectrally resolve the conventional clear-sky temperature and water vapor feedbacks in an idealized single-column framework, show that well-known partial compensation of these is actually due to almost perfect cancellation spectral at wavenumbers where H2O optically thick. This a natural consequence “Simpson's Law”, which says emission temperatures do not change with surface warming if relative humidity (RH) fixed. provide explicit formulation validation Simpson's Law, furthermore this naturally incorporated alternative RH-based framework proposed by Held Shell (2012, https://doi.org/10.1175/jcli-d-11-00721.1) Ingram https://doi.org/10.1029/2011jd017221, 2013b, https://doi.org/10.1007/s00382-012-1294-3), thus bolstering case for switching from feedbacks. also find negligible lapse rate feedback, suggesting impact changing rates depends crucially on whether or specific held